FAQs

After years of anticipation, we are now one step closer to knowing where the construction industry will need to push to meet the next wave of energy efficiency targets.  The Building Research Establishment (BRE) has published a new SAP methodology – SAP 10.

SAP is the calculation used to work out a dwelling’s emission rate, compliance with Building Regulations, EPC scores and predicted fuel costs. It is a vital assessment for compliance with Part L and Section 6, and is also used as part of planning submissions (for energy and sustainability statements).

First and most importantly, this new SAP methodology is not yet in use, although it will eventually replace the current SAP, which has been in place since 2013. Our Building Regulations are still using SAP 2012, and there’s no news on when this will change. When Part L / Section 6 are updated, we’d expect the SAP 10 method to be adopted.

Highlighting some of the key points and changes in SAP 10, we’ve compiled a short list of all you need to know about how we’ll be building in the coming years:
 
1. Electric heating will be more favourable
Since the last SAP update (2012), there’s been a renaissance in the installation of wind and solar farms, giving us greener energy. So much so that the average CO2 factor from the UK’s electricity grid has halved in just six years. This means the carbon footprint of electric based heating is going to be far more favourable and could mean we start to see panel heaters becoming a favoured option for some developments.

2. On-site electricity generation will have less impact
The reduction in the CO2 factor of the electricity grid sounds like good news all round, but there is a flipside… having greener electricity means generating electricity on site isn’t going to have as big an impact as it does today. So PV systems and CHP units aren’t going to be as much help when trying to improve SAP scores.

3. Heat loss assumption for DHN will increase to 50%
Developments with district heating networks (DHN) could notice a big drop in SAP performance. Currently, default heat losses from the pipework of DHNs are assumed to be 5-20% in SAP. Going forward, a new development with no evidence of heat losses will have to assume 50%! When you consider many large inner-city schemes use DHN, CHP and PV panels, this is all going to add up to make compliance for this type of development much trickier.

4. Lower overall heat demand
To give consistent results, SAP has always worked with lots of assumptions in the background. One of these is to do with the number of hours in a day where our heating is switched on. Latest research has shown we’re in our homes less, and using our heating systems less. This will lead to lower heating demands overall. Plus, manufacturers of Wi-Fi based heating controls may be able to help improve things further if they can prove their devices mean we use our heating even less.

5. Bespoke thermal bridging encouraged
As expected, thermal bridging and fabric heat losses are being given more focus. The default thermal bridging figures are increasing by a third, which means if there are any developers still using default thermal bridging data, this is likely to push them into adopting recognised calculations. The Accredited Construction Details have been removed from SAP 10 as the ‘better case’ defaults. This is to encourage developers to research and adopt better and more specific junction details, although you’ll still be allowed to adopt ACDs if you want to.

6. Bath and shower flow rates will be considered
For the first time, SAP is going to count how many baths and showers a dwelling has, with the proposed flow rates, and whether showers are fed by electric or mains. This information will be used to more accurately work out hot water demand and could increase emissions for dwellings that are expected to use lots of water.

7. Overheating risk more likely to show on dwellings
Our lovely summer has raised the concern of overheating in our homes. SAP runs a basic check for summer overheating risks, which usually only flags up issues on heavily glazed penthouse apartments. SAP 10 is being tightened up which is likely to mean more dwellings recording an overheating risk. We’d recommend a thermal modelling assessment for a more in-depth analysis where overheating risks are anticipated.

8. Excess electricity from PV panels can be stored
A welcome addition to SAP 10 is PV storage, where excess electricity can either be sent to a battery or to heat an immersion cylinder. Currently, SAP assumes that half of the electricity generated by PVs is exported straight back to the grid.

9. Updates to reflect changes in lighting technology
Lighting technology and the efficiency of lamps has moved so fast in the last decade, that SAP hasn’t kept up. SAP 10 will record the amount and type of lamps in a dwelling. The more LED and compact fluorescent bulbs, the better result you’ll get.

Since April 2006, a SAP or Standard Assessment Procedure Calculation has been a requirement on all new build and newly converted dwellings. The SAP Calculation demonstrates that the dwelling meets the requirements of Building Regulations Part L.

To complete a SAP assessment some of the things we need to consider are:

1. the size of your house
2. heat losses through walls, roofs and windows
3. orientation
4. heating and hot water types
5. lighting
6. ventilation
7. renewable technologies

The end figure is called a Design Emission Rate (DER) which is the predicted amount of kilograms of Carbon Dioxide created by your house every year, per square metre of floor space. This figure needs to be lower than the Target Emission Rate (TER). As a rule of thumb, the TER is what your house would achieve if built to the very limits of Part L Building Regulations, less 20%.

