Extension SAP Calculations & EPC's
When do you need extension SAP Calculations?
Building Regulations Part L1b require all extensions thats glazing area exceeds 25% in comparison to the extension floor area to have extension SAP Calculations or heat loss calculations carried out.
if your extension is 20m2, you have an ‘allowable’ area of glazing of 5m2 (25% of 20), if your extension does not exceed this figure, heat loss calculations or extension SAP Calculations are not a requirement for Building Regulations. However, if your extension does exceed the 25% figure, SAP calculations or heat loss calculations will be required to show compliance to Building Regulations.
Percentage Calculations, points to consider
if you are looking at running calculations to see if you require extension SAP calculations, these are a few things to consider,
All openings are considered within the calculations, glazed doors, windows & rooflights, be sure to include these areas.
If you are covering or removed any windows/doors in the process of the extension, these areas can be added to the 25%, this can be really useful if you are just over the 25% mark! For example, if you have a 20m2 extension, your ‘allowable’ glazing figure are up to 5m2, however, where the extension is being constructed the external wall previously had french doors which were 2.5m2, these will be removed to make the entrance to the extension. This 2.5m2 of removed glazing can be added to the 25%, therefore your ‘allowable’ glazing area increases from 5m2 to 7.5m2.