Knowledge Bank

insulated suspended floor
8th December 2020
  •  
  •  

Insulated Suspended Floors

It is commonplace in several structures to incorporate beam and block systems. These consist of a combination of pre-stressed beams made from concrete and fill in blocks. Conventionally, such blocks are also constructed from concrete. Yet, more and more, these are being replaced by polystyrene substitutes. So configured, this method avoids the need for insulation on top of suspended flooring. The happy result is more cost-effective and more easily installed.

Types of Precast Flooring System

In the construction of houses, there are three predominant kinds of precast concrete floors:

• Hollow-core
• Beam and block
• Lattice girder

These elements have been designed in a range of sizes that work with the most significant spans for domestic applications at all floor levels.

Beam and block

These elements cater for depths to a maximum of 225mm. They are used alongside standard blocks to facilitate quick fitting at a reasonable price. Suitable for all levels.
Ground floors may be thermally insulated by combining pre-stressed beams and expanded polystyrene blocks. This approach meets the expectations of Building Regulations (Document L), reducing running costs, and improving comfort levels.

Insulated ribbed floor

This composite unit approach is another means to achieve thermal insulation on ground floors.

Lattice girder

This is another combination of materials, where permanent concrete structures are employed with a topping of composite concrete to provide an exposed concrete finish.

Thermal Performance

Next, we consider the actual thermal performance of beam and block flooring. Such floors contribute to the overall thermal mass of a building and so help control inside temperatures.

Beam-and-block floors contribute to the thermal mass of a building, helping to improve its thermal performance and regulate internal temperatures. Even better performances can be achieved when polystyrene blocks are used to replace concrete infill blocks.

Several studies have revealed a shortfall of up to 30% between energy conservation calculations when comparing new homes with predicted conservation calculations derived during the design phase.

Changes were made to SAP calculations to enhance build quality as a means to close the gap:

• The standard for air-tightness was lowered. Higher thresholds result in more significant air leakage, which in turn causes increased heat loss.
• A shift in focus to improved thermally efficient bridging at junctions
• More effective central heating

Other Design Considerations

In the main, flooring systems require certification by a certification body (BBA or BDA, for example.) This is a useful form of quality assurance as, in practice, flooring may be constructed according to the National House Building Council (NHBC) standards.

Fire resistance

Beam and block flooring may exhibit a range of fire resistance depending on beam type and the chosen finish. It depends on the section’s size, but you can expect around 1 hour’s resistance per individual beam.

Sound resistance

Final floor specifications determine the sound resistance of flooring. Depending on the particular specification, beam and block flooring may be acceptable as intermediate flooring in housing or separating floors in residential accommodation with multiple occupancies.

Camber

Concrete beams which have been pre-stressed show an upward camber, dependent on the span and designed pre-stress.

End bearing

On masonry, end bearings need to be 100mm (75mm if steel). In most cases, end bearings don’t get bedded to the supporting wall—they sit on a damp-proof course to protect the steel.

It is possible for floor-beams to be notched to rest in steel on upper levels. However, this requires manufacturer consent on a design by design basis. If using blocks for infill on a load-bearing wall, the strength of both infill blocks and wall blocks must be equal.

Ventilation

Suspended floors sit atop a void, which requires ventilation conforming to should current Building Regulations. Varying site conditions will give rise to a range of values. It is also possible to include radon barriers within the design, although this requires input from a qualified building designer to vouchsafed the barrier’s continuity.

System variations

Insulation units can be constructed to form an unbroken strip of beneath T-beams, thereby removing thermal bridges.

On occasions, such systems prove unsuitable to stakeholders. Another way to achieve the same end is to place a top sheet onto the T-beams and put on a concrete topping.

To achieve the best heat performance may be combined, resulting in both systems, minimal heat loss at critical junctions. Insulation is available to clients in a variety of thermal grades. On the one hand, higher thermal grades can be made thinner. The downside is that higher thermal grades cost more.

Sustainability

Environmentally, there is considerable good news. EPS is judged a low global warming risk and has the potential to be used to pose no depletion to the ozone layer.

Furthermore, EPS rates A+ in the BRE Green Guide to Specification. The raw materials are also fully recyclable. Several manufacturers have pledged to offer schemes for the high-quality re-cycling of scrap material, where the quality of end products matches the quality of the original material.

Chris Nicholls
Commercial Director

Read More
external wall insulation
18th November 2020
  •  
  •  

Insulating External Walls

Thermal transfer through external walls is a significant concern to designers who are looking to achieve good ratings on their SAP Calculations, which is why optimal insulation is so important. Heat loss can be substantial; energy wastage due to inadequate insulation can account for thirty percent of all thermal inefficiency. It follows that selecting the correct materials used in the construction of external walls is critical if you intend to lower energy bills.

Positives

The insulation of walls is dealt with in Part L un the UK Building Regulations, which requires walls to have a U-Value of 0.3W/m2K. Three specific methods dominate contemporary thinking on wall insulation:

• Insulation of internal walls
• Insulation of external walls
• Cavity filling

Any of these approaches will result in an adequately insulated, comfortable feeling, draught-free living space. Two of the methods—internal insulation and cavity insulation—have the advantage of not altering a building’s external appearance, but this does not imply that exterior insulation is without merit, far from it.

Four reasons to choose external wall insulation

The elimination of condensation

In external wall insulation, the dew point is reached outside the building’s facade. However, with internal wall and cavity approaches, there is a danger that condensation may occur within walls without great care being taken—a highly undesirable state of affairs.

Weatherproofing

The whole structure is weather-proof, ensuring that load-bearing elements are protected from large temperature variations and damage caused by freeze-thawing. There is also less risk of thermal bridging.

The preservation of precious internal space

External wall insulation does not affect a building’s interior. As a bonus, retrofitting work may be executed without disruption inside the space. No need, therefore, for occupants to move out during refurbishment.

Aesthetic advantages

External wall insulation offers the perfect opportunity to enhance the outward appearance of structures. The materials come in a broad palette of colours and finishes. This especially applies when renovation work is carried out, yet even new-builds can benefit from seamless facades on rendered finishes.

Components for external wall insulation

Substrate EWI systems are versatile enough to facilitate installation on a range of substrates: brick and block, or sheathing on either steel or timber.

Insulation

Normally, expanded polystyrene, and mineral fibre board are the materials of choice here, with polystyrene having the edge on cost-effectiveness while, at the same time, facilitating design flexibility. For example, the creation of complicated forms or curves.

Polystyrene’s environmental credentials are excellent. Polystyrene boards contain no chlorofluorocarbons or hydrochlorofluorocarbons and come with an A+ BREEAM rating. They also come in a variety of thicknesses.

Mineral fibre board, manufactured from rock, does not combust and provides high-quality resistance to fire. Also, its vapour-permeability offers some noise-reduction advantages.

Repairs

Both types of insulation may be repaired, either mechanically or through the use of an adhesive—sometimes by combining both, depending on the precise circumstances (substrate type, wind, and budget, for example.) Typical adhesives include polyurethane foam and cement-based powder, although polyurethane foam has certain advantages.

Utility

Easily pistol-applied, efficiently handled, and transported.

Quick setting

More storable than non-compressed foam products. Less packaging is needed too.

Thermally equal to EPS

Having only one ingredient, no mixing will be required. Adhesives in powder form more often than not supply adhesive and reinforcement functions. On the downside, they do require mixing in water and will have a longer cure time. Occasionally, for example, with a substrate, mechanical fixing proves necessary in addition to adhesive measures.

The Reinforcement Layer

This layer comprises a wet product and a strengthening mesh. The combination of these materials spreads stress uniformly across the insulation surface. Reinforcement layers come in mineral and synthetic configurations (cement-free).

Synthetic

This type of reinforcement features high impact resistance and is chiefly used with fibre glass. And a thin coat application.

Mineral reinforcement

This type is suitable for any thickness of application and permits small irregularities in the insulation surface. It can be used with glass fibre or metallic mesh.
Finishes
Amongst the available materials, you’ll find renders and decorative elements. Cost-effective mineral cement or renders based on lime have the advantage of offering effective vapour permeability. However, they lack strength, come in a small range of colours, and can exhibit efflorescence.

Silicone renders offer excellent resistance to soiling and water. They are water-repellent and have above average vapour permeability. Synthetic material, which is acrylic-bound, has a high capacity to be bent or curved. They are available in many attractive and vibrant colours.
Hard cladding

Resin brick finishes mimic a natural brick finish, though they have the advantage of being light and are therefore easy to install. They also have excellent impact resistance.

Design issues with insulating external walls

Wind load

Often, the most significant force exerted on a building’s exterior. Several factors are involved in determining the actual force: Location, shape, size, and nearness to other structures or features, all playing a part. Wind load may result in unwanted building movement, destruction of all or part of the external cladding, and particularly vulnerable windows and roofs.

Optimal external wall insulation design is achievable only when informed by precise wind load data. Only a structural engineer is qualified to derive the calculations needed to accurately plot wind loads from information such as:

• Accurate building plans
• Building elevation data
• Geographical placement
• Setting (urban or suburban)
• The height of the structure compared to sea level.
• Surface finish
• Data on all significant building apertures
• Data on nearby structures

A bespoke fixing method is determined for each project following wind-load calculations.
Fire Although recently, interest in fire management has intensified, it has always been a critical design issue, most notably in the construction of high rise structures. Top of the range fire fighting defences can prove costly, which demands the earliest possible intervention in the design phase. Building Regulations (B) sets out the fire safety issues for construction projects.

