Knowledge Bank

3rd September 2019

What is Background ventilation or intermittent extract fans?

Also known as a System 1 ventilation system. Extract fans are used to serve moist spaces such as kitchens, toilets, and utility rooms for fast intermittent air extraction in this form of decentralised ventilation scheme.

The substitute air is supplied by a background ventilators. The phrase background ventilators relates to tiny air vents which enable air into a building, for example trickle vents in the windows or air vents in internal walls. Manual or automatic control can enable this system.

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2nd September 2019

What is Continuous mechanical extract (MEV)?

Also known as a System 3 ventilation system. Air from moist spaces like kitchen, toilets and utility rooms is extracted from this form of ventilation system.

The replacement air is supplied through background ventilators. Alternatively, when the building has a design permeability greater than 5 m3/(h.m2) @ 50 Pa, background ventilators (trickle vents) are not required. The system can either be a centralized system with a single fan connected to various rooms or a decentralised system (dMEV) with air extracted from each room by individual fans. There are two airflow rates, trickle and boost. Air heat pumps for exhaust air would be regarded as a central MEV form.

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30th August 2019

Mechanical Ventilation – Different types suitable for you and your home

System 1 – Background ventilators and intermittent extract fans

Extract fans are used to serve moist spaces such as kitchens, toilets, and utility rooms for fast intermittent air extraction in this form of decentralized ventilation scheme.

The substitute air is supplied by a background ventilators. The phrase background ventilators relates to tiny air vents which enable air into a building, for example trickle vents in the windows or air vents in internal walls. Manual or automatic control can enable this system.

Briary Energy System 1
Briary Energy Fan

System 2 – Passive stack ventilation (PSV)

The use of a passive stack ventilation (PSV) system is one alternative to provide domestic ventilation. This utilizes a mixture of the air flowing across the ceiling and the natural buoyancy of hot humid air to raise the humid, stale air from the kitchen bathroom, cloakroom, etc. up to the point of the roof ridge where it flows into the atmosphere.

The trickle vents in the windows and doors etc. draw fresh air into the building. PSV systems are energy efficient without the need for any electrical fans or control. The quantity of ventilation obtained mainly relies on the amount of external air movement and the external temperature. PSV systems offer very little control, although humidity-controlled dampers (which do not need electrical energy) can be installed in the ducting to avoid over ventilation.

A Passive Stack Ventilation system requires thorough design and installation as the air movement is governed by the temperature/moisture in the air. The ducting must be comparatively big (compared to systems that use fans to move the air) and as close as possible to the vertical without sharp bends.
Installing Passive Stack Ventilation in a new build or during major renovation is really only practical. In addition to the ducting, a roof ridge level ventilation for external air movements is included in the system to help extract stale air.

In double glazed units, trickle vents are needed to allow fresh air to enter the building to replace the stack’s stale air.

Briary Energy Passive Stack

System 3 – Continuous mechanical extract (MEV)

Air from moist spaces like kitchen, toilets and utility rooms is extracted from this form of ventilation system.

The replacement air is supplied through background ventilators. Alternatively, when the building has a design permeability greater than 5 m3/(h.m2) @ 50 Pa, background ventilators (trickle vents) are not required. The system can either be a centralized system with a single fan connected to various rooms or a decentralised system (dMEV) with air extracted from each room by individual fans. There are two airflow rates, trickle and boost. Air heat pumps for exhaust air would be regarded as a central MEV form.

Briary Energy System 3
Briary Energy CV2GIP

System 4 – Continuous mechanical supply and extract with heat recovery (MVHR)

MVHR is a form of centralized ventilation scheme that combines supply and extract in one system.

Typically, hot, humid air is obtained by a duct system from wet areas, such as kitchens, toilets and utilities, and is exchanged via a heat exchanger. Fresh air enters through the heat exchanger before being provided to spaces such as the living room or the bedrooms. The air is preheated. There are two airflow rates, trickle and boost.

Other types of ventilation systems are permitted to be used in the UK, such as demand controlled ventilation (DCV) and positive input ventilation (PIV). In order to satisfy the building control body, these schemes need to show that certain performance criteria, such as moisture removal or indoor pollutants, are met.

Briary Energy System 4
Briary Energy MVHR
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29th August 2019

What is Window Condensation?

