Mandatory bat surveys required before insulating homes, Council of State rules

Insulation companies and homeowners must conduct thorough investigations into the presence of bats residing inside cavity walls before carrying out insulation work. The Council of State ruled in a lawsuit between insulation company IsoSun and the provincial government of Utrecht that simply using a camera to look into the space between the walls is insufficient.

This ruling from the highest administrative court in the Netherlands could impact the entire industry's operating procedures and potentially hinder the Dutch government's plans to insulate 2 million homes by 2030.

In 2019, the province of Utrecht imposed a fine on IsoSun and ordered the company to conduct ecological research on bats. The company disagreed with this requirement, but the administrative court ruled in favour of the province. The court had previously determined that IsoSun failed to fulfill its duty of care towards bats.

The Council of State acknowledged that insulating cavity walls conserves energy and aids in achieving climate goals. However, bats are legally protected, and these protections are not easily bypassed.

Other stakeholders, including government bodies, species protection associations, housing corporations, and other insulation companies, were allowed to share their views during the case. From their responses, the court observed that "there have been many developments in recent years, and methods have been found for a more large-scale approach to home insulation that also considers bat protection." The court noted that these new methods can also benefit private individuals.

Small bats, particularly pipistrelles, often crawl into cavity walls. Filling these spaces with insulation material can harm and even kill them. A camera survey runs a high risk of overlooking them since a pipistrelle bat is only as big as a matchbox.

One solution is to commission an expert to carry out an ecological study, which can significantly increase the cost of insulation. However, there are alternatives. Municipalities can conduct research and implement measures to maintain bat populations within their territory. Afterwards, the province can grant an exemption for the entire municipality, eliminating the need for expensive ecological studies for each house. The court did not pass judgment on this approach but did explain it.

The Dutch Ministry of the Interior responded by expressing its intent to roll out large-scale research nationwide. To this end, it has already allocated 44 million euros. The regulation is now up for consultation, and stakeholders can respond until September 9.