Just a note on the dishwasher issue. We have a Bosch and its drying cycle is accomplished by using extra hot water (there's no element in the machine to directly dry the contents). If the door is left closed, no moisture escapes. Usually, though, I open the door as soon as the cycle has finished and find the hot damp air useful in winter to provide a bit of extra humidity. All that said, since the airtightness of my house was improved, excessive dryness in winter is a thing of the past, though I do now get a tiny bit of condensation on the windows if the exterior temperature is below about -10C. Having the house at a stable temperature inside (with all the wall surfaces within 0.5C of the air temperature) has made a big difference - only about 15mm on insulation was required to achieve this too.

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.

Posted By: Cav8andrewsuspect the improved air tightness

I 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.

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.

For 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.

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="" title="" >

is it all working now or still in progress, the last i saw you say i think was about making a new heat exchanger?

apart from my comments above, what I was actually going to say:

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.

Nik
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%

it is just the outdoor (ambient) RH from a weather station near you.
What goes on in your house is of no concern of mine

I hope they have steamy windows so they can't see me doing it