Condensation is a problem many homes are dealing with, building up on the inside of the windows and creating humidity in the home as well as humidity and moulding and ponding on the sill of the window, all of which can cause breathing problems over time.

Heating and ventilation to allow moisture-bearing air to escape outside is the best condensation treatment. Heating the room helps to keep the surfaces above the dew point, while ventilation helps to expel warm air from the outside.

Briary Energy Condensation

Here are some well-known condensation solutions:

  • Trickle vents are fitted to the tops of window frames and can help create ventilation and reduce condensation. The small opening allows for small amounts of ventilation to help reduce the condensation threat by allowing this moist air to escape. Sometimes, as double glazing can contribute to condensation as it prevents air from escaping to keep warm–this trickle ventilation is the perfect solution for retaining heat but maintaining ventilation. Most new windows should have these, or if it’s an issue with your current windows, it’s worth bringing them up in your new windows consultation process.
  • If your windows do not have a trickle ventilation or you are looking for a short-term solution, opening a window can help. This is only really possible when you’re at home and in the warmer months, though.
  • Use the extractor fan or open the shower window to ensure that the door to the bathroom is always closed. This can help prevent the circulation of moist air around the home.
  • Use the cooker hood and fan when cooking to prevent the circulation of moisture, especially when cooking on the frying pan and using a gas cooker.
  • Investing in a dehumidifier is one effective solution. You can pick up dehumidifying crystal moisture traps to put on window sills, which can be a good short-term and cost-effective solution as they can often be purchased for just over a pound. Alternatively, invest in an electrical one and always use it on the low economy. It is worth turning the setup higher to counteract the moisture when showering, cooking or dealing with humid washing.
  • Do not dry clothes inside; a rotary line can be a great solution both on sunny days and energy-efficient. Alternatively, before or dry pre-dry clothes in the tumble dryer in a well-ventilated home area.
  • Do not attempt to compensate for the problem of heavy curtains or nets as they can keep the glass cooler and increase condensation.
  • Invest in a good mould and mildew spray to help combat the problem and reduce the threat of lasting damage if you have mould or damp as a result of condensation.

If it is not addressed, condensation can be a real problem, so finding solutions is an important step in protecting your home from damage. But one of the best things you can do for your home is to invest in quality windows to help prevent heat loss and provide ventilation with trickle vents.

Now fight condensation before it’s too late.

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Commercial EPC
18th May 2019

Who needs an EPC?

Energy Performance Certification tests energy efficiency and environmental impact of buildings. Who needs an EPC?

Residential Buildings

  • There are no residential properties that do not require certification for energy efficiency. Selling or renting a home without an EPC is unlawful.
  • If your property is newly built, you need an EPC by conducting SAP calculations. These calculations ensure compliance with Part L of the Building Regulations.
  • When you upgrade or expand your property you’ll need an updated EPC, even if it already has one.
  • Residential properties need a revised EPC every ten years. Nevertheless, if the building facilities, such as a newly installed heating system, are significantly changed, it may need to be earlier.
  • As of 1 April 2018, issuing a new lease or renewing an existing lease on homes with an F or G energy rating will be unlawful.
  • Beginning 1 April 2020, this will apply to all private rented residential properties, whether it is a new lease or not.

Commercial Buildings

Commercial properties as residential properties are regulated by the same EPC criteria. There are some exceptions, though. An EPC is not needed for the following properties:

  • Places of worship.
  • Less than 50m2 stand-alone non-dwellings.
  • Industrial areas, workshops and low-energy non-residential farm buildings.
  • Temporary buildings with 2 years or less expected use time.
  • Non-residential agricultural buildings used by a company protected by a National Sectoral Agreement on Energy Performance Certification.
  • Please note that leasing non-domestic properties with low energy performance ratings will be unlawful as of 1 April 2023.

For more information about Energy Performance Certificates, or to find out about our other services, please contact us.

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29th June 2018

What is the difference between SAP and SBEM?

Each new building with a heating system needs to be tested against current government emission targets to check energy efficiency.

If you build houses or apartment blocks, every house requires a SAP calculation, ideally before onsite construction starts.

Any building that is not a house requires an SBEM calculation. Both SAP and SBEM base themselves on the same fundamental principles, but SAP designs itself to reflect our homes’ carbon emissions more accurately.

