Dehumidifiers

[tobydog]

Unfortunately our condensation is back already and it looks worse than last year. I can only put it down to opening up some of the lower walls when we removed the cement and there is still plenty of moisture coming out. Does anyone recommend a specific dehumidifier that would be suitable for a 3 bedroom house that I can site somewhere centrally and let it tick over 24/7? Energy efficiency is clearly a priority. It just needs to get us through the winter /spring. Thanks

 

[worms]

I'm happy with my Prem-I-Air desiccant wheel dehumidifier, the latest model of which is here.

 

[tobydog]

Thanks Worms. You mention Prem-I-Air but the link takes me to an Eco Air product. Are they the same company?. I was looking at the Eco Air range earlier and the reviews are excellent.

 

[Lime]

I have avoided dehumidifiers in the past.
However about 6 weeks ago the windows started to get wet again and I decided I'd bite the bullet.
I bought two cheap B&Q dehumidifiers (pump type about £100 each 10 litres/day) fitted with sensor controls and pipe drain if need be, otherwise a 1.5 lt capacity tank.
From the word go they have been a success.
I check throughout the house with a hygrometer so I know what I'm talking about and I recommend anyone with a dehumidifier to get one.
http://thermometer.co.uk/30-humidity-meters
The general humidity has been brought down from 60% and above to about 40% throughout most of the house.
Walls and floors are less damp and there is no water on cold windows at all.
Well worth the money.
Use the water collected to water greenhouse or lime sensitive plants as it is "soft".

As an added bonus, the pumped type of dehumidifier gives out more heat than the electrical power it consumes.
Latent heat and all that.... about a kilowatt hour for every 1.5 litres water collected.

I emphasise that the pumped type work best in warm conditions and are not good at low temperatures.

 

[worms]

Thanks Worms. You mention Prem-I-Air but the link takes me to an Eco Air product. Are they the same company?. I was looking at the Eco Air range earlier and the reviews are excellent.

Prem-i-air is the manufacturer, the products advertised on Amazon are sold by Eco Air which is a retailer of products from a number of manufacturers.

 

[worms]

I emphasise that the pumped type work best in warm conditions and are not good at low temperatures.

...which is why I opted for a desiccant wheel model.

 

[tobydog]

I need the dehumidifier for the main house where temperatures usually don't drop below 12 - 13 in winter even at night. From what I've read at this temperature both the desiccant and compressor types should work fine. I understand the desiccant type are quieter. I'm thinking of going for the desiccant type because I can then be less restricted as to where I place it due to noise levels. Any further thoughts? Thanks

 

[worms]

I think you should be able to get absolute figures for noise on the data sheets for each model, so that you can compare. Neither should be particularly noisy and on the lower setting my one is quite quiet, louder when it is on "turbo" mode. The only refrigerant dehumidifier I've had experience of was noisier, but they are probably quieter nowadays. I notice that in the customer reviews on the B&Q site, there was one complaint about one model being too noisy at night, but some people will complain about anything and noise is very subjective.

I need the dehumidifier for the main house where temperatures usually don't drop below 12 - 13 in winter even at night.

I'm not sure my house achieves that in summer!

 

[Lime]

IMO where the desiccant dehumidifier really scores is in low temperatures.
However I have read many reviews of several variety of dehumidifier and most are too subjective.
to get a true impression you need a hygrometer.

I've been reading some of the comments re.- the Meaco DD122FW-MK4
http://www.meaco.com/proddetail.asp?prod=DD122FW&review=all

The higher consumption of electricity would concern me as well as the lack of control.
The smell "problem" would make me have my doubts too.

Over to you worms.

 

[tobydog]

Overwhelmed with data at the moment. I currently think I'll go for the desiccant type because although I will use it in parts of the house that are going to be above 15C, I also want to use it in the old utility room which is not somewhere you want to hang around long on a cold night.

The final straw for me was actually last night. I normally keep my tools in the shed where they reside quite happily all year round without any problems. This included my trusty cold chisel that I used to remove the cement. The mistake I made was actually leaving it in the house (the old kitchen) as it's now gone all rusty . My very poor (and unsubstantiated) argument to Mrs. T. for leaving things in the house was that they would go rusty in the shed :roll: . I just didn't realise.

