Mould in buildings is simply a result of high humidity over longer periods of time. When we notice it on surfaces it's likely after the fungus has already developed a network of mycelia inside the construction and it can be difficult (or impossible) to remove it permanently. Fungi in buildings emit toxic metabolic byproducts that can impact on the occupants health. We can assist in designing a building envelope that eliminates the conditions under which these organisms thrive.
Every building material has specific properties that contribute to the whole construction performance. Heat transfer and vapour permeability are just two of many which we can analyse for a number of applications in different climates of New Zealand.
Water is nothing more than a molecule that floats around as a gas when warm and turn into a liquid when cooled down. Excessive water (vapour) in the air can be problematic without a ventilation strategy (kitchen, bathroom, bedroom). But temperature of surfaces can be the reason already normal indoor air creates problems. Usually, it is a combination of both.
“Why airtightness? We never needed it before! The house must breathe”. That’s correct, in the past we didn’t need it. But in our quest for lower energy bills and global movement to sustainability, we have no other choice but embrace it. And with increasing requirements for insulation we can’t ignore it. As the insulation increases so does the temperature gradient and air passing through gradually cools down, condenses and causes structural damage or mould
All these terms say something about the amounts of water vapour that can pass through a material (or not) on a scale from "plastic bag to GoreTEX".
Every building material, from paint, plasterboard, insulation, or cladding sits somewhere on this scale. Sometimes mixing different types, or placing them in the wrong location in the construction, means trouble.
In buildings we refer to thermal bridges as changes in the building material in the same layer, e.g. insulation between timber framing, or changes in geometry, e.g corners and junctions.
It is easy to pay less attention to those areas, because they can be small and too difficult to resolve the traditional way. But they can give you grief in the long term.