December 2023

Advertorial: Novia
PART L: THE ROLE OF ROOFREFLEX
The team at Novia explain how Aluthermo RoofReflex can solve construction issues
associated with achieving U-values required under the changes Part L...
In June 2022, Part L of the Building
Regulations was updated to include
revised U-values for new builds,
refurbishments, and extensions. These
updates are designed to improve the
energy efficiency of buildings and reduce
their carbon footprint. New Approved
Document L (ADL 2021) which came into effect on
15th June 2022, gives technical guidance on how to
meet the energy efficiency requirements contained
in Part L of the Building Regulations. There are two
parts to ADL 2021; Conservation of Fuel and Power,
Volume 1 – Dwellings, and Conservation of Fuel and
Power, volume 2 – Buildings Other Than Dwellings
(ADL1 and ADL2 respectively). These documents
set out the acceptable provisions for compliance
with Building Regulations with regards to energy
efficiency requirements.
The new U-value requirements for the three building
elements; roofs, walls, and floors, can be found in
the table above.
The most common way to improve on U-values is to
increase the amount of, or change the type of,
insulation. The ‘New Builds’ U-value requirement
for roofs is particularly difficult to achieve at 0.11
W/m²K. To get to these low levels, typically two
thicknesses of PIR insulation; 100mm and 75mm,
are used between the truss, and 25mm below rafter
for thermal bridging. Insulation distributors seldom
stock PIR boards greater than 150mm thickness,
hence the need for two separate boards between
the rafters. The extra cutting on site and cost of
multiple PIR insulation boards makes this a
laboursome and expensive solution. Often, deeper
trusses are used to accommodate more insulation.
This has a knock-on effect whereby soffit depths
must then be made deeper, as well as other
building elements needing to change to fit with the
new design.
Above: Table shows the new U-value requirements for the three building elements.
Other materials and technologies can be utilised to
help bring down the U-value without having to move
away from traditional building methods. Insulation
over the rafter is one such solution. Additionally, the
use of reflective membrane technology can help to
lower U-values down by creating low emissivity
cavities by reducing radiant heat transfer.
Introducing Aluthermo RoofReflex
RoofReflex is an insulated roof and wall underlay
membrane that is both airtight and vapour open. It
is fully compliant to BS EN 13859-1 and EN 13859-
2. It is CE approved as a breathable membrane and
is EN 1928 W1 waterproof compliant. RoofReflex is
normally used in conjunction with other standard
insulation products to enhance the overall U-value
of any installation.
RoofReflex is a highly flexible product which can be
used in a wide range of building designs to improve
U-values by virtue of an integrated insulation layer
laminated to a low emissivity surface. In certain
configurations the overall thickness of both the
insulation and the overall construction can be
reduced.
Unlike multifoil products which are used in the
same application, RoofReflex doesn’t rely primarily
on reflective technology for its thermal performance,
the bulk of the product is 0.0366 W/m²K insulation,
made from 100% recycled plastic bottles. This
gives the product a true thermal value which can be
used in a U-value calculator, as opposed to merely
having an R-value based on reflectivity alone.
RoofReflex’s reflective, low emissivity surface also
gives the product an additional level of
performance when it’s installed facing a
cavity.
How can RoofReflex assist with
new Part L U-value requirements?
RoofReflex is used in the external
element of walls and roofs, therefore not
contributing to the truss/stud depth. Owing to its
excellent thermal qualities, you can reduce the
amount of rigid insulation required. To give an
example of this in a new build roof scenario, the
introduction of RoofReflex above the rafter could
potentially reduce the PIR insulation between the
truss to a single 150mm board, and still achieve a
0.11 W/m²K U-value, when used in combination
with a highly reflective vapour control layer, such as
Novia VC200, behind the plasterboard within a low
emissivity cavity.
RoofReflex doesn’t only provide an alternative
solution to new Part L requirements, it can also help
to reduce solar gain in summer by reflecting heat
away from the building thanks to its reflective
surface. Additionally, being an insulation and not
just a multifoil, RoofReflex has acoustic benefits,
plus it will also help to reduce thermal bridging.
The modern-day aim is to build airtight and wellventilated
houses. RoofReflex is both airtight and
vapour permeable, and it has integral tape to
ensure continuity of airtightness.
With a great many benefits, RoofReflex is an
excellent solution to many of today’s construction
issues and there is peace of mind with every
installation, as RoofReflex is backed-up by a 10-
year warranty.
Contact Novia Limited
novia.co.uk
Novia Limited
38 TC DECEMBER 2023