As explained in our previous article about thermal mass: the perception of temperature is more important than the temperature itself, when it comes to comfort.
In Australia, energy rating assessments are done pre-construction, assuming competent application of all insulation and building materials as well as draught sealing all wall penetrations.
However, common construction practices often demonstrate misapplications and air leakages. Sadly, although there are regulations in place on how to install insulation and how to seal of wall penetrations, there is no one really responsible for checking all those details, neither the builder, nor the architect, nor the building surveyor. In fact, some tradies even take out insulation, so that they can work easier around cables, fixtures and fittings and don’t bother to put the insulation back in. For sure, as soon as the plasterboard sheets are one no one can even see the problem.
This means that although in theory the house should be energy efficient, the reality will be far from that. It will be draughty inside. Cold air can come in. The energy bills will be way higher than the energy rating did predict. And, as explained in our article about thermal comfort, it will be hard to feel comfortable inside your ‘well insulated’ home.
In Europe, energy efficiency is most often assessed or checked post construction, with special attention to the prevention of thermal bridges. Some countries require airtight buildings, and amongst other things, double glazing, solar energy for hot water and heating systems, the usage of storm water, greywater recycling, recycled materials and product life cycle considerations to minimise energy demand and carbon footprint.
A good star rating, well performing insulation and building materials are not a guarantee for well performing homes and for feeling comfortable inside the house. The building envelope needs to be treated as a delicate continuous shell. Each small gap and leakage will impair the energy efficiency and the well being of the occupants. It is essential to consider the end product in order to determine how energy efficient a building really is.
Therefore I am a huge fan of the passive house standard. It’s an holistic approach that not only looks at the materials and insulation you use. But also considers air-leakage and thermal bridges carefully, making sure you have a truely energy efficient home.