Part L1B Large Glazed Extensions & Conversions

A SAP calculation is generally required for extensions with excessive glazing...

Extensions

U-values (thermal elements i.e. walls, roofs etc.) for new extensions are generally similar to that of the existing dwelling, are not excessive and achieving Building Regulations approval is relatively simple. However if the glazing to the proposed extension is greater than 25% of the extension internal floor area, then a SAP calculation will be generally required.

The SAP calculation compares a basic compliant design for the whole dwelling with the proposed extension, the proposal should be no worse than the basic compliant option. Gladwood are able to carry out this assessment and provide cost effective solutions to achieve the pass you require.

Conversions/Material Change Of Use

If the proposed dwelling is deemed to be a material change of use, a SAP assessment will be required to demonstrate that the U-values to both retained and renovated thermal elements as well as all new elements comply with minimum standards set out in Tables 1,2 & 3 of Part L1B. It will also be necessary to show compliance with controlled services i.e. lighting, ventilation, heating & hot water.

Conservatories

If the proposed conservatory has a floor area of less than 30m² and there are existing patio doors between existing and new and no heating is being extended into the conservatory from the main dwelling heating system then Building Regulations are generally not required. However if there is no external grade doors between the existing dwelling and the new conservatory then a SAP calculation as noted above will generally be required.