Issue 33 web - Flipbook - Page 10
Shedding some light
on the new Part L
Stella Rooflight Director, Paul Trace, addresses the new rules for rooflights and thermal
Why the need for new regulations?
A major part of the UK’s commitment to meeting its
targets for carbon reduction is being driven by a tightening
of the Building Regulations surrounding energy efficiency
standards for homes.
What do the new regulations state?
For rooflights, skylights and roof windows (of which
the definition is crucially important), the relevant consideration is the thermal transmittance. This is measured as
a U-value in units of W/m²K, which stands for
Watts/meter square Kelvin. The lower the U-value the
more efficient the construction is at keeping heat flow
through the structure to a minimum.
The Ministry of Housing, Communities and Local
Government (MHCLG) argues that by making our buildings more energy efficient and embracing smart technologies, we can cut energy bills, reduce demand for energy,
and boost economic growth while meeting our targets for
carbon reduction and maintaining healthy environments.
As such it has introduced ‘The Future Homes Standard’
to ensure all new homes achieve a 30% improvement in
energy efficiency standards by 2025.
The new regulations deem the worst acceptable U-values
to be 2.2W/(m2K) for rooflights and
1.6 W(m2K) for roof windows.
Rooflights v roof windows – what’s the difference?
To correctly assess whether an element meets the new
limiting U-value figure, the U-value must be calculated
for the element in the appropriate plane – either horizontal or vertical. Now this makes a big difference, as testing
the same product in either a horizontal or vertical position
will make a significant difference to the resulting U-value
figure. With the vertical position providing a much lower
(better) U-value figure.
The new Building Regulations aimed at achieving these
targets will comprise five new Approved Documents,
which will come into effect in June 2022.
Manufacturers, architects, specifiers and customers
looking to install rooflights and roof windows will be
most interested in uplifts to the Approved Document L,
Conservation of fuel and power Vol 1: Dwellings.1
Above, coastal property with stainless steel Stella rooflights
Conservation & Heritage Journal