Condensation / damp

JonathanRyan

JonathanRyan

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Another thread made me think to post this.....

I live in a 3 bedroom detached house. It's called a "chalet style house" which means the first floor is basically built into the eaves and has sloping ceilings. About 18 months ago we had the roof removed, insulated and relaid - previously it was completely unlined. We have double glazing and cavity wall insulation. Recently, I figured out the whole house was damp. Like very damp.

I got some of those hygrometers off of eBay and the kitchen was reading 95% humidity, other rooms were 80+. So we've been running a dehumidifier flat out for about 4 days. When it's running, it will dramatically reduce the moisture in the air - shut it in the kitchen overnight and in the morning it's below 30% but it soon creeps back up. (This is a unit rated for a 5 bed house and we have it in the hall).

Any ideas on a permanent solution? Running the dehumidifier 24/7 os going to be noisy and expensive. I've been told a positive pressure pump might do the job or maybe I just need an extractor fan for the kitchen (the cooker hood doesn't vent out and we never use it). Prepared to spend a reasonable amount on fixing this as if I don't do something soon we'll need to fix it and replaster.

Who knows about this stuff?
 
I don't know much, but adding insulation and reducing air flow means that all the moisture in the air cannot get out - double glazing is another major factor as is drying washing on radiators, cooking rice/pasta etc, and even people sweat or breathe out a lot.

The simplest way to get rid of some of this damp air is by opening a window or two for an hour or so each morning - do you have trickle vents on any of your windows, as they need to be open. An extractor in your bathroom that has a timer will help, and as you suggest, fitting an extractor that extracts will too - stopping cooking, washing and breathing will too but may not be quite as helpful a suggestion...

We had a similar problem which I have got under control by doing the above - my dehumidifier is on for about an hour a day, but only on really wet days when people come in wearing soaking coats and shoes.
Better ventilation is a more permanent answer and we are working on that.
 
Did you by any chance previously have a chimney that has now been blocked ?
Where I used to live I had a lovely open faire that was used, others had there's blocked off and complained of damp
a surveyor told them that needed to vents in the blocked chimney to allow air flow
 
What temperature do you keep the house at? Damp is also relative to internal temperature. Keeping the house warmer as well as improved ventilation should make a difference.

This whole hermetically sealing your house idea is flawed. Draughts keep you and a building healthy.
 
I had a bad problem with condensation and damp a while back. I live in a 3 bedroom stone cottage from the 1880's. It's not long been renovated (about 3 years ago) and since then we have had the damp problem with mold. It's all sorted now with a few simple air vents in the windows (y)

I know nothing about building work even though 70% of my friends are joiners, but we had some fancy floor insulation fitted as well with vents to outside.
 
Like others have said, you essentially need air flow.

We live in a 1930s house and we've had a few damp issues. Not helped by no window vents. You can have a shower with the extractor and window open and the house still feels moist after.
 
A laser thermometer is also very handy as it will show you unexpected cold spots. It's also worth making sure all guttering and down piping is working correctly too.
 
Thanks. Yes, it's got noticeably worse since we renovated the roof. The problem is that either we have a porous roof that lets rain through or a sealed one that doesn't let moisture out :)

Gremlin said:
Did you by any chance previously have a chimney that has now been blocked ?
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We removed 2 chimneys when we bought the house (8 years ago). The third one we had capped when we had the roof done but it's capped with a metal cage. Lots of airflow but it keeps squirrels out.

srichards said:
What temperature do you keep the house at? Damp is also relative to internal temperature. Keeping the house warmer as well as improved ventilation should make a difference.
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That's an interesting point (and kind of obvious now you mention it....) heating hasn't been on once since Easter. It's about 20 degrees ATM but it's been a lot colder.
 
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Craig1912 said:
Thinking of getting one of these

http://www.nuaire.co.uk/our-products/search?m=1104&pt=1685

We use a dehumidifier but looking for something a bit more permanent. Our condensation isn't horrendous but since having new double glazing it's got worse. We have trickle vents and bathrooms and kitchen all have extractor fans.
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Yep - looking at that and similar devices. I'd be very interested to hear from somebody who has one. Not least re the noise.
 
