Test Report Overview



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 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 per year. Replacing 1F felt with a breathable membrane and additional insulation between the rafters can improve thermal performance by up to 87% and reduce CO2 emissions by 57%. These factors have a large impact on global warming and climate change.

Bats and breather membranes

In 1997 we invented the three-layer breather membrane. This technology is now used across the UK because it significantly reduces carbon emissions from dwellings.

In 2013 we became aware that our technology was causing a problem for bats. We contacted a PhD student, Stacey Waring, to find out more. She brought us samples of material which demonstrated that the nonwoven fibres used in the construction of the product (the fibres are half the width of a human hair)  could be broken by bats and fluffed up.


Some kind of protective layer, such as a net, to prevent bats getting access to the nonwoven seemed to be the answer but it’s size and dimension needed to be determined. Stacey offered to undertake sponsored research at a bat hospital. This work gave us answers on net mesh size (2 – 6mm). This would not only reduce access to the nonwoven by the bat but also maintain the breathability of the roofing underlay. We now needed to identify a net suitable for both roofers and ecologists.

We undertook trials of different nets using various adhesives. Stacey recommended woven glass fibre as being a suitably strong material but, unfortunately, its weight and cost made it impractical.  We had the same problem with many of the nets we trialled.


It was during this work that we noted that fibre breakage of the nonwoven did not necessarily lead to fluffing. It was the fact that there was no restraint on the bat’s ability to tease the fibre out that was the problem. We solved this by developing a sheet of breathable adhesive, which we laid down between the net and the nonwoven, thereby limiting any fibre breakage to the dimensions of each mesh square (<3mm). We now had two barriers to fluffing up; the net itself, and also a limit to the length of a fibre. How could this be tested?


Three tests were required to convert our bat hospital results into a test method to ensure industrial quality control:

 • The net. We adapted ISO 105 X12:2016 as a method for ensuring the abrasion resistance of the net was according to our specification

• The breather membrane. We found that a 3mm mesh size would not impede the breathability of the roofing underlay but would restrict access to the nonwoven material by the bat. Luckily, Stacey had already undertaken some helpful work in this area. By modifying a test method used by the textile industry to measure pilling (ASTM D3512 measures fibre breakage) Stacey had already modified this test method, so that it replicated the ‘plucking’ action of bats. She estimated that 3000 rotations of the pilling machine would replicate bat activity for approximately a year. We ran this test for 75,000 cycles ( this represented the 25 year life of a roofing underlay). There was no evidence of fluffing of the non woven layer.

• Batsafe. The whole structure was subjected to an aging test (EN13859-1:2010) to ensure that the finished product would still be structurally sound having been exposed to high roof temperatures over a long period of time

How safe is BatSafe?

Since innovation always precedes regulation it is inevitable that there is a period when products are commercially available before independent test protocols are established. During this period the consumer must be guided by evidence-based information along with trust in the efficacy and experience of the company developing new products. TLX Insulation Ltd has some experience in this area having developed test methods for evaluating the performance of new roofing materials that have subsequently been adopted by international bodies. 

On the basis of our research, experience and testing, it is our view that BatSafe will reduce the risk of bat/fibre entanglement. BatSafe is intended for areas where there is evidence of bats and should not be used where roosts are found.

Pilling Test


TLX BatSafe has been tested using the industry recognized Pilling Test method BS EN ISO 12495-1:2001, to measure its anti-fluffing properties. The Pilling Test was used to test the anti-fluffing of the product across its whole structure. The test was terminated at 75,000 rotations or before the fibre length exceeded 3mm.     

Standard Breathable Membrane




TLX BatSafe





Filament strand thickness test


Test to determine the filament thickness difference between a nonwoven breathable membrane and TLX BatSafe mesh. 

Average breather membrane filament strand thickness

Characteristic: Strand

Value: 15µm


Average TLX BatSafe mesh filament strand thickness

Characteristic: Strand

Value: 790µm



CE Mark

The functional breather membrane is CE-marked in accordance with harmonised European Standard BS EN 13859-1 : 2010

TLX BatSafe Technical data










Basis weight



Roll weight



MD Tensile Strength



MD Elongation



CD Tensile Strength



CD Elongation



MD Nail Tear (CE)



CD Nail Tear (CE)



MD Tear Strength



CD Tear Strength



Hydrostatic Head


cm H2O

Water Vapour Transmission (Sd)




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