Knowledge Bank

EPC certificate
18th November 2019

What is an EPC?

So, what is an EPC Certificate? The Energy Performance Certificate (EPC Certificate) measures the energy efficiency of a property on an A-G scale.

Energy Performance Certificates, launched in England and Wales in 2007, are a legal requirement to sell, lease or build a house. An EPC is valid for 10 years once it is issued.

The most efficient homes-which are expected to have the lowest fuel bills-are in Band A. The Certificate also tells you, on an A-G scale, about the impact the home has on the environment. Better-rated homes should have less effect on CO2 emissions.

The UK average property is in bands D-E for both ratings. The certificate provides tips on ways to improve energy efficiency at home to save you money and help the environment. EPCs also refer to commercial buildings, where a commercial epc is also measured on an A-G scale only by CO2 emission ratings.

Minimum Energy Efficiency Standards (MEES) Legislation

In April 2018, adopted Minimum Energy Efficiency Standards made it a legal requirement for all private properties to have an EPC score of at least an’ E’ before being sold or let. The law extends to both residential and commercial properties, while exceptions exist, for example if a property is a listed building.
Those who fail to make the necessary changes will impose substantial fines: up to £ 5,000 for domestic homes and up to £ 150,000 for non-domestic property.

What is involved?

If you need an EPC, you need a certified energy assessor like Briary Energy to perform an energy assessment.
Energy assessors may enter this data on-site or at home to generate an Energy Performance Certificate lodged in the central registry.

How do I get a copy of an EPC?

If you have the report reference number (RRN) or address, you can easily obtain an EPC by going to the register, or EPC finder.
For properties in England and Wales Landmark EPC click here.
For properties in Scotland, Scottish EPC Register click here.
For properties in Northern Ireland click here.

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SAP Calculations
18th November 2019

What Are SAP Calculations?

They might have flummoxed and annoyed you, but SAP calculations are a critical part of the design cycle for any residential scheme.

Building Regulations require SAP calculations and are required for all newly built dwellings in the UK. After 1995, a SAP score has been required for all new homes under Part L of the UK’s Building Regulations, so most developers will recognise it.
For many, though, it will be a new and often daunting part of the planning and building control process.
SAP Calculations do three things:

  1. They assess a SAP score (dwelling’s energy-related operating costs)
  2. They show compliance with Building Regs Part L
  3. To are used to generate an Energy Performance Certificate (EPC certificate)

You may also need  SAP calculations for conversion or SAP Calculations for extensions, but different rules apply.

What Does SAP stand for?

SAP means’ Standard Assessment Procedure.’ It’s the only official government-approved method for determining a new home’s energy score. SAP assessors must be accredited with a certification body. SAP is part of Building Regulations Part L.
A SAP score is a way to compare the energy output of different homes, resulting in a value between 1 and 100 + (100 reflecting zero energy costs and anything over shows you export electricity). The higher the SAP score, the lower fuel costs, and the lower carbon dioxide emissions.
The SAP calculations for new buildings determine an energy cost based on the dwelling construction, heating system, internal lighting, and any renewable technologies. It doesn’t include cooking fuel or appliances.

Why is SAP important to me?

Home builders will need to obtain a “pass” on their SAP calculations in order to comply with current building regulations. Without this calculation, the development is not approved and the building cannot be let or sold.
Nonetheless, there are other reasons why SAP is used. A SAP assessor may help the developer or architect shape a new dwelling’s energy profile, reducing energy use and carbon emissions.
The effect on the ground can be accurately measured and given by different built forms, heating systems and engineering.
Another important issue is that the SAP score communicates the property’s energy efficiency, and informs both purchasers and tenants of the Energy Performance Certificate (EPC certificate).

