How-to with TLX Batsafe - scenario 1: Newbuild

How-to with TLX Batsafe  - scenario 1: Newbuild

If faced with a new development in an area which is desirable, but the desirability also extends to nearby Bats, what is the best solution when faced with this concern?

When looking at a small development (perhaps surrounded by, or near woodland) the very proximity of this means it may also be a desirable habitat for bats, and as a protected species mitigation measures need to be undertaken to ensure their welfare – in particular, that the construction fabric does not pose a risk.

Recent research has shown there is a danger of bats becoming entangled in modern breather membranes, with their claws being caught by the membrane’s polypropylene fibres, resulting in the bat becoming trapped. Because of this, the ecologist’s initial recommendation is that bitumen felt be used in a cold roof design rather than a breather membrane. Because these felts are vapour-impermeable, this would mean that the loft would need to be fully ventilated.

So this (1f felt) is not the best solution at all, mainly because more heat loss would occur via the roof, not only because of the introduction of cold outside air to ventilate, but also because if 300mm of mineral wool insulation is specified for the floor of the loft, it would be less effective, since it’s permeable to air which would blow through the upper layers.

New house design can often offer buyers the opportunity of converting the loft to a room at a later stage and using it for storage in the meantime. The concern is that having a ventilated loft with an open invitation to the bats to use as a roost, can make things difficult for the future owners both in terms of a potential loft conversion and because of the droppings they might create, falling onto the insulation and any stored items, making it impossible to clean, not to mention a health risk.

It is also quite likely that on the outside of the roof individual bats might use the gaps under the tiles as transient roosts, though the risk of becoming trapped in such circumstances is small.

So, in terms of new build, what is the best way to proceed?installing tlx batsafe in a newbuild cold roof

A compromise can be reached by using TLX Batsafe breather membrane, which is a conventional membrane with 2mm mesh either side so bats can cling without risk of contacting the membrane in-between. A similar size mesh has been used in retrofit where roosts have been found within lofts under breather membranes. The product has also been tested using a machine designed to mimic the abrasion produced by bat claws over extended periods and is fully LABC certified.

There would then be zero risk to any bats roosting under the tiles as new build properties use a vapour barrier under the ceiling joists (which means that water vapour is prevented from entering the loft). So, having a cold unventilated loft is possible, which comes with the corresponding energy savings. In addition, with the loft completely sealed, there should be no entry points for bats and the owners would not need to share their loft space with visitors!

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