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New ventilation standards for homes - aimed to control levels of condensation - are leaving Hebridean homes scoured by the blast of Atlantic gales.

Now local people are rejecting insulation schemes provided by the Government as they now involve getting holes in the walls to let the air in and out.   

SNP MSP for Na h-Eileanan an Iar, Alasdair Allan, yesterday raised in the Scottish Parliament local concerns over new UK-wide energy efficiency requirements.

Alasdair Allan was speaking in response to the Ministerial Statement on the Scottish Government’s Heat in Buildings Strategy.  New UK-wide industry standards for retrofitting energy efficiency measures now require fixed mechanical ventilation and window vents.

This has reportedly resulted in a decline in the number of people in the Western Isles who are willing to have insulation installed by providers such as Tighean Innse Gall, due to the accompanying mandatory ventilation requirements, which can cause significant draughts in many types of Hebridean properties.

Following a meeting this week with Tighean Innse Gall, Allan said: “In order to continue to reduce emissions and meet Scotland’s ambitious climate change targets, we must all be working towards making our homes and workplaces more energy efficient.

"This should in turn help alleviate fuel poverty in the long-term. Current figures suggest that 56% of island residents are in fuel poverty, which is the second highest rate in Scotland. We must be doing everything we can to make home insulation attractive.

“However, the mandatory ventilation measures that Trustmark insulation providers are now having to adhere to seem to be somewhat counter-productive, and unsuitable for the local environment here in the Western Isles.

"The idea of cutting holes in walls in the name of ventilation in order to comply with these new regulations is understandably leading to people rejecting insulation schemes from providers such as Tighean Innse Gall.

“I look forward to meeting with the Minister for Zero Carbon Buildings and Tighean Innse Gall in order to discuss these issues in more detail.”

Stewart Wilson, CEO of Tighean Innse Gall, commented: "Over the last 20 years we have successfully delivered industry-recognised high quality insulation installations with customer care at the heart of what we do.

"It is therefore very concerning that we will have to apply the UK PAS standard for ventilation without considering the mean wind speeds we experience on the islands. This inevitably will mean the very people we are seeking to lift out of fuel poverty would be left with a much draughtier house risking even higher heating costs to maintain a level of comfort". 

The new rules are:


PAS2035 Annex C.2.1 For every dwelling proposed for improvement, the Retrofit Designer shall use the information provided by the Retrofit Assessor to assess the adequacy of the existing ventilation according to the following criteria.

C.2.2 - Existing ventilation shall be assessed as inadequate for the improved dwelling if one or more of the following are apparent:

  • there is evidence of condensation and/or mould growth in the dwelling;
  • there is no ventilation system, or the ventilation system is incomplete or not functional;
  • there are not undercuts of at least 7 600 mm2 beneath all internal doors, above the floor finish, to allow air to move through the dwelling;
  • there is no provision for purge ventilation of each habitable room (e.g. by opening windows) as required by Approved Document F [N11].


Each habitable room and utility room requires 6,500mm2 of background ventilation - this number relates to the air that flows through the size of the vent openings.

  • A window trickle vent would provide 4,000mm2
  • A 6x9 wall vent would provide 10,200 mm2