Product(s):	OpenBuildings Energy Simulator
	Version(s):	CONNECT Edition
	Area:	Part L

Overview

With the introduction of the 2021 PartL building regulations much more stringent building compliance requirements will be in place. This will impact many aspects of building design.

The major effects of this for energy assessors and for building compliance can best be seen by inspecting the 2021 BRUKL Compliance documents.

Details

The main changes to expect include:

Target Primary Energy Rate

Previously buildings achieved an overall pass upon considering CO2 emissions levels only, in the form of the BER (Building Emission Rate) and TER (Target Emission Rate). In addition to this, the energy of buildings is now measured via the BPER (Building Primary Energy Rate) and TPER (Target Primary Energy Rate). Both these targets must not be exceeded for a building to comply with the regulations.

Building Fabric U-value Check

Significantly lower minimum U-values for all building fabric types are to be adopted. This will require much improved building fabric materials, and more insulation.

To put this in context, for Walls the new standards will reduce the target U-value by approximately 25%.

Also note that Roofs are now subdivided into Flat Roofs and Pitched Roofs, each with their own U-value target.

Air Permeability

Buildings are to be made more air-tight with a reduction in the limiting standard for air permeability. This is changing from 10 to 8 m³/(h.m²) at 50 Pa:

DHW Minimum Efficiency

New minimum DHW efficiency standard, changing from 0.8 to 0.91:

New Minimum HVAC Efficiencies

The exact change will depend on the HVAC System Type selected, however for instance, for conventional boilers the minimum efficiency has changed from 0.91 to 0.93: