Condensation INSIDE, and how to deal with it.
There is something you need to understand: The air around us always contains water vapour. We, ourselves, are made up of something like ninety percent water. Its all around us, and part of us.
There's more:
Water is a primary product of combustion:
Fuel burned in air = carbon dioxide + water
That means the combustion that takes place whenever fuel is burned, whether its the gas fire or the food burned in your tummy to keep you warm, makes water.
The water vapour from the gas fire goes up the chimney or out of the flue (all being well), but the water vapour you exhale stays - mostly - with you in the room. The more bodies breathing in and out, the more water vapour there will be. Outdoors, this is carried away by the breeze. Indoors, if we don't deal with it by adequate ventilation, the moisture content of the air in that room will steadily increase.
There is something you need to understand: The air around us always contains water vapour. We, ourselves, are made up of something like ninety percent water. Its all around us, and part of us.
There's more:
Water is a primary product of combustion:
Fuel burned in air = carbon dioxide + water
That means the combustion that takes place whenever fuel is burned, whether its the gas fire or the food burned in your tummy to keep you warm, makes water.
The water vapour from the gas fire goes up the chimney or out of the flue (all being well), but the water vapour you exhale stays - mostly - with you in the room. The more bodies breathing in and out, the more water vapour there will be. Outdoors, this is carried away by the breeze. Indoors, if we don't deal with it by adequate ventilation, the moisture content of the air in that room will steadily increase.
Now, we need a to consider a bit of physics here, but I'll keep it as painless as possible.
The amount of water vapour that can be contained within any given volume of air will vary with the temperature. The warmer the air, the more invisible water vapour it can hold. When it can hold no more, the vapour will condense out as steam or fog, mist, or cloud, depending on the circumstances. If the temperature drops, fog will form. The cooler the air the thicker the fog. Warm the air and it will disappear again.
Few of us live in a foggy or even misty room (although a warm kitchen full of people and boiling pans on a really wet day can come close) but if this invisible water vapour comes into contact with a cold surface, it may well condense out as water droplets, in an otherwise warm room: Those very water droplets you see on the cold glass of those single-glazed bedroom windows on the right. If enough of them form, and those bodies in the room keep breathing out, they may well coalesce into bigger drops, then rivulets, and form a puddle on the window cill.
The amount of water vapour that can be contained within any given volume of air will vary with the temperature. The warmer the air, the more invisible water vapour it can hold. When it can hold no more, the vapour will condense out as steam or fog, mist, or cloud, depending on the circumstances. If the temperature drops, fog will form. The cooler the air the thicker the fog. Warm the air and it will disappear again.
Few of us live in a foggy or even misty room (although a warm kitchen full of people and boiling pans on a really wet day can come close) but if this invisible water vapour comes into contact with a cold surface, it may well condense out as water droplets, in an otherwise warm room: Those very water droplets you see on the cold glass of those single-glazed bedroom windows on the right. If enough of them form, and those bodies in the room keep breathing out, they may well coalesce into bigger drops, then rivulets, and form a puddle on the window cill.
Water vapour will condense on any cold surface that's below the local dew-point, not just windows. A cold wall will do the job just as well.
So! What's to be done?
There's rarely one simple answer. A multi-faceted approach is required.
First, deal with or eliminate the cold-spots. Double-glaze windows (SupaSash) for a great start.
Insulate walls and doors.
Second, ensure adequate ventilation. This is a problem in the winter, 'cos no one welcomes cold draughts, and we tend, these days to seal our homes up tight to keep them out. However, a steady change of air is vital in any living accommodation.
Most modern windows come with trickle vents. Many people dislike them simply because they let in the very draughts they dislike. Worse, if you live on a busy road, they let in noise. My personal preference is for separate ventilation arrangements in the exterior walls. There is a growing market for ventilators designed to supply a warm dry, fresh air stream, but a good old-fashioned air brick with hit & miss shutter is still the cheapest option.
What is really required is a slow but steady airflow through the building. That means that its not a good idea to overdo the draught-exclusion. One of the clever design features of old rising sashes is that they allowed a fair bit of air to pass without concentrated draughts. Replicating this; getting the right balance between adequate ventilation and a draught-free window, is something that every window designer frets over. (or should do).
There's rarely one simple answer. A multi-faceted approach is required.
First, deal with or eliminate the cold-spots. Double-glaze windows (SupaSash) for a great start.
Insulate walls and doors.
Second, ensure adequate ventilation. This is a problem in the winter, 'cos no one welcomes cold draughts, and we tend, these days to seal our homes up tight to keep them out. However, a steady change of air is vital in any living accommodation.
Most modern windows come with trickle vents. Many people dislike them simply because they let in the very draughts they dislike. Worse, if you live on a busy road, they let in noise. My personal preference is for separate ventilation arrangements in the exterior walls. There is a growing market for ventilators designed to supply a warm dry, fresh air stream, but a good old-fashioned air brick with hit & miss shutter is still the cheapest option.
What is really required is a slow but steady airflow through the building. That means that its not a good idea to overdo the draught-exclusion. One of the clever design features of old rising sashes is that they allowed a fair bit of air to pass without concentrated draughts. Replicating this; getting the right balance between adequate ventilation and a draught-free window, is something that every window designer frets over. (or should do).
the greenest option
You don't HAVE to put up with windows streaming with condensation! SupaSash can fix it.
SupaSash fixed this window in Hackney....
Read about Condensation OUTSIDE here.
...and this one in Erdington.