Yep , think that's it . If we whacked the heating up and vented all the windows constantly there'd probably be no condensation problem. In attempts to reduce heatloss through reducing uncontrolled ventilation and improvements in airtightness and insulation (especially when only part done) it creates a condensation problem . One of the problems with low energy refurbishment is how to deal with and reduce it.
Most the houses on my estate suffer from it , unless you jack the heating up. I think the problem is also increased by high occupancy rates in lower volume homes. Most of the larger houses I work on have considerably less problem, as the occupancy per m3 is considerably less.

Nick , not really a hinge problem , more getting them to shut/open the door, as they cant reach the handles

Mircowaves still produce water vapour as they heat the item. But i beleive they can be more efficient in their use of energy to cook things. (quicker as you say)
From Mikes link http://www.norwich.gov.uk/Housing/HousingInformationAndAdvice/documents/Condensationanddamp.pdf
Two people active for one day 3 pints
Cooking and boiling a kettle 6 pints
Having a bath or shower 2 pints (surprised this isn't higher)
Washing clothes 1 pint
Drying clothes 9 pints
Using a paraffin or bottled gas heater 3 pints
Total amount of moisture produced
in your home in one day 24 pints

from VH's info
Average source, break down - (one that makes more sense to me)
45% from showers, 35% from drying clothes, 13% from cooking, 7% from breathing/sweating
so different views there.

Posted By: jamesingramIn attempts to reduce heatloss through reducing uncontrolled ventilation and improvements in airtightness and insulation (especially when only part done) it creates a condensation problem .

James, surely it's the reduced ventilation that causes the problem? I know what you mean about part-done insulation - I have that problem myself - but the insulation is not actually causing condensation. It just concentrates the condensation in the uninsulated areas.

Not necessarily accusing you - but I think there's a slightly Puritan notion about, that higher indoor temperatures are themselves conducive to condensation. It's true that humans, pets and plants emit more water vapour at higher temperatures, but I'd be surprised if that wipes out the benefit of having warmer surfaces. Most of the other ways in which a warm house promotes vapour production - by encouraging people to dry washing indoors, for example - are down to behaviour, not physics.

Posted By: rhamduJames, surely it's the reduced ventilation that causes the problem?

Exactly. Condensation starts when the surfaces are colder than the dew point. But heating the surfaces isn't the only solution. You can also reduce the dewpoint, by opening the windows and letting some fresh outside air in and some stuffy moist air out.

There does need to be a concerted (local) government campaign to really make people aware of the issue of not producing high humidity in the first place...closing doors in moisture producing rooms and venting off at source. I mean a real ongoing campaign. amazingly there are people on this forum that 'own up' to getting serious condensation.

I have a studio, above an office, in an a Victorian terrace house. I sometimes sleep in the studio too. The office has cooking facilities, but no showering and clothes-washing facilities. There is an internal connecting door so it's still like a habitable place and the internal temperature drops to 12-15 in the office overnight. There is never any condensation except occasionally, if a frosty still night if I have stayed over, on the single glazed studio windows, but that disappears quickly in the morning

The purpose of this comment is that little moisture is produced, even when people boil up stuff in the office (vented off at source).
The topic recently popped up in conversation with one of the 'mature ladies' in the office who says there's mould everywhere in her house. I started down the road of quoting much of the content of this thread (architect for with over 40 years experience!): oh she would not have it...took it very personally, and became very defensive.

So it does need to be regular (Autumn/Winter every year) advice from good official sources...perhaps even grants for at least extracts, or retro fitting MVHR, en masse, to stop mass deterioration of the nations health and housing! Unless it's a hidden agenda of course!!

Posted By: djh

Posted By: rhamduJames, surely it's the reduced ventilation that causes the problem?

Exactly. Condensation starts when the surfaces are colder than the dew point. But heating the surfaces isn't the only solution. You can also reduce the dewpoint, by opening the windows and letting some fresh outside air in and some stuffy moist air out.

I agree completely , probably wasn't clear in my post. insulation is not the problem ( though part insulation creates cold spot which concerntrates the problem to those areas as we've mentioned.)

But , "attempts to reduce heatloss through reducing uncontrolled ventilation and improvements in airtightness"
seem completely pointless if you're just going to leave a window open all the time.
My north wall is solid and cold , if i leave the rads on those walls on low and/or vent continually I'll probably have no problem other than a high fuel bill

So reducing source of moist air and managing at source without excessive venting, as we've all suggest, is the way to go,
(improving the walls insulation levels with EWI will of course help, maybe completely solve the problem ?)
That being said , if you look around some of the build forum on the webs there's various concerns by tenants of social housing that have had EWI ( usually incomplete , skeiling not down etc.) that are having dreadful problem with condensation and mold that they never had previous to EWI or insulation work (due to increased fabric airtightness) and not being up on the in and outs of the subject point the finger straight at the EWI.

Posted By: caliwagThere does need to be a concerted (local) government campaign to really make people aware of the issue of not producing high humidity in the first place...closing doors in moisture producing rooms and venting off at source. I mean a real ongoing campaign. amazingly there are people on this forum that 'own up' to getting serious condensation.

