Bats and Breathable Roof Membranes
Ecological considerations flow right the way through a scheme, from its initial conception, through the design stages, and onto the construction and operational phases of a project. Seeking the advice of our ecologists upfront, ensures that constraints are identified and dealt with in a timely manner, and opportunities are woven into the scheme as it progresses. One of the areas where ecological considerations are relevant, is with regards to building materials.
Development projects over the last twenty years, have seen an increased focus on sustainability. This encompasses a wide range of considerations in areas such as ecology, energy efficiency, water and waste. In the drive to achieve more sustainable buildings, there can occasionally be conflicts between the interests of different areas – modern roofing membranes being a case in point.
Modern roofing membranes and bats
The last fifteen years has seen an increase in the use of roofing membranes. These are designed to replace traditional methods of ventilation, and allow the roof of a building to breathe; whilst this may be good news for energy efficiency, it has proved to be bad news for bats.
The installation of modern roofing membranes (primarily breathable roofing membranes), has led to bats becoming entangled in the filaments by their feet or wings, resulting in the eventual death of the animal. The localised areas where bats affect the membrane, may also compromise its functionality.
Why do bats matter?
Bats are an important part of the natural world. They are classed as an ‘indicator’ species in the UK, as changes to their conservation status is indicative of wider changes in biodiversity, for example, insect population status or habitat degradation. Being insectivores, bats are also great for pest control, which benefits habitats such as crops and gardens.
As a result of significant declines in the number of bats over recent years, all species of bat are afforded the highest level of protection in the UK. This protection makes it illegal to intentionally kill, injure, capture or disturb bats, and to damage, destroy or prevent access to roost sites.
What does this mean for your project?
In terms of sustainability targets for projects, biodiversity is an important consideration, and is an area currently undergoing increased focus and integration as part of development as a whole, in line with growing awareness of its critical importance; this is being reflected in biodiversity’s increased integration into planning policy in areas such as biodiversity net gain.
The Bat Conservation Trust is actively involved in ongoing research into the safety of roofing membranes. They state that “currently the only ‘bat safe’ roofing membrane is bitumen 1F felt that is a non-woven short fibred construction”. Bitumen 1F is hessian reinforced.
Current advice from the Bat Conservation Trust comprises:
breathable roofing membranes/unwoven membranes should not be installed into a roof used by bats; and,
only bituminous roofing felt that does not contain polypropylene filaments should be used.
As far as Building Regulations compliance goes, the Bat Conservation Trust indicates that bitumen (considered to be a high resistance underlay) is acceptable if appropriate insulation is provided.
For further advice regarding bats and development, our experienced ecologists are here to help, so please do get in touch.