Clearview National January 2019 - Issue 206 | Page 66

CONSERVATORIES&SOLIDROOFS
Staying on the right side of
regulations for rooflights
» » FROM DOCUMENT K TO
previously approved Documents M and N,
there’s a raft of regulations regarding fixed,
opening and access rooflights, that as you all
know, must be addressed before progressing
any building work.
However, as homeowners increasingly look
to cut their heating costs and the government
continues to place pressure on UK businesses
to reduce their energy usage through the
European Energy Directive, Sabahudin Medic,
Head of Engineering and Quality at Roof
Maker, explores how adhering to Document
L1B* will not only ensure you’re legally
compliant, but enable you to offer customers
the most thermally efficient rooflights
available.
‘Roof Maker’s range of
flat, pitched, fixed and
opening rooflights range
between 0.6W/m²K -
1.0W/m²K, providing a
range of products that are
way below the industry
recommendations’
Whilst Document N explores the protection
against manifestation and impact of glazing,
the suitability and requirement of opening
rooflights and safe access for cleaning,
Document L1B is a key reference when
ensuring the correct U-value and suitability
of the rooflights you are looking to install in
both commercial and residential builds. The
current L1B Building Regulations were last
updated in 2016 and below I explore the key
considerations you should explore.
Approved Document L1B places rooflights
under the umbrella of ‘controlled fittings’,
which includes a new window, roof window,
rooflight or door that also incorporates a new
frame. In the event that glazing is replaced in an
existing dwelling but the existing framework is
maintained, this is not regarded as a controlled
fitting and, as such, is not notifiable and does
not have to meet Part L standards.
66 » JAN 2019 » CL EARVI E W- UK . C O M
The maximum allowable U-values are
specified in Approved Document L, which
deals with the conservation of fuel and
power. The following maximum U-values are
taken from Table 2, which can be found on
page 15 of the Approved Document L1B.
Product U-Value:
Roof 0.2 W/m 2 k
Wall 0.3 W/m 2 k
Floor 0.25 W/m 2 k
Party wall 0.2 W/m 2 k
Swimming pool
basin 0.25 W/m 2 k
Roof windows,
glazed rooflights 2.0 W/m 2 k
Pedestrian doors 2.0 W/m 2 k
For notional domestic buildings, to
conform to the CO2 and fabric energy
efficiency targets and the limiting values
for individual fabric elements and building
services, the below U-values must be
adhered to. These U-values are substantially
reduced when compared to the maximum
allowable.
The U-values for the notional domestic
building are as follows:
Product U-Value:
Roof 0.13 W/m 2 k
Wall 0.18 W/m 2 k
Floor 0.13 W/m 2 k
Party wall 0.00 W/m 2 k
Roof windows,
glazed rooflights 1.40 W/m 2 k
Glazed doors 1.40 W/m 2 k
You should here note that the U-values
for rooflights given in Approved Document
L1B are based on the U-value having been
assessed in the vertical position. For units
assessed in a plane other than a vertical
position, the standards within Approved
Document L1B should be modified by
making adjustments in relation to the slope
of the unit as noted in BR 443.
In addition, Approved Document L1B
states that if a window is enlarged – or a new
one is created – the area of rooflights should
not exceed 25 per cent of the total floor area
of the dwelling, unless compensating measures
are incorporated elsewhere in the project.
This must be considered within the planning
process.
If contractors want to take this one step
further, the BREEAM ‘Excellent Rating’
is considered the water mark for buildings
wanting to achieve better ratings, and the
minimum standards for roofs are 0.16 W/
m 2 K.
With regard to notional domestic buildings
and U-values in particular, a U-value of 1.4
can easily be achieved by specifying and
installing rooflights that feature triple glazing.
Triple glazing has been a point of contention
within the industry for years, however, it offers
enhanced thermal performance and reduced
noise pollution, without making the product
significantly heavier or more expensive.
‘offer customers the
most thermally efficient
rooflights available’
Another area installers should consider
when trying to improve the energy efficiency
of a client’s home when recommending
rooflights is the addition of an insulated
aluminium frame. Combined with triple
glazing, these rooflights will easily surpass the
regulations of Document L, a benefit that
customers will be pleased to know will help to
contribute to the decrease of their quarterly
energy bills.
Roof Maker’s range of flat, pitched, fixed
and opening rooflights range between 0.6W/
m²K - 1.0W/m²K, providing a range of
products that are way below the industry
recommendations.
For further information, visit:
www.roof-maker.co.uk
*Document L1B: https://assets.publishing.
service.gov.uk/government/uploads/system/
uploads/attachment_data/file/697629/
L1B_secure-1.pdf