External wall insulation systems have to be constructed to halt the fire’s spread up the exterior of tall buildings. The essential requirement is for horizontal fire-breaks from the 2nd storey up. Vertical fire-breaks may also be mandated to recent the room-to-room spread. Furthermore, cavity fire breaks must seal the cavity at each opening (windows, for example.) Precise details may vary but must, in every instance, meet both fire-officer and building regulation requirements.

Detailing Facade insulation requires detailing of sills and windows. Measures must be robust here, and to ensure weather-tightness, a sealant is necessary around window/door openings.
Under the ground level, external wall insulation must prevent water infiltrating insulation. Drainage underneath the system plays a part in minimising rainwater splashing, striking the lower section of the facade. Insulation beneath the damp-proof course commonly uses extruded or expanded polystyrene.

Read More
saving water
9th November 2020
  •  
  •  

Saving Water and Energy

Introduction water and energy usage

Flushing toilets can account for up to 75% of water usage in the washrooms of commercial buildings

Climate change threatens to result in sea level rises which may swamp low lying countries across the planet. Yet this is not the only effect of global temperature rises. The looming shortage of already scarce freshwater is also likely to have a huge social impact on communities everywhere. Here we will examine the issues arising from the supply and demand of water and try to explore how buildings may be designed be more sustainable and save water.

The facts about water use and wastage

Ninety seven percent of the world’s water exists in the form of undrinkable sea water. Of the remaining 3 percent, 2 percent is tied up in glaciers. That leaves a mere one percent of freshwater for the almost 8 billion inhabitants of our planet to share. To make matters worse, the Earth’s population continues to rise at a rate 1 percent per annum. Key facts include:

  • Water use has increased by 600 percent in the last century
  • Over 1000 million people live at the mercy of water shortages
  • Amongst scientists the concept of water stress has become commonplace. When the water supply in a country falls below 4,600 litres per person per day, this is the definition of water stress
  • Countries where less than 2,700 litres a day is available are considered subject to water scarcity.
  • Absolute water scarcity arises when the figure falls to 2,700 litres per person per day.
  • The water availability calculation indicates that there are currently 49 countries water stressed, 9 where water is scarce and 21 in a state of absolute water scarcity.
  • Mostly in the developed nations 75 % of water usage originates in flushable toilets in commercial buildings.

The prospect for 2050, according to some scientists, is for hotter summers and unpredictable rainfall patterns. Such conditions will exacerbate our water problems. There will be at least 10 percent less freshwater available; rivers will lose 50-80 reductions in water flow.

Some postulate that we can reduce our consumption over the next quarter of a century by taking simple steps:

The problem with wasted water

Our biggest problem is that we do use an awful amount of water. The average consumer uses approximately 140 litres a day; most of this in the bathroom or toilet. According to the ONS, the United Kingdom will, by 2050, have ten million more mouths to feed. This will inevitably lead to water shortages unless action is taken now.

The question of how much water we actually waste is both informative and exasperating. One quarter of the UK’s water is lost due to leaks. And every legal is significant, because, for example, one dripping faucet loses around 5,500 litres of water each year.

Another illustration of the scale of the problem is the fact that If every adult in England and Wales simply turned the tap off while they brushed their teeth, enough water would be saved to service half a million homes. And fill nearly 200 swimming baths. And those figures are for every single day!

Progress has been made.  Over 20 years ago, changes to water by-laws ensured that “no flushing device installed for use with a WC pan shall give a single flush exceeding 6 litres”.  But while this was a commendable step forward for water conservation, many thousands of older toilets are likely still to be operating on a 13 litre flushThis is the ideal scenario for new installations, but many older toilets could be still using as much as 13 litres of water per flush.

Choosing to target commercial premises for water savings seems like a useful place to start, especially since a lot of water is wasted in such buildings. In buildings where there are no urinals, three quarters of water usage results from washroom flushing. Hand washing from taps accounts for a further 30 percent.

Water shortages are not uniformly experienced over the country as a whole. Scotland and Wales have adequate water, for example. By contast, the Greater London Authority considers that is is nearing its limit, with projected problems by 2025 and concerning shortages by 2040. From a global perspective, hotter countries and regions experience the biggest problems (unsurprisingly). Southern Europe suffers annually because of the huge summer influx of tourists and the prevalence in the area of farming.

Reducing demand for water to reduce watse

Human psychology makes the problems of water conservation even trickier because of the way people see water’s place in their lives. Some consider any restrictions to their use of water as an infringement of their quality of life. When the authorities in one city in Australia, set out to convince residents to shower less  they were surprised to met resistance. Yet the same people warmed to the idea of installing flow-regulators that automatically conserved water from showers.

Behavioural change is only one front in the battle to more efficiently manage this dwindling resource. Other solutions are needed. One initiative in the UK—called Waterwise, seeks to reduce daily consumption below 100 litres per person per day. A second important target set by Waterwise is to reduce leakage by half.

The big water companies have also set targets: to eradicate almost half a million leaked litres every day in the five years from 2020. And in a set of precautionary measures the Environmental Agency has drawn up plans for a series of new built reservoirs and desalination plants, pipe networks and canals which herald a period of rapid expansion in the deployment of transfer projects.

Changes to Building Regulations and how to reduce water wastage

Changes to the 2015 edition of the Building Regulations included optional provisions for increased water efficiency.  Such regulatory measures , shows a willingness at local government, to make a difference. Key movers in the construction industry will need to continue raising awareness of future water shortages with their customers. They have the power to introduce water saving technology though they may well have to convince budget holders of the need to invest in such equipment by making an argument around the total cost of ownership.

Technology in the washroom

Recent research into potential washroom savings, modelled an office of two hundred staff. They assumed that workers visited the toilet three times during working hours, and washed their hands for half a minute at a time. For the purposes of the study they also assumed that water would cost £0.0018/litre. On this. model’s assumptions the research team concluded that simply by introducing ten high efficiency taps, savings of £3,400 over a three year period could be achieved. That’s. over two and one half million litres.

There is no shortage of water saving devices on the market today. From electronic sensor taps, to tap aerators and self-closing taps. From spray taps to mixer taps fitted with brakes. Water savings showers and urinals are also available.

Digital Water Management

Digital water management systems may be used to strictly control water usage in buildings. In such systems, fittings can be linked into a network which is centrally monitored. Overall savings per building can be as high as 30 percent.

Recovering lost heat

Heat recovery shower channels are uncommon but effective. Heat recovery products in general show heat savings of up to forty percent.

Assessment

Organisations such as BREEAM and LEED (a building certification scheme) have established standards and benchmarks to determine an asset’s sustainability, which award credits for meeting a list of efficiency standards.

Conclusion

Our industry has never been better placed to drive the changes to water consumption that are necessary to save the planet. Here’s a short list of questions worth asking, before starting your project:

  • Which economic factors are in play?
  • Is it possible to reduce my operational costs?
  • Are there any budget-compliant water-efficient products on the market that fit my project?
  • Are there any capital allowance factors to consider?
  • Do environmental considerations impact my project?
  • Which building regulations must I comply with?
  • Am I bearing in mind that my customers have become more aware and sensitised to the impact our behaviour is having on our planet?

Chris Nicholls
Commercial Director

Read More
value engineering
30th October 2020
  •  
  •  

The Benefits of Value Engineering

Like many concepts, Value Engineering proves the adage that necessity is the mother of invention. VE arose, in the mid forties, from the need to discover innovative routes to product improvement and cost reductions at a time when shortages in manpower and raw materials were rife.

So, what exactly is Value Engineering and how does it work? In the wake of the Second World War, General Electric set about creating a methodology that sought to systematically offer to produce goods at the required quality at the lowest possible cost. The rules of this early methodology apply just as much now as in the forties, even in this less austere age.

Value Engineering is, in practice, a means to extract optimum investment value. It thrives still in the construction sector. Importantly, it must not be confused with cost-cutting per se. It is best described as a systematic set of procedures to secure essential functions at optimal cost, factoring in such economies, in considerations as capital, labour, and energy consumption.

For maximum bang for your buck Value Engineering is best undertaken early in a project, though it may effectively be applied at any stage in development. The core value comes from the multi-skilled people who know most about the job under consideration. Working in teams, such staff members are best placed to analyse the ‘as is’ before applied innovative engineering concepts to improving designs, materials and methods, but—and this is crucial—without compromising the client’s specification in terms of economy and function.

A Staged Approach

Value Engineering can be split into three distinct phases: Planning, design and methodology.

Planning

The planning phase benefits greatly from workshopping techniques which allow independent teams to subject the client’s facility to ergonomic scrutiny; facilitate the refinement of the client and end-users expectations; and set out the project’s key deliverables.

This is immediately followed by the active consideration of alternative means to achieve the same ends. Finally, the budget is re-considered to see whether proposed changes are financially manageable.

