Part L changes 2020 - What you need to know

By the end of the year, updates are expected to be published to Part L of the Building Regulations in England and Wales. These changes are designed to raise the energy performance of properties and form part of the Government’s wider strategic commitment to achieving net-zero carbon emissions by 2050 (2045 in Scotland). In this blog, we’ll take a look at these changes and what they will mean when installing a roof.

Part L sets the energy performance targets that all buildings in England and Wales have to meet. As control of the Building Regulations is devolved, the requirements are different in the two countries. Both countries also provide their own technical guidance handbooks – called Approved Document L – which explain how to keep your construction compliant with the regulations.
 

The first properties to be impacted will be new homes. Both England and Wales ran consultations into changes to the Part L requirements for these properties which closed in the Spring. Work is underway to publish the final requirements before the end of the year (along with revised versions of Approved Document L1A). Further consultations are expected later in the year looking at the requirements for all other properties.
 

The consultations set out clear worst case U-values which roofs on all new homes will need to meet.

These are 0.13 W/m²K in Wales and 0.16 W/m²K in England. It is highly recommended, however, that installers look to go above and beyond these minimum requirements. Roofs can act as a key source of heat loss on a property, and by insulating them correctly from the outset, it is possible to achieve significant energy and cost savings year-on-year. This is even more important with performance targets for existing homes also set to tighten over the coming years. By getting the envelope right from the start, you can allow customers to avoid costly insulation refurbishment work further down the line and ensure you are properly prepared for the future changes.

We would suggest adopting a U-value of 0.11 W/m²K which is the value proposed in the notional dwelling for both Welsh consultation options. By using Polyisocyanurate (PIR) insulation, which has a low thermal conductivity and is therefore a more effective insulant than hybrid alternatives which use materials such as mineral fibre, it is possible to keep the construction slim whilst hitting this target.
 
Building Innovation can work with you to develop a fully calculated tapered or flat roof scheme which meets both your requirements, and those of the Building Regulations/Standards.
 

Aside from the thermal performance of each element, the consultations also tackled detailing when installing insulation. They recommended removing the Approved Construction Details (ACDs), the detailed drawings of junctions which can be used at present to estimate heat loss values for these areas.
 
Part of the reason for this is that poor detailing has been identified as a key contributing factor in the so called ‘performance gap’ between the estimated energy performance of a building and its actual performance. Rather than relying on standard set of details, therefore, the new requirements aim to encourage contractors to generate their own drawing for junctions to raise standards.
 

Building Innovation can support you at every stage from initial consultation to site delivery and can help to develop details to ensure the construction is well insulated and fully compliant with the new requirements.
 
If you have a flat or tapered roof project on the horizon and you need some advice, get in touch with our expert team. Thermal performance that’s calculated, not estimated.