In Europe, strict regulations are in place to control thermal bridges and air-leakages to minimise the energy needed for heating and cooling. Furthermore, due to the colder climate, a lot of structural damage can occur if heat and vapour is able to ‘travel’ through building materials.
Unlike in Europe, the significance of avoiding gaps and thermal bridges is commonly unknown and not a regulatory requirement in Australia. Common practice often shows that there is barely attention paid to minimising gaps and thermal bridges, leading to unwanted thermal bridges and air-leakages and therefore increases the need for cooling and heating.
Requirements to minimise thermal bridges
Maximum values of heat transfer through thermal bridges are specified and need to get incorporated into the energy ratings. Windows and doors as well as junctions of different building parts and materials require much detailing during the working drawing stage, as well as on the building site. It’s the architect’s/designer’s responsibility to find and draw solutions to overcome thermal bridges, and the builder’s to build accordingly.
Although air-leakages and thermal bridges are not accounted for in energy ratings, they can majorly limit the ability and the potential benefits of insulation and other passive solar design solution. Consequently even a house with a 6, 7 or 8 star-energy rating could be draughty in winter. Avoiding air-leakages and thermal bridges means minimising unwanted heat gain or loss and therefore reduces the energy needed to cool or heat a building.
PASSIVE HOUSE PRINCIPLES
The Passive House Standard is a holistic construction certification standard that aims at avoiding thermal bridges throughout the construction.
“Passive buildings are thus comprised of a set of design principles used to attain a quantifiable and rigorous level of energy efficiency within a specific quantifiable comfort level under a “fabric first” design philosophy. To that end, a passive house building is designed and built in accordance with five building-science principles:
Thermal Bridge Free Construction
The insulation not only needs to be sufficient in thickness but also needs to be continuous. This means keeping penetrations through the insulation to an absolute minimum, and if not avoidable then using materials that are less conductive to heat (i.e. timber in place of metal) and/or incorporating thermal breaks (whereby a material that doesn’t conduct heat well separates the two conductive elements). Otherwise your wonderfully insulated building will have a number of thermal highways that will cause increased energy consumption and increased condensation risk whilst impacting thermal comfort.
An essential part of every Passive House is an air tight building envelope (see the requirement in the certification criteria). This ensures that there are only a very limited amount of gaps and cracks within your envelope, giving you full control over your internal environment and significantly improving thermal comfort – no more draughts!
Sufficient insulation is what’s needed within the building’s envelope, providing enough thermal separation between the heated or cooled conditioned inside environment and the outdoors. This improves thermal comfort and reduces the risk of condensation (no more cold internal surfaces in winter!).
Passive House (High Performance) Windows
It’s not just the solid areas of your building envelope that need to have good levels of insulation but your windows too. No more single glazing, but instead low-emissivity double or triple glazing with thermally broken or non-metal frames. The size of the windows should be appropriate to each orientation, to allow solar radiation to penetrate during the winter months (free heating!) but not result in too much solar radiation during the summer. Watch out for how well they’re sealed too, as leaky windows just won’t do.
Mechanical Ventilation Heat Recovery
Now this doesn’t mean that you can’t open your windows! The incorporation of a mechanical ventilation unit means that you simply don’t need to rely on opening them to achieve good indoor air quality. The unit effectively recovers heat and coolth that would otherwise be wasted whilst also filtering the air that’s coming into the building. This leads to fewer pollutants in the air and a lower risk of condensation meaning a healthier indoors.”
Want to know more about how to avoid thermal bridges and the passive house principles? Please don’t hesitate to call or email us.