The Design Phase

This is where some of the most intensive work takes place. Designs will have advanced to the schematic stage. The key tool here is, again, the workshop—typically up to 40 hours long—at which client and VE representatives meet face to face to unpick the details of the proposed design. The emphasis lies in reviewing design, budgets and the implementation plan. Value is a tricky concept, its definition varying from client to client and even from one project to the next.

Approach

The workshopping stage brew aka down into five distinct stages.

The information Stage

Participants need to fully understand the project background and context, especially conditions which led to the current design strategy in the past. This is in most cases the job of the design architect, who makes a formal presentation on the topic. Key functions and issues arising therefrom are thoroughly analysed. Equally essential here is the need to determine, as precisely as possible, the client definition of ‘value.’

Creativity

Having understood the facts and definitions determining the overall project, teams move on to speculate on possible improvements. What if we change this parameter? Or substitute this material for that? Workshop participants actively focus on changes that would reduce overall cost while still preserving the client’s values and desired outcomes. This idea generating phase is non-judgemental—there are no bad ideas, just different proposals. The more ideas generated, the better; these will be thinned out and harvested in the next phase.

Evaluation

Now Value Engineering teams and client representatives confer to agree the criteria for evaluation of the ideas harvested in the previous phase. Ideas most likely to lead to added value or reduced cost.

Product development

The focus shifts in this phase to describing the pros and cons of recommendations. Each recommendation is presented within the context of the differences between this and previous versions. Detail may now be sufficient to merit the inclusion of diagrams and cost calculations.

Presentation

In this final phase the deliverable is a written report. This is accompanied by an oral presentation of the key facts and issues. To establish which proposals will carry forward to manufacturing, the following factors are discussed:

  • All recommendations
  • Project rationale
  • Main cost impacts

An analysis of cost savings arising from a comparison between PVC-U vs Aluminium and wood might usefully and practically illustrate VE is action. Evidence exists for significant savings when choosing PVC-U  over aluminium and wood—savings of at least 35% for instance. Cost benefits ramp up with increases in the U value.

One U-Value study on a 0.8 value for U demonstrated up to 60% savings over aluminium. PVC-U turns out to be far more energy efficient, better value for money, and virtually maintenance free. At the same time, achieving these savings does not come at the cost of compromised aesthetics or day by day performance. The use of PVC-U offers massive improvements in thermal efficiency over traditional alternative materials.

Pitfalls

Although VE is a proven-in-the-field discipline, it remains possible for even seasoned practitioners to make errors—often down to time constraints. There is a number of ways in which VE teams can actively guard against poor judgement.

Refuse to compromise on quality

It is not uncommon, where budget savings prove mandatory, for poorer quality products to be chosen. Yet the earliest design choices are often made on the basis of aesthetics and function. Bear in mind that it is usually possible to consider an alternative which is more cost effective but which preserves the desired aesthetics and functions.

Don’t close your mind to alternatives

VE allows practitioners to re-consider alternatives in light of recent industry changes, such as the availability of ‘new’ materials, not on the table when the project began. A good example might be where hardwood flooring figured in an initial specification but later benefited from the substitution of luxury vinyl flooring once it came on the market.

Stay Ahead

Last minute interventions by VE teams are not uncommon and are usually driven by the need to drive down costs. Consider, however, the value of early intervention by VE teams. This facilitates the possibility of importing raw materials or having some elements of the design custom built, where cost savings can be achieved.

Product Network Expansion

Any project will originally have included a sub-contractor list of preferred suppliers. It is essential, when VE teams get involved in making changes, that the original selection of providers is expanded. Doing so often throws up opportunities to switch supplier and save on budget.

Carpe Diem

VE teams can seize the opportunity to re-examine earlier work and seek improvement. Is the client still getting maximum value?

Hold to the production schedule

When VE teams arrive late in the project they need to take care that however well meaning their proposed changes they should, wherever possible, avoid altering the delivery date of the overall project.

Don’t budge on quality

Again, the easiest of VE interventions is to substitute for a cheaper alternative. The problem here is that doing so often involves a compromise on quality.

All Aboard!

It is an essential element of change management that as much effort is expended on getting all project stakeholders on side, as possible. The first part of this process is the need to gain common agreement that change is necessary. A common analogy is that of the burning building. The change manager’s task is to get every one out of the old building (the existing state) and into the new building (the desired state). In a large project there are often those who do not accept that the building is on fire. If this happens on your project, do everything you can to get everybody on the same page. This will avoid disruption as the project develops.

A Case Study

Company A, a house-builder, decided to change their specification to avoid timber. Their drivers were, ease of use for occupants and weather tightness. The houses in question were to be erected in a controlled zone outside of a well-known city centre. This meant sustained interaction with the appropriate council. The council needed to be convinced that PVC-U could be introduced without loss of aesthetics

These discussions were fruitful, and ended with the council agreeing that the PVC-U could be substituted to good effect.

Value

The inclusion of Value Engineering into any design process, increases value and reduces cost. Even during then construction phase, value can still be added, through a mechanism known as VECP: Value Engineering Change Proposals. This often results in some form of gain share arrangement whereby the VE team share in the monetary gains afforded to their clients. NA win-win scenario.

Check and check again

Any project benefits from the kind of scrutiny that takes a second look at previous decisions as the project proceeds, always checking whether the client is still receive expected results. Previously, in would be fair to say that VE was primarily seen as a budget reduction mechanism, watering down the true intent of VE. Recently however, there has been an industry-wide return to the spirit of VE. The increasing prevalence of VE workshops has transformed the construction industry in recent times. This allows clients and service providers to work more harmoniously together to mutual benefit.

The role of digital technology

A proliferation of software applications which have been purpose built for the construction industry, enhance the ability of planners to conceptualise and even visualise the benefits of proposed changes. This software facilitates a sophisticated view of concepts such as ‘total cost of ownership’ Applications make it relatively easy to calculate a client’s return on investment through the use of algorithms which track real-time cost benefits across environmental, social and financial bottom lines.

Before such helpful technology existed, projects were often loaded, by default, with parameters from previous projects. Modern software allows for far more granularity—factoring in local market, economy, wage structures, climate and so on so that calculations are project specific. Software gives the client what the client most wants: a holistic approach, through their medium of these new and sophisticated digital tools.

Chris Nicholls
Commercial Director

Read More
thermal break
19th October 2020
  •  
  •  

A Guide To Thermal breaks

Thermal breaks hinder or eliminate heat passing from one part of a structure to another where a differential exists between spaces. The main objectives of thermal bridging are to prevent condensation and lower energy loss. Critically, material choice can make a significant difference to the outcome of any intervention.

Here we consider various aspects of thermal bridging, including energy transfer and fire risk.

Why is a thermal break important?

Contemporary design and the regulations that govern them embrace the significance of conservation of energy and the need for occupant comfort. Advances in the science of materials and their manufacturing techniques have given rise to structural thermal breaks, which address the problems caused when building elements pass between areas where a temperature differential exists.

Evidence abounds about the effect on the building of poverty of detailing. Energy losses may have significant impacts on building performance—concerning the energy needed to raise or lower the temperature of a location and the financial and environmental costs.

In this regard, building regulations inform designers about minimum requirements for acceptable thermal performance. It is worth pointing out that energy loss is not the only downside to low thermal bridging; condensation and mould growth is another.

Applications of thermal breaks

It is possible to factor into any building detail, a calculable risk of thermal bridging, which often arises in conditions where there is a pronounced differential, such as in a warm server room or cupboard or in warm areas where the humidity is elevated (swimming baths and breweries are two good examples.

There are two main kinds of structural thermal breaks: Mechanical and solid-state. Mechanical includes situations where structural and compressive insulating elements combine as a means to adjust for thermal under-performance. Solid-State Thermal Break Plates, by contrast, may be observed in regular connections as ‘spacers.’

Energy depletion

Scientifically, every material may be assigned a value for heat conductivity. Every material has a value to indicate its thermal conductivity. In general, components with high-end structural properties also display low thermal conductivity. Such material must either be supplemented with more thermally useful materials to achieve acceptable levels of performance.

It is possible to calculate conductivity and adjust findings according to their intended environment. In this way, heat loss may be quantified for three types of elements: Plane, Linear, and Localised.

Condensation

Thermal transmission values assist in the calculation of likely performance. The greater the chance of detecting moist air, the greater the risk of moisture condensation, and all the problems that brings.

CE marking

Unfortunately, a European Standard does not exist to cover structural thermal breaks—therefore, no CE mark for thermal break products.

Materials testing 

Manufacturing standards facilitate the comparison of a variety of materials through tests designed to be independent. New products give rise to new assessment standards. Currently, there are no specific standards for solid-state structural thermal break plates. It is, therefore, imperative that critical parts are subject to independent authentication.

There are many kinds of material testing. In general, they vary by the intended use of the product. This is important to designers because materials with apparently similar properties may perform quite differently in different real-life situations.

Design and thermal performance

The sole existing method for establishing the performance of point connections—known as Finite Element Analysis takes quite a bit of time and is complicated. And because there is little standardisation between building projects, details often vary significantly.

Current regulations demand assessing the risks of heat loss and condensation, to equivalent British and European Standards, and Building Research Establishment (BRE) reports.

Farrat structural thermal break plates can be successfully incorporated in most scenarios. Their flexibility offers designers more leeway to find appropriate solutions.