SAP stands for the Government’s Standard Assessment Procedure (SAP) for assessing the energy performance of dwellings. The indicators of the energy performance are energy consumption per unit floor area, an energy cost rating (the SAP rating), an Environmental Impact rating (based on CO2 emissions) and a Dwelling CO2 Emission Rate (DER).

The SAP rating is based on the energy costs associated with space heating, water heating, ventilation and lighting, less cost savings from energy generation technologies. It is adjusted for floor area so that it is essentially independent of dwelling size for a given built form. The SAP rating is expressed on a scale of 1 to 100, the higher the number the lower the running costs.

An EPC (Energy Performance Certificate) provides a rating for the energy efficiency of a building. The ratings are set against standard criteria to enable one building to be compared with another of a similar type. EPCs are similar to the certificates now provided with domestic appliances such as refrigerators and washing machines.

They give information on the energy performance as well as the environmental impact through carbon emissions. This information is rated on a scale of A to G, where A is the best and should have the lowest fuel bill. The average UK property is in bands D to E.

Yes, whenever a building is constructed, sold or rented out, a certificate detailing its energy performance must be made available. This can either be to the owner or, by the owner, to the prospective buyer or tenant. No certificate may be older than 10 years.

Accredited Construction Details (ACDs) were developed to assist the construction industry in achieving the performance standards required by Part L of the Building Regulations. The details focus on the issues of insulation continuity, with the aim to minimise thermal bridges and improve air tightness at junctions within the building envelope.

As the overall heat loss of new buildings is reduced through improved fabric standards and air tightness, the heat lost through thermal bridges at junctions represents a much higher proportion of a building’s total heat loss. ACDs therefore play an important role in lowering the impact of new buildings on the environment and also meeting ever more stringent Building Regulations’ requirements.

Enhanced Construction Details (ECDs) focus on heat losses that occur at the junctions between building elements and around openings. They improve on the performance delivered by the standard Accredited Construction Details (ACDs).

They are designed to help the construction industry achieve performance standards that exceed those set out in Part L1A of the Building Regulations. They also assist developers and builders to achieve the energy requirements in the Code for Sustainable Homes.

Photovoltaic (PV) panels are definitely an option to consider and can provide a significant improvement in the SAP Calculation but they are not always necessary to meet the requirements of current Building Regulations. By focusing on good levels of thermal performance in the walls, floors, roofs and windows, and using efficient heating controls it is possible to meet current performance standards without the need for renewables.

Although electric heating is 100% efficient it is very expensive compared to other fuel types. SAP Calculations take into account the cost of heating the building, therefore, the more it costs to heat the building the worse the rating will be.

The same theory applies to the DER (Dwelling Emission Rate); an electric heating system is 100% efficient but in SAP Calculations electricity is assumed to be generated by coal fires power stations, which produce high levels of CO2. As a result the calculated emissions from an electrically heated dwelling will generally be more than for a comparable gas based system.

Most local authorities now expect planning applications for all new developments to be accompanied by an Energy Statement or an Energy Strategy Report. Alongside the SAP Calculations, Energy Statements or Energy Strategy Report set out how a development can reduce its predicted CO2 emissions through the use of on-site renewable and other energy sources.

Energy Statements are based on an initiative originated by Merton Borough Council to force all development to reduce reliance on the National Grid and generate site based renewable energy, known as the Merton Rule. Energy Statements usually require a development to reduce CO2 emissions onsite by 10 to 20% through the use of on-site renewable energy sources.

SBEM stands for Simplified Building Energy Model. SBEM is a computer program that provides an analysis of a commercial building's energy consumption. SBEM estimates the monthly energy use and carbon emissions of a building. iSBEM is the Interface tool for the Simplified Building Energy Model developed for CLG in compliance to the EPBD.

A design stage assessment should be carried out first. There are nine categories that make up the assessment, these are:

1. Management
2. Health and Well being
3. Energy
4. Transport
5. Water
6. Materials
7. Waste
8. Land Use and Ecology
9. Pollution

Each category contains a number of individual credits, these all add up to give a final BREEAM rating. A post construction check is carried out near completion of the building and the final BREEAM certificate can be produced.

Code for Sustainable Homes is the Governments official measure of how environmentally friendly a dwelling is. The benefits of a Code rating include a higher potential income from rent/selling, reduced energy costs and a more comfortable living environment.

Regulation 17k requires only that a notice is given to the building control body within five days of the completion of work. The notice needs to state the potential consumption. However, in practice, a copy of the completed calculation table should be submitted to the building control body.

To ensure the fittings and appliances are specified during the design stage, the Water Calculation should be completed initially and then revised if those fittings subsequently change.

