March 2022

Roof Windows
BRIDGING THE GAP
Colin Wells, Head of Technical at Keylite Roof Windows, looks at how installers can ensure
their builds remain compliant, sustainable and deliver optimum levels of wellbeing for
homeowners.
The heating and powering of buildings
currently accounts for 40 per cent of the
UK’s total energy consumption , a figure
which demands government action to ensure
change.
On the 15th of December 2021, the UK
government published an updated version of
Approved Document L: Conservation of Fuel and
Power.
This change means that from the 15th of
June 2022, new homes in England must
produce around 30 per cent less net carbon
emissions, and existing homes will be subject
to higher standards when it comes to added
extensions and thermal upgrades, all in a
step towards net zero carbon building in
2025.
Two of the biggest areas of heat loss are roofs
and windows, and from June this year the
specification and application of a roof and its
Colin Wells
materials must be compatible with the rest of the
building design.
The purpose of Approved Document L is to ensure
energy efficiency in buildings.
The Target CO 2 Emission Rate (TER) and Target
Fabric Energy Efficiency (TFEE) rate are the
From June 2022, homes must produce
30 per cent less net carbon emissions
“When it comes to heat
loss, one of the biggest
issues is thermal
bridging, when all too
often double glazing
is seen as the main
culprit of this”
minimum energy requirements for a new-build
dwelling.
To showcase that a building complies with
regulation requirements, Dwelling CO 2 emission
Rate (DER) and Dwelling Fabric Energy Efficiency
(DFEE) rates are calculated, and both must be no
higher than the TER and TFEE.
When it comes to heat loss, one of the biggest
issues is thermal bridging, when all too often
double glazing is seen as the main culprit of
this.
However, despite meeting relevant standards
it’s often in the installation of a product where
cold bridging can occur, reducing its thermal
efficiency.
Installation of roof windows is often left to the
manufacturer’s discretion, with most stipulating
that a gap is required around roof windows
to enable on-site adjustments and ease of
installation.
This gap is supposed to be ‘filled in’ after or
during installation to reduce the impact of
thermal bridging.
However, this is rarely stipulated in building
designs and the retrofittable product of a
thermal foam is often not on specifications,
Continued on page 64
62 T I MARCH 2022 PRACTICAL CONTENT FOR THE GLAZING INSTALLER & HOME IMPROVEMENT SPECIALIST