Condensation in loft: How to dry / fix

[mattysk]

Hi all,

I know this is a common problem and covered on many other threads but my question is really about drying. We have condensation all over our roof in the attic (more about below if people are interested).

I have dessicant dehumidier - this basically sucks in moist air, takes the moisture out and fans it out as warm dry air.

I was thinking about putting that up in the loft for a few days but I'm worried that even though the air coming out is dry, its still adding heat and moving the air around in the loft. Could this potentially make the condensation worse?

Many thanks in advance!

A bit of history for those interested:

I had insulation put down last year so I'm thinking that its related. We do also seem to be producing loads of moisture. I bought a Hygrometer and the house seems to average about 70%. We're trying to open the window more when showering, cooking and drying clothes. I've also just bought a dehumidifier so hopefully we'll get that under control. I don't think that we do is excessive, we're just a normal family but I guess that with the windows being shut and the central heating on, normal families produce too much water!

Anyway - in the loft we are getting the insulation people back around to fit "easy vents". This will be the first thing to try but I get the feeling I'll be back on here sooner or later! The insulation does have a big gap around the eves and the eves themselves are dry so its a lack of ventilation higher up.

 

[JohnD]

We're trying to open the window more when showering, cooking and drying clothes.

Do you mean you are draping wet washing around the house? Then it will always be wet and no-one can help you.

//www.diynot.com/forums/viewtopic.php?t=160032

And no extractor fan when showering?

 

[mattysk]

I'm afraid that yes we are drying washing next to radiators.

I've previously lived in double glazed houses where we've done this. Some have had more people living in them and been smaller than our current house. It seems a shame to have to buy a tumble dryer and pay for the running costs when I've never seen this problem before. Feels like paying for something that should be free!

Having said that, if clothes really are the issue then maybe I don't have a choice. I was hoping that buying a dehumidifer would be good enough. If its really drying clothes that is the problem then there must be millions of people with this issue who just don't know about it. Maybe there is?

I had previously assumed that you needed a vent (which we don't have room for) for a tumble dryer but searching around there are condenser types so maybe if I continue to have problems I'll need to save up for one of those. Just another thing to go wrong though!

Is this the only alternative? Could it really be down to washing clothes?

 

[mattysk]

sorry, just saw your post about exctractor fan.

We have quite a big window in the bathroom I must admit that we have been bad at opening the window when its cold outside. Started doing this now.

Should that be enough? The external wall in the bathroom is basically taken up by a window and a bath so we'd have to have one put into a double glazed window. I'm guessing this will also be costly. Also do they need to be plugged into the mains somehow?

My other concern (and I guess this could also happen with windows) is that the eaves are directly above the bathroom window so any moisture could be going straight back into the attic.

 

[mattysk]

I've been reading all the posts that your link goes to and we are guilty of quite a few of those.

I guess I've just always been lucky not to have this issue previously. I also spoke to the person who lived in the house before (there were 5 of them and 3 of us). He'd never had this problem but they had electric heaters and little insulation.

Do you think that while I'm trying to sort this out I should use my dessicant de-humidifier up there?

On a little side note (I'll start a new thread if you think its worth it). We are getting the black spots on the nails in one of the rooms. Its right above the window and the near the eaves. The problem is that I don't want to pull the insulation any closer to the eaves but it sounds as though the problem is that its too cold above as the insulation doesn't quite reach that far. Any solutions?

Thanks in advance!

 

[JohnD]

the dessicant will absorb a tiny amount of water, perhaps a few ounces.

You can get a ceiling-mounted extractor that has a duct run through the loft to vent outside. Flop insulation over the duct to prevent condensation inside it, and tilt the horizontal run down towards the outside.

 

[dhutch]

the dessicant will absorb a tiny amount of water, perhaps a few ounces.

I too cant really see a dessicant dehumidifier doing much, how are you drying the dessicant, in the oven under the loft space...?

THe only way to solve it is to get the ventillation sorted, so why not just crack on and do that!



Daniel

 

[mattysk]

It's one of these that I've got:

http://www.meaco.com/proddetail.asp?prod=DD8L

Seems to remove lots of water from the house since I bought it (I've had it on full and it collects about 2 litres) so it seems to me (at least) that this could really help dry the loft out. Not a permanent solution just something to get rid of what's up there. Just a bit worried that by adding heat under a cold roof I'd do more damage than good!

