Moisture is everywhere around us, The air contains moisture.
We produce moisture ourselves by breathing and transpiring.
That produced moisture together with the moisture of cooking, showering and washing will add up to about 10L of moisture per day for a family of 4.
If your house is not ventilated enough, most of that moisture will remain in your house.
Leading eventually to problems that we can observe in mould, fungus, pests, timber swelling or peeling, timber rot and windows condensating. This all will result in a smelly and unhealthy home.
Hot air can contain more moisture than cold air, but when hot air flows by a cold surface like windows the air will cool down and condensate on the pane surface.
Even double glazed windows made from thermally not broken aluminium will condensate.
Starting with the frames and the sills. This will continue until the relative humidity level inside drops to about 55 percent.
Thermal bridges like not thermally broken windows should be regarded as construction flaws.
As even new houses don't have a moisture barrier on the inside of exterior walls, the excess moisture can penetrate the construction and start its devastating work.
In unheated rooms where the temperature can drop below 15 degrees C the air can not hold as much moisture as in heated rooms, that's why bedrooms & bathrooms usually have more moisture problems.
New houses made from concrete, wood and other materials usually take 12 to 18 months to dry, depending on drying conditions. Open your doors and flush the warm humid air out of your home for about 15 minutes as often as possible.
Solutions
Insulate your walls, roof / ceiling with the highest R values as possible.
Ventilate every day for at least 15 minutes.
Invest in a mechanical ventilation system with air intake trough a ground pipe, preheating the incoming fresh air.
Double glazing with the lowest possible Ug values.
Use thermally broken windows.
Be aware of thermal bridges in your house construction.
Keep bath and bedrooms above 15 degrees.
Apply a moisture barrier also on the inside of your exterior walls. This can be best achieved with 9mm ply sheathing.
