Building Energy Efficient homes – 6 ways to reduce the energy performance gap

Building Energy Efficient homes – 6 ways to reduce the energy performance gap

The importance of improving the energy performance of buildings is widely acknowledged, with the UK government using Building Regulations (SAP and SBEM calculations and CO2 emission targets) to control, monitor and regulate energy efficiency within the built environment.

However, although all new developments are hitting the targets on paper, there is now significant evidence that suggests that new buildings are not performing as well in use when compared to what was predicted at design-stage. This difference between anticipated and actual performance is known as the performance gap.

How big is the performance gap?

Recent studies suggest that in-use energy consumption can be between 50% and 150% higher than estimated within the compliance calculations carried out during the design stage.

What causes the performance gap?

• Building energy performance is not solely dependent on how the building is designed and constructed. How the building is run and maintained will also have a significant baring on actual energy consumption.

• Predicted energy calculations for Building Regulations are based on standardised conditions (for example, standardised occupancy patterns and density). These assumptions can vary greatly from the actual conditions for buildings in use.

• Variations from the design specification that occur during the construction phase are not always communicated to the design and compliance teams, and may not be factored into the predicted energy calculations.

• Skills gaps can contribute to poor construction (for example, poor insulation detailing).

• Certain energy uses are not included within the predicted energy calculations, e.g. servers, external lighting, lifts etc. Some of these energy uses may be significant.

So how can you start addressing and reducing the gap?

#1 Good communication across all teams involved in the project

Some of the biggest issues are around communication. It can be a struggle communicate the intended energy performance for the design from the earliest stages. It is important to clearly show and share the design intent all the way through to the detailed or developed design.

The project’s energy aspirations must be communicated to the whole delivery team: all those responsible for designing, procuring and managing the project.

It is crucial that the key requirements around the driving forces of the energy efficiencies, such as airtightness or building commissioning, must be passed on to the subcontractors from the procurement process so they can be priced and included in the contract.

Also important is the communication back from site about what is, and what is not buildable.

#2 Do not start the build until the design stage is completed and ALL plans have been checked and compared

It is crucial that the design stage is sufficiently complete before onsite building is commenced. This will not only avoid any costly onsite delays or errors, but it will also stop the need for construction details being changed or even made up onsite.

All drawings and plans must be checked against each other – for example overlaying ventilation drawings with structural layouts – to make sure that designed routes are viable so that when energy measures such as ducting are installed, it won’t need re-routing, which could result in higher energy use.

#3 Don’t forget unregulated sources of energy

One point to remember is that the calculations that need to be undertaken for regulatory compliance do not account for all energy uses in buildings. They are commonly misinterpreted as predictions of in-use energy consumption, when in fact they are simply mechanisms for assessing compliance against the Building Regulations.

One area rarely considered at the design stage is the unregulated sources of energy consumption such as small power loads, server rooms, external lighting, and so on are. These typically account for more than 30% of the energy consumption in office buildings so must be included for a more realistic prediction of energy-use.

#4 Don’t use the guidelines as a minimum

The energy performance gap can be exacerbated by a tendency within the construction industry to see regulations as the ceiling rather than the floor of what must be achieved. This mindset needs to be changed with the global need to mitigate climate change through energy savings within the building sector.

#5 Take guidance from an independent professional source

One key to making sure all parties get it right is to bring in external independent professionals to carry out testing and commissioning. This will make sure that the initial calculations are correct and that the plans are followed.

#6 Monitor & Evaluate

Once the project has started onsite, check on progress and maintain a regular quality evaluation process. One good tactic can be to set out a benchmark plot – take the time to get everything right on this, and monitor performance to learn from potential mistakes. 

Need professional guidance?

Closing the energy performance gap is a very complex issue that requires input and collaboration from all areas of the project. At Energytest we offer a fully consultative service giving you professional advice on the design and construction of low energy and sustainable buildings, and practical solutions to achieving compliance. Talk to us today to see how we can help.