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Energy services - frequently asked questions

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What does SAP mean?

SAP is the shortened form of Standard Assessment Procedure and is used to assess a dwelling's energy performance.

Why do I need an SAP rating?

Approved Document Part L and Section 6 of the Scottish Building Standards require an SAP calculation to be carried out to demonstrate compliance with energy performance requirements.

SAP calculations are also required to demonstrate energy performance in the Sustainability benchmarks such as the Code for Sustainable Homes and in some planning conditions.

When should I have an SAP assessment carried out?

The earlier the better. DER/TER calculations need to be submitted to building control before work starts on site, however getting them done further in advance will allow for the energy efficiency of the dwelling to be considered whilst it is being designed ensuring a cost effective solution to compliance is achieved.

What is an EPC?

EPC stands for Energy Performance Certificate and shows a dwelling's energy efficiency and CO2 emissions. An EPC will also have recommendations on how to improve the property's energy performance.

Why do I need an EPC?

Every dwelling for sale requires an EPC to demonstrate the energy performance of the dwelling. We provide EPCs for new build properties only.

When can I get an EPC?

An EPC for new build dwellings is an "As-Built" certificate so the dwelling should be near completion before the EPC is issued. If the dwelling is in a suitable state for an air leakage test to occur then an EPC can be issued.

What is the difference between an SAP assessment and an EPC?

SAP is generally a term that describes the design stage DER/TER (Dwelling Emission Rate/Target Emission Rate) Calculation, an Energy Performance Certificate is calculated from an As-Built SAP and represents the dwelling as constructed included an air test result.

What information do I need to provide to get an energy calculation done?

SAP calculations and EPCs require drawings of the dwelling (floor plans, elevations, sections and site plan) as well as a build specification. An EPC will also need an air test result either for the specific or similar dwelling.

How do I pay for energy ratings?

We charge retrospectively for SAP and EPC calculations which means you won't pay for them until they are complete. An account with NHBC is required for retrospective billing.

Do I need SAP for every dwelling on a site?

SAP calculations submitted for building control should demonstrate the performance of all the dwellings on the site. Due to the number of items that will cause the calculation to vary, a large proportion of the dwellings will require an SAP assessment and builders often have an SAP for every dwelling.  This also helps with a plot specific Predicted Energy Assessment (PEA) and also Code for Sustainable Homes assessments.

Do I need an EPC for every dwelling?
Every dwelling needs a plot specific EPC.
What is Thermal Bridging?

Thermal bridging occurs where insulation cannot be continued. Non linear repeating thermal bridges are caused by wall ties and timber battens etc, and is taken into account in the u-value calculations. Linear thermal bridges occur where two different elements occur such as corners and where the ground floor meets the external wall.

For more information on thermal bridging see NHBC Technical Extra 3.

NHBC Technical Extra 3

What are accredited construction details?

Accredited construction details are a set of drawings that show how to build specific details in a dwelling to reduce thermal bridging. Building to them will result in lower heat losses through thermal bridging and lower your Dwelling Emission Rate. Other details exist that will allow you to reduce your DER further and your Energy Assessor will be able to help.

For more information on thermal bridging see NHBC Technical Extra 3.

NHBC Technical Extra 3

What is the party wall by pass?

The party wall bypass is where heat escapes from a dwelling through the cavity party wall between dwellings. The heat loss can be prevented by filling and sealing the cavity.

For more information on the party wall bypass see NHBC Technical Extra 3.

NHBC Technical Extra 3

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