There are a lot of things that you need to consider when you’re self building. Paper work will be one of the last things on your mind but getting a SAP (Standard Assessment Procedure) ‘pass’ is vital to getting the all important EPC (Energy Performance Certificate) and the resulting sign off from the buildings inspector.
Here we cover our top five tips to getting the SAP rating that you want, but before we start, here’s a little refresher on SAP.
What is SAP (The Standard Assessment Procedure) for Dwellings?
The Standard Assessment Procedure is a set of calculations based on the size of your planned (or completed) home which assume a standard occupancy and living style. They incorporate information about the thermal performance of the materials used, the heating systems and the any heat losses or gains such as solar gains. This allows the comparison of energy performance between dwellings, which means that you have a good idea of the energy performance of a home before you move in and the government can set and gradually improve the energy performance of the county’s housing stock by raising the standards needed. Find out more in our in depth article about SAP.
The SAP calculations produce a SAP rating; a number from 1-100 where 1 is the least energy efficient. It is possible to have a SAP rating over 100. This is when the home actually generates more energy than it uses, and exports the excess back to the Grid. These SAP ratings are used and displayed in the EPC (Energy Performance Certificate) which is required every time a home is built, sold or rented. This is a stipulation of the Building Regulations, Part L; find out more about Approved Document L here.
Top Tips for Getting a Low (or ‘Pass’) SAP Rating for a Self Build
Obviously it is very important to get the SAP rating that you need as failure to do so will mean that the building cannot be signed off by the building inspector. Failure to pass at a late stage can mean some very expensive and frustrating remedial work to get the SAP rating up to the required number. Here are our top 5 suggestions to avoid this:
- The early bird gets the right SAP rating: The earlier that you start to think about your SAP rating the better. We mean at the drawing stage. Ideally you or your architect should submit the drawing to a SAP assessor to calculate your initial SAP rating before you even submit the plans for planning permission. Making changes to the drawings is considerably easier and less expensive than changes during the build
- Get Zoning and Heating Controls: While the type of heating system that you use, including any secondary heating will have a huge impact on your SAP rating, it is possible to improve the SAP score considerably by planning and fitting sophisticated heating controls. You are ‘rewarded’ in SAP for having the ability to control the heating so that it is only used where and when it is needed
- Get to Grips with u Values: All building material will have a u-Value, which is a measure of how effective they are at stopping heat passing through them. The lower the u-Value the better the material is at retaining heat; the better it’s insulating properties are. Plan and use the materials with the best u-values you can get and afford. This will mean that you have ‘credit in the bank’ when it comes to the SAP calculations and your scrabbling for a pass. If you don’t it is nearly impossible, and certainly very expensive to retrospectively change the materials to more efficient ones
- Doors and Window need special attention: This is closely related to the u-value argument described above, you need to ensure that the doors and windows that you choose have the lowest possible u-values that you can get or afford. Doors and windows are the places where most energy is low (according to SAP) so making these more efficient will improve your SAP score. While you can probably make a decision on the openings later in the project, these items generally represent a significant portion of the build budget so it is worth planning then early
- Air Testing for SAP: It is almost certain that you will be required to have an air test which measures the air change rate for the new dwelling, or effectively how much air the home leaks. You need a certain amount of ventilation in order to get fresh air into your home, but too much can signal that you are losing nice warm air and gaining cold air from outside making to the dwelling’s thermal performance poor. This is measured by conducting an air test, where air is blown into the house and the amount lost is recorded. If you get an air test done yourself in advance of the formal test you will be able to address any issues and could boost your ‘score’ ensuring the all important pass
The SAP rating and EPC are yet another hurdle that you will need to get through before getting your home passed by the building inspector, and with a little forward thinking this will not be one that trips you up. While it is potentially an onerous task and an added layer of bureaucracy we feel that the cause is a good one, not just for the environment, but also for those that will live in the home when it is finished enjoying lower energy bills – and this is not just you as the self builder but all the generations that will come after you!
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