Top Five Tips for SAP Success
How Do I Make Sure of a Pass?
It’s fair to say that developers and architects didn’t need to pay much attention to SAP in the old days – but recent years have brought significant changes to the SAP metrics and Part L Building regs. Starting work without a design stage SAP assessment is not an option!
This is primarily because CO2 emissions targets have tightened enormously – driven as they are by European and UK climate policies. An average new build designed just 5 years age is highly unlike to pass the regulations today.
We are often asked to explain why some builds fail and some pass, and it isn’t always easy to give a straight answer. Numerous factors can play a part, from the size of a boiler to a junction in a wall, to the thickness of insulation in a floor, to which direction the house is pointing!
Some factors can be beyond the clients control – for example having no connection to mains gas could mean having to use an oil or LPG system. These fuels have higher cost and CO2 emissions factors within SAP, and as the Target Emission Rate is set based on a mains gas system, you take a hit.If we ignore the wider climate change issues, resist technicalities, and assume we are not trying to produce a zero carbon house, we can tie down a few good principles which will give you a good chance of success:
1. Minimum u values are there to be beaten, not followed
If the fabric of the building is well insulated, you will not need fancy renewable technologies to get you through. Design as much insulation into the walls, floors and roofs as you possibly can.
2. Windows and doors lose a lot of heat
Pay attention to the u values on the openings you are specifying and get them as low as possible, ideally 1.4 W/m2K or less
3. It’s not the boiler, it’s the controls
Zoned heating and load / weather compensators for boilers will often have a more significant effect on the SAP rating than the system itself.
4. Get it airtight
All new builds require Airtightness Testing on completion and the resulting figure goes into the SAP Calcs. Make sure the envelope is sealed and get a pre-test check carried out.
5. Pay attention to thermal bridging
This is heat loss through junctions with external walls. Follow a scheme such as Accredited Construction Details (ACD’s) which will allow us to avoid using default figures. For our guide see our page on Thermal Bridging.