Reducing condensation in the loft

ThisIsWeird

TuppenceHapenny said:

ThisIsWeird said:

Yes, we need more info from TH - what is the actual issue, and is it just an occasional 'winter' one?

The house isn't always heated properly in winter and the loft hatch is sometimes left partly open to allow heat from the house into the loft (to help prevent a frozen pipe), so there will be more moisture than normal entering the loft, though only in very cold weather.

I wonder if using a fan to circulate air around the loft will also induce air to flow in and out via the soffit vents, therefore helping to remove any moisture that the circulating air has evaporated?

As FreeBear has said above.

Allowing heat from the house up into the loft is a no-no - it can cause more issues than it may guard against.

Bear in mind that, without any ambient/inherent warmth in the water, lagging won't ultimately prevent freezing, so you need to take other steps to ensure you don't suffer from frozen pipes. The simplest is usually to drain them :-)

To make the best decision on how to protect, you need to outline the actual situation - is the house heated at all? If so, when and how? If not, ditto.

Albermarle

ThisIsWeird said:

TuppenceHapenny said:

ThisIsWeird said:

Yes, we need more info from TH - what is the actual issue, and is it just an occasional 'winter' one?

The house isn't always heated properly in winter and the loft hatch is sometimes left partly open to allow heat from the house into the loft (to help prevent a frozen pipe), so there will be more moisture than normal entering the loft, though only in very cold weather.

I wonder if using a fan to circulate air around the loft will also induce air to flow in and out via the soffit vents, therefore helping to remove any moisture that the circulating air has evaporated?

As FreeBear has said above.

Allowing heat from the house up into the loft is a no-no - it can cause more issues than it may guard against.

Bear in mind that, without any ambient/inherent warmth in the water, lagging won't ultimately prevent freezing, so you need to take other steps to ensure you don't suffer from frozen pipes. The simplest is usually to drain them :-)

To make the best decision on how to protect, you need to outline the actual situation - is the house heated at all? If so, when and how? If not, ditto.

Although I have seen advice to do that many times ( leaving the loft door open when away in the winter and the heating is on low).
I never realised that it could cause its own issues.
Every day is a school day !

Lorian

Even If you go up to put the Xmas decorations away you need to do it really quickly. If I have to go up there this time of year I shut all the doors to all rooms first, but I could be accused of being a bit obsessive about humidity. 

ThisIsWeird

Albermarle said:

ThisIsWeird said:

TuppenceHapenny said:

ThisIsWeird said:

Yes, we need more info from TH - what is the actual issue, and is it just an occasional 'winter' one?

The house isn't always heated properly in winter and the loft hatch is sometimes left partly open to allow heat from the house into the loft (to help prevent a frozen pipe), so there will be more moisture than normal entering the loft, though only in very cold weather.

I wonder if using a fan to circulate air around the loft will also induce air to flow in and out via the soffit vents, therefore helping to remove any moisture that the circulating air has evaporated?

As FreeBear has said above.

Allowing heat from the house up into the loft is a no-no - it can cause more issues than it may guard against.

Bear in mind that, without any ambient/inherent warmth in the water, lagging won't ultimately prevent freezing, so you need to take other steps to ensure you don't suffer from frozen pipes. The simplest is usually to drain them :-)

To make the best decision on how to protect, you need to outline the actual situation - is the house heated at all? If so, when and how? If not, ditto.

Although I have seen advice to do that many times ( leaving the loft door open when away in the winter and the heating is on low).
I never realised that it could cause its own issues.
Every day is a school day !

I may be overstating the issue. I guess that a good column of rising warmish air from the house would naturally vent away very quickly from the loft. After all, air wont flow up unless the loft air is being driven away first! And, it shouldn't add to the cond up there since there's no-one living in the house, so theoretically no moisture being produced.
But, what a waste of energy if the heating is left on. There must surely be a better way?

Slinky

ThisIsWeird said:

Albermarle said:

ThisIsWeird said:

TuppenceHapenny said:

ThisIsWeird said:

Yes, we need more info from TH - what is the actual issue, and is it just an occasional 'winter' one?

The house isn't always heated properly in winter and the loft hatch is sometimes left partly open to allow heat from the house into the loft (to help prevent a frozen pipe), so there will be more moisture than normal entering the loft, though only in very cold weather.

I wonder if using a fan to circulate air around the loft will also induce air to flow in and out via the soffit vents, therefore helping to remove any moisture that the circulating air has evaporated?

As FreeBear has said above.

Allowing heat from the house up into the loft is a no-no - it can cause more issues than it may guard against.

Bear in mind that, without any ambient/inherent warmth in the water, lagging won't ultimately prevent freezing, so you need to take other steps to ensure you don't suffer from frozen pipes. The simplest is usually to drain them :-)

To make the best decision on how to protect, you need to outline the actual situation - is the house heated at all? If so, when and how? If not, ditto.

