How does an external wall insulation influence indoor climate?
The current statutory energy saving guidance calls for the air tightness of the outer layer of a building to minimise heat loss and achieve the highest possible energy efficiency. This also affects the indoor climate of a house and makes it necessary for an appropriate ventilation system and also calls for a change in user behaviour towards energy efficiency.
Moist air that occurs for example, when showering, cooking or breathing, must be transported from the rooms to the outside. If poorly ventilated, the humidity in the rooms will be increased significantly and the building may eventually develop mould and thus become a risk to the health of its residents.
Without changes in temperature, there is no condensation - and no mould.
Uninsulated exterior walls tend to cause a build up of mould more frequently than well-insulated walls. This is because the uninsulated walls cool down more on the low temperature points. Therefore, the wall is much cooler than the room climate and as a result, this causes condensation which leads to moisture being retained in the wall. Mould can form when there is inadequate air circulation, particularly in outer corners and behind large furniture.
External wall insulation prevents this from happening by shifting the coolest point on the external wall to the insulation layer. Through insulating, the temperature of the inside of the wall is raised so that it barely falls below the room temperature, therefore condensation cannot be formed on the inner walls.
A professionally-applied external wall insulation system therefore helps to prevent heating and ventilation problems and eliminates mould. Not only that, even the indoor climate is noticeably improved. By equalising the temperature, drafts are eliminated which are common in uninsulated houses. Also, less heat is needed in order to achieve a comfortable room temperature.
In order to achieve a comfortable indoor climate, the external wall insulation system must be installed correctly. This is particularly true with regard to the connection details - for instance, window cills, shutter boxes or ports surrounding windows and doors. It is important to avoid gaps and thermal bridges in the airtight envelope around the building.
Tips for a healthy indoor climate
Proper ventilation is essential for a healthy indoor climate. Here are some tips:
- Let air out intermittently - open windows fully, but only briefly - say for about 5-7 minutes. Longer periods can cool down the wall around the window, and brings only a negligible exchange of air in the room.
- Note the relative humidity of 60 percent should not be exceeded.
- Heat up the home evenly and avoid large temperature differences. If you have some areas you require keeping cooler for example, the bedroom, close the door to stop the cooler air getting out.
- Take care with uninsulated basements, they should be properly ventilated, especially in the summer. Air from outside enters the basement, where it condenses on the cooler walls. Ventilate basements in summer only when the outside temperature is lower than the temperature in the basement - for example, cool nights.