March 2020

Rooflight Refurbs
ROOFLIGHT REFURBISHMENT –
CONSIDER THE CARBON IMPACT
By William Mcdowell, National Business Development Manager – Rooflights for Hambleside
Danelaw.
Think about it: rooflight refurbishment is a
huge opportunity for roofing contractors.
According to the Chartered Institute of Building
(CIOB), 70% of the buildings currently standing
will still be here in 2050 – the target date set by
Government to reduce carbon emissions by
100% of 1990 levels.
The highest quality current GRP rooflight offers a
lifespan of approximately 30 years (NARM
NTD09) thanks to improvements in technology.
However, older industrial buildings will need to be
refurbished to gain benefits such as optimal
daylighting, enhanced thermal performance and
improved service life.
Overlooked
Often, rooflights are overlooked by the building
owners and occupiers – largely, because the
rooflights they have are so discoloured and/or
dirty, they do not perhaps even realise the
rooflights are there.
As a contractor, you face three
options to pitch to the client:
re-sheeting, overcladding or
just rooflight replacement.
With each, there is the further
consideration of straight like for like,
upgrade, and/or increase of the rooflight area.
Each will depend on project aims and objectives,
budgets, and site considerations such as
timeframes, whether the building operation will
continue during the contract.
“As a contractor, you
face three options to
pitch to the client: resheeting,
overcladding
or just rooflight
replacement”
William McDowell, Hambleside Danelaw.
Carbon impact
The carbon impact of buildings
is inevitably going to play a
bigger and bigger part. We all
know the benefits of rooflights in
terms of BREEAM – their provision of
natural daylight within, their potential
contribution towards energy consumption within
if insulating versions are incorporated. Note, a
useful point to bring into specification is that it
costs four times more to heat a building than to
light it, and there is an argument to increase the
rooflight area.
The misconception surrounding the ratio between
rooflight to roof area is being brought to light.
Historically the accepted lore was that 10% of
the roof should comprise rooflights.
Independent research commissioned by the
National Association of Rooflight Manufacturers
(NARM) now challenges that. The research used
SBEM (Simplified Building Energy Model) to quantify
CO2 emissions for the notional building with varying
rooflight area. The conclusion was that, at 12%
rooflight area, it passed the target within Building
Regulations Approved Document Part L.
A rooflight area of 15-20% achieved savings in
running costs of £5.92/m²/yr (at prices current
when the report was compiled), and reduced
emissions by 28.7kgCO2e/m²/yr. Note, the cost
of energy in £ and CO2 required to light a building
artificially is accepted to be far greater than any
potential heat loss through rooflights.
Any small incremental increase in the cost of
upgrading to a higher specification i.e. a double
skin in place of single skin, is more than offset by
42 TC MARCH 2020