Carrying out comprehensive Finite Element Analysis requires consideration of both direct connections between materials and surrounding materials, which can also significantly impact outcomes.

Third-party BRE global certification can offer a competitive advantage over the competition. A database exists to give SAP 2016 access to the data.

These details apply to the following specific structures:

  • storage facilities
  • offices
  • retail premises
  • dwellings
  • residential buildings
  • Schools
  • Sports halls
  • Kitchens

A final SAP calculation at this stage is required to determine the thickest permissible break plate to ensure optimal performance.

Thermal break recommendations (principal checks)

Establish thermal break requirements. For optimal performance:

  • Design in the littlest cross-sectional area of penetration of end connectors
  • Use the least cross-sectional area of bolts
  • Choose the thickest thermal break plate possible
  • Select only materials with low thermal conductivity
  • Place any thermal break connections in the building’s insulation.

Structural performance

The correct use of materials plays a critical role in performance, so make sure that you comply with manufacturers’ specifications in all cases. Also, take account of the material’s capacity for load dispersal from high-loaded points of a connection.

It’s a fact that material to material connections may torque under load. For this reason, make sure that the selected structural thermal break can deal with such loading. It would be best to avoid compromises over the short and long performance of connections with exceptional flexibility.

Fire performance

Tall buildings, since the Grenfell fire, now have much stricter requirements regarding building envelopes. Structural thermal breaks form no part of most recent Document B regulations, though they are a critical aspect of constructing tall structures’ fascia.

In common with most building materials, structural thermal breaks may be manufactured with various flammability and performance factors under fire loading. Designers discovering that the risk of fire in their construction is high should opt for fire-resistant material.

Deciding on the specification for structural thermal breaks is crucial. For this reason, endeavour to ensure that all performance criteria are known to all stakeholders. As a safeguard, ensure that the end product fully conforms by explicitly identifying manufacturers by name and product.

Mostly, thermal breaks feature in areas where fire protection is unnecessary. In cases where a fire rating is required:

  • Apply a board fire-protection system
  • Consider sprayed fire-protection (after checking compatibility)
  • Design the connection assuming a total loss of thermal break material as the result of an accident.

Fire protection rules stipulate the amount of time afforded to occupants for escape and fire personnel for ingress. This is mostly down to the properties of materials that contribute to the fire load and easy combustibility or cause the fire to spread.

Chris Nicholls
Commercial Director

Read More
underfloor heating
19th October 2020
  •  
  •  

The Advantages of Underfloor Heating

We are all by now familiar with home convection heating delivered by the radiator. Radiators can be efficient, but they do pull cold air over floors as a prelude to heating it. The concept of underfloor heating (UFH) seeks to improve on this situation by raising the temperature of a room from the floor up. Basically, with UFH, the entire floor surface acts as a single heating element, raising the air temperature above it.

Here, we will explore the benefits of UFH, examining specific issues such as energy and installation costs.

 

How does Under Floor Heating work?

UFH circulates heated water through loops of plastic pipes fitted beneath the floor. In the process of ensuring that the floor is warmer than any other part of the room and allowing the air to cool as it ascends, heat is provided at the most beneficial point. As a consequence, much less heat is lost through roofs — an environmental bonus.

UFH impacts on home design directly. Because pipework is hidden, designers and architects have greater scope to incorporate customer favoured design elements. A good example would be floor to ceiling windows, ideal for flooding internal spaces with natural light.

 

The healthy home

Also, convection heating is arguably less healthy—at least 12% of the United Kingdom population is thought to suffer from respiratory conditions like asthma. The reason is simple. Convection heating encourages the agitation of airborne dust. UFH is based on radiant rather than converted heat, and therefore, atmospheric agitation is reduced by comparison.

A second health issue concerns the ability to keep convection systems clean. Convection heaters provide a haven for dust and germs, rendering them hard to keep clean. It would help if you got under and behind them to do a thorough cleaning job. And if dirt and germs are not removed, there’s a chance they will be breathed in by occupants.

 

Governmental Influence

The UK government is set upon eliminating central heating systems powered by gas in new builds by 2025, as part of what is being called the Future Homes Standard. The straightforward substitution of electrically powered heating as gas is phased out isn’t an attractive answer — they are too expensive to run. A home run on electricity alone will have a high energy bill, almost four times more costly than the gas equivalent.

Furthermore, electricity is comparatively inexpensive, with some systems outputting less than is fed in. On the other hand, an air-source heat pump, especially when coupled with UFH, can produce 4kWh of energy for each 1 kWh of input.

 

Measuring heat pump efficiency

To measure any heat pump’s efficiency, you will need to calculate its Coefficient of Performance (CoP). This technical calculation indicates how efficiently ground or air source heat pumps may heat dwellings in optimal conditions. By this calculation, an air source heat pump’s efficiency may reach four, with ground sources heat pumps pushing that to five.

In practice, heat pumps can output four or five heat units for every single unit of electricity input. By way of comparison, electric heaters register about 100% efficiency (one unit of electricity makes one unit of heat). The efficiency of modern oil or gas boilers doesn’t get much above 90%.

 

Why choose UFH over radiator-based systems?

UFH works more effectively when used in conjunction with renewable energy sources than with radiators.

  • Heat pumps extract heat from outside ambient air to warm properties. There is always enough external heat at the coldest times of the year that can be converted to energy. In the UK, at least, heat pump technology and UFH make great partners.
  • UFH utilises more surface area. This allows such systems to run at 45 degrees instead of 80 degrees C, significantly reducing energy demand.
  • Combined, the system can run cheaper by between 15 and 40 %.

 

Safety

Hospital statistics indicate that burn injuries within the home most commonly occur from physical contact with radiators. Annually, more than 3,750 under-5s are treated for burns in UK hospitals. These alarming figures put radiator burns in the same league as hot liquids, hair straighteners, and clothes irons for burn injuries in young and old. UFH has the advantage of being hidden within the house’s infrastructure, eliminating the possibility of contact burns.

 

Flooring

Many of us choose tiles or stone over carpet for flooring. But tile and stone can get cold. And because radiators heat only upwards, floors will stay cold. In autumn and winter in the UK, this can prove uncomfortable. UFH has excellent advantages here since the entire floor, in effect, becomes one giant radiator; the floor stays warm, whatever the finish.

Scientific Research was carried out by a combined team from The Carpet Foundation and the Underfloor Heating Manufacturers Association. Five types of carpet and two kinds of underlays were tested. Results showed no detrimental effects from any carpet and underlay combinations. They found that combined thermal resistance under 2.5 togs allows underfloor systems to operate effectively in more technical language.


The right materials

For maximum efficiency, the most appropriate materials must be selected for the construction of pipework. The material of choice for professionals is polyethylene (PE-RT (polyethylene raised temperature), if possible. The use of non-PE-RT material, such as in a standard quality plastic pipe, would not meet the required level of oxygen permeability (See below). PE-RT benefits include:

  • Strong
  • Highly flexible
  • Non-corrosive
  • Frost and creep resistant
  • High impact strength, a capacity that allows the distorted pipe to revert to its starting shape quickly.
  • Constructed from a substance that prevents oxygen diffusion.
  • Environmentally friendly.

 

The importance of oxygen diffusion to UFH

The large amount of pipework involved in UFH projects means it is critical that oxygen cannot significantly permeate the pipe since oxygen ingress may damage and increase maintenance costs.

Using pipes not harmful to the environment is given in today’s climate. PEX pipework contains toxins that are difficult to dispose of. By contrast, the PE-RT pipe is environmentally safe and easily recycled.

 

Control

Because UFH differs markedly in operation from other forms of heating, it is essential to understand its control. Accurate control is critical for efficient working. For example, since UFH systems take longer to heat up or cool down than radiators, this needs must be considered when designing a programming system. A 7-day programmable thermostat is needed to optimise your system. Besides, most recent upgrade options include the capacity to control such systems from a smartphone or tablet.

 

Choosing the right system

Consumers have several choices when it comes to UFH. All are capable of installation during the construction of the house itself. Most often, pipework is built into the floor during construction. But there are other build-up choices available too.

  • Joisted
  • Structural
  • Floating
  • Low profile
  • Bespoke

Professional design and robust installation are critical. UFH systems must also be carefully, perhaps even meticulously balanced for optimal performance. On top of this, occupants need to be shown how to optimise their UFH systems—chances are it’ll prove quite different from what homeowners have been used to.

Different settings may be needed. You may be required to turn the system earlier than you are used to and run it for longer, although it will use less power.

These considerations point to the engagement of a specialist UFH contractor, an expert skilled in all aspects of project engineering from design and value engineering through installation, balancing, testing, and the generation of homeowner’s guides.

Chris Nicholls
Commercial Director

Read More
1st October 2020
  •  
  •  

Parts L and F of building regulations: Planned Changes

Committing to a target of net-zero carbon emissions before the middle of this century is challenging enough. Existing stock must be upgraded, and this will be time-consuming and costly. In addition to this, construction companies will need to ensure that new-builds are also up to scratch.
In the vanguard of legislation falling out of the ambitious zero-carbon target setting, will result in the publication of revised Parts L for new dwellings and F of the Building Regulations for new dwellings in England and Wales. When they come into force, these regulations will set out the requirements for the energy performance and ventilation of the property.
These documents have been designed as a natural step towards more stringent standards due to come into force in 2025. This raises the importance of a phased approach for the construction industry since they will have not only to ensure current regulations are adhered to, but also ensure they can up their game to comply with 2025 standards.
Here, we’ll consider the most critical sections in Parts L, and F consultations in England and Wales, in what ways they are limited, and in particular actions construction practitioners need to take to prepare for 2025 standards.

