Glazed Extension

SAP L1b Extensions

If your proposed extension or renovation includes large areas of glazing, it is likely that Building Control will ask for Part L1b SAP Calculations or demonstration of minimum U-value compliance.

SAP Calculations for Glazed Extensions

Highly glazed extensions are very popular but many of these extension designs do not comply with the minimum standards of Part L1b regulations. The requirement being that the area of new glazing accounts for no more than 25% of new extended floor area however by upgrading or over compensating other construction elements the negative impact of larger expanses of glass can be off-set. If the whole dwelling is receiving a refurbishment then there may be many more options available to off-set other elements of construction to show an improvement of the overall energy efficiency of the dwelling. We can guide you through the options which fall into two categories being the ‘Whole-dwelling method’ or ‘Area-weighted calculations’ depending on the individual circumstances of your project.

We can also assist you if the construction work has commenced or has even been completed and Building Control has asked for proof of compliance either by demonstrating U-values or undertaking a retrospective SAP assessment. Contact us to discuss your project and we can advise you of the best and most cost effective rout to gain compliance.

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Get a free quote for your SAP L1a glazed extension. Just upload your plan here.

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