The reality of daily energy use in A-rated homes

SEAI funded research

As homeowners and residents across Ireland strive to reduce their carbon footprint, we rely on the Building Energy Rating (BER) system to help us achieve Zero Energy Buildings (nZEB) compliance. We all know that A-rated homes are the most energy efficient - but how do they perform in the reality of daily use, compared to expectations? 

SEAI funded the nZEB101 project under the RDD programme to gather answers to that question; to uncover data from a large sample of homes built and retrofitted to high nZEB standards to observe how they performed. The lead researcher was Oliver Kinnane, UCD Associate Professor in Sustainable Building Technology, who oversaw a collaborative effort between academic experts and low-energy dwelling professionals. 

Research findings

The nZEB101 project found that most of the A-rated homes monitored are under-performing when it comes to the BER design expectation by an average of one band. This observation will inform the design of new low-energy homes across the country and will help SEAI to identify and promote ways in which issues can be addressed. The project found that while occupants report high levels of satisfaction with A-rated homes, “comfort take back” is often evident, which counteracts the energy efficient qualities of their homes. This happens when occupants of energy efficient homes increase internal temperatures following the installation of energy efficient measures, something that must be considered when designing low-energy houses. 

Reccomendations

The nZEB101 project’s recommendations include;

• the implementation of a whole life carbon approach to the evaluation of A-rated homes
• post-occupancy evaluations of retrofit and new builds
• widespread up-skilling of heat pump installers with greater care and checking of installation
• on-site testing of building fabrics using heat flux sensors at the time of retrofit or new build works
• guidelines for tenants on how best to operate energy efficient homes and their technologies
• stricter building controls, and revision of the Dwelling Energy Assessment Procedure methodology to account for more realistic internal (and external) temperatures

The data gathered through the nZEB101 project will ensure that we capture the necessary design and operations lessons to inform future design -  not just for project participants, but for wider industry.