A Knauf Insulation roofing system has been specified by architects,
the Stanley Bragg Partnership Ltd, for use on a new primary school
in Great Dunmow, Essex. The system uses Polyfoam® Pitched
Roofboard, Polyfoam® Raftersqueeze and Knauf Breatheline to form an
insulated pitched roof. Roofing contractors, Lodge Roofing, were
impressed with the system, giving it top marks for both ease and
speed of installation.
Great Dunmow’s new primary school will be the seat of learning for
around 400 pupils when it opens its doors for the new school year
in September 2005. The 14 classrooms, two halls, library, kitchen,
offices, toilets and ancillary rooms are laid out in two blocks
linked to form an L-shaped building. Designed by Colchester
architects, the Stanley Bragg Partnership Ltd, the school is being
built by Haymills (Contractors) Ltd for the Governors of Great
Dunmow Primary School.
Around 2,300m2 of the roof is of insulated, pitched roof design
using Glulam trusses and timber rafters finished with an outer skin
of natural Spanish slate. Being an insulated roof means installing
insulation at rafter level and, to meet the Building Regulation’s
Elemental U-value of 0.20W/m2K, the architects chose Knauf
Insulation’s Polyfoam® Pitched Roof Insulation System.
The system uses three Knauf Insulation products. Two layers of 50mm
thick Polyfoam® Raftersqueeze were specified between the rafters
with a single layer of 60mm thick Polyfoam® Pitched Roofboard laid
over them. Knauf Breatheline was used to provide an underlay and
vapour permeable breather membrane between the roofboard and
slates.
Polyfoam® Raftersqueeze is a rigid board designed to fit between
rafters irrespective of their designed or actual spacing. The
secret of its success lies in the deep grooves formed parallel to
its long edges which allow a degree of lateral compression. Having
been cut roughly to size, the board can be easily push-fitted –
‘squeezed’ – between the rafters, giving immediate retention and
overcoming irregularities in the timber.
Polyfoam® Pitched Roofboard was specifically designed for use in
pitched roof construction. Its strength, combined with rebated,
shiplap edges on all four sides, means that joints between
individual boards do not have to coincide with supporting timbers.
This makes it ideal for over-rafter, pitched roof insulation as
reducing the amount of cutting makes installation very quick: the
boards are simply laid across the rafters and secured with
spiral-type fixings.
Phil Lodge, Managing Director of Newmarket-based roofing
contractor, Lodge Roofing, was impressed with the system, saying,
“We hadn’t used Raftersqueeze before and were intrigued, and a
little sceptical, about the concept. When it arrived on site, I
immediately took a piece up on the roof, trimmed it roughly to size
and stuffed it between two rafters to see if it worked. It did – in
fact it was quite a job to get it out again! We’re very impressed
with it and would certainly use it again as it really did speed up
fixing the insulation between the rafters.”
Polyfoam® Insulation products are made from high performance, 100%
ozone friendly, extruded polystyrene. The rigid boards have
excellent insulation properties and a high compressive strength yet
remain lightweight and both easy and quick to cut and install.
Polyfoam® Raftersqueeze has a thermal conductivity of 0.030W/mK and
is available in three thicknesses – 50mm, 65mm and 75mm – and comes
as a standard size board of 1200mm x 600mm. Polyfoam® Pitched
Roofboard has a thermal conductivity of 0.029W/mK and is available
in a range of thicknesses from 35mm to 75mm and in a standard size
of 1250mm x 600mm.
Knauf Breatheline is a strong, lightweight polypropylene non-woven
fabric with excellent tear and drape characteristics. Classified as
a breather membrane, it offers little resistance to the passage of
water vapour, has been independently tested and holds three BBA
Certificates together with their IAB equivalents.
More information about Knauf Insulation’s products can be found at
www.knaufinsulation.co.uk or by calling 08700 668 660. Please quote
PR 310 05.
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