That wouldn't have been true this year in most of the UK - warm but very wet. So, someone with a dedicated dehumidified drying room would have certainly been tempted to use it all through the summer, but not wanted the heat gained.

Tony - you must live in a different country - can't believe you manage to dry washing outside all year round - are you sure SWMBO doesn't nip to the launderette when you're at work :)

Posted By: Ed Davies

Posted By: funcrusherEd Davies : I said you need airtight room.

Yes, an airtight room is necessary but it's not sufficient. My point was that the airtightness has to be inboard of the insulation - just fixing insulation on the walls of an airtight room would be a problem. Obvious to most but perhaps not all so worth mentioning, I thought.

If the dehumidifier is doing its job, and the room the cabinet's in is not arctic, then it seems unlikely that any inside air leaking past the insulation would get to a dew point ....... or a meringue?

Hmm, a first floor laundry room sounds attractive but our washing machine - chosen for its carbon and energy efficiency - is hardly quiet. It's a real screamer when it starts spinning. So I'd be very nervous about putting it anywhere near the bedrooms.

Also I'm hoping that the MVHR will do the job instead of having to add a dehumidifier.

Posted By: djhHmm, a first floor laundry room sounds attractive but our washing machine - chosen for its carbon and energy efficiency - is hardly quiet. It's a real screamer when it starts spinning. So I'd be very nervous about putting it anywhere near the bedrooms.

Also I'm hoping that the MVHR will do the job instead of having to add a dehumidifier.

Our current model (a cheap Electrolux as an emergency buy when our old one failed at a bad time) is also really noisy, with an annoying high pitched whine from the direct drive motor. Our previous (but now deceased) Bosch was much quieter.

With copious amounts of solar PV and thermal the plan will be to use it mostly during the day (on delayed start) when no-one is in the house. The only adjacent bedroom will be the guest bedroom, which won't be used too often.

We will also have beam and block floors and solid block partition walls which will hopefully block much of the noise. I might have to consider some vibration absorbing feet on it though if it does turn out to be too noisy.

Posted By: Chris P Bacon

Posted By: MarkBennettOur first floor plant room

Tanking the room, a high threshold and a floor drain would also be a good idea.

Agreed and in the plans!

my aunty has her 3 inverters (2 x 3kW wind, 1 x 3kW solar) located in her drying room as the only form of heating in that room. I used to get confused and close the door to the drying room (passageway to the garage) in winter to keep the heat in the house warm, then realise the drying room was actually warming the kitchen slightly when the wind turbine and solar were pumping away.

It does cause condensation issues though, which we helped to regulate by installing sheeps wool insulation directly above the drying room, kitchen and bathroom, which despite my scepticism, actually made a noticeable difference to the condensation on the windows (as did filling the aluminium framed trickle vents with sheeps wool insulation, as the moisture was condensing on the cold metal surface, which turned from -10 to +5 deg surface temperature at around -15deg external air temp).

Posted By: MarkBennettOur current model (a cheap Electrolux as an emergency buy when our old one failed at a bad time) is also really noisy, with an annoying high pitched whine from the direct drive motor.

Ours is a Panasonic that comes at the top of the green lists.

I might have to consider some vibration absorbing feet on it though if it does turn out to be too noisy.

You could try suspending it on bungee cord
Better isolation than an air table

My old neighbour had one, she never said it did not work

We have a utility room that is well insulated and air tight to the outside although there are gaps around to internal door that links it to the kitchen. It has a large (2400l) thermal store in it that gives off quite some heat even though it is insulated and it dries clothes (on one of those ceiling mounted racks with a pulley) very effectively in the winter. The room has a conventional electric vent to the outside but I sealed it up with some tape last winter as it was creating a lot of drafts and losing heat to the outside.

I have been thinking about putting in a single room MHVR vent instead of the existing vent but this post makes me wonder if it might be a better idea to use the dehumidifier I already have in the shed.

Any ideas / opinions anyone.