SBEM designs itself to reflect CO2 from any other building type, from offices to hotels, from warehouses to sports halls.

There is a grey area for student lodging and nursing homes. If the apartments are in general self-contained (i.e. each has its bedroom, kitchen and bathroom), then individual SAP calculations are required.

SBEM calculates any common areas such as corridors, shared lounges and staff rooms.

SBEM defines guesthouses and residences as commercial properties in either category, even if the building’s purpose is a house. In such cases, we would refer to the local building control to see if they have any preference.

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Briary Energy
18th September 2017

SAP L1B extensions, do the calculations right the first time, don’t pay twice.

Unfortunately, there are some architects and builders using a simplified spreadsheet to give L1B compliance to building control for extensions, with inaccurate and misleading results. This is something that more and more local authorities are noticing and gives a very real risk of having your extension fail current building regulations compliance.

Part L1B of the building regulations, clearly states: –

4.23 If the window is enlarged or a new one created, then the area of windows, roof windows, rooflights and doors should not exceed 25 per cent of the total floor area of the dwelling unless compensating measures are included elsewhere in the work.

Highly glazed extensions are very popular but many of these extension designs do not comply with the minimum standards of Part L1b regulations. The requirement being that the area of new glazing accounts for no more than 25% of new extended floor area. However, by upgrading or over compensating other construction elements the negative impact of larger expanses of glass can be off-set. If the whole dwelling is receiving a refurbishment there may be many more options available to off-set non-complying elements of construction in order to show an improvement in the overall energy efficiency of the dwelling. The correct way to demonstrate compensating measures elsewhere in the extension, is by an accredited SAP assessor carrying out an L1B SAP calculation, therefore providing building control with Proposed and Notional SAP/DER worksheets and a covering report showing their methodology.

Approved document part L1B ‘Conservation of fuel and power in existing dwellings’, which was brought into effect from 1 October 2010 with several amendments in 2013 and 2016. Sets out the requirements for renovations, extensions and consequential improvements to energy performance.

There are other ways of demonstrating compliance with the regulations but in terms of the most straightforward, following the guidance in the Part L1B is the simplest. The Regulation itself is
straightforward, in order to comply with Part L1B there are 3 sections referred to: –

  1. Regulation 4A – Thermal Elements – if an element is replaced it should meet the minimum requirements, and if new it should also meet minimum requirements of thermal efficiency.
  2. Regulation 17D – applies to existing buildings with a total useful floor area of over 1000m2 where the proposed work consists of an extension, initial provision or increased capacity of any fixed building services.
  3. Regulation 17 E – Where appropriate an Energy Performance Certificate (EPC) should be provided.

As mentioned earlier, some architects and builders are using a simplified spreadsheet, which in essence is a way of calculating the Area Weighted U-value of the extension elements. This is a method that can be used if one element is slightly out or because the building has a Listed Status or for reasons why a particular measure cannot be implemented, for example cost effectiveness of implementation. Showing an area weighted U-value calculation, which compares the as designed extension to one that elementally meets the regulations, can help show compliance. The trouble is, often this is not enough or these figures are doctored or created in order to achieve a ‘quick win’.

Don’t allow yourself to fall into the trap, whether you’re a builder, conservatory installer or the end user. Delays in building control approval will cost you hundreds if not thousands of pounds. Whether it’s at the time of building your extension or when you come to sell your house. The last things you want to risk are additional costs from having to retrospectively improve say, the insulation in the fabric or replace a boiler just so that you can meet regulations. In some extreme cases, solar panels may need to be installed. All are realities that we see far too often, because SAP calculations weren’t done or were done wrong at design stage.

Allow one of our accredited SAP assessors to carry out the correct L1B calculations, giving you improved design flexibility and guiding you at every stage, in order to achieve a pass every time. Give Briary Energy a call 020 3397 1373 or send your drawings to for a quick 24 hours turn around.

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Briary Energy Conventions
25th July 2017

SAP 2012 v7.0 Conventions – Briary Summary

Summary (in effect from 31 August 2017 v 7.0)

For any and all Scottish SAPs refer to further differences on the 38 page document. In short, most Scottish regulations are more onerous.

