Dehumidifiers…are they the answer to my problem?

2 years after some house renovations the front room and the sofa smell a little damp. The room is at the end of the house and hence probably doesn’t get a lot of air circulation (it’s also the gable end).

It’s an old stone built house and other rooms have various degrees of moisture in the lower walls however they’ve been like that for about 20 years and cause us no issues really (perhaps wooden flooring doesn’t let the moisture escape so it does so through the walls)

Anyway, I’ve just become aware of dehumidifiers…could a unit in my front room keep moisture levels down, air circulating and thus cure the damp smell (or at least it not getting worse)

If so…which and what sort do I need???

Cheers

Quite possibly. It’s fixed the (slight) damp issue in my basement.
More air circulation would usually be the first port of call though.

They help but one of them running intermittently won’t do much for the damp levels within a house overall, even a small one. We’ve found opening the windows early in the morning for 15-30 mins before the heating comes on far more effective in reducing any effects of damp. Colder drier air heats up more easily and tbh I haven’t noticed a difference in warmth since the habit of letting air circulate early am. I like the fresh cool air too.

Yeah, it’ll certainly help but won’t solve the problem. We use one in the winter months when drying clothes inside.

Hiya,

We too have a stone house. Our damp problem was caused by poor pointing and wrong pointing material. Once I removed the cement pointing and replaced with lime mortar, all was good. I also dug down on one side and fixed drainage and let the walls breathe better it was all fixed.

Oh yes are the walls clad?

BR

JeZ

We live in a three hundred year old, solid brick wall cottage and have a dehumidifier running on low most of the year and it has cured all of the damp and black mould we used to get especially on our gable walls.

Dry air is easier to heat so the running costs are offset by reduced heating costs.

Positive air fan would sort it or maybe an extract fan with humidistat. If not possible Meaco dehumidifiers are good especially if you can run a drain hose from the unit . Otherwise you have to empty the reservoir often.

Maybe light the fire? That’ll draw the air through it like when it was built

They do work very well. We use ours in the kitchen to dry clothing, with the added benefit the moisture from cooking is removed – we no longer get mould forming on the bay window in the kitchen.

There are three types. Cheap Peltier ones that aren’t great, compressor ones that work well, and desiccant, The latter is supposed to be best, but reviews say they guzzle electricity so check the power consumption.

As reccomended off here we bought a maeco 8litre zambesi desicant dehumidifier.

Works a treat. Got timer controls so we don’t run it 24/7

Compressor dehumidifier with a 12-16l daily capability will work well.

We too have a stone house. Our damp problem was caused by poor pointing and wrong pointing material. Once I removed the cement pointing and replaced with lime mortar, all was good. I also dug down on one side and fixed drainage and let the walls breathe better it was all fixed.

Oh yes are the walls clad?

+1

What renovations did you have done? In old houses with no damp proof course, the walls need to be able to breathe so that they don’t get damp. That means lime mortar on the outside and lime plaster on the inside – no cement, because it doesn’t breathe. It also means traditional paints that are breathable. I would also be checking the drainage outside the property, corresponding to where you have the damp inside.

There are three types. Cheap Peltier ones that aren’t great, compressor ones that work well, and desiccant, The latter is supposed to be best, but reviews say they guzzle electricity so check the power consumption.

I’ve just posted about this as I’ve just been looking into buying one….. it’s not exactly that clear cut.

As above what were the renovations? Was adequate ventilation put in?

Positive Pressure Systems would help, and actually I think are a good thing in any old has that has a dampness about it.

TBH I am not a fan of the dehumidifier, yes they take the moisture out, but they dont help air circulation

If you are anywhere near North Yorkshire you can have the one I have sitting around doing nothing. (was used in previous house)

Bonus, just managed to fix the old dehumidifier that sits in the detached garage protecting the tools, bikes and camping gear. It’s a good 20 years old but the buttons had gotten unreliable and had a mind of their own eventually resulting in them doing nothing.

Was about to bin it then thought I’d try and access the circuit board and ‘buttons’. Got it to bits and the board was full of fluff. Brushed off and blasted the whole board and buttons with electrical contact cleaner. Back together and it’s working again.

