Imagine it is winter.
You wake up in the morning, put on your favourite hand-knitted wool socks and walk to the kitchen to have breakfast. But something is different today, your left toes are cold, you start to shiver and feel uncomfortable.
What happened? The fabric on the toes has worn-out, there is even a little gap. The socks that used to keep your feet warm and cosy have a leakage and they are not able to keep you warm any more.
The same principle applies to a house. The building envelope’s task is to protect its occupants from the environment and to keep them warm. The building envelope needs to be a continuous shell, each little breach will negatively influence the overall performance and reduce the insulation’s potential benefits.
Thermal bridges and air leakages will increase the need of supplementary mechanical cooling and heating, but they will also increase the Relative Air Velocity and the Mean Radiant Temperature which will negatively influence the well-being and the comfort of the residents.
Thermal bridges are paths that heat can pass along, regardless of your insulation. A thermal bridge is formed when your insulation layer is bypassed by a very conductive material, allowing heat to be transferred through a wall, ceiling or floor. Thermal bridges allow heat to sneak past your insulation and reduce its overall effectiveness.
Ventilation on the other hand is the process of “changing” or replacing air to regulate temperature and moisture control amongst other things
By applying the right design features, natural ventilation and cross ventilation can be used to control indoor temperature and therefore reduce the energy bill significantly.
Or going even one step further, using a heat recovery ventilation system to regulate the indoor temperature and air quality. In short, thermal bridges and air leakages will increase the need of supplementary mechanical cooling and heating and will make you feel uncomfortable.
Please be aware: Air-leakages and thermal bridges are not accounted for in energy ratings, they assume air-tight buildings. But sadly, this is far from reality. This can majorly limit the ability and the potential benefits of insulation and other passive solar design solution and can turn a good designed 7 or 8 star home on paper into a cold and draughty home.
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.