Economic ' Heat V Ventilation' to reduce Mold

[N_Cook]

And you can site it where the fan will circulate air where its otherwise most stagnant mold-inducing

[The Natural Philosopher]

My experience suggests that would probably eliminate condensation altogether.

You might still get some on a slabbed concrete floor with no insulation, but I wouldn't expect much on the ceiling.

Carpet and underlay solves the floor.

roof insulation is not hard to install either.

I lived in a top floor flat for a year with solid walls single glazing and no loft insulation. It was f****ng cold. water poured of the sash windows and the walls got damp unless I kept an electric fire on all the time

[john west]

Returning to the original question about the unused bedroom (see below)

Is it a cold air flow (ie window slightly open ) or is it heating from the house upstairs landing that mold dislikes most ? Thanks.

__________________________________________________________

Elderly couple in terraced house built in 1936 with single skimmed walls. (so no insulating air space between an inner and outer wall). So being careful with not wasting heat is important what with the high cost of energy.

They have had mold easily growing on walls behind sofas and rarely moved furniture. So maintaining some air movement and some warmth become necessary to stop mold. Which is not difficult when rooms are regularly used.

But there is one small bedroom on the north facing side which is readily susceptible to mold since it is a very 'rarely' used room.

Generally all upstairs rooms are kept with their doors shut all day as that has been recommended to maintain heat in the house. (Reduces wind blowing through the house carrying away any warmth).

The question in this post is about what is the best way to treat this 'rarely' used little room to Economically reduce Mold.

Is it to leave this bedroom window open very slightly which gives some air flow, but let the room gets quite cold. Or is it to open the radiator slightly whilst keeping the door and window shut? Or leaving the door open to get some of the heat and air from the landing which seems good. But doing that is going to cost in terms of gas bills since this cold room will constant take heat from the upstairs landing and hence the rest of the house. Not increasing the Gas Bill if this can be avoided is largely behind this question. Grateful for any opinions.

[Theo]

Mould needs moisture to grow. Dry it out and it stops growing.

Fresh air will remove some humidity (although not always - eg when it's foggy or raining), and heating will make the air carry more water away, unless the heating itself adds more moisture (eg open gas flames). If you have both you can evaporate the dampness off the surface and carry it out the window.

But at the end of the day you need to remove the source of moisture. You need to stop it getting wet in the first place.

Theo

[Animal]

what sort of monster is this dehumidifier? Domestic models are typically 200w or a bit less. In a healthy house they should be not drying much of the time. 1.5kWh would be 7.5hrs of nonstop running every day - something's really wrong if that's happening.

Minimum clothes drying cost is to just hang them up. Next lowest is use a fan. Dehumidifiers will dry them too but not so quickly.

For the op, a dehumidifier is the cheapest option. It's also the most effective & sure to work.

[Animal]

Once you dry the air some, air movement will be immaterial. I'd put the dehumidifier wherever the prime source of damp is, typically bathroom or kitchen.

[Animal]

If the op's place is single skinned brick, do yourself a big favour and insulate it. You might find then there's no damp problem, maybe. Paying attention to the way insulation deals with damp is important.

Depending on how tight on dough the situation is, and how damp, there is the option to paint the wall/s with mould killing paint. Sometimes it's enough.

[RJH]

Yes, I was surprised. It's a Silvercrest SLE 420 A1, max 400ishW ISTR. So about 4 hours, assuming it's at 'full' setting on the clothes drying setting. In fact it was a bit rubbish, and seemed to capture a fraction of the water of the dryer.

Otherwise, it seems to work well - about 5l/8 hours when I very occasionally use it in the cellar during summer.

Anyway, the moral for me is check to see how much electricity the dehumidifier is using if you go that route.

Yes, obviously, but the thread was about reducing mould. An open window and a fan might help but that brings in a set of new problems.

Agreed, but it won't cure anything - it's a short term fix.

[Spike]

Others have suggested a dehumidifier. I would add using a desiccant-wheel type (works down to 1degC whereas a compressor type might be 15degC minimum) with a variable humidistat setting. If it has a 'low power' setting all the better, use that.

[David]

I think the consensus is that you are asking the wrong question if you are looking for the best/ most cost effective solution.

Cheers

Dave R

[Animal]

400w means either a site type machine or a desiccant wheel type. From the picture I presume the latter. Either way 400w is excessive for the job. And putting a dh on 'clothes drying' cycle to dry clothes is a pointess waste of electricity. Standard set point works fine, and uses, it varies but a tenth the energy is typical.

or pick a suitable machine & RH setting. Don't use desiccant wheel machines in a heated house, they use a fair bit more energy. They're for unheated spaces.

It's a good long term solution, often the best one.

[Andrew]

Even an industrial dehumidifier wouldn't use that much power. My 1986 Ebac Homedry is rated at 0.35Kh, 1.8amp (240 V), but when plugged into ine of those wattmeters it shows 250watts.

[Andrew]

I did my front two bedrooms, both North facing with nasty 'solid' (*)

9 inch blockwork and plastic shiplap on the front in 1992.

(*) 9 inch blocks with 2 large hollows allowing internal air cycling. Dreadful stuff.

Back then all there was was eps in 1 inch thick sheets, plus something 'new' with a pink panda logo on it, which was probably extruded poly but was four times the cost, so I just used inch thick poly on the inside after ripping off the plaster and mortaring all the 9-inch block perps which had been left *open* !!.

The improvement with just this minimal insulation was amazing mostly I suspect because I had fixed the horrendous air-leakage issues.

The larger bedroom with the class 2 flue blocks for the Baxi Bermuda back boiler below was tolerably comfortable with the rad off and just the end gable wall nice and hot from the flue blocks.

Don't underestimate the amount of work to extend sockets and overboard with PB, including the window reveals. I ripped all the plaster off them too and jemmied off the galvanised mesh from the upper reveal then made my own insulated PB and glued this around the reveal using foaming PU plasterboard adhesive.

Also, cheapo EPS is open cell, so you need to put a vapour barrier on the warm side before plasterboard, or use the foil-lined PB and seal the joints with double sided tape.

[Andrew]

The technical name for this construction is 9-inch solid wall. Single-skinned implies a single 4-inch brick of block wall, as would be the case in an outhouse or garage.

[RJH]

It's the wheel type.

I just used the drying clothes setting because I was drying clothes - not sure why it's there if it's pointless. But you may be right - in that it's a cosmetic energy wasting setting just put there to sell the machine. FWIW the manual says:

[Animal]

that's the game.

the mode does speed up clothes drying, but not by much. And it uses somwhere vaguely around 10x the energy. It's not really useful, other than as a sales thing

All dehumidifiers are less effective as air temp drops because dewpoint and thus water vapour content is proportional to temp. But compressor types also rely on enough temp drop to cause condensation, yet the compressor system has temp limits on its operation, and limitations on restarting. So at low temps they're initially feebly effective then not effective.

A 200w or less compressor machine with a decent variable electronic humidistat is the main good point. I'd also avoid old machines with coarse cooling heat exchanger.