A ‘ pass ‘ is obtained by several compliance goals around:

    • How well the dwelling fabric absorbs heat
    • Construction quality and system commissioning.
    • Solar Gain
    • Dwelling CO2 predicted emissions

Emissions are Key

The DER / TER figures are used to achieve the benchmark emission target Through comparing the Target Emission Rate (TER) with the expected Dwelling Emission Rate (DER), CO2 emissions are measured.
In the SAP calculation, this target rate is set using a set of baseline values, by comparison to a notional housing of the same size and shape.
Importantly, developers and councils are now using these numbers progressively as a means of achieving certain goals–from achieving green targets and local recycling policy to determining Section 106–type community contributions.

Fabric Energy Efficiency

Homes built in England after April 2014 are also assessed on Fabric Energy Efficiency. This is not a carbon indicator, but energy demand per m2 per year in units of kilowatt-hours. How well a home absorbs the energy it produces can impact its CO2 emissions as well as be measured separately for compliance calculation.
The performance of fabric energy is measured using estimates from DFEE / TFEE. As with emissions a range of baseline values depending on the size of the property is used to set the target under SAP.

What’s Involved in an SAP Assessment?

Accredited SAP Assessors will take an architect’s plans and drawings that establish a clear specification for the heating, ventilation and air conditioning (HVAC) specification for the dwelling.

The assessor will either digitally or manually scale off these plans to create a dwelling(s) template in SAP software.

There will then be analysis of the dwelling that takes into account the chosen lighting, heating and ventilation systems, thermal elements (walls, floors, roofs and openings). The calculations will also take into account any renewable technologies that may be planned for the building.

The different factors of the chosen heating, lighting and ventilation systems are introduced–different items are chosen from the databases of the manufacturer where they are identified.

How Do I Make Sure of a Pass?

It is fair to say that designers and architects have not paid much attention to SAP in the past–but since the significant changes in 2005, SAP 2009 and again in 2014, compliance with the SAP regulations and, in effect, Part L of the Building Regulations has become much tougher. Working without a SAP model now causes more problems!
This is mainly due to the immense tightening of the CO2 emission targets–driven by European and UK climate policies. The average 5-year-old new build is significantly different to today’s regulations.
We are often asked to explain why some builds fail and some succeed, and it’s not always easy to give a straight answer. Numerous factors will play a part, from the size of the boiler to the junction in the wall, to the thickness of the insulation in the floor and in which direction the house is pointing!
Some factors may be beyond client control–for example, having no mains gas link may mean having to use an oil or LPG network. Such fuels have higher cost and CO2 emission factors within SAP, and as the target emission rate is set on the basis of the mains gas system, you are hitting.


Every day we run SAP calcs–spanning single self-constructions up to 30 storey apartment blocks, so we have a good idea of what works and what doesn’t.
If we disregard the broader issues of climate change, avoid tactics, and conclude that we are not trying to create a zero carbon home, we can tie down some good principles that will give you a good chance of success:
There are minimum u values to beat, not followed. If the building material is well insulated, no fancy renewable technologies are required to get you through.
Pay attention to the u values on the openings you specify to get them as low as possible, preferably 1.4 W / m2 K or less.
It’s not the boiler it’s the controls that will often have a more significant effect on the SAP score than the boiler itself.
Get it airtight. All new builds require the completion of the Air Permeability Test and the resulting figure goes into the SAP Calcs. Ensure that the envelope is sealed and conduct a pre-test review if possible.
Pay attention to thermal bridging. This is heat loss across outer wall junctions. Follow a scheme like Accredited Construction Details (ACD’s) that will allow us to avoid using the default information. See our Thermal Bridging section for our guide.

Start as Early as Possible

The one key point is to start early–even more important than those above. If we get a set of plans halfway through a construction, there’s not much we can do to improve the building’s energy efficiency.
This situation often leads to a lot of bad practise and generally the introduction of unnecessary, costly technology added in hindsight just to pass building regs or satisfy a planning requirement.
Prevent this by communicating as early as possible with your SAP assessor in the process–often before planning has even been submitted, and definitely well before building applications for regs.

Is SAP just for New Builds?

Not at all, most extensions, conversions and change of uses require SAP calculations under Part L1b of building regulations.