 

[Penners]

the pumped type of dehumidifier gives out more heat than the electrical power it consumes.

Hooray!! Perpetual motion at long last!

 

[worms]

IMO where the desiccant dehumidifier really scores is in low temperatures.
However I have read many reviews of several variety of dehumidifier and most are too subjective.
to get a true impression you need a hygrometer.

I've been reading some of the comments re.- the Meaco DD122FW-MK4
http://www.meaco.com/proddetail.asp?prod=DD122FW&review=all

The higher consumption of electricity would concern me as well as the lack of control.
The smell "problem" would make me have my doubts too.

Over to you worms.

Hey, I'm not in the business of dehumidifier sales and have no axe to grind, I just said I was happy with mine!

The complaint about the power consumption was from someone who was using it on turbo mode all the time - this setting switches on a heater element to warm the air to aid laundry drying, so no wonder it was using more electricity! I'm not looking for it to get the house down to 45%RH, anything below 60% is a real achievement here! (Although the laundry mode is actually quite good if you want to dry laundry!)

Lack of control? There are more settings on it than I need and if you need to set to a very specific RH setting then, no, mine won't do that, but if you are that demanding, then perhaps a separate humidistatic switch might be a better option, since RH settings are reputedly unreliable, particularly in the vicinity of the machine itself.

I've not noticed the smell issue - I can tell when it is on, in the same way that you can tell when a room or car has the air-con on, but the same was true of an old refrigerant machine I once used.

 

[Lime]

worms what is the wattage of the DD122FW ?
I have not seen it mentioned.
The compressor ones I bought are rated at 180 watts (tops) but when I measured them they consumed 130 watts each.

They have an RH control which appears to work quite well.
They should not be switched off at the plug or by a time switch otherwise the electronics may get damaged.
They also have a defrost cycle too if ice ever builds up.

I can tell when it is on, in the same way that you can tell when a room or car has the air-con on, but the same was true of an old refrigerant machine I once used.

I have been completely unaware (in that sense) of the ones I have.
No smell whatsoever.
Their sound is about the same as a fan heater.

 

[tobydog]

Okay - time for an update.

I went for the Eco-Air Classic Dessicant Mk 4 about two weeks ago. Does it do what it says on the tin? Sometimes!!

It's not the cheapest unit to run at a minimum of 380 watts. I have plugged it into a meter and it's pretty much spot on. Put it in turbo / laundry dry mode and it jumps to 690 . 380 is in the mode to bring RH down to 55-60%. Put it in the mode for 45-50% and in goes to 420.

The humidity in our house is all over the place at the moment. We had a dinner last night. I ran the unit on the landing for 2 hours after the meal and all night in the old kitchen where I've been digging up the edges of the floor. In the morning the old kitchen was bone dry, every other window in the house was soaking wet and, in our main bedroom which is above the old kitchen, I woke at two in the morning and could hardly blink or swallow it was so dry despite our window being soaking. I know temperatures plummeted last night but it will be some time before I fully understand the house and the best way to use the unit.

Haven't given up yet.

 

[Lime]

Thanks for the update tobydog.
I've been using my compressor dehumidifiers for a couple of months now.
Over that time I have formed a reasonable idea of how my house "works" with regard to humidity.
Prior to their purchase my house had a general RH of around 60% measured using my hygrometer. (see link I gave previously)
I had no idea whether our way of living caused the high humidity or it was just the house.
I found that much of our furniture had mould growing on it and the house often felt clammy.

The dehumidifiers run continuously (set to 40% RH) and it took the first month for the humidity to settle down.
During that time, if a dehumidifier was switched off, the RH rose quite quickly to previous levels.
I assume this was because the fabric of the house was still relatively damp.

Surprisingly, use of the shower and baths does not produce much extra humidity and I attribute that to opening the bathroom windows after use and shutting the doors for at least an hour.
However my wife attempting to save electricity by drying semi-dried clothes on the clothes horse did make a considerable difference to the amount of water collected... but the dehumidifiers coped very well and maintained @ RH 45% .

