Constant 48-53% rh, 21 degrees c and hardly any heating required. A world away from the freezing home with water pouring down the windows that I used to live in. Should be building all new homes to Passive house standard.
I posted on here last week due to a wet wall inside my house which I'd assumed was rain bring driven through single skin brick, but people pointed out that it might well be condensation instead. As the suggested step one was to get a dehumidifier I got a Meaco 20l one.
When I turned it on it was reading in the mid-70s and after having it run constantly for a week I came down this morning to the high 48s and it had automatically turned itself off.
The wall isn't wet any more.
@soundninjauk nice one. Worth monitoring humidity in the house and making sure there is adequate extraction/ventilation particularly in bathrooms and kitchen. It will be the coldest wall in the house and the point where condensation forms first.
ours sits about 75% ish. more in a morning 1900 red brich house with cold floors (air bricks) and cavity wall insulation.
We used to get water running down the walls every morning. Last year we boarded the cold walls with insulated board. Nothing as bad this winter and RH moving towards 65% ish.
we still get enough water in the morning to fill a karcher widowvac (that i got for christmas 🙂 ) from one set of windows and its lifted the paint off the windowsill.
Ive wired the bathroom extractor (that was one of these constant on trickle ones) to be on boost all the time now and that has also helped a lot.
I have a dehumidifier running 9am to 9pm. although this is about 10 years old so maybe its worth replacing?
Before fitting a PIV unit, high 70’s, sometimes into the 80’s. Mould issues and constantly wet windows in winter.
Dried up within days after fitting PIV unit and now I don’t even monitor it.
nice one. Worth monitoring humidity in the house and making sure there is adequate extraction/ventilation particularly in bathrooms and kitchen. It will be the coldest wall in the house and the point where condensation forms first.
Ta! We've got a Nest system and the thermostat is in the kitchen/big open plan family room, plus some protect smoke/CO sensors throughout the house that apparently also measure humidity (including one in the kitchen, and one near the bathroom on the first floor). Currently it's reading inside humidity of 53%, although I forgot to look to see what it was last week before I plugged in the dehumidifier.
The extractor fan in the bathroom has always struck me as a bit weedy (we moved in coming up for a year ago) but as it does seem to do something it's not yet made it to the top of the list to replace. I do have trickle vents open in the window though.
How humid is your house?
Very. We have got on top of the problem now but it was pretty bad. Having the windows open a bit overnight and judicious and targetted use (kitchen, bathroon) of de-humidifier have improved things a lot. I have also fitted a load of lap vents in the loft but not been back up to see if that's made any difference up there. That was worryingly damp up there.
We have a somewhat sprawling bungalow which tend to be the worse for damp and poor ventilation. The main bedroom was pretty damp (at the end of a corridor) I've somewhat sorted this with a meaco dehumidifier and stopping my wife hanging her towel on the rad in there. Also upgraded the extractor in the bathroom and sorted out the temperatures in the house by fitting a wiser system. I run the dehumidifer at 65% which is on the high side, but since the house runs at 16 degrees (otherwise the oil bill is insane) that's actually the same absolute humidity as 45% at 21 degrees. Walls aren't wet and certainly no mould.
We do get condensation on the old aluminum patio windows which is addressed with a karcher vac but long term i need to replace. I would fit a PIV system but the obvious place to put it is tricky as the loft above that area is semi converted. I guess long term i'll fit some kind of MVHR system which is apparently not that hard to do DIY in a bungalow. Short term i'm going to add some trickle vents to the windows.
Nest in the living room says it's currently 34% and 19c. No signs of mould anywhere (70s bungalow)
currently at 49% according to the nest thermostat - its surprising how quickly the humidity changes on a day by day basis, I think its usually somewhere between 45% and 65%.
We do not have a dehumidifier.
We have Tado and I've been tracking this as the windows get very wet in our old stone house with no lack of draughts.
One room was sitting at 85% and no amount of dehumidifying seemed to help at all. Finally tracked it down to a leaking TRV, weeping round the pin and the Tado was damp inside! Swapped the valve itself and room now back in the 50's and Tado still working, luckily. Doh!
I have a condensation issue that ironically is realated to 'good' ventilation. The issue is that in a 60's house we have a ventilation brick in the corner of the room, origionally with no control over the airflow. In the winter this results in cold air blowing along and cooling an internal wall that then suffers condensation and mold. Reducing the ventilation improves things but to prevent condensation I'd need to block it compleatly reducing the ventilation to the house to window trickle vents only. Is there a better solution?
Have you tried making it more diffuse?
Depends alao if you have any extractors and if the combustion appliance that the vent was originally for is still present.
If not, Id just block it up and rely on the trickle vents, but we dont know the other particulars. Are the floors suspended or solid?
Before fitting a PIV unit, high 70’s, sometimes into the 80’s. Mould issues and constantly wet windows in winter.
Dried up within days after fitting PIV unit and now I don’t even monitor it.
^^^ This ^^^
Worst I saw it was 87% we had waterfall windows, black mould in bedrooms, wet walls. I had constant asthma and the carpets felt damp. We still get a little condensation in the windows, which are single glazed Yorkshire Sash, but none of the other issues. It currently reads 44%.
At the same time as fitting the PIV I removed about 36 big bin bags of loft insulation that had been triple layered and also stuffed down into all of the eaves. I possibly removed too much but at the time we had interstitial damp; the insulation was hip deep and when I reached down through it my hand and arm came out wet.
Basically it was so deep that warm air condensed within the fibre rather than allowing evaporation into the loft.
As mentioned above, if I was to fit another I’d buy the heated version as the cold air is noticeable.
It’s not that simple.
Yes I appreciate that, depends on temp etc, but most british houses in winter with 70% RH are going to get condensation issues. I only speak form experience of managing condensation across a range of properties and measuring changes in internal vs external RH as fans function and heating comes on etc.
thats a point. keep your house at 21deg and 70% RH is a lot more moisture content than if you keep it at 18deg.
dewpoint at 18deg/70% is about 12.5 deg.
Just a mild warning about PIVs and humidity. If you're forcing new air into a building, without a balanced extraction, that old hot, damp air has to go somewhere. If you've got air bricks/vents etc, it shouldn't be an issue as it'll vent that way, but it can force it's way into walls/ceilings/floors, cool, and condense on surfaces, causing internal damp and potential for mould or moisture issues. Even a small pressure differential can cause a large air flow.
Often it's a good idea to have a balanced, or close to balanced, incoming/outgoing ventilator (ideally with heat recovery) to avoid this...but they can be much more expensive, so initially less appealing. Essentially, make sure you've at least got a path for the air to vent through.
I possibly removed too much but at the time we had interstitial damp; the insulation was hip deep and when I reached down through it my hand and arm came out wet.
Basically it was so deep that warm air condensed within the fibre rather than allowing evaporation into the loft.
So what's needed there is a vapour barrier at the base of the insulation and no vapour barriers within the stack of insulation. Once you have a vapour barrier moisture can't get into the insulation from teh house and even a tiny temperature gradient though the insulation will eventually dry it out and prevent it getting wet again.
Often it’s a good idea to have a balanced, or close to balanced, incoming/outgoing ventilator (ideally with heat recovery) to avoid this…but they can be much more expensive, so initially less appealing. Essentially, make sure you’ve at least got a path for the air to vent through.
I thought this also, but having fitted six in various houses this year, all they have is trickle vents, bathroom/kitchen extract fans. Has made huge differences across the board. We fitted them a some problem properties about 10-15 years ago and they fixed all issues. However the recent ones are all due to the no heating, and wet relatively warm weather.