I have a studio, above an office, in an a Victorian terrace house. I sometimes sleep in the studio too. The office has cooking facilities, but no showering and clothes-washing facilities. There is an internal connecting door so it's still like a habitable place and the internal temperature drops to 12-15 in the office overnight. There is never any condensation except occasionally, if a frosty still night if I have stayed over, on the single glazed studio windows, but that disappears quickly in the morning

The purpose of this comment is that little moisture is produced, even when people boil up stuff in the office (vented off at source).

Wouldn't it be more to do with that it's victorian terrace with single glazing , so a leaky fabric , with lots of uncontrolled ventilation?

Posted By: caliwag
amazingly there are people on this forum that 'own up' to getting serious condensation.

what, is it the dirty secrets of an energy efficiency refurbisher ?

Posted By: jamesingramI also wonder if it's a locality thing as well , I live in Slough , so the name in itself is a bit of a give away.
Thame valleys always had a bit of a name for having a high asma rate ( not sure how true that is)
Even if we vent windows all day , since early september indoor humidity levels rarely drop below 65%

I am also in the 'dry' southeast (Brighton) but on a day like this we might as well be in Manchester. And cos it's mild, the AH is going to be pretty high. Basically these high-AH conditions will arise for part of the year anywhere in the British Isles, and buildings have to cope with them.

Unless I am very much mistaken, high humidity is not in itself unhealthy - in fact, people used to buy humidifiers in order to survive in centrally-heated houses. The health problems arise from moulds, dust mites and other nasties that grown in damp conditions. In a well insulated house, 65% RH is probably nothing to worry about, because there will be no cold places where water can condense, and therefore no mould. Perhaps someone on the forum can recommend the temperature and humidity levels that will successfully control dust mites?

Posted By: jamesingramI've read somewhere it's recommend indoor RH <50% for dust mite control.

So you'd have to keep the windows closed and a dehumidifier running for most of the summer.

Posted By: seascapeDishwashers are also culprits

for what? All the moisture in my dishwasher is contained within it - plates go in dry and come out dry. Washing by hand supposedly uses more water, splashed around, with the wet crockery either drying in the air or by tea towel which then dries in the room.

Posted By: jamesingramBut , "attempts to reduce heatloss through reducing uncontrolled ventilation and improvements in airtightness"
seem completely pointless if you're just going to leave a window open all the time.

Actually I don't think improving airtightness would be wasted even if leaving a winodw open all the time was what was being suggested. But it isn't.

You only have to open the window for perhaps half-an-hour or so a day, or shorter if it is windy. We just moved to an old Victorian house that appears to have very little insulation. I happily dry all the clothes indoors (my wife doesn't when she does it, she cares more) and apart from a little condensation on windows, there are no consequences. Our gas and electricity bills are way below what the utility companies predict. I expect the previous occupants kept it much warmer. But a few air changes don't cost a lot.

Posted By: mike7I grew up in 'fuel poverty'. No CH, no DG, but no mould except on the glazing bars. The windows acted as dehumidifiers.

Exactly!

Please don't get me wrong. I generally think that minimising vapour production is a good idea. I certainly wipe the shower down and put lids on pans etc. But it isn't the be all and end all. Ventilation is also very important.

Simon - my dishwasher vents warm air into the kitchen from the front control panel when it's on the drying cycle. I presume it's got moisture in it from the wet dishes as they are dried.

Posted By: Gavin_Aclothes were dried outside on the lines (even across the back lanes in the terraces).

In this part of Brighton there used to be numerous laundries. Many of the buildings survive and are used for other light industries or for housing. One house near here has a huge garden running between all the other gardens. The house has a big back extension which used to be a laundry. The long garden was used for drying.

Laundries were killed off in the 1950s by the laundrette. The laundrette was killed off by the domestic washing machine. All this was happening at the same time as open fires were replaced by central heating.

Possible nanotechnology dehumidifier:

http://www.adafruit.com/blog/2012/11/22/scientist-develops-bottle-that-draws-water-from-the-air/

Posted By: Gavin_A

Posted By: Mike GeorgeYes, there is a fundamental problem with Building Design - its that the vast majority were built in a different age (building wise) When coal fires blazed and kept the masonry way above dew point; and when ventilation was considered far more important than heat loss.

Nowadays we have many many people in fuel poverty who cannot afford to heat their homes and consequently keep such masonry above the dew point. In addition, such condensation leads to mould and serious health problems, particularly in children and the aged

For them the advice offered here is critical

I think you'll find that average temperatures in houses is way higher now than it used to be in the days of coal fires, certainly in any room other than the main living room.

what coal fires would have done is to suck a lot of air through the house when lit, and mean all houses had open chimneys in most rooms, meaning all these rooms would have had a lot more ventilation than now they've mostly been closed up.

most houses probably didn't have showers back then either, which would knock a significant volume of moisture off, and clothes were dried outside on the lines (even across the back lanes in the terraces).

Agree, but my point about Coal fires was not about air temperature, It was about the temperature of surfaces. These would have been above Dew point and also the walls would have been substantially drier in areas which are typically wet /damp nowadays. (remembering that damp walls have a negative affect on surface temperature)

The walls would also been made up of materials which would more easilly permit the flow of vapour ..All subjective I know..