Contact our friendly team today on 020 3397 1373 or use the contact form here.

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Thermal Bridging Calculations
16th November 2019

Thermal Bridging

A thermal bridge (sometimes referred to as thermal bridging, a cold bridge or thermal bypass) describes a situation in a building where there is a direct link between inside and outside via one or more thermally conductive elements than the rest of the building envelope.

This will result in unnecessary heat transfer across this component, its internal surface temperature may vary from other, better insulated internal surfaces, and condensation that occur when hot, humid internal air comes into contact with the potentially cold surface. This condensation can cause mould growth.

Thermal bridges are common in older buildings, poorly constructed, poorly insulated, with single-skin construction and single-skin glazing.

Thermal bridging can occur in modern buildings due to poor design or poor workmanship. This is normal when building components penetrate through its isolated material, e.g. through glazing, or where the framework penetrates the building envelope, e.g. on balconies.

Nonetheless, as buildings have become better insulated, with increasingly strict regulation, so thermal bridges that may have previously been considered negligible in terms of a building’s overall thermal quality may actually cause considerable thermal inefficiency. There is potential for such inefficiency at each opening and junction (even in party walls).

For example, thermal bridges can be classified as’ repeating’ where wall links periodically bridge the cavity, or’ non-repeating’ such as wall junction or lintel.

The Approved Document Part L of the Building Regulations (Conservation of Fuel and Power) state that’ Building fabric should be built so that there are no fairly avoidable thermal bridges in the layers of insulation created by gaps in the various elements, at the joints between elements and at the edges of elements such as those around window and door openings.’

Thermal bridges in completed buildings can be exposed with thermal imaging cameras, but they can be very hard to rectify, particularly if replicated throughout a house.

Briary Energy can complete Thermal Bridging Calculations, please contact us for further information

Find out more

What is a PSI Value?
SAP Calculations
SBEM Calculations

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SAP Calculations for Extensions
6th September 2019

What is continuous mechanical supply and extract with heat recovery (MVHR)?

Also known as a System 4 ventilation system. 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.

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SAP Calculations for Conversions
5th September 2019

What is a trickle vent?

A’ trickle vent’ is a device that enables your home to flow clean air. It is connected to the top of your window and helps to maintain a constant airflow all over your home. This is essential since the development of dangerous chemicals can have a negative effect on your health in your home. An excellent ventilatory system avoids the spread of house mites and other microscopic organisms by eliminating such items as moisture and condensation.

Trickle ventilation allows constant refreshment of the air in your home. Even if you’re on holiday or don’t like to leave your windows open for a night, the trickle vent still allows air to pass through it. Keeping your indoor air clean in a safe and cost-effective way. They also have an open and close action so that you can control them whenever necessary–you want to keep the heat in and the cold out in the winter months, for example, so that you can close the vent to a more convenient time.

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SAP Calculations for Extensions
5th September 2019

How to Pass an Air Tightness Test

How to pass an air tightness test first time

An Air Tightness Test (also known as Air Leakage Test, Air Pressure Test, Air Permeability Test) is a government-controlled test to ensure buildings do not leak or hold too much air.

Air leakage increases heat loss and if air cannot move freely enough, mould, rot, damp and condensation can be dangerous for occupants.

What You Need To Test

As you probably know, newly built residential properties require an air leakage test for Building Regulations (as per Approved Document L1A). Also known as air testing, air pressure testing, and air tightness testing.

Designed ventilation systems are excluded from this test, so our technicians will tape all fans of extractors, chimneys, MVHR units, etc. to give real test score.

Briary Energy wants to help our customers ensure their buildings pass this test first, so we’ve designed a simple checklist and easy guide to pass an Air Tightness Test.

