Despite new efficient technologies, the actual performance of the heating, cooling or ventilation system of buildings is often worse than calculations or declarations. The good news is that EU policy makers have just committed to tackle this performance gap in the new energy performance of buildings directive (EPBD), writes André Borouchaki.
André Borouchaki is Chief Technology Officer at Danfoss.
I am sure this sounds familiar: You see that your hotel room has a new ventilation, yet you are desperate to open the windows because the air quality is poor. There is a new boiler in the basement of your multi-family house, but still, tenants complain about some apartments being overheated, while others are too cold.
What seems like random is a pattern that can be observed in many buildings across the EU. Investors are dumbfounded by the less-than-expected real-life energy savings, whilst occupants suffer from poor indoor comfort or air quality.
This is what is called the performance gap between expected and actual performance of heating, cooling and ventilation systems in our buildings. And this gap can be large.
Failure by system design
The failure is often made when designing and assessing the technical building systems: they are optimised for full load performance only. But these full load conditions persist only for a few hours of the year. For example, a heating system is often designed to correspond to minimum outdoor temperature of -15°C, when for the bulk of the heating season outdoor temperatures will be higher.
It means that a building with a “good” full load rating could perform worse during other times of the year, which are the real-life use conditions. It would be like rating the energy performance of a car at full speed only.
Under real-life use conditions, the system needs to deliver only a fraction of the energy output. This is also referred to as part load.
The good news is that technology is available to optimise the energy use of technical building system at varying part loads while maintaining comfort and air-quality.
How can the new EPBD help?
A recent assessment of Ecofys estimates that, in a conservative scenario with basic control technologies, optimising heating, cooling and ventilation systems including at part and full load would deliver €36b per year by 2030 in the EU – in addition to the savings triggered by replacing obsolete boilers by modern efficient boilers or heat pumps. With well-known technologies with low upfront investment and fast payback.
Negotiators from the EU institutions introduced a small provision that can have a huge impact for large buildings: Inspections must include an assessment of the capability of heating, cooling and ventilation systems to optimise their performance under part load operating conditions.
This is easy to do. For example, just have a look and see if the water circulator, fan or cooling compressor can adjust water or air flows to actual needs – so called variable speed pumps, fans and compressors. Or check if the radiators have a thermostatic radiator valve controlling the room temperature. A simple check list could be used by the inspectors depending on the building type.
The building owners will then know if the installed heating, cooling, ventilation systems can control part loads. If not, he will know what are the missing capabilities and functionalities and be able to take well-informed investment decision.
This is a good step for increasing trust of investors, improving living conditions for people, improving air quality in cities, and reducing greenhouse gas emissions.
Now the ball is in the national field to make the most out of this new approach set out in the EPBD. Thinking “actual performance” and “part load” needs to be in national laws for renovations and for new-built, and not only for the bigger buildings as required by EU law. It should be applied to all buildings at least when the heating or cooling generator is replaced or radiators are exchanged.