Factors that affect the calculated water consumption of a dwelling include:

1. The flow rate of showers and taps;
2. The capacity of baths;
3. The flushing capacity of WCs;
4. The consumption per place setting of dishwashers;
5. The efficiency of water softeners (where present); and
6. Whether there is any on-site rainwater or grey water harvesting.

External taps, bath taps, swimming pools, Jacuzzis and bidets are not included in the calculation process.

Information can be found from manufacturers. The calculation should be based upon the data for the fittings actually installed.

As with new build dwellings, the SAP Calculations assess overall thermal efficiency whilst also determining the amount of energy that will required for the internal services such as heating, cooling, lighting and hot water systems. The SAP Calculation also determines carbon (CO2) emissions. Unlike new build properties conversions do not have to fall under any prescribed limit.

As well as demonstrating compliance with Part L1B of the Building Regulations the SAP Calculation is used to produce the Energy Performance Certificate which is required as part of the Building Control sign off procedure whilst also being required for any marketing of the property (for sale or rent).

As with new build dwellings, the SAP Calculations assess overall thermal efficiency whilst also determining the amount of energy that will required for the internal services such as heating, cooling, lighting and hot water systems. The SAP Calculation also determines carbon (CO2) emissions. Unlike new build properties conversions do not have to fall under any prescribed limit.

As well as demonstrating compliance with Part L1B of the Building Regulations the SAP Calculation is used to produce the Energy Performance Certificate which is required as part of the Building Control sign off procedure whilst also being required for any marketing of the property (for sale or rent).

What do I need to provide to the SAP Assessor?

1. Floor plans, building elevation and section drawings;
2. Details of the buildings location and orientation;
3. Specification for the construction of all floors, roofs and external walls;
4. Specification for all windows and doors within the buildings external envelope, including frame material, width of gap (if multiple glazing) and emissivity of glass;
5. Details of the primary heating system (such as the make and model of the boiler) and associated controls;
6. Details of the hot water system, including cylinder size, details of any insulation to the cylinder and pipes, and associated controls;
7. Details of any fixed secondary heating (such as a wood burning stove);
8. Details of any mechanical extract or ventilation systems (for example, the number of mechanical extract fans);
9. The number of standard light bulbs and the number of low energy light bulbs; and
10. Details of any renewable technology, such as solar hot water or photovoltaics.

Compliance with Building Regulations Part L1B is automatically achieved if the envelope of the extension is sufficiently well insulated, the area of openings is within the 25% allowance and building services within the extension are of a sufficient standard.

However for greater design flexibility SAP Calculations can be used to demonstrate compliance with Building Regulations. By conducting a “whole house” CO2 calculation it is possible to show that any aspects of the design that do not meet the minimum standards of Building Regulations have been compensated for elsewhere. These are known as “trade-offs” and can include exceeding the minimum thermal standards elsewhere within the extension, or by making improvements to the heating or the insulation within the existing dwelling.

Two SAP Calculations are required to demonstrate compliance with Building Regulations. The first is based on the existing dwelling, with a ‘notional’ extension of the same dimensions as the proposed extension, and all other aspects conforming to the maximum standard design limits of Building Regulations. This effectively provides a total carbon emission target value.

The second SAP Calculation is based upon the existing dwelling with the actual proposed works and associated specifications. If the carbon emissions of this second calculation are shown to be less than the notional value from the first calculation the works are deemed to be compliant with Building Regulations.

Conversely, if the actual carbon emissions are initially shown to be too high, additional energy efficiency improvements then need to be identified within the new extensions build specification or alternatively the existing property until the calculated carbon emissions fall below the notional target value.

Our Energy Assessors undertake the SAP Calculations from plans and specifications. We have also developed a simple checklist so you understand exactly what information we require. These factors ensure we can provide a full report with SAP calculations within 3-5 days of receiving the information. All SAP customers benefit from a full consultation service to help you achieve the requirements of Building Regulations.

As well as providing a fast and accurate SAP Calculation at a market leading price, our experienced SAP Assessors provide economic and feasible solutions to ensure your extension complies with Building Regulations, no matter what the design.

We will assess your project to Part L1B of the Building Regulations, and liaise with your Building Control Provider to ascertain their full requirements. We will then provide a report covering all aspects required in Part L1B of the Building Regulations.

1. Floor plans, building elevation and section drawings;
2. Details of the buildings location and orientation;
3. Specification for the construction of all floors, roofs and external walls;
4. Specification for all windows and doors within the buildings external envelope, including frame material, width of gap (if multiple glazing) and emissivity of glass;
5. Details of the primary heating system (such as the make and model of the boiler) and associated controls;
6. Details of the hot water system, including cylinder size, details of any insulation to the cylinder and pipes, and associated controls;
7. Details of any fixed secondary heating (such as a wood burning stove);
8. Details of any mechanical extract or ventilation systems (for example, the number of mechanical extract fans);
9. The number of standard light bulbs and the number of low energy light bulbs; and
10. Details of any renewable technology, such as solar hot water or photovoltaics.

