Green Building Forum - Ways to reduce condensation in the home : a list Sat, 09 May 2026 04:58:02 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162014#Comment_162014 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162014#Comment_162014 Thu, 22 Nov 2012 13:16:27 +0000 seascape Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162021#Comment_162021 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162021#Comment_162021 Thu, 22 Nov 2012 14:13:30 +0000 Paul in Montreal
Paul in Montreal.]]> Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162027#Comment_162027 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162027#Comment_162027 Thu, 22 Nov 2012 17:13:30 +0000 Cav8andrew Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162032#Comment_162032 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162032#Comment_162032 Thu, 22 Nov 2012 18:59:17 +0000 Paul in Montreal Posted By: Cav8andrewPaul, slightly away from the main topic but what did your 15mm of insulation comprise of.

In some locations, foil-faced poly isocyanurate boards, in others, we blew in cellulose behind existing plaster and lath - the "cavity" in that case was between 1/2" and 1". One wall (that is triple-brick with 8" of stone as well for good measure) we used 1 1/2" extruded polystyrene, but about 1/3 of that wall is actually window (but it faces North and was always very cold). I attached furring strips (battens) on top of the insulation boards and then drywalled on top of that, fixing various out-of-true issues with the walls at the same time.

Before the work was done, we'd had an energy audit during a stable period of cold weather (with a temperature of -11C outside for about 3 days) - the coldest inside surfaces were about 14C, for a nominal air temperature of about 20C. (This measure was used to estimate the R-value of the walls for entering into the hot2000 model which used to compute the annual energy usage and the amount of "improvement" grant that was to be awarded [as this was post the 1st set of renovations]). Now the interior surfaces stay within about 0.5C of the air temperature. The wall's have a fairly modest R (or U) value, but it is much better than it was and the reduction of air-leakage (and convection paths behind the plaster and lath that remains) has made a large difference. You really don't have to add much insulation to a solid wall to reduce the heatloss by 3/4. Over here in such old solid wall houses, the recommended maximum insulation is between about 25-30mm only.

Paul in Montreal.]]> Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162033#Comment_162033 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162033#Comment_162033 Thu, 22 Nov 2012 19:36:18 +0000 Cav8andrew Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162035#Comment_162035 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162035#Comment_162035 Thu, 22 Nov 2012 19:42:07 +0000 SteamyTea Posted By: Cav8andrewsuspect the improved air tightnessI have comes to the conclusion that it is the most important (within reason or a single skin tend would do). I think Paul has some better figures on it though.]]> Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162037#Comment_162037 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162037#Comment_162037 Thu, 22 Nov 2012 19:52:47 +0000 jamesingram Posted By: SteamyTea
Posted By: Cav8andrewsuspect the improved air tightness
I have comes to the conclusion that it is the most important .
Yeah, really helps reduces heatloss, but then you have to open a window to stop the damp and mold :shocked:]]> Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162038#Comment_162038 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162038#Comment_162038 Thu, 22 Nov 2012 20:07:00 +0000 SteamyTea Posted By: jamesingrambut then you have to open a window to stop the damp and moldOr make your own MVHR like I did earlier in the year.:wink:]]> Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162039#Comment_162039 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162039#Comment_162039 Thu, 22 Nov 2012 20:14:05 +0000 Paul in Montreal Posted By: jamesingramYeah, really helps reduces heatloss, but then you have to open a window to stop the damp and mold

The way we mitigate against damp (well, we don't get any in winter because the cold air is really dry) and mold is to keep internal surfaces above the dew point. This means keeping the heating on at a level that will accomplish this (I experimented with setbacks on the thermostat but gave up - it's easier just to keep a constant temperature, but, I do work from home). We keep the windows closed from October till March! Another thing that makes it easier for us in North America is that houses tend to have quite a significantly larger volume than those in the UK - this greatly reduces the concentration of anthropogenic water vapour, keeping the RH lower than would be the case in a smaller building.

