In most European countries, thermal mass is used as a matter of course. Although it takes  longer to heat up a house which contains a lot of thermal mass, it also takes a long time to cool down again. The thermal mass releases constant heat to the rooms and therefore heaters only need to be on a low setting or turned off completely.

Having said this, thermal mass is even more important in summer. Especially with the extreme heat waves we are seeing here in Australia. The thermal mass can soak up a lot of the heat and can reduce the need for mechanical cooling by a lot.

Unlike in Australia, split systems and ducted heating are rarely used overseas as they use only convective heat. The main focus lies on radiant heaters as they heat thermal mass. The main form of heating in Europe is hydronic heating, mostly in form of hydronic heating panels, but also as in slab heating. Other sources of radiant heat are wood or gas fire places. Hydronic heating is also way more allergy friendly than ducted heating or split systems. But this is more the subject for a separate blog post.

If thermal mass is combined with effective insulation and has good solar access, the interior is perceived to be comfortable, without the need for additional heating, even if the external temperature is well below 20°C. The combination of thermal mass and well performing insulation is a condition of passive solar design, as well as low and zero-energy housing.

If you are planning to even go a step further and build according to the passive house standard, thermal mass can still be really helpful, but hydronic heating is not that important anymore. Passive Houses in our mild Australian climate perform that well, that you barely need any heating or cooling. So typically one small split system installed somewhere inside the house is more than enough to help to take the cold edge out in winter and the cool down the house again in summer.

Thermal mass is an effective way to reduce the need for mechanical heating and cooling and to increase the comfort and well-being of the occupants. In order to perform at its best, it needs to be located appropriately and sized adequately, with a careful eye on insulation and thermal bridges.