Going to try and get on with ventilation but its going to take a while. If it involves buying a tumble dryer and installing vents in the bathroom / kitchen I wonder if its just as cheap to rip out the insulation? Pretty sure I didn't have this problem before it was installed.

 

[masona]

I have dessicant dehumidier - this basically sucks in moist air, takes the moisture out and fans it out as warm dry air.

Up to a point but returning warm mositure back into the room! The only way is more ventilation, I prefer soffit vents at the bottom and ridge tile vents or upper roof tile vents at the top for air flow circulation

 

[AronSearle]

In the loft?

Moisture in the rooms shouldn't be getting into the roof, or not enough that the eaves ventilation can't deal with it.

Do you have vapour backed plasterboard on the ceilings, and do you have any holes (poorly sealed down lighters, or a hole in the extractor ducting).

 

[mattysk]

No - the ceilings aren't vapour backed. Is there something I can coat them with? The house was built in 1970.

I've had a look around and there's one tiny gap in the airing cupboard, and a couple of tiny ones at floor level in the bathroom (both upstairs). Not much but I will be sealing them.

The loft hatch is well sealed.

I have vents near the eaves, I think these are ridge tiles (slightly raised at the edge of the roof) and there seems to be quite a few. When you open the hatch you can feel the air and cold.

Near the eves are dry but its wetter near the top so the company that added the insulation are going to put easy vents higher up so try and get the ait circulating up there.

There is also a sort of raised tile right on the apex of the house. Under this is an old pipe that I think was used in the original air heating system. When you look up the pipe you can see daylight and I can actually feel a little wind under that which I though would be helping. There's a little water under this so I'm not sure if this is condensation dripping or something to do with the driving rain that we have had.

We have a condenser boiler but the condensing part goes to the soil pipe in the bathroom. Although thinking of it, doesn't that have to vent outside through the roof to remove smells? Perhaps its worth me asking the plumber around to take a look and make sure that its not an issue?

The only other source of heat up there could be a hot water pipe that goes to the bathroom.

I don't think this started happening until we put down insulation. The surveyer just said that "whenever you put down insulation you change the thermal dynamics of the house" - which kind of makes sense to me but if that involves structurally damaging the house, or paying for all the various fixes there surely comes a point where removing insulation, or at least a layer of it becomes cheaper than the extra gas used to heat the house!

 

[mattysk]

I have dessicant dehumidier - this basically sucks in moist air, takes the moisture out and fans it out as warm dry air.

Up to a point but returning warm mositure back into the room! The only way is more ventilation, I prefer soffit vents at the bottom and ridge tile vents or upper roof tile vents at the top for air flow circulation

That's what I was afraid of. Although I'd hoped that the air it puts back in would be dry.

 

[JohnD]

doesn't the machine have a bucket or drain hose where the collected water can be taken away?

I don't understand how an electric dessicant device works. Usually dessicant suggests a material like silica gel which absorbs the water, then is dried out again by heating in an oven or something.

 

[mattysk]

From the manual - this is how it works:

A desiccant based dehumidifier draws the air in from the room over a filter and passes it over a rotating wheel that is full of a material called Zeolite which absorbs the excess water out of the air. The wheel is now saturated and needs to be regenerated. A heater in the base of the dehumidifier blows warm, dry air over the Zeolite to force the moisture out of the wheel. The Zeolite is now ready to dry again and the warm, wet air from the wheel hits a metal surface which ensures the excess moisture condenses and the water drips into the internal tank. The heat used during the drying process is mixed with the dry air to ensure that the air that comes out of the dehumidifier is not just drier but 10-12°C warmer than the air that came in

So reading through that, the air that comes out would be drier but I'm a little concerned that by heating the loft it would create more of a difference between outside and inside temperature and would create more condensation. At least for a short while while it get to grips with the moisture. Hmmmm not sure really.

I have another question that is related. If my windows are slightly open, would that let moisture out or bring damp outside air in? If it brings damp outside in, then I don't understand the point about condensation problems being caused by double glazing. I'm guessing that it depends on the time of year?

 

[JohnD]

outside air is usually colder than inside air.

cold air holds less moisture than warm air.

A metre³ of hot dry air in the Sahara contains more water than a metre³ of cold damp air in Manchester.

The humidity reading will be higher in Manchester but the amount of water will be lower due to the temperature difference.