Targets

Control of Building Regulations is devolved within the UK. Recent consultations in England and Wales concerned themselves with parts L and F of the Building Regulations for domestic properties. The documents deal with different requirements. Each document contains recommendations on how to become compliant. So far, consultation has taken place solely on requirements concerning new domestic properties. Non-domestic and refurbishment standards will follow close on their heels.
The Part L requirements have been constructed around a core performance measurement, which must be achieved for every property. In the past, this target related to a carbon emissions target. Most recent consultations produced two alternatives for further reducing the emissions target. For England, 20% or 31% (preferred) reduction over the current requirements. For Wales, the targets exceeded that of England— 37% (preferred) or 56%.
This requires some explanation. The calculations indicate reductions in carbon emissions. However, these were constructed around a new metric–primary energy. The carbon emissions metric has not been discarded; it has been retained as a back-up metric.
This change proved necessary because they do not directly measure energy efficiency. While efforts continue to decarbonise fuel, and in the end, to power dwellings with zero-carbon electricity, low emissions figures reveal little of importance about the energy efficiency of property in regular use. The primary energy measurement has been designed to generate a more precise figure for total energy use, factoring in the energy required for fuel preparation and a property’s ultimate energy demands.

Primary Energy Calculations

Each fuel type is calculated to have a primary energy factor (PEF), starting with the amount of energy employed during upstream production.
Factors include:

  • Planting and cultivation of biofuel sources
  • Extraction
  • Processing and transformation
  • Transportation
  • Transmission

All PEF factors are worked out in advance and are contained in the Standard Assessment Procedure (SAP) specification. Energy demands are then worked out for specific uses. Examples include:

The energy required in each case is then multiplied by the PEF matching its fuel type. The addition of these figures provides the total primary energy demand for the property.
Here’s an example of how to calculate primary energy demand for heating:
(property energy demand/efficiency of heating technology) x PEF
Let’s start with a property heated by totally efficient electric powered panel heaters rated at 10,000kWh. We know that the fuel factor for electricity is 1.501, allowing us to derive primary energy demand as follows:
(10,000kWh / 1) x 1.501 = 15,010kWh
Primary energy calculations consider all renewable energy generated on-site to be subtracted from overall energy demand. For example, if we included a PV array producing 1,500kWh for exclusive use in the above-mentioned property, the calculation becomes:
([10,000kWh – 1,500kWh] / 1) x 1.501 = 12,759kWh
Dropping of the Fabric Energy Efficiency Standard
It is generally agreed that the move from carbon emissions as the primary indicator of how energy-efficient a property is, to Primary Energy Calculations, offers a more accurate snapshot. There have been critical voices, however, about the way in which is to be implemented in the draft in force in England.
The current situation is that the English Approved Document for new dwellings (ADL1A) uses the Fabric Energy Efficiency Standard (FEES). This sets minimum energy performance targets for the fabric elements of buildings. To simply the system when primary energy targets were introduced in the 2020 version of Part L, some argued for the removal of FEES. This meant that to exercise control over a building’s fabric performance would require the use of the worst-case backstop U-values. This is what currently happens in Wales because the FEES was never introduced in that country. However, the backstop U-values proposed for England are less onerous than their existing Welsh counterparts (as shown in Table 1 below).

Heat loss elementsCurrent England ADL1ACurrent Welsh ADL1AEngland 2020 proposedWales 2020 proposed
Floors0.25W/m²K0.18W/m²K0.18W/m²K0.15W/m²K
External walls0.30W/m²K0.21W/m²K0.26W/m²K0.18W/m²K (flats 0.21W/m²K)
Flat and pitched roofs0.20W/m²K0.15W/m²K0.16W/m²K0.13W/m²K

Table 1: Area weighted worst-case backstop U-values for new domestic buildings

This gives rise to an anomaly. Primary energy calculations permit the deduction of contributions from on-site renewable energy. Potentially, this could see homes constructed to these backstop U-values. Meaning homes constructed under 2020 Part L with renewable generation would require more heating than those constructed under current standards using FEES.
This seems to fly in the face of the very reasons for upgrading Part L. It could also worsen differences between the actual energy performance of dwellings and what the design predictions indicated, as a result of adopting heat pumps to meet the heating and hot water requirements.

In winter, heating and lighting demand is high. At this time, air-source heat pumps tend to underperform as temperatures dip. PV output falls too at a time of shorter days and lower sun angles. If there is energy waste in homes, carbon measurements could well end up higher than they currently are.
Fuel bills will be impacted as a result. The Committee on Climate Change (CCC) predicted that existing proposals could result in domestic bills that 50% above those for homes built to English requirements.
It is concerning that this estimate fails to factor in on-site technology running costs. In the end, this could leave many in fuel poverty. Affordability is best achieved by pursuing fabric efficiency to reduce demand to a minimum.
Construction companies, in England and Wales, need to consider such changes within the timescale of the next five years. The English version states that the 2025 requirement is supposed to require that carbon emissions from domestic assets be between 75% and 80% lower than at present.
At these levels, attaining a high degree of fabric performance is likely to become compulsory. If so, perhaps a better way forward than masking leaky homes with renewable technologies, it is vital to use the next five years to raise construction standards and to adapt supply chains for future solutions.
It may help to view this up-skilling process within the context of probable requirements in 2025.

2025 Part L and F requirements

English and Welsh approaches indicate a pressing need to combine low-carbon heating systems with an extremely high fabric standard specifications. It is likely; therefore, that triple-glazing will be required. Building elements will have to conform to the U-value limits shown in table 2.

ElementExpected U-value requirements in Welsh Part L 2025Expected U-value requirements in English Part L 2025
External wall0.13W/m²K0.15W/m²K
Roof0.11W/m²K0.11W/m²K
Floor0.11W/m²K0.11W/m²K

Table 2: Expected minimum U-value requirements for Part L 2025 in England and Wales

The CCC offers more detail still on how a net-zero home might perform. They say that homes must be extremely airtight and supported by timber-framed mechanical ventilation heat recovery (MVHR), and with a space heating demand of 15-20kWh/m2/yr.
To conceptualise this figure, the Passivhaus Trust estimates a typical UK home has a space heating demand of around 130-140kWh/m2/yr. This would represent a considerable change, yet it is achievable. From an international point of view, the net heating in the city of Brussels has been restricted to 15 kWh/m2/yr since 2015, and by 2020 Denmark’s demand for space heating in residential buildings will be reduced to 20 kWh/m2/yr.
Perhaps more significantly, the demand for space heating of 15kWh/m2/yr is also a requirement of the voluntary Passivhaus energy performance standard.
In common with CCC recommendations, the Passivhaus requirement is for highly airtight properties with an air-leakage rate of just 0.6 ach @ 50Pa and ventilation through MVHR. Even then, high levels of insulation won’t be enough—properties will have to be virtually thermal-bridge free. The primary energy demand must also be regulated to ≤ 120 kWhm2 / yr, and the specific cooling load must be regulated to ≤ 10 W / m2.
Properties may be certified only after careful assessment to ensure real-world outcomes match expectations. Such a rigorous approach supports high construction standards, and results show that Passivhaus properties regularly meet or exceed targets for energy performance. Traditionally, Passivhaus standards were considered more relevant to self-builds. It has become more common, however, for these standards to be applied to larger-scale projects.
In short, there is enough evidence, from various sources, to confirm that such requirements could be achieved when scaled up. We also have some idea of how to meet them. Offsite solutions like structural insulated panels (SIPs) work well for Passivhaus. The modular format of such panels lends itself to achieving faster build times. They provide superior thermal performance, airtightness and insulation continuity. This may reduce stress on site workers – a key component is given that there still does not seem to be an end to the current skills shortage.
The CCC’s data show that immediate action to investigate approaches and up-skill workers would bring the limitation of space heating on all new dwellings to Passivhaus levels (15 kWh/m2/yr) by 2025, eminently within reach.

2020 Part L and F

With an eye on requirements in the pipeline, a ‘fabric first’ approach sounds most practical for project teams, concentrating on getting quick wins. Were fabric-first methodologies to be adopted first, and quickly become standardised, it would be easier to upgrade building construction methods, so they take future requirements into consideration.
Although not necessary, the fabric criteria set out in Option 1 of the English consultation and Options 1 and 2 of the Welsh consultation tend to be a fair jump-off point, with U-values corresponding to the estimated limit values for the 2025 standards (see Table 3 below). The airtightness requirements within Welsh Option 2 offer a similarly reasonable path to 2025. Project teams could begin to gain a thorough understanding of the new airtightness approaches and the effective installation of MVHR systems.