Although I have seen advice to do that many times ( leaving the loft door open when away in the winter and the heating is on low).
I never realised that it could cause its own issues.
Every day is a school day !

I may be overstating the issue. I guess that a good column of rising warmish air from the house would naturally vent away very quickly from the loft. After all, air wont flow up unless the loft air is being driven away first! And, it shouldn't add to the cond up there since there's no-one living in the house, so theoretically no moisture being produced.
But, what a waste of energy if the heating is left on. There must surely be a better way?

My OH turned the heating down to about 7 degrees in his (new to him) house when he came to mine to help me prepare to move into his a couple of weeks later. The house got pretty cold as it was December. When we arrived there with all my stuff, he put the heating up to something like 20 degrees. He went into the loft a while later to put some stuff up, and it was raining condensation off the rafters and the sarking felt was glistening in the light. Never seen anything like it.  We thought there was a leak. Fortunately it stopped when everything settled over a few days termperature wise, but it was a scary thing to occur.

ThisIsWeird

Slinky said:

ThisIsWeird said:

Albermarle said:

ThisIsWeird said:

TuppenceHapenny said:

ThisIsWeird said:

Yes, we need more info from TH - what is the actual issue, and is it just an occasional 'winter' one?

The house isn't always heated properly in winter and the loft hatch is sometimes left partly open to allow heat from the house into the loft (to help prevent a frozen pipe), so there will be more moisture than normal entering the loft, though only in very cold weather.

I wonder if using a fan to circulate air around the loft will also induce air to flow in and out via the soffit vents, therefore helping to remove any moisture that the circulating air has evaporated?

As FreeBear has said above.

Allowing heat from the house up into the loft is a no-no - it can cause more issues than it may guard against.

Bear in mind that, without any ambient/inherent warmth in the water, lagging won't ultimately prevent freezing, so you need to take other steps to ensure you don't suffer from frozen pipes. The simplest is usually to drain them :-)

To make the best decision on how to protect, you need to outline the actual situation - is the house heated at all? If so, when and how? If not, ditto.

Although I have seen advice to do that many times ( leaving the loft door open when away in the winter and the heating is on low).
I never realised that it could cause its own issues.
Every day is a school day !

I may be overstating the issue. I guess that a good column of rising warmish air from the house would naturally vent away very quickly from the loft. After all, air wont flow up unless the loft air is being driven away first! And, it shouldn't add to the cond up there since there's no-one living in the house, so theoretically no moisture being produced.
But, what a waste of energy if the heating is left on. There must surely be a better way?

My OH turned the heating down to about 7 degrees in his (new to him) house when he came to mine to help me prepare to move into his a couple of weeks later. The house got pretty cold as it was December. When we arrived there with all my stuff, he put the heating up to something like 20 degrees. He went into the loft a while later to put some stuff up, and it was raining condensation off the rafters and the sarking felt was glistening in the light. Never seen anything like it.  We thought there was a leak. Fortunately it stopped when everything settled over a few days termperature wise, but it was a scary thing to occur.

Probably just coincidental, with a cold spell coupled with little wind?
If no-one is living in a property, then next to zero moisture is produced. Ergo, you can leave an empty house stone cold, but properly ventilated, with no resulting damp issues. But with frozen pipes :-)

TuppenceHapenny

Can anyone confirm (or dispute) the following description?
Using a fan to circulate air round the inside of the loft will create a pressure difference between the loft space and the outside air. That will cause a flow of air into and out of the loft via the soffit vents. Therefore, the circulating air will evaporate condensation in the loft and the air flows in and out via the soffit vents will be effective at removing the resulting moisture-laden air out of the loft. So the overall effect of the fan will be a drying effect in the loft (at least if used when the outside air has relatively low humidity).
Presumably the soffit vents only provide ventilation normally because on some days the air flows outside (ie. breeze) creates a pressure difference between the inside and outside of the loft leading to a ventilation effect (so if the air outside is static there's little or no ventilation occurring)?

Grenage

A fan in the loft, taking air from the loft and pushing it across the loft will not affect air pressure. 

Soffit vents work to some degree on still days if there are ridge vents, as the warmer air escapes through the top and new air can replace it from the soffits.

ThisIsWeird

I suspect a fan will help to evaporate the droplets and keep it suspended in the air, which will then allow it to escape via the normal loft cross-ventilation, but it won't be down to 'pressure difference' between the inside and out.
Bottom line - some visible condie is quite normal on the underside of the cold felt at certain times of the year, but is very rarely a cause for concern.
Personally, I would monitor it, and go from there. As soon as you have a couple of mild, dry days, chances are it'll be gorn.