  • All external walls, floor and roof are fully fitted (including doors, windows and cladding)
    All your windows and doors should be fitted. Access doors, such as internal garage doors, should be airtight and can not be temporarily sealed for testing. Trickle vents should be closed.
  • All fittings are installed (including all lights & sockets)
    Before testing, light switches, light fittings, appliances and sockets must be properly fitted as temporary sealing is not permitted. If these elements are not fitted before an air leakage test, poor results may result from air loss.
  • Complete plumbing work
    All bathroom fittings should be complete. Bathrooms are a common hotspot for air leaks, with air leakage sources prevalent in bath and pipe work. Before fitting the bath panel, vanity unit covers, extractors and any boxing in, you should look for sealed air leakage paths.
  • Know your Design Air Permeability Rate
    Make sure your SAP calculations have been completed for each plot and you have a record of the target result for each property. You can find this number on your SAP report, where it can be listed as a q50, DAP or Air Permeability Figure.
  • All service pipes are sealed through external walls and ceilings
  • All skirting boards are sealed top & bottom.
    As a common source of air leakage, all skirting boards should be sealed with silicone sealant. For optimum results, we recommend sealing skirting boards above and below, as carpets and other floor finishes will not prevent air leakage.
  • Any doors to unheated garages are fitted with draft excluders
  • All loft hatches / storage doors are fitted with suitable draft excluders
    Also check any access points to the loft are fitted with hatches to be used when handing over the property.
  • All housing services (pipes, cables, stacks, etc.) are boxed in and sealed.
  • The property has at least one standard size door, not more than 2.25m tall by 1.1m wide.

Potential Risks of Early Testing

ATTMA, the Air Tightness Testing and Measurement Association, recently published guidance stating that 70% of dwelling tests fail because the testing firm is called in too early.

This can be an expensive error, and can mean paying for re-tests as well as the wasted man hours and even penalties for delayed handover.

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4th September 2019

What is Air Tightness Testing?

Air tightness testing is a recognised method of measuring the extent to which air in the building fabric is lost through leaks. Air leakage testing or air pressure testing is often made reference to as it.

Air leakage is the uncontrolled flow of air through fabric gaps and cracks (often referred to as infiltration or draughts) rather than ventilation, the controlled flow of air into and out of the building.

Too much air leakage results in the occupants having unnecessary heat loss and discomfort. Building regulations now place greater emphasis on the quality of the building’s fabric as the government strives to reduce CO2 emissions from new buildings.

How is the Air Tightness Testing done?

Briary Energy has three skilled engineers, accredited with IATS. All tests are carried out in accordance with the strict technical guidelines prescribed by ATTMA (Air Tightness Testing Measurement Association).

In a nutshell, a fan or a number of fans are installed at a suitable external opening and the building is pressurised over a range of different pressures.

Before the test is conducted, it is important for us to calculate the building’s external envelope accurately to reflect the conditioned space within the completed building.

The test is measured at an average of 50 Pa for each m2 of building fabric in air flow m3 over an average hour period. Complex? Try this – a typical large detached house on the floor, walls and roof would have about 400m2 of exposed fabric. A test figure of 10 would give 4000m3 of leakage over an hour at 50 Pa or as a Quite a lot of leakage we think you’re going to agree with!!

Passive ventilation must be temporarily sealed before the test is performed. The HVAC plant is switched off and sealed temporarily. The exterior envelope is closed with all its openings. All doors are temporarily open internally. It is necessary to fill the drainage traps.

During the test, site workers may stay in the building or remain outside until the test is complete. There are no health risks to site workers who stay in the building during the test; however, the fan noise may cause some discomfort.

When is the Air Test needed?

To meet the minimum standards set out in Approved Document L1A, an air pressure test on three units of each type of dwelling, or 50 percent of all instances of that type of dwelling, whichever is less, should be performed on each domestic development. The frequency is explained in this chart.

Number of Dwelling Types Number of tests on dwelling type
1 or 2 1
3 or 4 2
5 or more 3

Approved Document L2A requires testing of all non-domestic buildings over 500m2.