 
2020 England proposal
Option 1
2020 Welsh proposal
Option 1
2020 Welsh proposal
Option 2
Floors0.11W/m²K0.11W/m²K0.11W/m²K
External walls0.15W/m²K0.13W/m²K0.13W/m²K
Flat and pitched roofs0.11W/m²K0.11W/m²K0.11W/m²K
Thermal bridgingGlobal value Y = 0.05; or individual values from SAP table R2 (Option 1 values)Global value Y = 0.05; or individual values from SAP table R2 (Option 1 values)Global value Y = 0.05; or individual values from SAP table R2 (Option 1 values)
Air permeability553 + mechanical ventilation heat recovery
Photovoltaics installedNoYesYes

Table 3: Selected notional dwellings building parameters

Both consultations highlighted the need to stop thermal bridges degrading the overall performance of the dwelling. With this in mind, they recommend that the Approved Construction Details (ACDs) are removed from new versions of Part L as these are inappropriate when engaging with the new fabric standards.
Universal backstop thermal bridging level values used within SAP will also get worse. Yet, avoiding them will require project teams to calculate their own thermal bridging values or use model construction details from non-government databases which contain independently assessed thermal junction data. This will require careful attention to detail if compliance is to be achieved.

Chris Nicholls
Commercial Director

Read More
BREEAM
25th September 2020
  •  
  •  

How does a BREEAM assessment work?

What does BREEAM stand for?

BREEAM, or the Building Research Establishment Environmental Assessment Method, is an international building standard around the energy performance and sustainability of new non-domestic buildings.

BREEAM Assessments are primarily carried out on new non-domestic construction projects, but can also be carried out on domestic refurbishment projects

Since launching in 1990 to be the first building environmental impact of its kind, BREEAM has become a highly regarded building standard in over 50 countries. Since launch, BREEAM’s aim has been to ensure there is a positive social and economic impact of a building whilst limiting the environmental impact of its construction and use. BREEAM also enables buildings to be recognised for the commitment to sustainability in their design, materials, and construction.

Why is BREEAM important?

BREEAM is an internationally recognised standard for building sustainability. Clients who demonstrate that their projects have a commitment to sustainability in their design and construction by scoring highly through BREEAM’s assessment criteria will receive the benefits of lower running costs, higher property market value, and a more desirable place to live and work for tenants. 

What does BREEAM cover and how is BREEAM rating calculated?

BREEAM assessed buildings will receive a benchmark score based on a number of factors, such as:

  • The BREEAM rating level benchmarks
  • The minimum BREEAM standards
  • The environmental section weightings
  • The BREEAM assessment issues and credits

BREEAM Assessment Categories

When one of our accredited assessors is calculating a build project’s BREEAM rating, they will focus on calculating the building’s sustainability and environmental impact based on the following categories:

  • Energy
  • Land use and the building’s ecological impact
  • Water usage
  • Pollution
  • Materials
  • Management
  • Health and wellbeing 
  • Waste
  • Transport

Each category has its own sub-category, standards, and sustainability targets that are used to calculate the score for each category.

These are all used to calculate a building’s BREEAM rating, which is graded in order of Outstanding, Excellent, Very Good, Good, Pass, and Unclassified.

What is the BREEAM Assessment rating process?

1. Decide which BREEAM Standard applies to your building project

There are multiple BREEAM Schemes that can apply to different types of building projects. The different schemes and their applications are:

  • BREEAM Communities – for the planning stage of your project
  • BREEAM New Construction 2011 – for design and construction 
  • BREEAM in-use – for currently in-use buildings
  • BREEAM Refurbishment –  for existing building refurbishment

2. Appoint a licensed and approved BREEAM Assessor and register your project

You can use BREEAM’s finding tool to find an approved assessor, or you can contact one of our qualified experts about your building project. Briary Energy is a very experienced approved BREEAM assessor who have helped many client in the past. Your project will be registered through your appointed assessor to the BREEAM assessment body.

3. BREEAM pre-assessment

By working closely with you, your assessor will calculate a provisional score of what your building project is likely to achieve.

4. Gather necessary information

Collate together any necessary information related to your project and pass this on to your assessor.

5. Assessor review

Your assessor will review your building project and will submit your assessment to the BREEAM Certification body for rating.

6. Receive your BREEAM score and certificate

How Briary Energy Can help With Your BREEAM Assessments

Briary Energy are experienced in carrying out BREEAM Assessments that have helped our clients increase market value and reduce running costs on their new buildings. Our expert team will work with you to make the BREEAM assessment process quick and easy. 

Contact us about our BREEAM Assessment.

We also provide SAP calculations for new buildings. Contact us to find out how we can help you save around £800 per plot.

Read More
17th August 2020
  •  
  •  

Natural Ventilation

At a time when all things’ natural’ seem to have taken centre stage, natural ventilation, in contrast to mechanical methods, exhibits a number of advantages worth considering, including:

  • Significant energy savings
  • Improved indoor air quality
  • Space savings

To capitalise on these advantages and to optimise its effects, it may prove helpful to explore the science behind natural ventilation and to consider how to avoid mistakes during its implementation.
In principle, natural ventilation is easy to define: it is no more complicated than circulating fresh air from outside a building, through its interior in a way that offers a pleasant, superior-quality inner environment, achieved without the use of fans (and therefore saving energy).
Choices in how to deploy natural ventilation vary along a technological continuum. At one end you have simple ventilation systems that require no more than the manual opening and closing of windows. At the other extreme, a high degree of automation takes over, with computer systems taken control of actuators which open and close ventilation on the command of the CPU. Such systems stabilise building temperatures, keeping air quality stable. Somewhere between these extremes, you will find methods which combine high and low tech solutions: computerised controls taking over when it’s expedient to do so for optimum performance.

The argument for

Finding positive reviews of natural ventilation systems isn’t difficult. The London Plan, Building Bulletin 101 and PSBP Baseline Specification all sing natural ventilation praise. The following six key advantages stand out:

  1. Energy Savings: Energy savings of between forty-seven and seventy-nine per cent through completely switching to natural ventilation, or by augmenting mechanical ventilation with natural ventilation (Source: Fraunhofer Institute for Building Physics). The Carbon Trust calculated that naturally ventilated structures made average energy savings of £30,000 a year when compares to industry-standard benchmarks buildings utilising air-conditioning.
  2. Lower costs: Eight case studies demonstrated that natural ventilation and hybrid systems show payback periods under 12 months (Source: Carnegie Mellon University). Further savings of eighty per cent over the lifetime of such systems manifest through reduced cost of capital, operations and maintenance.
  3. Healthier environments: Buildings with controllable windows and natural ventilation were shown to lower health costs by 0.8-1.3% in comparison to systems involving sealed windows and mechanical ventilation. Also, in such cases, absenteeism fell by 3.2%, and symptoms of sick-buildings syndrome fell by an impressive 65% (Source: Carnegie Mellon University).
  4. Improved Productivity: It has also been shown that between 7% and 8% improvements are possible in children’s test scores in schools which had manually operated windows as opposed to schools where fixed windows were the norm (Source: Heschong Mahone).
  5. Higher user satisfaction scores: Further research produced evidence of 77% user satisfaction when considering spaces with natural ventilation. The comparable figure for mechanically ventilated areas was 50%. Carnegie Mellon’s investigation also demonstrated a year on year productivity gain of up to 18%.
  6. Plant space-saving: Natural ventilation frees up overhead space and plant rooms offering the possibility of designing smaller buildings or finding innovative ways to use the extra space.

Perceived difficulties

Where more significant buildings are concerned, natural ventilation is often thought of as more challenging. The perception is that, in larger structures, it is problematic to accurately calculate performance. There are also problems with overheating, draughts, unacceptable noise levels and security. All of these issues can be rigorously mitigated by taken a professional design approach, resulting in higher performance at a cost-effective level.

The science of natural ventilation

Natural ventilation leverages the science of wind pressure and thermo-dynamics to circulate air in space. The thermo-dynamic aspects of the issue prove especially useful in more significant areas where there is high heat gain or in situations where the wind is absent.
Professional guidance can be found in the CIBSE publication, AM10′ natural ventilation in non-domestic buildings”. This document examines the limitations of one-sided ventilation only if the ratio of the ceiling height to the depth of the room is only 2.5. For this reason, one-sided ventilation is usually restricted to shallow-plan offices with low occupation.
A method known as cross-ventilation is the preferred option when ventilating spaces characterised by having vents on opposing faces, roof-lights, louvres into corridors, shared spaces, or atriums to take advantage of cross and stack ventilation. Cross-ventilation allows better control of airflow through the excellent control of vents in areas of differential pressures. This improves the distribution of incoming fresh air and removes stale, warm air more uniformly across spaces.
Key to natural ventilation strategy is night-cooling. At night, the cooler night air is offered controlled ingress to the building, using automatic vents to reduce the fabric and content temperatures of the building. This permits the building’s mass to absorb a portion of the excess heat, assisting in the stabilisation of air temperatures during the following day. In effect, lowering temperature highs and keeping rooms at a comfortable temperature for longer.
Heavy-duty construction materials like concrete add to the thermal mass of the building, maximising the potential for temperature stability. In a typical structure of medium mass, night-cooling can make a significant difference. Get the night-cooling strategy right for such a building, and you might expect to lower unwanted peak temperatures as much as 10C and to lower the time rooms record higher temperature by more than 60%.
The downside to night-cooling is that you will need to exercise more care over security. It is highly desirable to have the capacity to accurately set opening limits for vents. And to have some means to feedback vent position data. The highest quality fixings must be employed to keep security levels high at times when vents are open.
Spend a lot of effort into the design stage of your natural ventilation strategy to ensure success. You must also gain a comprehensive understanding of the ergonomics of daily building use to maintain a stable environment and high energy performance.
The thermo-dynamic attributes of the situation can be complex. Ventilation demand varies throughout the day as temperatures and air quality levels rise and fall in the face of continual changes in heat gains and occupancy levels. In addition, forces influencing ventilation rates (wind pressure, wind direction and temperature differentials) vary over the course of a day too.
You need to continually understand current ventilation needs and match them with the external conditions that will impact on their delivery. There is a fine balance to be struck here — over-ventilation causes draughts and unwanted heat loss, but under-ventilation can cause overheating and lower indoor air quality.
The demand for ventilation and external conditions need to be continuously reviewed. Care should be taken to moderate vent opening so as to prevent excessive swings in temperature and air quality to optimise the delivery of an effective indoor climate.