I have found, though, that it doesn't take much (internal) insulation to reduce the heatloss by a sufficient amount to keep those surfaces above the dew point. If the walls are warm, you feel warmer for a given air temperature as they're not radiating cold at you. Prior to the improvements, even though the air temperature said it should feel warm, it didn't, due to the cold radiators that the walls effectively had become. Another thing that works in favour for my house is the ground floor feels warm because the basement beneath it is heated (by warm air - which rises to the floorboards). If your feet are warm, you tend to feel warmer. So it's kind of a passive UFH system.

Paul in Montreal]]> Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162040#Comment_162040 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162040#Comment_162040 Thu, 22 Nov 2012 20:22:30 +0000 Cav8andrew Today with the weather chucking everything at us it is amazing how stable the temperature has remained. Its very noticeable that there is no feeling of the ambient heat being ripped out of the space and non of the feeling of a chill wind cooling the body. Obviously the level of insulation is important in retaining heat but I am convinced the attention to detail and the opportunity to carefully detail the air tight envelope has been hugely important in not only maintaining the level of heat but also the sense of comfort re. the sensory perception on the skin. I can only agree with others comments re. the worth of good air tight detailing.
Sorry bit off topic.]]> Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162041#Comment_162041 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162041#Comment_162041 Thu, 22 Nov 2012 20:29:55 +0000 jamesingram Posted By: SteamyTea
Posted By: jamesingrambut then you have to open a window to stop the damp and mold
Or make your own MVHR like I did earlier in the year
Just fitted a little unit (2nd hand ebay) for upstairs , might make some diy box to grab that bit more heat from it. ie. run exhaust from hrv and air-in before hrv through it , if I get a quiet day.
To early to say if it'll improve things , but cetainly fresher/better air in north facing bedrooms at night (waiting for my CO2 meter to come back form the supplier to see changes there.) as we keep these windows closed due to traffic/urban noise.
Truth is, what I really need to do is EWI my NE and NW walls to bring them up to the standard of the rear of the house (SE), then damp will be a thing of the past , i hope :smile:]]> Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162043#Comment_162043 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162043#Comment_162043 Thu, 22 Nov 2012 22:38:57 +0000 nikhoward Posted By: SteamyTea
Posted By: jamesingrambut then you have to open a window to stop the damp and mold
Or make your own MVHR like I did earlier in the year.https:///newforum/extensions/Vanillacons/smilies/standard/wink.gif" alt=":wink:" title=":wink:" >

is it all working now or still in progress, the last i saw you say i think was about making a new heat exchanger?]]> Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162044#Comment_162044 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162044#Comment_162044 Thu, 22 Nov 2012 22:40:43 +0000 nikhoward Posted By: Cav8andrewFor the last month we have been, for the first time, working within a fully insulated and airtight roof space (I think its probably the first time I have ever had an opportunity to spend a noticeable amount of time in such an environment)
Today with the weather chucking everything at us it is amazing how stable the temperature has remained. Its very noticeable that there is no feeling of the ambient heat being ripped out of the space and non of the feeling of a chill wind cooling the body. Obviously the level of insulation is important in retaining heat but I am convinced the attention to detail and the opportunity to carefully detail the air tight envelope has been hugely important in not only maintaining the level of heat but also the sense of comfort re. the sensory perception on the skin. I can only agree with others comments re. the worth of good air tight detailing.
Sorry bit off topic.

good points, we are starting to reach that point too]]> Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162046#Comment_162046 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162046#Comment_162046 Thu, 22 Nov 2012 23:21:28 +0000 nikhoward
Been following this thread with interest. We have had lots of problems with Damp - combination of breached DPC, South West Water (big) mains leak, neighbours leaky drain, house empty for 2 years before us, condensation (more venting, improved insualtion, dehumidifier), failing 50 year old bitumous DPM (new DPM and floating floors to half the house), DPC and DPM not in any way meeting up (tanking). Also followed and commented onthe Babs30 (I think) thread from about a year ago.