Suz is saying all the stuff I meant to but failed to..!

srichards said:
What temperature do you keep the house at? Damp is also relative to internal temperature. Keeping the house warmer as well as improved ventilation should make a difference.

This whole hermetically sealing your house idea is flawed. Draughts keep you and a building healthy.
Click to expand...

srichards said:
A laser thermometer is also very handy as it will show you unexpected cold spots. It's also worth making sure all guttering and down piping is working correctly too.
Click to expand...

srichards said:
Some useful stuff on this page: http://www.medway.gov.uk/housing/councilhousing/repairs/condensationdampandmould.aspx

I'd definitely set the CH stat to 18C and make sure the property doesn't get colder than that.
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I heat recovery system would do the job but might cost you. They extract warm moist air while sucking in new air. The cleaver thing is the warm extracting air heats the cool air coming in.
 
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Problem, with modern houses, is that they are "too" air tight. Good air circulation is essential.

All good advice given already, but something we found beneficial, was how we locked our windows. We have a type that can be locked but still allow a small amount of air in, i.e. the window is essential opened a few mm. Totally safe btw.
Also, probably something obvious, but don't dry clothes on radiators, etc. as you would just be releasing more water into the air.
 
neil_g said:
Check your insurance. Some will not cover you if the window is on the catch and not shut completely.
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Everest Windows (actually that may be part of the problem). They lock partly open.
 
neil_g said:
They may lock but they're still only screwed into plastic and provide a nice gap for a crow bar.

Still worth checking your insurance small print, I have seen it before.
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These are from back when Everest were still good ;) The promo videos used to show that they stood up to a big bloke with a 4 foot pry bar. Basically the 4 bolts go into different housings. All steel and none accessible from the outside. But yeah, I know what you mean about insurers :)
 
rjbell said:
I heat recovery system would do the job but might cost you. The extract warm moist air while sucking in new air. The cleaver thing is the war extracting air heats the cool air coming in.
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I think that's what my mate just built into his new house. Looks a neat bit of kit and has multiple vents going to different rooms. It sucks the warm air out but heats up the cold air coming in, like you said.
 
we had a company come to install cavity wall insulation free, they said they needed to put open air bricks in all rooms, i said that defeats the object of insulation as during winter you cant close the air bricks and it will blow a gale through the house, they said thats good, you need air flow, i said dont bother.
 
JonathanRyan said:
Yep - looking at that and similar devices. I'd be very interested to hear from somebody who has one. Not least re the noise.
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I have a Nuaire Drimaster Heat model, every morning we used to wake up with water dripping down all the windows. I first purchased a Karcher window vac and that helped clear the windows but never fixed the cause.

Its easy to install, on the standard setting it blows quite strongly into the house but I set it down a couple notches and its very quiet, basically it filters then blows fresh air from the loft into the house. I noticed a big difference after 2 days, after a week it went from drenched windows to a very light misting on the bottom of the window and it stopped any minor mould issues.

The motor is incredibly efficient and I never noticed any real difference in bills, its also got a built in stat for the heater so if the temp drops to a certain level the heater kicks in, I never bothered with the heater so couldve save a few quid and got the regular version but I can see some using it.

Oh, that dramatic difference included cooking without venting outside, showering with doors open etc. and keeping the windows shut most of winter, after all you're replacing moist/stale air with clean air from outside thats filtered.
 
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JonathanRyan said:
Brilliant - thanks.
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No problem, Ive recently had a big loft conversion done so Im a little concerned about the condensation as I have nowhere to fit my Drimaster and Ive seen moisture on the lower parts of the windows already. Hopefully it will fit in the little eaves space I have left or Ill be Ebaying it.

Highly recommend the product though. It takes a little while to hit a balance in your home between effectiveness and more 'breeze', I started on a higher speed and just notched it down every few days till I got the perfect setting for my home. Mine was fitted on the top floor in the center of the landing to distribute air around all areas and downwards.
 
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