1.04 Thermal Bridges must now be signed off before producing an EPC.
2.01 Confirmed dimensions for garage within dwellings, see Apendix 4.
Appendix 4. Dwelling dimensions (the diagrams below show how to measure height of storeys in order to calculate volume of dwelling)

Multi-storey dwellings
Dwelling without a garage & Dwelling with a garage

Blocks of flats
Block of flats without a garage & Block of flats with a garage

The difference in the approach to floor heights is due to the method of calculating thermal bridging of junctions. For blocks of flats the space between floors is already included in the psi-values, while the space between floors in other dwellings is not included, therefore the area of wall should be added.
2.03 Voids are no longer included in the volume calculation, but the full internal height of the external wall should be included as normal.

2.07 Where the roof insulation follows the shape of the room, the U-value of the walls and ceilings to the unheated roof voids should be calculated as normal with the room–in-roof shelter factor applied.
Where the insulation is contained entirely within the rafters, the U-value of the sloping ceilings should be multiplied by a factor of 0.72, and the resultant U-value used for the walls and ceilings to the unheated voids spaces. The new stud like elements are called Ashlar walls or Ashlar roof/ceilings.

4.03 Solar powered vents should be entered into SAP software as passive vents.
4.06 Disregard a single individual ventilator with heat recovery, if individual intermittent ventilators with heat recovery installed in each wet room, treat as natural ventilation with intermittent extract fans; if continuously running – treat as default Decentralized Extract Ventilation; in this case the heat recovery element is disregarded.
4.07 Positive input ventilators – In the case of PIV supplying preheated air from the loft – specify the actual number of extract fans, with a minimum of 2 extract fans required.
5.02 Swimming pools, U-value as the surrounding floor, ignoring the basin, but the u-value of the basin walls should be provided to building control separately.
5.04 g-values for BFRC windows are usually less than 0.5 and should be checked if greater. In the case of manufacturer-declared properties of windows the data needed as U-value, g-value for the glazing and frame factor. Documentary evidence of these data is required.
For windows and roof windows that are NOT vertical BR 443 gives U-value adjustment which can be applied to windows and roof windows depending on the inclination.

5.07 If a T-value for any junction is not available use the applicable default value from SAP Table K1 (see 5.08 for exceptions). The following junctions in Table K1 have no ACDs associated with them and so no ACD reference number: E8, E9, E16, E17, E19, E20, E21, E22, E23, E24, E25, P1, P6, P7, P8, R1 to R9. If no calculated value is available use the default T-value.

5.15 Thermal mass parameters can be calculated (but as per BR 443 do not include internal doors), or treated as being low, medium or high using the global values of 100, 250 or 450 kJ/m²K given in SAP 2012 Table 1f .
5.16 An oriel window is a form of bay window, which projects from the main wall of a building but does not reach to the ground.

Method 1: Oriel window modelled by detailed analysis

Ueffective takes into the account heat losses associated with thermal bridging so Ψ-values associated with sills, jams and lintels are zero.

6.13 In the case of community heating treat electric underfloor heating of small rooms (i.e. wet rooms) as a secondary room heater (panel, convector or radiant heater).
7.05 Instantaneous electric showers are included in the total number of showers in the dwelling but should NOT be included in the number of showers served by the WWHRS, because electric showers cannot have a WWHRS. For as-built assessments documentary evidence in the form of a completed WWHRS checklist is required.

Method 2: Oriel window not modelled

You can download a copy of version 7.0 of the SAP Conventions here.
To discuss your project requirements, please contact us.

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Part F
7th April 2017

Building Regulations Part F – Ventilation

A recent study published in the journal Building and Environment, has found that people working in green buildings; with optimum ventilation, lighting and heating controls; think better in the office and sleep better when they get home.
As well as in the work place, this ethos can be transposed to the home. A ventilation strategy is best considered at the earliest stage of design of residential dwellings. We are often called upon to advise best ventilation solutions, and asked to explain different systems on offer:

System 1 – Intermittent extract fans with background ventilators
This is the most common approach to meeting Building Regs Part F. Extract fans are located in bathrooms, kitchen, and utility rooms. These fans can operate in conjunction with light switch, remote switch, pull cord, humidistat, presence detector, or timer. They must comply with ventilation airflow rates set out in Part F, dependant on number of bedrooms and occupancy levels, ensuring that adequate air quality is provided indoors for occupants.
In addition, background ventilators (usually trickle vents) are fitted to windows to provide the whole building ventilation, and provide air to the extract fans, which will aid to remove odours and humidity.
This is the simplest system available, both to install, and for occupants to control. Fans though, must be regularly maintained, in order for best efficiency, and to reduce any potential noise issues.

