Cold bridges: the hidden culprits behind moisture and condensation

A thermal bridge often occurs in all places where insulation does not connect properly. You can therefore sometimes detect a thermal bridge very clearly around exterior doors and windows, where the insulation is not optimally connected to floors or the door and window openings themselves. A few millimetres of opening are enough to allow a thermal bridge during a cold winter period. Of course, a few millimetres of insulation loss will not cause serious moisture problems, but it will slightly increase energy bills.

Some examples of places where thermal bridges can occur:

• Transition from a wall to a window
• Window frames
• Eaves
• The place where the floor is in contact with the cavity wall

You cannot always see a thermal bridge, but you can feel it. If you rub your hand over a piece of wall or floor and notice a difference in temperature, you are dealing with a thermal bridge. If you see black mould or condensation on concrete slabs or windows, that could also be an indication of a thermal bridge.

Cold bridges are the cause of a lot of moisture problems in the home. Especially alarming is the structural moisture damage it can cause on the cold wall. A cold bridge weak enough to cause the wall temperature to drop below 14°C works moisture problems such as condensation in hand. Where indoor moisture (which is naturally present in warm indoor air) can condense against walls, get fungi a chance to form and moisture stains also develop. Houses with condensation and mould are additionally just not good for the health. Moreover, it is bad for plastering, wallpaper and/or painting. With wood structures, it can then cause the wood to rot, resulting in instability. It is a real domino effect.

Because the walls at the level of a thermal bridge cool down significantly, the natural moisture in the air will condense in these places. Not only do cold bridges cause moisture problems, but they also cause another major problem: energy and heat loss. As mentioned earlier, thermal bridges create a temperature difference between the wall where there is a thermal bridge and the rest of the house. So in winter, you will need more energy to heat your home, resulting in higher energy bills. With today's high energy prices, you naturally want to avoid these.

The Flemish government encourages homeowners to better insulate and airtight renovate houses (think cavity wall insulation or crepi / exterior wall insulation). A renovation aimed at eliminating cold bridges has several benefits for property values:

• A more positive K-level (a degree of thermal losses through the building envelope)
• A more positive E-level (a measure of a building's overall energy performance)