JD

Make my own MHVR? Is that easy to do? where might i get a design or some ideas? I see the shed beckoning!

Jw

I think we can calculate which is best - dehumidifier or MVHR:

An energy star dehumidifier uses about 0.7KWh(elec) to condense 1litre of water(link below). In the process, it will liberate an extra 0.63KWh (latent heat of condensation) - but the wet clothes will have needed precisisely this heat to become dry, hence the room heating level is actually just the electric energy used.

In contrast, an MVHR is complex. Lets start with the perfect one, 0Watts and 100% efficient - even in this case, a suitable MVHR does not collect the latent heat from the air, so to dry out 1Kg of air, we will loose all of the 0.63KWh of heat. Real figs are tricky for the rest - but in our case(we do dry clothes with MVHR in the winter, so I can give you an order of magnitude) - 11W(elec) for 24 hours dries a load of washing(and the rest of the house) with probably ~3litres of water. Thus the elec energy used is 0.26KWh (of which guessing 0.1KWh is due to the washing).
This 0.1KWh=360KJ of energy should have moved 720000litres of air = 720m^3.
At 11degC outside, 19C inside, then this involves movement of 720m^3*1297J/m^3/C *11C = 10.3MJ = 2.8KWh of heat.
Of this 2.8KWh, 8% is lost (our MVHR is 92% efficient), so we loose 0.224KWh of heat.

Thus a good dehumidifier uses 0.7KWh(elec), and liberates 0.7KWh(heat) to dry our clothes.
A good MVHR uses 0.1KWh(elec) + 0.85KWh(heat) to dry our clothes.
So using a dehumidifier instaed of an MVHR is like a heat pump of COP=(0.7+0.85+0.7-0.1)/0.6=3.6

I think from the above information that a dehumidifier is hard to beat *if all you want to do is remove moisture*, and you want the heat recovered. I highlight this, as I really doubt this is the case generally. Most houses have CO2 in them, and reasons why you need an air change anyway. In an earlier thread I highlighted a friend of mine who had migranes due to excessive use of a dehumidifer in an airtight house!


http://www.best-dehumidifier-choice.com/energy-star-dehumidifier.html

just to encourage doubters: When I first outlined my idea, my younger son (like me and my elder son) an engineer decided to try the concept in a smallish9 x 9ft room he uses as a study. Its a room in a 1939 house with a double-glazed window in the only outside wall, but not benefiting from any insulation upgrade etc. His working wife (with much washing from small children) was doubtful - but has found it so successful she has thrown away her tumble dryer. Furthermore, there were no undesirable impact on shared use as a study, complete with computer etc.

On washing machines in kitchens.

From my perspective as a small Landlord, the current single most controversial (structural damp or lifestyle damp?) area for landlord/tenant disputes at present is condensation/damp - made worse by the trend to airtightness and extra insulation, and it's becoming more important to design out potential for these disputes to happen.

Therefore these days I'm deliberately not even installing washing machine plumbing in kitchens, and making it physically impossible for washing to be draped over radiators.

It all goes in a dedicated utility room/cupboard with a good drying and extract setup, and a rotary dryer outside. Electric regs make it tricky to install washing machines in bathrooms, of course, though I have done them in boiler cupboards where they can share 2 pipe stack effect ventilation.

Personally we've always had washing machines in bathrooms since I was a kid in the 1960s, but I've been in the same house for a loooong time now.

Matt W

Hi Ed - yes, I think the latent heat should improve the "efficiency" of an MVHR. In fact, I wouldn't be suprised if the 92% quoted for my unit cheekily assumes 50% or so internal RH, and lower UK-winter levels of outdoor AH, helping the heat exchanger.
Even a 100% efficient MVHR can't actually recover this latent heat though, whilst an ERV can, but in doing so it keeps the house humid so won't dry your clothes.
My friend Wiki who is always right says:" a heat recovery ventilator (HRV) can only transfer sensible heat"