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Published on 22 April 2016 09:13

Reducing the Performance Gap Through Fabric First-NLU

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Key Learning outcomes
  • Introducing the performance gap and recognising its impact
  • Identifying why the performance gap exists and solutions to address it
  • ‘Fabric first’ – benefits of continuous insulation and calculated construction details
  • Understanding the impact of thermal bridging on energy efficiency
  • The importance of airtightness

We all see adverts for new cars that quote carbon emissions and fuel efficiency figures, and maybe you’ve bought a new car based on those claims. Does it achieve the performance you expected, or have you had to adjust your expectations to meet what the car is actually capable of?

Even if you don’t look at performance data, nearly all of us are aware of the emissions scandal that surrounded Volkswagen and their engines. Disparity like this, on any scale, is a performance gap.

There is an increasing body of evidence that our built environment suffers a similar problem. Various studies examining differences between the energy efficiency of buildings ‘as designed’ and the actual ‘as-built’ performance have shown that, in extreme cases, heat losses from both domestic and non-domestic buildings are as much as three times greater than anticipated.

We buy homes based on Energy Performance Certificates and compliance with Building Regulations, putting trust in everybody involved with delivering our building stock that what gets built reflects what was intended at design stage. But if that compliance isn’t translating to reality, how can we address that and deliver the right quality buildings?

1.0 Why the performance gap matters

To some extent, how we live in a building is as important as the building itself. Just as the way one person drives a car changes how it performs compared to someone else driving it, so being more careful about the way we use energy is to the benefit of a building’s performance.

But that doesn’t mean construction quality can be ignored. Healthy, comfortable and thermally efficient buildings should be standard – not ‘added value’. The focus in future may well be on measuring as-built performance, with regulations based on what is achieved rather than what should be achieved.

Changing climate
That will take time to implement, however. Time we don’t necessarily have, because climate change is already happening and the impacts are likely to be "severe, pervasive and irreversible" (Intergovernmental Panel on Climate Change, 2014). Statistics show that CO2 emissions, global temperatures, average sea levels and the cost of energy are all rising, resulting in environmental, economic and social impacts globally.

These impacts, as well as the continuing depletion of finite resources, will only get worse if the status quo is maintained. Even if the realities don’t appeal to our conscience or sense of responsibility to future generations, the effect will be felt by our wallets. Fuel poverty is a very real problem for many homeowners, and reliance on imported energy will only raise prices further.

If the energy consumption of a building is greater than calculated at design stage, then its CO2 emissions will also be higher than predicted. The UK Climate Change Act 2008 (and the Climate Change (Scotland) Act 2009) committed to an 80% reduction in greenhouse gas emissions by 2050, relative to 1990 levels, with suggestions after the 2015 Paris climate talks of going even further.

Our building stock accounts for half of total emissions, but the current disparity between real performance and the compliance achieved on paper means the 2050 target will not be met.

Numerous organisations have researched the performance gap and canvassed the opinions of industry. Perhaps the most notable is the Zero Carbon Hub, a non-profit organisation established to look at the delivery of zero carbon homes in England. The Scottish Government have also drawn on the Hub’s expertise when proposing solutions.

Achieving comfort
The performance gap matters because it is in the interests of us all to expect and achieve better performing buildings – for physical, emotional and financial comfort.
The global scale of climate change is hard to comprehend, but if we all aim to make our individual buildings perform better we can have a positive impact.
The global scale of climate change is hard to comprehend, but if we all aim to make our individual buildings perform better we can have a positive impact.
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