Sharing your house with Bats?


Helping to reduce those CO2 emissions

Roofing and insulation practices have changed considerably in the last 30 years or so, with the drive to be zero-carbon. Legislation requires that when re-roofing or doing a conversion, the insulation should be upgraded to current standards, which means putting mineral wool on the floor of a cold ventilated loft, or insulation board between the rafters if there is a room in the roof or vaulted ceiling. Using a modern breather membrane rather than the old bitumen felt reduces or eliminates the requirement to ventilate with cold outside air, so saving heat.

There may be guests in the property you’re not aware of…

However, our houses may be home for more than just the families inhabiting them. Bats, which are a protected species in the UK, also make use of the roofs. Larger species require a loft space or similar to inhabit, and colonies of smaller bats may also be found there, especially if there is a summer maternity roost which they return to year after year. Smaller species, e.g. the 40mm long pipistrelle, prefer to roost in crevices such as under roof tiles and overhangs.

Conventional breather membranes are not suitable?

Unfortunately it has been found that where breather membranes have been used, the bats’ sharp claws pull out the unbreakable polypropylene fibres of the breather membrane, becoming so entangled that they cannot escape and so die.

Where does this leave the home owner?

Where does this leave the home owner wanting to re roof or convert a barn? If bats are found or known to be present, an ecologist must be consulted to prepare a mitigation plan, which would depend on the bat species and its requirements. Depending on the circumstances, this can range from providing a bat box to tailoring the roof structure to be suitable for the species found - but very often it means recommending the use of a bitumen felt. This then requires a 50mm ventilated space beneath if used with rafter-level insulation, and may then prevent energy efficiency requirements being met.

You’ll still need to act if there are Bats found in the area

Sometimes, even if there is no evidence of bats in the roof, but the local area is known to have bats, measures must still be taken to prevent them being harmed should they decide to get under the roof tiles, and a bitumen felt is still required.

Spring Hall, Halifax is a prime example

Take the example of Spring Hall in Halifax, the subject of a recent case study: no evidence of bats was found in the roof structure, yet since they were known to inhabit the surrounding woodland mitigation measures were required. But with only 75mm deep rafters and a lath and plaster ceiling intruding into that space, using a bitumen felt would mean that NO insulation was possible, so heat would escape straight through the roof!

TLX Batsafe provides a workable solution

The recently developed TLX Batsafe breather membrane proved the ideal solution here, enabling some insulation to be fitted, yet with no risk to bats should any decide to take up residence.


Read the Spring Hall case study HERE

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