It’s tatty, yellowed, but stops damp well in the garage. I’ve had times when all the surfaces are sweating due to a sudden temperature change outside.

Needed something fixing as our tent is polycotton and prolonged damp will do it no favours.

We went PPV.

Not looked back. Cost 350 quid to fit but has reduced our condensation issues to nil.

We used to get condensation on the windows….and we coped. Quick karcher vac and it was gone.

Replaced those windows with new double glazing. -the dew point moved to the dormer cheeks due to poor insulation- and this meant mould.

The PPV has removed that. I’d have loved to have gone full heat recovery ppv but there was no realistic way to do that without tearing the entire upstairs down 🙁

Having lived in a flat where the landlord deemed dehumidifiers a solution to the issue….. Id move house before I used that solution again. Effing racket , go away for the weekend and the dehumidifiers filled and return to that musty damp smell … No thanks

On the back of the info’ from this fantastic forum ordered a Meaco DDL8. Ran it since Tuesday, just got humidity down to fifty percent (two bed ground flooor maisonette). Wish id got a humidity meter at the start to get an initial reading (ThermoPro TP65C is great). Yes, it’s a little expensive to run. About a £1 a day, but the heating hasn’t been on so a save there. And the best news the damp / condensation has just about disappeared. Happy with that. A lot quieter than the old compressor type, lighter too.

A lot quieter than the old compressor type

Compressor dehumidifiers are very relevant and probably more efficient for your use case [if you’d read the Meaco info linked above!]

A dehumidifier will possibly just mask the issue. In a solid stone building damp on the inside of the walls doesn’t come in from outside, unless your gutters or pointing are shagged, it runs from the inside out over, water vapour from breath, cooking, washing & bathrooms condensing on the first cold surface it finds. If you’ve added insulation to the wall, not provided a vapour barrier surface or not fastidiously sealed it, you’ll end up with interstitial condensation between the new warm wall and the old cold one and potentially damp where you’ve got any bridging.

When establishing a vapour barrier, you have to be obsessive patching every nick, indentation or crack in kingspan’s barrier surface. Socket backings also need taping with foil tape, sealing cable openings and screw holes.

We’ve done this so well in our new kitchen that we get CO2 alerts if the extractor isn’t run on very low when we’ve got people over. We’ve a pair of MrXBox MHRVUs to go in the loft to provide ventilation to the house. They’ll be installed in the coming months but for now the extractor works fine.

They do work, and are arguably more efficient at heating than a lot of options because they emit substantially more heat than they use electricity.

But it takes a fairly big dehumidifier to do even a small job.  They’re best for small, sealed, unheated spaces, like boats left over the winter.

When it comes to keeping a house dry, you’ve got easy access to dry air (the outside world, cold air holds very little moisture) and heating.  So a better option is probably to just circulate some air from outside, then warm it up.

To put some numbers to that, lets say the house has a volume of 300m3

at 21C and 100% RH (say you’ve just cooked some pasta), that’s about 5.5kg of water.

At 5C it’s 1.8kg.

So just opening a couple of windows for a minute to fill the house with fresh air will remove 3.7kg of water.

It takes ~135kJ to heat that air back up again, or 0.04kWh.

TL:DR I have a dehumidifier in my gym-shed over the winter months to deal with the moisture when I’m not in there.  When I am in there I just open the windows.  Having said that, a reasonably efficient dehumidifier is probably as cost effective at heating as gas/oil and better than electric, so may well pay back over a few winters anyway.

There are three types. Cheap Peltier ones that aren’t great, compressor ones that work well, and desiccant, The latter is supposed to be best, but reviews say they guzzle electricity so check the power consumption.

Desiccant – works well in the cold (i.e. a shed / boat / garage) , expensive to run.

Compressor – works best at room temp, cheapest to run

I’ve got the DBBL8 in the shed on a timer, it comes on a couple of hours a day time just before I intend to use it to take the edge off the chill so it’s doing two jobs in one.