A warm damp place is a haven for mould, mildew, fungus and rot. A rotten damp log in the woods is place where microbes can thrive in harmony with nature. The inside of our home, walls cavities or basement is not where we want this element of nature to thrive. Moulds and fungal spores are floating around in the air everywhere. In small amounts they are a healthy part of clean fresh air. Most of these microbes need all of the following to thrive:
- Air but little air movement
- Food Source
Many also prefer a dark environment. A basement without proper sealing from moisture and no ventilation can be a perfect breeding ground for unwanted microbes.
Less noticed but just as dangerous is the inside of a poorly constructed leaky house wall. In a moderately well sealed house without mechanical ventilation this moist air must go somewhere. If it travels through small cracks and holes in the walls it will (in the winter) meet cold surfaces.
As warm air can hold more moisture than cold the cooler moist air will at some point drop moisture within the wall. If the outside of the wall assembly is sealed better than the inside then the wall may never dry out. The wood in walls can be a food source for some microbes. Rotting wood can be a food source for others. One microbe can feed on another. This process of collecting moisture and breeding mould, mildew, fungus and rot can create a toxic mess not to mention undermining the structure of a building. These conditions can also attract insects and vermin. The feces from these larger life forms become food for yet more airborne microbes.
As weather and pressure conditions in and around a home are continually changing these toxins can them be drawn back into the home through the same path that the moisture first entered the wall. More and more people are becoming more and more sensitive to environmental toxins within their environment.
Avoiding these creating these toxins within our home is the best defence. A building envelope that is well sealed on the inside and vapour open on the outside is the best approach in a cold weather climate. Just as important is keeping humidity levels in the house down below 50% and providing a constant circulation of fresh air to all places in the house.