Bats and breathable roofing membranes

Preliminary Roost Assessment

Bats and Breathable Roof Membranes

Bats are a frequent consideration when it comes to development projects and the planning process. In the UK, there are currently eighteen species of bat, seventeen of which breed here. Bats are afforded the highest level of legal protection. This makes it an offence to intentionally kill, injure, capture or disturb bats, and to damage, destroy or prevent access to their roost sites.

In the UK, bats eat insects, making them important for pest control. They are also categorised as an ‘indicator species’, which means that their conservation status is used to assess the wider health of the natural environment, providing important information regarding habitat degradation or changes to insect populations, for example.

The need to consider bats as part of a development project runs right through a scheme’s lifespan, from initial conception and design, through to construction and operation. One area where this is applicable is with regards to building materials, specifically roofing membranes.

The last fifteen years has seen an increased focus on sustainability when it comes to buildings. This has led to the development of various types of roofing membranes, which are designed to replace traditional methods of roofing ventilation. However, whilst the installation of these membranes aids energy efficiency, many of them are harmful to bats (primarily breathable roofing membranes), whose wings and feet can become entangled in the fibres, leading to the death of the animal and localised damage to the integrity of the membrane itself.

Roofing membranes and your bat project

Across the board, biodiversity is receiving greater focus as part of the planning system, as demonstrated for example by the requirement for  Biodiversity Net Gain to be integral to a development project – benefiting biodiversity by leaving it in a better state than before. Biodiversity considerations are also important in association with general sustainability targets for schemes.

Consequently, the Bat Conservation Trust is involved in research into the safety of modern roofing membranes for bats.

The current advice from the Bat Conservation Trust is that at present, “the only ‘bat safe’ roofing membrane is bitumen 1F felt that is a non-woven short fibred construction” – bitumen 1F is hessian reinforced.

The Bat Conservation Trust states that:

In response to concerns about the acceptability of bituminous roofing felt, The Bat Conservation Trust indicate that bitumen is acceptable under Building Regulations compliance, if appropriate insulation is provided. Bitumen is considered to be a high resistance underlay.

Our ecologists are highly experienced when it comes to bat surveys, in relation to all stages of a development project and the planning process. Seeking  the advice of our ecologists as early on in a scheme as possible, ensures that any constraints are identified and addressed in a timely manner, and ecological opportunities are woven into the scheme as it progresses, meaning that areas such as choosing appropriate building materials can be integrated into the project upfront.