I live in a 1970s 3 bed detached bungalow with very bad mould problems caused by condensation (we're told by an independent damp report). The worst rooms are two bedrooms which have external north facing walls which are less than a meter from the side of the garage, creating a passage way that gets hardly any wind and no sun.
We have double glazing but no trickle vents. We're having cavity wall insulation done in a few weeks. We've fitted a humidistat fan in the kitchen which is really loud and has now been running for nearly 24 hours set at 75% relative humidity!! so this is definitely not an option for the bathroom or bedrooms. We've been leaving windows open a bit in the bedrooms but this isn't great for security and also it is getting cold now.
I've been looking into positive ventilation but am now thinking a heat recovery system may be better as more environmentally friendly than heat all going outside and also with no trickle vents in the windows I'm not sure where the damp air would go. If there were holes wouldn't the air be circulating anyway and therefore no condensation problems??
Sorry for the long post but we've alrady spent £100 on the humidistat fan which so want advice on the pros / cons or peoples experience of these two options as there's no point getting the cheaper option of pos. ventilation if it's not going to work.
Mike George
posted on 16-10-06
Hi Primarni.
The cavity wall insulation should make a big difference as it will result in less heat loss and therefore higher internal air temperatures. This will also result in wall surfaces which are warmer and therefore less likely to attract condensation.
Of course it all depends how much water vapourb you are putting into the air. Do you dry clothes on radiators? Do you use a shower a lot?
I would wait and see what happens before considering what to do next.
Hope this helps
Mike
Primarni
posted on 16-10-06
Thanks for the reply. I think we do create a lot of humidity - at least two long showers each day, the bathroom is in the corridor with all three bedrooms. There is a fan in there and we keep the door shut and open the window wide and leave it open a few hours after showering but our bungalow is sort of in a dip, with high trees all round so we don't get much wind at all, so hours later the mirror is still steamed up. Also forced to dry clothes inside a lot of the time due to working full time and weather, am hoping to get an outside vented tumble dryer soon which should help....but not with electricity bills.
I think lack of ventilation is the biggest problem as we moved out of the worst mouldy bedroom into one with more internal walls that had been fine, and after a month or so there was mould in the wadrobes in that room too. We're now still in that room sleeping with window open and so far it's okay but I don't want to have the windows open all winter.
Do you know what relative humidity of a room should be? The humidistat fan in the kitchen is set at about 72% and has been constantly running since yesterday morning. There is some damp washing in there but window is also open so am starting to wonder if it's faulty?
Hopefully the insulation will help as you say.
Mike George
posted on 16-10-06
Primarni. I would not be too worried about the %RH at least until you see how your house performs when it is well insulated. It may be that opening the window all day is counter-productive, especially if the temperature outside is very low and the air is very damp. Reducing the internal temperature merely reduces the moisture bearing capacity of the air, meaning that condensation occurs at a lower air temperature - a vicious circle in a badly insulated house
Thanks for the link - so as long as the RH is less than 100% we shouldn't get condensation, but as the temperature drops, the amount of humidity to make it at 100% is lower....I think!! I've got an exam tomorrow I'm supposed to be studying for, I would probably do better if the exam was on condensation and ways of curing it!!
Paul in Montreal
posted on 16-10-06
You will get condensation if you have any surface which is at or below the dew point of the air in your house - no matter what the RH level is. It sounds like you have several problems - poor insulation being one and excess humidity being another. A RH figure of something like 50% will be far more comfortable and it sounds like opening your windows is making things worse, as is the drying of clothes inside. You may want to look at a de-humidifier if your insulation improvements don't solve the problem. The good thing about a de-humidifier is that at least you will get back the latent heat of condensation which will offset its running costs somewhat (it is essentially a mini heatpump).
