Part L · Extensions
Love natural light? So do we. Building Regulations Part L normally limit new glazing to 25% of the new floor area. When your design exceeds that, we carry out Notional and Proposed SAP assessments to keep your vision — and your compliance — on track.
Related: SAP / EPC overview · PSI & U-Value calculations · Water Efficiency (Part G) · Air Tightness Testing · Mechanical Ventilation Testing
Why EAC South West
We model smart trade-offs so you don’t have to compromise your design.
Balance higher glazing with targeted fabric and services improvements.
We assess from architects’ drawings and product specs — saving time and cost.
We propose pragmatic options — never leaving you with a fail.
Method
A reference extension that meets Part L limits.
Your design with higher glazing.
To PASS, the CO₂ emission rate of the dwelling + Proposed Extension must be no greater than the dwelling + Notional Extension. We tune the spec to get you there without overspecifying.
How we can save you money
The process often reveals cost-effective upgrades that align with wider renovation plans — helping you invest where it matters.
Checklist
Send drawings/specs electronically or by post — we’ll take it from there.
Send your drawings and spec — we’ll deliver a clear, compliant SAP package fast.