Airflow Management

A thorough scientific understanding of how air flows through an opening is essential to a successful natural ventilation strategy. In a cross-ventilation situation within a context of typical wind pressure, airflow through a window will not be linear (relative to its opening position.) Put another way, a slightly open window exhibits a proportionally larger volume airflow than will the same window when fully open.

Wind tunnel data on windows open to a variety of degrees show that up to 60% of airflow can take place in the first 5% of the opening. The scientific import of this is that for the optimum effect we need to exercise a fine level of control so we can open windows using small by highly accurate adjustments around a baseline of the optimal vent position. We need not bother too much about swings of greater magnitude as these have the potential to negatively impact on comfort and energy performance.
The ability to adjust precisely and in a timely way is critical. System lag in traditional systems using 0-10v type controls do not facilitate the desired fine levels of control needed for an effective method. There is a danger of undesirable vent positions, leading the system trying, and failing on occasions, to adequately compensate. The upshot of this can involve excessive operation and unsynchronised windows. It is the lack of acute control and the absence of window position feedback that creates a risk to system optimisation.
Luckily, a digital solution is available. Hi-tech window actuators with high-sensitivity position control and feedback make window control easier with the ability to modulate tiny, trickle vent positions accurately during winter months.

Controlling Natural Ventilation

Manual

The simplest and cheapest method of controlling natural ventilation is to open and close windows manually. Unfortunately, this introduces human risk factors leaving the effectiveness of the system to the performance of human agents. Psychologically, it is a commonplace for performance to suffer in situations where no single individual has responsibility for window operation. You often find in schools and offices that opening and shutting windows results from feelings of discomfort. And this means that conditions must already have deviated from optimal.

Manual (with ‘traffic lights’)

A more intelligent approach would be to pair a manual control system with a ‘traffic light’ system communicating with air and temperature sensors capable of detecting when windows are to be opened or closed.
Research into schools reveals that to be able to vary conditions in the sort of densely occupied space that most schools represent might necessitate up to 40 changes to vent positions every day to keep temperatures within optimum parameters. This may seem manageable, but considering a typical class with four windows might require 160 daily window adjustments, the situation looks a little more daunting. In practice, sensors tend to be ignored, and windows are likely to stay open or closed for longer than necessary for optimal performance. A further disadvantage of manual window systems is their lack of capacity to take advantage of night-cooling.

Intelligent Systems

Build an automated natural ventilation system after careful due diligence and planning, and there’s a good chance of a significant performance improvement. Swiss studies have shown that rooms with automated windows held acceptable temperatures for three times the length of time demonstrated by rooms with manual windows. The advantages didn’t end there, though: The automated rooms managed 50% more hours with good air quality, and at a 15% energy saving.
A robust specification for a window control system is critical to success. In the simplest case, automated window systems are fully open or fully closed. There are no positions between these extremes. You could design a simple system with incremental control, say by adding the capacity for windows to be half-open, but to really achieve the finer levels of control typical of a high-performance natural ventilation system there are two main considerations:
It sounds obvious, but it is essential that a programmable building management system (BMS) is programmed by specialists and experts in the field of natural ventilation which have experience with sophisticated control regimes.
Compared to natural ventilation systems, many common BMS applications just have basic requirements, with simple on or off settings. But, a successful natural ventilation strategy demands a more sophisticated degree of control and the ability to manipulate larger numbers of concurrent variables such as room and outdoor temperature, internal carbon dioxide levels, wind speed and direction in relation to the capacity of ventilation openings. Understanding how to optimise vent positions can be achieved only by those with the skills and experience of complex control algorithms. You want to aspire to a ‘measure twice, cut once’ approach. Get the system designed right first time and avoid post-installation ad hoc adjustments arising from user complaints. Any system specification must guarantee fine levels of control of the vents, in accordance with all variables influencing performance. Specifications should also include clearly stated operational expectations.
There should be an insistence that window actuators and related onboard technology must be able to support percentage positional commands via BacNet or similar network communications, as well as position feedback to confirm the expected fine degree of control.
Some automated systems assembled from a variety of third-party components may complicate design and installation. Another way is to install a packaged system a solution provider who can supply all or most of the parts you need. This optimises integration and performance of the system, and shortens the chain of responsibility, raising the chances of timely delivery.

Design Factors

The design of facades for automated natural ventilation takes many forms. Automatic high-level top-hung outward opening windows work particularly well because they offer a higher degree of flexibility for automation as well as larger opening areas.

Other Benefits

In winter, colder outside air enters through small controlled openings to mix high in the room, reducing draughts that can arise from side hung or low-level windows. From a health and safety point of view, the risk of fingers being trapped is virtually eliminated. Small high up apertures for night-cooling are also far less of a security risk, especially compared to openings at ground floor level.
The proposed high-level automated windows cover most eventualities, although they may be augmented by low-level manual windows where there is a need for a larger ventilation area. And to give users a sense of control over their environment—an important consideration—consider including a manual override of automated high-level windows via a keypad.

Choosing the right actuator

Window and window positioning specifications determine optimal actuator size. Critically, selection should be made on the basis of the orientation and weight of the opening section as well as the extent to which it needs to open. The larger the load and the bigger the opening, the bigger the actuator needed. Consider cable locations early in the design process. Wider windows may require more than one actuator.
24V DC actuators with additional intelligence features are to be preferred.

Controls

Local power supply units generally need a 13a mains power supply and are capable of controlling up to 20 actuators in as many as 10 independent control groups. This arrangement facilitates one controller, servicing multiple windows in multiple zones.
Consider having temperature and CO2 sensors in every room. This is the best practice. The BMS system typically uses a weather station communicating with room sensors and fed seasonal information to determine best vent positions at all times.

Chris Nicholls
Commercial Director

Read More
4th August 2020
  •  
  •  

Understanding PAS 2035 and PAS 2030:2019

It’s one thing to acknowledge climate change; it is quite another to take practical steps that will make a difference. The introduction of reasonable levels is a particular challenge for the UK for historical reasons: over 50% of the housing stock was built before the 1965 Building Regulations brought in introductory regulations governing insulation.

Home dwellings account for 14% of greenhouse gas emissions. Meeting the ambitious net-zero target for emissions by 2050 (UK), 2045 (Scotland) is going to require shrinkage of heat emissions by 95 per cent. This figure looks even more daunting when considered in terms of CO2 tonnage. Because that’s a reduction from 2,345 Kg (current) to 138 Kg, that’s a challenge.

The size of this challenge is truly overwhelming. There will need to be a concerted effort to increase the energy efficiency of all homes. However, this is small potatoes compared to the vast retrofit programme that will be required—something that has never been attempted before. Given that such a programme will involve every single dwelling in the country, it isn’t surprising. Contractors have their work cut out to plan how this work could be carried out.

Of course, standards must be defined to guide the retrofit work, which is why the UK Government brought in a Retrofit Standards Framework, specifically to prevent piecemeal implementation of so significant a change. In effect, the government have set out three logical steps for the industry:

  • Carry out a property by property assessment of each property
  • Produce a medium-term plan of action
  • Introduce approved measures

What is PAS 2035 and what does it mean?

PAS 2035 is the key document. It sets out clear guidelines for contractors by offering a procedure for building assessment, a guide to selecting the most appropriate EEMs and instructions for long-term monitoring. The document also lays down minimum standards of qualifications, roles and responsibilities, for anyone carrying out retrofitting. The updated PAS 2030 can be seen as a companion to PAS 2035 since it focuses exclusively on commissioning, installation and hand over of EEMs.

Before 2015, unease grew concerning a perceived gap between energy efficiency promised and energy efficiency delivered and at the end of 2016, the Bonfield review was published. This report laid down 27 primary recommendations and suggested a brand new approach to retrofit projects which was to be underpinned by the introduction of a Home Quality Mark in addition to new codes of conduct and practice. The review also proposed a cradle-to-grave framework for the delivery of retrofit energy efficiency.
Efforts have been made by the UK government in tandem with an appointed implementation board, to put the review’s recommendations into effect.
In terms of quality assurance, an extension to the existing quality mark to encompass repair, maintenance and improvement, retrofits and energy efficiency sectors. This opens up a future in which retrofit schemes may be entered into only by TrustMark-registered companies.
In common with other such schemes, companies seeking accreditation will need to be formally assessed by a qualified certification body. Recently the government adopted three new requirements:

  • PAS 2030:2019 – Specification for the installation of energy efficiency measures in existing dwellings and insulation in residential park homes
  • PAS 2031:2019 – Certification of energy efficiency measure installation in existing buildings and insulation in residential park homes
  • PAS 2035:2019 – Retrofitting dwellings for improved energy efficiency. Specification and guidance.

