What’s the most cost-efficient Part L specification?

Glass Mineral Wool

What’s the most cost-efficient Part L specification?

Part L of the Building Regulations now contains a ‘notional dwelling’ recipe, showing an example route to compliance for a typical home. The specification includes details of fabric, U-values for walls, roof, floors, windows and doors, as well as parameters for thermal bridging, heating design and air permeability. 

But the notional dwelling is purely illustrative and rigidly copying it could lead to unnecessary expense.  

Let’s look at an example:

The notional dwelling features a U-value of 0.18 W/(m2K) for the walls and 0.11 W/(m2K) for the roof. The former is relatively costly and the latter is arguably an under-specification. You could easily achieve a U-value as low as 0.09 W/(m2K) here, just by adding more insulation to the loft. This would be a cost-effective solution which avoids altering the plot footprint.  

A tailored approach 

The important thing to remember is that you have options. So instead of trying to emulate the notional dwelling, choose a tailored solution, that suits your project’s specific requirements and budget.  

Knauf Insulation is already working with several housebuilders who are taking this approach. In one case, revised whole-house recipes have been identified, saving the housebuilder over £1,000 per plot, without adjusting their existing plot footprints. 

Your next steps 

To find your most cost-efficient route to compliance, undertake calculations using the latest SAP methodology and determine the ideal whole-house recipe for your specific build. It’s also worth taking advantage of any free tools which may be available from your insulation provider. For example, Knauf Insulation products can be used in conjunction with our free online U-value calculator and Psi-value calculator

For further advice, speak to our Technical Support Team