Mind the Gap

The blog was first published by the Scottish Civic Trust on their website, as a think piece prior to their 2015 annual conference.


Over the last decade, John Gilbert Architects has taken increasingly interest in the performance of our projects and the gap between design intention and performance in use. As part of this investigation, we have set up a dedicated building performance service (Hab-Lab) for our new build and retrofit projects. We’ve invested in the technology and skills to benchmark performance against our design data and national standards. We are also looking at new ways of helping residents understand how to use their homes better and educate ourselves on what works and doesn’t work for people. This approach to performance is still new within the construction industry and I’ll look at some of our current frustrations below!

A quick straw poll via Twitter reveals that although people understand the performance of their cars and mobile phones, very few people understand the performance of their homes. This correlates with our experience of designing new homes and retrofitting old ones. People find it difficult to optimise the performance of their homes, to control the heating and try to eliminate draughts (or ventilation) causing significant health issues.

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If people don’t understand performance, don’t value housing performance or the benefits of better performing homes, then they are effectively expecting the design and construction industry to think about this for them. But is the construction industry really that interested?

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After the Volkswagen fiasco, it is easy to be cynical about performance data from cars but it is unfortunately a fact that within the construction industry that new homes very rarely perform anywhere near their design intentions. Before we look at issues in existing housing, it is important that the performance gap in our new homes is eliminated, that users can get them to perform as predicted and can be comfortable and healthy within them. Are designers and contractors liable for the poor performance of new homes? Why is it that as designers we have no involvement in the education and management of housing stock? Shouldn’t the designers be more involved in the handover of projects, working with users and helping optimise performance?

In retrofit, the performance problems are more acute, approximately 30% dwellings in Scotland are defined as “hard to treat”, which means that the dwelling characteristics pose tricky problems for reducing energy consumption. Whilst there is a massive insulation programme starting within Scotland, and energy efficiency of our existing stock is defined as a national infrastructure priority, there are many areas where indiscriminate insulation work is storing up health and building fabric issues.

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The ECO scheme is perhaps the biggest retrofit funding programme and combined with HEEPS ABS funding gives funding to social landlords for upgrades to rented and owned homes. ECO funds external insulation and there are basic installation standards but has a great many funding exclusions which pose serious difficulties for retrofitting housing well.

For instance, the lack of funding for designer involvement in a project means that there is no consideration of the performance of the whole house, the criteria is simply how cheaply the insulation value of the fabric can be bumped up to a default standard. This means that tricky problems such as thermal bridges, exposed close walls or existing pipework is often left uninsulated, leaving space for mould growth and severe heat leaks. There is no allowance for ventilation which means we could be sealing up these houses, with mould potential, leading to asthma and other health issues.

A key issue with ECO is that the funding available is not aligned with the cost of the work, more with the cost of the carbon it theoretically offsets, therefore difficult types such as tenements either receive inappropriately cheap and flimsy interventions or are totally ineligible for funds. Most worryingly, cheap plastic-based internal insulation is being used on our traditional buildings, dramatically altering the moisture movement in walls and floors which has a high risk of accelerated rot and decay over time, actually encouraging the deterioration of buildings which previously had a long life.

It is extraordinary that the main funding for retrofitting and improving the performance of our existing building stock has very little performance input. If ECO is the only option, then we must rewrite the rules. It is clear to us that substantial sums of money are being invested in retrofit projects which are not achieving the performance aims and could be actively deteriorating our buildings and health.