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When building residential properties, the government recommends the use of the Standard Assessment Procedure (SAP), a method system that helps in rating the energy use within residential buildings. EPC (Energy Performance Certificate) is a tool used in residential properties for energy efficiency rating, A (most efficient) to G (least efficient).

EPC is always valid for ten years and is required whenever a property is being built up, sold or rented. Therefore, before you can start building residential buildings, it is crucial that you comply with Part L1A of the Building Regulations which states that SAP 2009 assessment must be undertaken and submitted to the Building Control.

When conducting the SAP assessment, it is important to engage accredited energy assessors. After completing the building, the SAP assessment is then upgraded to As-Built SAP calculations. This is to incorporate any changes that have altered the initial design of the building.



New Builds and Conversions costs from 80 pounds + VAT for a single unit. For multiple duplicating properties, it will cost 30 pounds plus VAT. In addition to the calculations, there is also unlimited advice on how to comply with Part L1A of the Building Regulations. Additionally, SAP calculators will also run different calculations on the software many times at no additional price.

However, the cost of lodging the EPC upon the end will cost you 35 pounds plus VAT per unit. Also, if you have excessive furnishing calculations for extensions, it will cost you from 150 pounds with VAT included.

On the other hand, the SAP is also used as a method of measuring the overall energy efficiency when it comes to self-contained properties. Therefore, the government will recommend the system purposely for giving an Energy Performance Certificate (EPC) in regards to newly built dwellings. When it comes to the SAP, many factors are used when rating the energy efficiency.

Some of these rating factors influence the materials that are used in construction, thermal insulation of the building fabric, the air leakage ventilation equipment, efficiency, control of the heating system, and solar gains through openings of the dwellings. It can also include factors such as the fuel used when it comes to providing space and water heating, ventilation, and lighting.

Where the building has a fixed air-conditioning system, the rating will not be affected in any way by the location, but if that’s not the case, energy for space cooling will be used as a rating factor. The other probable factor to be considered is the renewable energy technology.



It is essential always to know the detail of every SAP calculations such as when the house extensions require SAP calculations because it can lead to confusion. One of the most important things you should know is that it will depend on many factors especially with the amount of glazing.

The glazing shouldn’t more than ¼ of the floor area plus any amount of glazing that is taken out, and if it is, SAP calculations are required. However, according to Part L1B, a more flexible approach is taken when it comes to highly glazed extensions. This more flexible approach allows you assess to the house with the expansions included. However, it should be built to match the body regulations stipulations, that is with the exact your values and amount of glazing.

This can be then said to be Notional Extension. In this case, the SAP calculations will be required to be done afresh that is for the house in the extensions as they are built. Also, in such a case, the carbon dioxide produced from the home and extension shouldn’t be higher than the carbon dioxide from the house and the Notion Extension.

The primary purpose for doing this is to ensure that the carbon dioxide that is emitted is not worse than what is required by the building regulations. In case it is more than what is expected, you can use other alternatives. For instance, you can use glass in the extensions especially during the summer season because of the solar high gain and for less heat loss during winter.


L1A – SAP calculations for new dwellings

The Building Control will require you to give the SAP calculations for a new building if in the UK. Most of New Builds designs will not comply with the requirements of the Part LIA and mostly will depend on where and when you started the process as long as you don’t exceed the target for carbon emissions. If you’re constructing a home in England, you have to meet the requirement on thermal performance fabric in construction.


Before you start on the site, a design-stage SAP calculation showing pass should be provided to the Building Control as they assess the dwellings using different designs as specified.


This is the last calculation that must be submitted to the Building Control after any changes are incorporated in the report about the alterations of design, manufacturing details for the heating systems and as-recorded permeability rate. The EPC is offered in the final stage.


In Scotland, design-stage SAP calculations are required before the work starts on site. As-built SAP calculations plus EPC are required after construction.

What do I need to provide to the SAP assessor?

  • Floor plans, elevation drawings, section drawings and a site plan;
  • Construction specification;
  • Mechanical and electrical specification; and
  • Details of any renewable technology, such as solar hot water or photovoltaics.



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