Collectively, these specifications offer a thorough framework for energy efficiency retrofits on domestic properties. Companies should start now, to familiarise themselves with these specs—by 30 June 2021, it will be mandatory for certification bodies and companies registered under the TrustMark scheme to comply with them. As is the case with any robust system, compliance will need to be evidenced.

PAS 2035 – A whole-house approach

The third document listed above—PAS 2035:2019—offers the most comprehensive understanding of the entire Retrofit Standards Framework. Everything from assessment, design and monitoring is explained. PAS 2035 takes a pragmatic, so-called ‘whole-house approach,’ in recognition of the fact that there is no solution set that will fit all circumstances. This way, all aspects of the property require careful, holistic evaluation in advance of any EEMs being put in place. The ‘whole-house’ approach further recognises that insisting that all features are raised to an identical high standard is not only impractical but ill-advised.
PAS 2035 covers risk assessment and whole-dwelling assessment. This process encompasses:

Considering how retrofitting may impact on each. PAS2035 adopts a philosophy that raises considerations such as the protection of occupant health, wellbeing and comfort above those of merely upgrading the energy efficiency of the property.
20–30-year planning

  • Medium-term planning aims to determine a suitable improvement level, given any constraints. At the end of this period of consideration, the idea is to deploy a collection of EEMs.
  • Plans should include a review of unintended consequences arising from potential interactions between EEMs.
  • A precise order in which EEMs are to be deployed must also be included, with consideration given to any knock-on effects.
  • Plans must be formatted in a future-proof way, to facilitate inevitable changes.

Fabric first

A cost-effective method of improvement, emphasised in PAS2035, is the fabric first approach, which is both robust and cost-effective—an approach PAS2035 suggest should be taken into account in the planning process. Essentially, this means taking the following sequential steps:

  • Upgrade the building to a reasonable state of repair concerning pointing, brickwork integrity and damp
  • Replace older light fittings with low-energy bulbs and lighting units.
  • Improve temperature controls
  • Tackle more significant, possibly more costly upgrades to the fabric of the building, e.g. by installing insulation, thermal bridge/air leakage reduction, installing ventilation.

Actual scopes of work evolve from issues noted in the first building assessment. For example, contractors may be restricted in the range of work that can be carried out on listed buildings. In the same way, a risk-based approach is preferred for older properties.
Poor decisions taken in the design phase can significantly reduce effectiveness. For this reason, PAS2035 singles out the need to ‘concentrate on the interfaces’. This ensures that junctions are watched closely to make sure insulation layers and air barriers are continuous and thermal bridges dealt with effectively.
When this has been achieved, contractors can concentrate on residual heat and energy requirements and dealing with them as effectively as possible. This includes which renewable technologies are appropriate.

PAS 2035 facilitates best practice by offering guidance on methods for monitoring and evaluating properties and by considering ways that feedback from one project can be made available to others, for continual improvement.

Raising awareness

An essential facet of PAS 2035 is that it seeks to give a voice to occupants, putting their views front and centre of the refurbishment process. This certainly inspires consumer confidence, but it also acknowledges that occupant use is capable of undermining the effectiveness of EEMs, and even exacerbate the performance gap between the designed and actual performance of the building. An instantly recognisable example of this phenomenon is when occupants living in highly insulated and airtight buildings leave windows open while running heating systems.
PAS 2035 goes further with consultation by ensuring that occupants are kept informed of all developments in improvement plans relating to their properties. Updates are reasonably comprehensive, providing as they do, details about how interventions operate and explanations why they were scheduled in a specific order. Data is also provided to ensure that post works, energy efficiencies achieved during the retrofit are maintained over the longer term.

Data warehouse

In support of the Retrofit Standards Framework, an online data warehouse has been created. This enables the logging of work at one location and makes it available to other sites in real-time, facilitating an integrated approach. More value has been created with the introduction of a property hub that provides a window to view useful information for homeowners.

Roles and responsibilities

As a means to validate competency, several pivotal positions have been created within the Retrofit Standards Framework. PAS 2030 and PAS 2035 set out clear and mandatory vocational or professional qualification requirements. In reality, individuals may hold any number of posts simultaneously. As a check on this flexible arrangement, post holders must be sufficiently qualified, and any potential conflicts of interest must be made visible from the outset.
Of all roles, that of Retrofit Coordinator has primacy. The person in this role has responsibility for end-to-end project oversight. The Retrofit Co-ordinator:

• Commissions measure design
• Contracts installers
• Acts as the homeowner’s advocate

It does not matter who employs the Retrofit Coordinator. The client can do this, or any other party for that matter, so long as he or she is responsible for protecting the client and the public’s interest, and for ensuring compliance with PAS 2035.
PAS 2030 and PAS 2035 set out a series of well-defined steps through which all retrofit projects should proceed:

Step 1.
A conversation takes place between the Retrofit Adviser and the householder. The plan includes reducing consumption, through property improvements and adjustments to occupant behaviour.

Step 2.
The householder has the option to explore a range of improvements. If this exploration is taken up by the householder, the retrofit coordinator conducts a risk assessment informed by the contents of various key documents:

• Current Energy Performance Certificates
• Surveys
• Interviews with occupants and or owners
• Site visit observations

From these inputs, each property is graded A (lowest) to C (highest), and this grade will determine the future trajectory of the project. The risk assessment is repeated and updated as new measures are implemented.

Step 3.
Retrofit assessors carry out a whole-dwelling survey, to include a comprehensive review of:

• The property’s heritage, construction and dimensions
• Current services
• Defects and improvement opportunities
• Existing planning constraints
• U-values
• Moisture properties and suitability for improvement.

For risk paths B and C, further considerations are required, including:

• Occupant appraisal. Have they special requirements?
Ventilation review
Air permeability assessment
• Yearly fuel consumption and estimated emissions
• A significance estimate following BS 7913:2013 which is a guide to the conservation of historic buildings.

Step 4.
The retrofit designer now considers all the data collected and sets about designing a bespoke package of EEMs, paying close attention to fabric EEMs and to measures that might potentially interact. If dealing with risk paths B or C, the retrofit coordinator must include an improvement option evaluation before completing the retrofit design, calculating payback period and carbon cost-effectiveness.
Step 5.
At this stage, the retrofit coordinator sets out a twenty to thirty-year improvement plan, in which improvements are sequenced to achieve the optimal long term benefit of the owner. Close attention to sequencing has a further advantage: designer needs to ensure that one measure does not hamper another.
Step 6.
Improvement plans are discussed with the customer, including any required statutory approvals. Following from this retrofit installers receive briefings on design, sequencing new technologies.
Step 7.
PAS 2030 guidance is used to inform the installation of EEMs by retrofit installers. Responsibility for compliance lies with the installer, who must also supply evidence.
Step 8.
The retrofit installer monitors testing and commissioning of EEMs.
Step 9.
The retrofit coordinator assures an effective handover to the occupant or owner of the property. The transfer will include an on-site inspection and clear safety information, care and maintenance. The coordinator retains testing certificates, commissioning records and other paperwork, giving the client access. They will also suggest creating a new EPC and undertaking any further work arising.
Step 10.
At this stage, the role of retrofit evaluator comes to the fore. PAS 2035 requires the evaluation of retrofit projects, and the retrofit evaluator may have to monitor the site over time to confirm if expected outcomes have been met. And also, of course, to provide feedback to the whole supply chain.
Step 11.
The retrofit evaluator visits homeowners, no later than three months from handover, to carry out a brief questionnaire evaluation. This seeks to confirm whether expected outcomes from the previous work have been achieved. At this point, homeowners may register complaints or dissatisfaction.
If any interested parties conclude that there has been a significant shortfall in performance, two possibilities open up: intermediate and advanced. Such additional steps may include:

• Airtightness testing
• Fuel use metering
• Thermographic survey

Intermediate measures must be carried out within six months of handover; advanced measures within two years. The retrofit evaluator circulates recommended remedial actions.

TrustMark-registered business deadline

As referred to above, a transitional period—valid until 30 June 2021—has been introduced to allow firms time to reach the required standard and gain certification. Companies intending to trade under the TrustMark scheme must be certified to and compliant with PAS 2030 by the deadline.
As the Retrofit Standards Framework transitions responsibilities out of PAS 2030:2019, registered companies must also be able to prove compliance with PAS 2035, following certification.

The big picture

Upgrading homes to improved energy efficiency standards presents a massive task—and opportunity to today’s construction industry.
The Retrofit Standards Framework offers a clear and systematic approach to this work. In adopting this approach, industry professionals can be sure they are ready for the challenges of delivering retrofits that meet expectations and provide value to homeowners in the long-term.

Chris Nicholls
Commercial Director

Read More