The actual test results must be better than the estimated SAP or SBEM design figure. There is an exemption for testing smaller sites and non-domestic buildings of less than 500m2, but this automatically triggers a higher value of 15–but to be honest it is now almost impossible to get a building that complies with this higher figure.

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4th September 2019

Air Test – Frequently Asked Questions

How long does an air test take?

There are many things to consider when performing a test; the size of the building to be tested, its complexity and also the air leakage to be achieved. Most tests can be completed in 1-2 hours, although some may take much longer if low air leakage rates like AECB Silver Standard or Passivhaus are required.

When will I get the results?

Usually, results are given at the end of the test and a full report and compliance certificate is issued within 24 hours.

What is an air leakage test?

Air leakage testing is the method of calculating air leakage caused by uncontrolled ventilation such as pipe and skirting boards, etc. The air test is part of the information required for Part L calculation (SAP or SBEM) and is ultimately required for EPC production.

Do I need an air test and what’s it for?

If it’s a new building, then the likelihood is, yes, as set out in Part L (ADL) of Building Regulations Approved Document. As well as satisfying ADL, it also helps to reduce carbon emissions due to heat flow through unwanted building fabric gaps. For example, we can use it to detect and use building fabric deficiencies in conjunction with smoke testing and infrared thermography.

What happens if a building fails a test?

We work with the client to help a building pass a test. If too much work is needed, the test will require another visit.

How much is an air test?

Air tightness testing prices start at just £50 per plot. Size, complexity, location and quantities all affect the quotation, so please get in touch for more information.

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4th September 2019

Basics for Home Ventilation

What is Ventilation?

Ventilation is an air exchange between a dwelling’s interior and exterior. Ventilation in a home is primarily aimed at removing polluted indoor air and replacing it with’ new’ outside air.

What does purge ventilation mean?

Essentially, windows are opened. Manually controlled ventilation of rooms or spaces at a comparatively elevated pace to rapidly dilute pollutants and/or water vapor. . window opening).
Sometimes referred to as rapid ventilation, this is a rapid exchange of large amounts of air between rooms or between rooms and outdoors, and is usually achieved by opening a window or a door.

Benefits: Assists in the removal of occasionally occurring pollutants such as smoke and smells or smoke from cooking or painting and furnishing.

What is rapid ventilation?

Rapid ventilation is essentially purge ventilation. It is the rapid exchange of large quantities of air between rooms or rooms and the opening of the windows or the doors.

Assists in removing sometimes contaminated products, including the smoke and odours from the cooking process, or smoke from painting and decorating.

What does Extraction Ventilation mean?

It is an active extraction, by mechanical means, of air from the rooms, generally with a fan or air conditioning.

Ventilation for extraction is required in spaces where pollutants and surplus vapour like kitchens and bathrooms are frequently subjected to. Such rooms may be extracted permanently or intermittently.

Benefits: Limits the distribution in the entire housing of fumes and pollutants

What does Background Ventilation mean?

This is the passive air flow through ventilation in and out of rooms and is accomplished through’ a tiny ventilation opening intended to provide controllable ventilation across the entire construction.’

Ideal positioning of background fans 1.7 m above ground level should prevent noticeable drafts.

Trickle fans are perfect for this requirement. Different instruments can be used to open and close open vents for home residents ‘ operations.

Benefits: Background ventilation by trickle ventilators can provide a safe, draught-free and coherent supply of oxygen even if the windows are closed.

Why do I need Ventilation in my home?

Circulating air decreases the risk of producing damaging indoor pollutants in the home. This helps provide the occupants of a home with a safe and comfortable inner setting.

The Building Regulations Advisory Committee in England and Wales requires’ there must be appropriate ventilation means for individuals in the building.’ In Scotland, the Building Standards state that’ all structures need to be ventilated so that the building’s air quality is not a danger to the occupants ‘ health or the building itself.’

Part F ventilation testing can ensure your fan setup meets current regulations.

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4th September 2019

What is passive stack ventilation (PSV)?

Also known as a System 2 ventilation system. 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.
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