Should I increase my cavity widths?

DriTherm install

Should I increase my cavity widths?

With changes to Approved Document L (Part L) of the Building Regulations requiring lower U-values across all elements of a building, it’s worth considering increasing the cavity width of your walls. 

The required minimum U-value to achieve compliance within the new Part L is 0.24 W/m2K and this can still be achieved by using 100mm of our DriTherm® Cavity Slab 32 and either a standard or lightweight aircrete block. However, with the new regulations, building to 0.24 W/m2K might not allow you to achieve SAP compliance across the full building. 

Achieving compliance within SAP calculations requires an overall level of thermal performance from each of the building elements within a property, meaning that having higher performing elements can counteract the lower performing areas. 

That’s why more housebuilders are now choosing to specify 150mm cavities. 

By building with a cavity of 150mm and using DriTherm® Cavity Slab 32, you will be able to achieve a U-value of 0.17 W/m2K which is more likely to contribute to whole house compliance. When the Future Home Standard arrives, regulations will tighten further, so it’s worth making the move to 150mm now, to futureproof your designs.