Condensation in Loft


Postby tony77 » Tue Dec 15, 2009 12:01 pm

Could someone offer me some advice.

Our roof suffers from condensation in the colder months of winter. We believed we had remedied the problem when a roofer put 6 roof vents in earlier this year. During the mild end of the winter and obviously the summer, the roof was bone dry.

Suddenly since the cold snap has started the old problem has returned with avengance. The felt on the inside of our roof is saturated, despite the roof vents. Although the weather is cold, there's no wind, and therefore no air flowing around the roof.

The roofer who fitted the vents seemed puzzled as to why they hadn't done the trick. He confirmed our insulation was adequate. Can anyone suggest a way of sorting out this problem, does anyone suffer from this in their roof too.
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Postby Perry525 » Sat Dec 19, 2009 6:36 pm

There is a lot of misunderstanding regarding condensation.
Condensation is not about ventilating lofts.
Its all about your life style.
You cause condensation!
Condensation is down to water vapour that you produce in your day to day living.
Boiling a kettle, taking a shower or bath, doing the cooking, lots of things you do like hanging up wet washing indoors all put water vapour into your home.
Even your breathing, especially young children and animals running around.

This water vapour is held in the air in your home, until it reaches a cold surface.
On reaching a cold surface like a window, or the inside of your loft, the air cools and the water vapour in the air settles on a smooth surface like a mirror or window and forms visible condensation.
At the same time air is cooled by cold plastered walls and ceilings, where it moves into the surface and makes the walls and ceilings damp – its not always visible.

The way to deal with it is to block up all holes in the upstairs ceiling, make sure the loft trapdoor fits well, air tight is a good description. Keep the water vapour from entering the loft.
As plaster is totally transparent to water vapour (about 1.4 litres of water can move through an 32 square foot area of plaster a day) painting it with gloss paint is a good move.

Keep the kitchen and bathroom doors closed.
If you have extractor fans use them while and after cooking or taking a shower or bath.
If you don't have extractor fans then fit them.
An alternative is buy and use a dehumidifier, one that can extract about two litres of water a day (or more) will help.
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Postby vijendrasnv » Tue Dec 29, 2009 7:10 pm

We had the same problem in our room in winter season,did the insulation once again but in summer season.The problem is little bit less but not completely. :twisted:
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Postby Perry525 » Wed Dec 30, 2009 10:33 am

Condensation disappears during the summer, with the interior of the home warming.
Winter, is the time when condensation shows.
With cold walls, ceilings windows and floors.
Keeping in mind that we all breath out about 1.5 litres of water every 24 hours, old people less, young active people and animals more, we have to deal with this.
One way of getting rid of condensation is open a window for a short period, as water vapour always moves from warm to cold, a lot of it will disappear outside, however so will a lot of your expensive heat.
Another way is to raise the temperature of the room and keep the temperature steady all the time,, then the walls etc warm up and condensation doesn't show.
Where the above are expensive to do, then buying and using a de-humidifier will do the trick.
A de-humidifier produces heat which helps to raise the temperature of the room and in so doing it chills a coil inside that attracts the water vapour in the room, the down side is that when people turn their heating down or off overnight this is the time when the de-humidifier needs to be on, but it does make a noise and lots of people find this irritating – they turn the de-humidifier off at the time when it is most needed.
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Postby Rob260 » Sun Jan 10, 2010 10:53 pm

I recently had a new roof and now the loft is dripping with condensation. We did not have condensation before on the old roof and nothing else has changed since the addition of the new roof to explain why this has happened. The loft hatch is sealed, the loft is well insulated(exactly as it was before) without blocking the eaves/soffits, there are no water tanks, no holes in the ceiling, and no addition of any extra humidity due to change in lifestyle/amount of heat used etc...there is also ventilation via the soffits and facias. Nothing has changed other than the roof.

So can anyone please help and explain what the problem might be?
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Postby Perry525 » Mon Jan 11, 2010 11:09 am

[quote="Rob260"]I recently had a new roof and now the loft is dripping with condensation. We did not have condensation before on the old roof and nothing else has changed since the addition of the new roof to explain why this has happened. The loft hatch is sealed, the loft is well insulated(exactly as it was before) without blocking the eaves/soffits, there are no water tanks, no holes in the ceiling, and no addition of any extra humidity due to change in lifestyle/amount of heat used etc...there is also ventilation via the soffits and facias. Nothing has changed other than the roof.

So can anyone please help and explain what the problem might be?[/quote]

We are of course in the middle of one of the coldest periods for thirty years, so comparing this with what has gone before is perhaps wrong?
Thinking back to your old roof, why did you change it?
Depending on how old it was, it may well have been full of holes?
Probably your new roof has a waterproof membrane across it, put there to stop the leaking roof, letting water into the loft – and at the same time (perhaps) being water vapour permeable to let the moisture out?
The condensation you are experiencing is due to water vapour rising through the home into the loft.
From what you write, one is led to the conclusion that whoever designed the new roof, they were relying on the passing wind to clear the loft of water vapour.
However, during these past days there has been no wind and their strategy is proven useless.
Just like the Government who are spending millions of pounds on windmills that have produced zero amounts of electricity over the last weeks – no wind!
Condensation in the home is due to life style.
You make the water vapour – it rises passes through the plasterboard ceiling into the loft.
Sealing the trap door and filling all the holes in the ceilings and walls doesn't stop the water vapour passing through the plasterboard.
Up to 1.5 litres of water can move through 12.5mm plasterboard 8x4 sheet in 24 hours at 30°C.
At lower temperatures a bit less.
Plasterboard is very good at slowing the progress of fire, as it contains so much water it has to boil the water off before burning through.
Your solutions are:
Having filled all holes and gaps in the ceilings including in light fittings, paint the ceilings with gloss paint – to slow the passage of water vapour.
Pull the ceilings down fit thick plastic sheet under the joists and re fit etc;
Buy and use a de- humidifier.
Change your life style, create less water vapour, if you have extractor fans in the bathroom and kitchen use them keep the kitchen and bathroom doors closed.
Open the windows for a short time each morning, especially in the bedrooms where you will have created water vapour by breathing and sweating overnight.
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