I also try to do all things mentioned in this thread - venting bathroom/kitchen when showering/cooking, no washing drying inside (except towels), opening windows, lids in pans, etc

So all in all close to my heart.

So as an experiment I monitored RH today whilst playing with venting, heating, dehumidifier, etc (while fitting celotex between rafters):

Time o/s temp i/s temp RH Comment
closed
0800 7 20 82 heating off
closed
0900
open
1000 ? ? 62
open
1200 11 ? 66
closed
1300 12 17 73
open
1500 ? ? 68 started chucking it down
open
1540 ? 19 66
closed
1600 76 put on dehumidifier
closed
1615 ? 19 67
closed
1700 9 ? ? heating on
closed
1800 ? 19 56
closed
1900 dehumidifier off
closed
2200 heating off
2300 ? 20 64

open or closed bewtween times is windows open or closed, no cooking, no laudery, no dishwasher, no shower during study. Lots if windows open and very very windy day. Wish I has put all this in excel, would have been easier (oh well).

Our RH has been better since increasing house volume by about 60%, but has got a bit worse since installing the windows/velux's upstairs (instead of just breather membrane).

Conclusion? Well it does not take that long for RH to drop when you open a window, but it starts to creep up when you close it (but not really sure why), RH went up when it began raining, dehumidifier gets RH a bit lower than venting but tales a bit longer. Is HRMV the only option to reduce RH to an acceptable standard?

I welcome some comments from you people who know much more than me.]]> Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162048#Comment_162048 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162048#Comment_162048 Thu, 22 Nov 2012 23:37:30 +0000 nikhoward Posted By: jamesingram
Posted By: SteamyTea
Posted By: jamesingrambut then you have to open a window to stop the damp and mold
Or make your own MVHR like I did earlier in the year

Just fitted a little unit (2nd hand ebay) for upstairs , might make some diy box to grab that bit more heat from it. ie. run exhaust from hrv and air-in before hrv through it , if I get a quiet day.
To early to say if it'll improve things , but cetainly fresher/better air in north facing bedrooms at night (waiting for my CO2 meter to come back form the supplier to see changes there.) as we keep these windows closed due to traffic/urban noise.
Truth is, what I really need to do is EWI my NE and NW walls to bring them up to the standard of the rear of the house (SE), then damp will be a thing of the past , i hopehttps:///newforum/extensions/Vanillacons/smilies/standard/smile.gif" alt=":smile:" title=":smile:" >

getting one off ebay also crossed my mind as a cheaper way of HRMV]]> Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162055#Comment_162055 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162055#Comment_162055 Fri, 23 Nov 2012 07:03:47 +0000 SteamyTea It is all ready to go just waiting until I turn my heating on fully.

Your ambient RH yesterday was like this:

Hour , RH
0 , 95%
1 , 94%
2 , 93%
3 , 90%
4 , 90%
5 , 88%
6 , 85%
7 , 85%
8 , 84%
9 , 83%
10 , 82%
11 , 80%
12 , 81%
13 , 81%
14 , 86%
15 , 92%
16 , 98%
17 , 97%
18 , 96%
19 , 98%
20 , 98%
21 , 98%
22 , 97%
23 , 96%]]> Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162069#Comment_162069 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162069#Comment_162069 Fri, 23 Nov 2012 15:29:20 +0000 jamesingram Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162072#Comment_162072 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162072#Comment_162072 Fri, 23 Nov 2012 15:48:31 +0000 SteamyTea What goes on in your house is of no concern of mine :wink:]]> Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162073#Comment_162073 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162073#Comment_162073 Fri, 23 Nov 2012 16:05:17 +0000 davidfreeborough Posted By: SteamyTeaWhat goes on in your house is of no concern of mineUnless you're one of ST's neighbours, in which case he'll nip around when you're out to read your electricity meter!:bigsmile:

David]]> Ways to reduce condensation in the home : a list https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162074#Comment_162074 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6773&Focus=162074#Comment_162074 Fri, 23 Nov 2012 16:09:36 +0000 SteamyTea ]]>