Springhall saved by
When Springhall was re-roofed, it was also made into a suitable home for bats with the TLX Batsafe
breather membrane. A spokesperson from the company explains more about the product to RCI readers
This imposing Gothic revival
mansion has been used as the
Calderdale Registry Office
since 2009, although since it was
built in 1871, it has been used as a WW1
hospital, a guest house and a ballet studio.
There was a complete internal renovation
in 2009, creating office space in the upper
storey, but only now has it been
re-roofed – which of course then requires
an upgrading of the insulation.
How was the heat loss
Since an uninsulated roof has a U
value of 3.87 W/m2K – which means
that for every square metre 3.87 Watts
of heat are being lost for every degree
temperature difference between the
outside and inside – the office workers
in the rooms in the roof must have been
freezing! This may have been the norm
when it was accommodation for the
servants, but it is not acceptable now,
nor desirable in terms of energy loss.
Rafter-level insulation was the
There was little scope for improvement,
however, as the rafters were only
75mm deep. The loft void was too
small and inaccessible to consider
putting insulation over the ceiling, so
rafter-level insulation was the only
option. With 75mm rafters, the buildup
would normally be to use a breather
membrane and 50mm PIR board and
a vapour barrier beneath, but over the
sloping ceiling sections, there were lath
and plaster ceilings, which meant that
the effective rafter depth was reduced.
A tempting home for bats too?
A final complication was that, although
a survey had shown no evidence
of bats in the roof, the proximity of
woodland meant that there was a
possibility that bats may use it in
Since bats become tangled in fibres,
there is a requirement to use a bitumen
felt where they are found to be using
a roof. The problem here from an
insulation build-up perspective is that
this then requires a 50mm ventilated
space underneath. If this were to be
implemented in the roof overlying the
offices, then in 75mm rafters with a
A new bat friendly breathable membrane is
Bats are a protected species in the UK and play
an important role in the ecosystem. Until now,
when bats are found, only Bitumen 1F felt has
been used. This has come at a considerable cost
to the thermal performance of the roof, because
1F felt requires extra rafter space if insulation is
used; in old buildings this is often not possible.
Properties with an uninsulated 1F felt roof can
release up to
10 tonnes of CO2
1F felt with a breathable membrane
additional insulation between the rafters
can improve thermal performance by up to
emissions by 57%.
factors have a large impact on global warming
and climate change.
It was critical that a product was invented
to protect bats from traditional breathable
membrane, but also allow for refurbishment
of properties in accordance with Approved
Document L of the Building Regulations.
TLX Batsafe was invented by TLX Insulation.
The major issue with breathable membranes
and bats is the fibres used within the product
become damaged and flu up when in contact
with bat claws. These fibres can then entangle
the bat, which can cause them to die. TLX Batsafe
is designed with a protective mesh either side of
the product, which allows contact for the bat and
enables the breathable membrane to function.
50mm ventilated space and a lath and
plaster ceiling intruding, this would
leave room for no insulation at all – so
the office workers would continue to
freeze and Calderdale Council would
be seeing heat vanish!
A membrane which is both
energy saving and no danger
A pragmatic solution was found by
making use of TLX bat safe breather
membrane. This is a standard
BBA-certified breather membrane
sandwiched between two layers of
mesh. The mesh is sufficiently small
to prevent bat claws from pulling out
fibres from the breather membrane
below, yet will offer space for them to
crawl around on.
What about testing?
Starting its development in 2014, TLX
Batsafe has been tested extensively,
firstly with live tests at the IOW Bat
Hospital, followed by lab testing using
the industry recognised pilling test
method and finally a fibre filament test.
By using Batsafe this meant that 30mm
of PIR board could be accommodated,
which allowing for the usual membrane
drape and the lath and plaster intrusion,
was able to achieve a U value <0.7 W/
m2K, which corresponds to an 82%
saving in heat loss.
Calderdale Council is now making
considerable savings in its heating bills,
the office workers are warmer, and
should any bats take up residence, then
they will be safe.
January 2019 www.rcimag.co.uk 87