The way to understand this is: Water vapour is created by people in their home. It is produced by cooking, washing, drying, breathing, sweating, fish tanks, flowers, plants, animals.
When you breath out your breath is 100% full of water vapour. You probably breath out a litre of so every 24 hours.
Water vapour is programmed by nature to head for the nearest cold surface or area.
The molecules of water vapour are so small, they can pass through the structure of many solid objects. If you have rough cut wood, they can enter the wood itself where they condense if it is cold below dew point. If enough water vapour enters a piece of wood, mould can form, or even wood rot can start.
Like so many things in buildings, there is a lot of misunderstanding.
In the majority of instance as long as the wood heats up in summer and dries after being exposed to water vapour it does no harm.
But, there is big business involved, lots of people rely on this for their living.
So, while you can get rid of water vapour by opening a window and letting it out.....at no cost to you!
The accepted process is to line a room with a water vapour proof sheet, to stop the water vapour passing into the roof, condensing on the nearest cold piece of wood and causing mould or wood rot.
Then, usually the water vapour condenses on the nearest cold window, where it makes a mess, that can be soaked up with a towel.
When you have a plasterboard wall, plasterboard is transparent to water vapour, it passes through without making it wet, fibreglass insulation is also transparent, ditto.
However, you do want to make your room easy to heat, and once again, fibreglass is not the best product to use, fibreglass lets heat pass through, it also suffers from wind washing, that is to say that a draft passing fibreglass, pulls all the heat from it, water vapour can and does freeze inside fibreglass, when it melts, it makes it wet and useless as an insulation. Fibreglass only works well, when it is enclosed, like in a plastic bag or box. Finally, because you can never guarantee an air tight fit, warm and cold air can pass between the fibreglass and whatever it is supposed to fit next to.
The only useful insulation is always based on closed cell technology like polystyrene, polyurethane etc, which can be an interference fit, or if your cutting and measuring is not very accurate, it can be sealed with cans of spray foam.
The best currently available, if installed correctly is sprayed foam – this is expensive, but it does last for the life of the building and saves heating and cooling money all year round – for ever.
When you breath out your breath is 100% full of water vapour. You probably breath out a litre of so every 24 hours.
Water vapour is programmed by nature to head for the nearest cold surface or area.
The molecules of water vapour are so small, they can pass through the structure of many solid objects. If you have rough cut wood, they can enter the wood itself where they condense if it is cold below dew point. If enough water vapour enters a piece of wood, mould can form, or even wood rot can start.
Like so many things in buildings, there is a lot of misunderstanding.
In the majority of instance as long as the wood heats up in summer and dries after being exposed to water vapour it does no harm.
But, there is big business involved, lots of people rely on this for their living.
So, while you can get rid of water vapour by opening a window and letting it out.....at no cost to you!
The accepted process is to line a room with a water vapour proof sheet, to stop the water vapour passing into the roof, condensing on the nearest cold piece of wood and causing mould or wood rot.
Then, usually the water vapour condenses on the nearest cold window, where it makes a mess, that can be soaked up with a towel.
When you have a plasterboard wall, plasterboard is transparent to water vapour, it passes through without making it wet, fibreglass insulation is also transparent, ditto.
However, you do want to make your room easy to heat, and once again, fibreglass is not the best product to use, fibreglass lets heat pass through, it also suffers from wind washing, that is to say that a draft passing fibreglass, pulls all the heat from it, water vapour can and does freeze inside fibreglass, when it melts, it makes it wet and useless as an insulation. Fibreglass only works well, when it is enclosed, like in a plastic bag or box. Finally, because you can never guarantee an air tight fit, warm and cold air can pass between the fibreglass and whatever it is supposed to fit next to.
The only useful insulation is always based on closed cell technology like polystyrene, polyurethane etc, which can be an interference fit, or if your cutting and measuring is not very accurate, it can be sealed with cans of spray foam.
The best currently available, if installed correctly is sprayed foam – this is expensive, but it does last for the life of the building and saves heating and cooling money all year round – for ever.