Display Energy Certificates (DEC) show the actual energy usage of a building, its Operational Rating, and offer information to the public in relation to the energy efficiency of a building. The certificate must always be displayed in a visible place.

Operational Rating means a numeric indicator of the amount of energy consumed during the occupation of the building over a period of 12 months.

The Display Energy Certificate differs from its domestic/commercial EPC counterpart in that the DEC incorporates an Asset Rating and Operational Rating, since December 2009 DECs have only been issued for public buildings.

Only buildings with a total useful floor area of 250m2 that are occupied, or part occupied, either by public authorities and institutions offering public services to large volumes of people are affected by this legislation.

Where a building is partly occupied by a public authority, or a relevant institution, the authority or institution handles displaying a DEC and having a valid Advisory Report.

Other private organisations occupying the building, irrespective of the size they occupy, do not need to display a DEC.

• Improve energy efficiency by implementing recommendations in the Advisory Report. 
• Act as a mechanism for setting energy efficiency targets and allow clients to actively monitor energy consumption and encourage improvements.
• Provide an opportunity to publicly demonstrate good energy performance.
   

TM59 Design methodology for the assessment of overheating risk in homes was developed and published by CIBSE in 2017.  The aim was to address the industry gap with regards to overheating assessments of residential properties.  Prior to TM59 being developed, there were no specific industry criteria to base overheating in homes.  As such, energy assessors and consultants would likely use differing model set ups with no real benchmark on which to base the results.

TM59 has detailed compliance criteria, which differs dependant on ventilation type, and room type. There is a set of defined profiles which cover occupancy, lighting, and equipment heat gains.  Dynamic simulation modelling is the only way to demonstrate compliance with TM59.  By undertaking these calculations the risk of overheating in your project can be identified at an early stage and a solution provided.

It’s important to carry out the TM59 assessment and report at the design stage of a project.  If the initial design is assessed and is falling short of the requirements, it allows for changes to be made prior to construction beginning.  Alterations to the design may include resizing windows, increasing the window opening capability, amending the glass specification to reduce solar gain, or perhaps amending the layout so that rooms are different sizes or oriented differently.

In response to this increasing level of risk, CIBSE developed an adaptive methodology to assess the predicted level of thermal comfort within a building. This assessment can be carried out at the detailed design stage by way of Dynamic Simulation Model. 

The TM52 overheating compliance criteria is as follows;

• Criterion 1: Hours of Exceedance – The number of hours during which ∆T is greater than or equal to one degree (K) during the period May to September inclusive shall not be more than 3% of the occupied hours.
• Criterion 2: Daily Weighted Exceedance – To allow for the severity of overheating the weighted exceedance shall be less than or equal to 6 in any one day.
• Criterion 3: Upper Limit Temperature – To set an absolute maximum value for the indoor operative temperature the value of ∆T shall not exceed 4K.

The Simplified Building Energy Model (SBEM) is a government approved calculation tool that provides an analysis of a building's energy consumption.

SBEM calculates the energy cost and carbon emissions generated to heat, light, ventilate, cool and provide hot water to a building. SBEM calculations are also used to show compliance with Part L of the Building Regulations, and should be applied from the design stage of the build process.

Building Regulations Part L2A 2013, implemented in April 2014, presents far greater challenges for new commercial buildings.  The main changes from the 2010 edition are:

• The notional building used to determine carbon dioxide targets is the same size and shape as the actual building, constructed to a concurrent specification. The Part L 2013 specifications have been strengthened to deliver 9 per cent carbon dioxide savings across the new non-domestic building mix relative to Part L 2010.
• A wider set of notional buildings has now been defined for top-lit, side-lit (heated only) and side-lit (heated and cooled) buildings. The notional building air permeability has been further subdivided by size.
• A summary of the Part L 2013 notional buildings is published at Table 5 in the approved document with the full detail in the National Calculation Methodology (NCM) modelling guide
• If the actual building is constructed entirely to the notional building specifications it will meet the carbon dioxide targets and the limiting fabric and buildings services parameters. Developers are, however, free to vary the specification, provided the same overall level of carbon dioxide emissions is achieved or bettered.
• The document consolidates the amendments made in December 2012 requiring the feasibility of high-efficiency alternative systems to be taken into account before construction commences.

The challenge to meet these standards falls to all parties involved in new build non-residential development including developers, architects, building services engineers and contractors. Without a consistent and integrated approach towards compliance, the likelihood of failing to meet these standards is significantly greater and it is likely that either cost or delay will be incurred within any project.