System 2 – Passive Stack Ventilation
This is a non-mechanical system. Passive stack vents, in various locations throughout the dwelling, will extract any odours or moisture, using the principle of convection, via ducts. Trickle vents will allow the supply of air into the dwelling.
The system, although with no running costs, is dependent on local weather, which can provide risks of over and under ventilation.

System 3 – Mechanical Extract Ventilation
This is a system which covers continuous Mechanical Extract Ventilation (MEV). It is either a Whole House Centralised MEV system, or a Localised Decentralised MEV fan.
The centralised system is usually located in the loft, with ducts running from the unit to all wet rooms, controlling the humidity levels in these rooms, by drawing any moisture from the air.
The decentralised system contains separate fans in each room, again drawing moisture from any wet room.
Also with system 3, background ventilators will be fitted to all windows (except wet rooms).
The system is considered a more effective ventilation method, continually working at predetermined rates – these rates will be calculated according to tables available in Part F. There are potentially less ‘noise issues’ than system 1, as long as the duct work is installed efficiently.

System 4 – Mechanical Ventilation with Heat Recovery (MVHR)
Heat Recovery provides fresh, filtered air, energy efficiency and a comfortable all year round climate. The system runs continuously providing a constant flow of air. Extract fans extract any odours or moisture from the air of any wet room in a dwelling. This extracted air is passed over a heat exchanger, which then transfers the heat to the incoming air, to be distributed via ducts, to all other habitable rooms in the home. The flow rate is easily controlled, and boosted to relieve any higher levels of pollutants.
This is a more sophisticated ventilation method, and no trickle vents are required. Again, ducts have to be installed well in order to maintain efficiency of system.

There are also other systems of ventilation that are certified by the British Board of Agrement (BBA), most notably Positive Input Ventilation. This system controls condensation by diluting and replacing high humidity levels to control condensation. It is a sophisticated all year round system; highly efficient, benefiting from solar gain from the loft space to provide heat distribution.

For each of the ventilation systems to be effective, air must be able to flow through the dwelling. Part F make provision for this by having all internal doors undercut to keep a gap of 10mm above any finished floor surface.

Briary Energy are always available to advise on a solution that meets your need. Good indoor air quality is highly underrated, and as the recent study proved, can make you healthier, happier, brainier, and well rested. Sounds good to me….

Part F Ventiliation

Part F Ventiliation

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Smart Meter
22nd March 2017

Smart Meter Roll Out

The government are currently in the process of rolling out smart meters to all UK homes. So far 3.3m first generation smart meters have been installed in UK homes. The plan is by the end of 2020, around 53 million smart electricity and gas meters, will be fitted in 30 million homes and businesses.

Smart meters are set to replace every conventional gas and electricity meter in the country. They use wireless technology to allow energy companies to read the meter remotely via the mobile phone network, therefore you will only be billed for actual energy used, putting an end to estimated readings, which should lead to fewer billing complaints. They will also allow the home owner to better gauge the families energy usage.

Discussing the subject in the office, one smart meter owner explained how more focus is placed on turning lights off when not required, and only using heating when required; and ‘educating’ family members to do the same. I compared this to my recently acquired FitBit, enticing me to walk a few extra steps, or take an extra flight of stairs, whereas before I would have remained firmly sat at my desk; in order to reach my daily target!! In both cases, it highlights that awareness is a good thing, and whilst the owner of the smart meter has not noticed a drastic change in their energy bills; they spoke positively about the meter, and expressed that having the data usage on clear display has been ‘interesting’. Studies have shown, however, that having a smart meter currently reduces household energy consumption by an average of 3%.

There is some negative press involved in the roll out; namely that the whole scheme will end up costing an estimated £11bn; the predicted cost for each replaced meter will be £200, and this can only be a figure to be borne by the public via increased energy bills. A secondary factor is that the meter may become redundant when a customer switches energy supplier. Second generation meters are being planned which will alleviate this problem.

Whilst prudent advice may be to hold out for the second generation meters; the government is committed to this roll out, and the overwhelming factor is that energy consumption WILL be reduced – a consideration to mull over as I strive for my 10,000 steps!!!

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