This month the house and the dehumidifiers have been running as I wish to go on.
The electronic controls are set for about 40% RH.
They switch themselves on and off depending on the humidity.
I have one dehumidifier in the rear of the house that serves the dining area (with tiled floor) and kitchen.
The other is situated on the landing serving all other other rooms and hall (with tiled floor).


I have just measured the house:
Kitchen and dining area 35% RH @ 22°C
Hall and landing 42% RH @ 17°C
Front rooms (facing north) 45-47% @ 13°C
Rear rooms 44-46% RH @ 21°C
(In comparison to an average of 60+% RH before)

Extra electrical consumption over November 121 kWhrs continuous use.
That figure includes more use of the washer/drier!

The house feels warmer.
The windows are much drier.
This morning was cold and some windows had a little condensation on them but after the curtains/blinds were opened it disappeared within the hour.
In general I collect about 4-6 litres of water a day depending on the weather.
(As opposed to 8-12 litres when first started)
I am very satisfied with their operation so far.

My conclusion is that the house and weather are mainly responsible for the humidity, not us!

 

[biffvernon]

Is an RH of ~40 always a better thing than ~60?

 

[tobydog]

Lime - thanks for the info. I don't think I could afford to run two dehumidifiers however it definitely sounds as though your house had way more damp than ours. I mentioned earlier about my chisel going rusty in the old kitchen. When I moved things around on Saturday in order to dig up the concrete floor edging I noticed that the back and sides of the armchair were moldy. This backed onto my earlier excavations so there was / is clearly a fair amount of moisture coming out of the floor. The dehumidifier is now correcting this which is great.

My moisture survey continues. Despite leaving the house yesterday morning with soaking windows all round (very cold, floor excavations and steaming veg on Sunday), by the time I returned in the evening everything was dry. I even put the dehumidifier on in the old kitchen and got very little. The very cold icy and dry weather must have sucked the moisture out / replaced it and corrected the situation.

So my mid term conclusion here is to check the weather forecast next time before we have a dinner party :roll:

As for 40 RH versus 60 - based on personal experience 40 would be too dry for me. Like I said earlier, we ran the unit at 55-60 directly below our bedroom Sunday night and we were spitting feathers by 2am. I could re-position it but to run it at 40 would be very noisy.

 

[Lime]

Is an RH of ~40 always a better thing than ~60?

I gather the big dangers to furniture, paintings and other artifacts are sudden large changes of RH and the two extremes of 75-100% and 25-0% RH.
http://cool.conservation-us.org/byauth/brownjp/humidity1997.html
In my case I have come to the conclusion that a large proportion of moisture in my house emanates from the tiled floors on earth coupled with some walls that are damp.
The situation has become more problematic over the past few years because as energy prices have risen the wholesale ventilation of the house has been reduced to minimise wasted heat.
Couple that with better draught prevention throughout and because the children have left home not all rooms are now heated the likelyhood of condensation has greatly increased.

My aim is to minimise mould and damp, dry out any structural damp and stop window condensation without causing damage.

 

[Zebra]

in order to dig up the concrete floor edging

Tobydog, are you making one of those evaporation trenches around the edges of a concrete slab? Digging it up and filling with limecrete? If so, any tips? I've dug my slab up around the edges but not filled it in yet.

 

[tobydog]

Any tips? I did but now I'm not sure. I'm lucky in that the concrete slab was laid leaving up to 75mm around the edges between the walls. As the house is far from square and true this does come down to nothing in places so is touching the walls. I'm only doing two walls where I have brick beneath the sole plate.

The gap was filled with a mixture of sand and broken soft reds which is good but it was capped off with 100mm of concrete / cement. I chipped my way through this and removed the rubble and it's 250mm - 300mm deep in most places. I originally intended to fill it to within 25mm of the tile level with expanded clay pellets and then top it of with something lime based. The problem is that I've read that these clay pellets have very low capilliary action which would not necessarily help getting the moisture to the top.

I need to do some more Googling but I reckon there must be someone on PPUK who has done this before.

I need to leave mine for a few months to dry out, re-build the wall under the sole plate, and render the brick. Apparently my sole plate in the old kitchen at least is worth saving.