Dehumidifier in a cold house

heavymental

Reading articles and reviews on dehumidifiers is getting too much! We live in an old Welsh 2 bed cottage and in winter it's cold and damp. I bought a hygrometer to check on this and as I sit here now it's 14 degrees and 71% humidity (in the house). Admittedly we're a bit tight with firing up the oil fired heating but with the price of fuel we tend to keep it to a few hours a day and light the woodburner in the evening if we're in. I'm looking at adding some insulation in the loft and am also considering replacing the cement render with lime render to allow more breathability.

In the shorter term I've decided to get a dehumidifier to combat the issue and have decided a dessicant option would be best so that it works efficiently in the cold temperatures. The only thing preventing me from deciding and buying something is the power consumption especially with the bigger units. I'd whittled it down to the Ecoair DD1 Classic. I was hoping if placed centrally it would sort out the whole house but not sure if that's the case now.

Anyone got any thoughts or experience?

ddraver

Erm, not the best anecdote but the one in my parents house that's about that size only does the room it's in. Not to bothered by cold mind

joeyhalloran

Our Maeco DD8L seems to do the whole house when we run it in the upstairs landing. In Autumn our humidity got up to the 80% which is why we got it. We now run it now and again and maintain ~60%.

Desiccants are more power hungry but they are more effective for larger areas and they output heat, which sounds like you may want.

I think the DD8L is ~330w or 600w per hour, something in that range.

surrey_commuter

certainly no expert but I thought that old buildings had better natural ventilation and whilst I get your point about render I would look at other sources of damp (ie guttering).

If dehumidifier is costly to run work out if cheaper and/or more pleasant to turn the heating on for longer

First.Aspect

I live in an old stone Scottish cottage. The only way you are going to get on top of it is to warm the fabric of the house up a bit, so you reduce the condensation on the outside walls. When we first moved in it was -5 outside and the place hadn't been occupied for a few weeks, possibly longer. I reckon we burned through half a tank of oil warming the place up that first time.

Console yourself that this will be the only oil fired boiler you ever own. Sooner or later sales of new ones will be illegal and we will have an air source one in place of the nice green tank.

daniel_b

Ages ago we had discovered a long standing leak in our then kitchen - the joists and some of the floorboards were saturated, and some floorboards needed to be replaced.

I ordered a Dimplex 10 litre dehumidifier, but I think they made a mistake and sent me a 20L one instead, which was handy as it cost me £79.99, and I think it should have been at the time £160 odd.

Anyway, I digress, it did a good job in the kitchen, and latterly I now use it in my garage to try and reduce the moisture in there, as my turbo started going rusty :-(

I'll double check the model, but it does a good job, I normally have the dial set at about half way, and in this kind of weather it normally fills the tank within a day - it's certainly helped a lot with the moisture in there, which would otherwise be doing nasty things to the turbo, bikes, car, and various electric bits.

I run it hear round, but during the summer months it does pretty much nothing at all.

I haven't noticed a massive increase in leccy usage, but equally I don't think it would be strong enough to look after an entire house or floor.

rjsterry

heavymental said:

Reading articles and reviews on dehumidifiers is getting too much! We live in an old Welsh 2 bed cottage and in winter it's cold and damp. I bought a hygrometer to check on this and as I sit here now it's 14 degrees and 71% humidity (in the house). Admittedly we're a bit tight with firing up the oil fired heating but with the price of fuel we tend to keep it to a few hours a day and light the woodburner in the evening if we're in. I'm looking at adding some insulation in the loft and am also considering replacing the cement render with lime render to allow more breathability.

In the shorter term I've decided to get a dehumidifier to combat the issue and have decided a dessicant option would be best so that it works efficiently in the cold temperatures. The only thing preventing me from deciding and buying something is the power consumption especially with the bigger units. I'd whittled it down to the Ecoair DD1 Classic. I was hoping if placed centrally it would sort out the whole house but not sure if that's the case now.

Anyone got any thoughts or experience?

71% RH is really not good for your health or the building. Ideally it should be be about 50%. So definitely worth addressing.

As others have suggested, it is worth checking gutters and downpipes to make sure they aren't contributing to the problem. Also, if your kitchen and bathroom don't already have extractor fans, fit them to get the place better ventilated. These will be much cheaper to run than a dehumidifier, and if you do still go for one it will take some of the load off.

rjsterry

surrey_commuter said:

certainly no expert but I thought that old buildings had better natural ventilation and whilst I get your point about render I would look at other sources of damp (ie guttering).

If dehumidifier is costly to run work out if cheaper and/or more pleasant to turn the heating on for longer

They rely on having a fire burning in each room to keep air moving and remove moisture.

Defblade

Living in a stone Welsh house running on oil myself, I'd strongly recommend a Positive Input Ventilation system, eg Drimaster. It's basically a big fan that sits spinning quietly in the loft, pushing fairly dry, fresh (and given your insulation isn't the greatest, pre-warmed!) air into the house.
Sorted our streaming windows in about 48 hours and black mould problems over the next few weeks. You'll have no worries about providing air outlets in old stone!

It seems silly pushing relatively cold air into the house, and like it would need a lot more heat input to keep the house warm, but actually as it pushes the damp air out, the dry air takes far less fuel to warm it than warming air+water, so the heating bills go down

If you're set on a dehumidifier, then a desiccant is the type to get from your description, but they certainly are power hungry - I've got one in our detached, knackered, and damp-from-every-angle garage and it does a good job, at that cost...

Condensers really don't work well in cooler temps - we ran one in the same garage previously, trying to dry a car out, and might as well have not bothered.

heavymental

Defblade said:

Living in a stone Welsh house running on oil myself, I'd strongly recommend a Positive Input Ventilation system, eg Drimaster. It's basically a big fan that sits spinning quietly in the loft, pushing fairly dry, fresh (and given your insulation isn't the greatest, pre-warmed!) air into the house.
Sorted our streaming windows in about 48 hours and black mould problems over the next few weeks. You'll have no worries about providing air outlets in old stone!

It seems silly pushing relatively cold air into the house, and like it would need a lot more heat input to keep the house warm, but actually as it pushes the damp air out, the dry air takes far less fuel to warm it than warming air+water, so the heating bills go down

Cheers everyone for the advice. I'm pretty sure the house is all watertight with no guttering issues etc so think it is just the fact that it's a cold house and we live in a damp part of the world. It's a sunny morning here after early rain but the humidity outside is close to 90% so I won't be opening the windows today. I had looked at the PIV systems before but what I don't understand about it is that if the outside air is humid (as it is today) is it any good pumping air from the loft (which is just air from outside effectively) into the house? Also our loft is a bit smelly!

I decided to go ahead and get the dehumidifier and was amazed at how much water it pulled out of the air. Our bedroom was where it was most noticeable as the sheets felt clammy when it was really damp. I had thought before purchasing that I'd be running the unit in the house during the day but I figure that moist air will gradually be seeping in anyway so couldn't stand the thought of burning all that electricity. I've just been running it in the bedroom for a couple of hours to keep on top of it in that room and it's been a lot more comfortable although by the morning the humidity is creeping up again. I'll run it in the living room if it gets that really damp feeling but for now I'll just run it now and again I think and put it away in the summer when we can have the windows open more.