Condensation in bedrooms. Positive Input Ventilation PIV?

rangor gubbins

rangor gubbins

rangor gubbins

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Anyone got experience with installing a PIV fan unit?
Our house is old-ish, but has been refurbed with lots of insulation and double glazing, there are no radiators and all heat is provided by underfloor heating and an ASHP. When we put the (wooden) windows in we decided not to have trickle vents. For most of the year its fine but when its very cold outside we get quite a lot of condensation on the windows and its goes mouldy.
Running the wood burning stove helps a lot, but I'd like a more constant solution to the condensation. I originally thought that we should retrofit some trickle vents. However, our house is in quite an exposed position and i think we'd get a lot of draft coming through the trickle vents.
I'm wondering if positive input ventilation would work.
It would be installed so that it will move air from our loft (which has lots of insulation in and under the rafters, so is not cold) to the main corridor on the first floor, which connects the bedrooms and bathroom. But I'm not sure whether it will reduce/stop condensation in the bedrooms if there is not much air gaps in those rooms for the fresh air to push out the humid stale air.
 
If you have a warm loft PIV needs to be installed above that. Otherwise you would just be moving the same air from one room to another rather than from outside to in.
Have you thought about a dehumidifier?
 
Watching a program on television last night with Denise van Outen, she spoke to a German guy who insisted that to remove condensation, open all windows wide for at least three minutes every day before closing them and heating the house again. Apparently it is common practice and the heating is far more effective as the air is dryer.

Note I have not tried this as we don't suffer from condensation so should be treated as hearsay.
 
robj20 said:
If you have a warm loft PIV needs to be installed above that. Otherwise you would just be moving the same air from one room to another rather than from outside to in.
Have you thought about a dehumidifier?
Click to expand...
above the loft is the outside!
The loft is well insulated but i don't think its air tight. i see what you're saying though, we might just be moving house air from the loft to the first floor, and it finds it way back up there again, without bringing much fresh air in.
Maybe i should do some humidity measurements and see what the levels are in the first floor and loft.

I guess an alternative setup would be some kind of MVHR system, with ducting bringing in air from the outside.
 
We have really bad condensation in our house. I have partially solved it with a dehumidifier but it's too small, so I am thinking of buying a bigger unit. Now I've been looking at PIV's and they sound like they will solve the issue but I don't like the idea of cold air being blasted into the landing and hallway.
 
Hagar said:
Watching a program on television last night with Denise van Outen, she spoke to a German guy who insisted that to remove condensation, open all windows wide for at least three minutes every day before closing them and heating the house again. Apparently it is common practice and the heating is far more effective as the air is dryer.

Note I have not tried this as we don't suffer from condensation so should be treated as hearsay.
Click to expand...

Yep, this works from a technical standpoint. If you let in outside air that is 5ºC and 90%RH, heating it up to 20ºC will reduce the relative humidity to 35%.
 
panthro said:
We have really bad condensation in our house. I have partially solved it with a dehumidifier but it's too small, so I am thinking of buying a bigger unit. Now I've been looking at PIV's and they sound like they will solve the issue but I don't like the idea of cold air being blasted into the landing and hallway.
Click to expand...

Doesn't blast air, although it does reduce the temp a little. I have it on setting 2. I bought the heated model but I don't use that function
 
This can be a problem with sealing air gaps and adding insulation to a house. Humans create a lot of damp air! The water has to get out somewhere or you get condensation no matter what.

You can turn the heating up, in which case the air can carry more water as it exists through normal gaps here. Or you can buy a dehumidifier. Or you can open a window just a tad. The best way is to install a heat-recovery ventilation unit in the loft. This not only gets rid of damp air, it gets rid of stale air too.
 
SpellowHouse said:
This can be a problem with sealing air gaps and adding insulation to a house. Humans create a lot of damp air! The water has to get out somewhere or you get condensation no matter what.

You can turn the heating up, in which case the air can carry more water as it exists through normal gaps here. Or you can buy a dehumidifier. Or you can open a window just a tad. The best way is to install a heat-recovery ventilation unit in the loft. This not only gets rid of damp air, it gets rid of stale air too.
Click to expand...
Our house used to have a hot air system as it was a 1970s build. The previous owners changed it to gas central heating but left the air vents in the ceilings in. They only sealed them up prior to us moving (the vents were still in when we viewed the house). We also built a 2 storey extension so I am guessing all of this has created the condensation problem.
Any recommendations on what type of PIV I should be looking at?
I've read that PIV's blow the loft smell into the house. Surprised they don't come with better filtration.
 
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Until you get your solution in place, if you don't want the windows to get mouldy, then dry them off using a squeegee and a microfibre cloth (which you can wring out into the sink) at least once a day. You could also use a Karcher Window Vac designed for this purpose.
 
I've considered PIV for our 1900's house, but as we have suspended timber floor, no carpet downstairs and none of the doors really seal underneath.. I'm not sure it make any difference with pushing air out.

We have the windows open often, keep the house warm - but still get condensation around the windows in the bedrooms. I think the actual fix here is better windows.
 
We have a dehumidifier running over right. From looking at live usage it seems to cost about 1-2p an hour. The amount removes varies but is usually 1-1.5 litres in 10 hours. No real window condensation since using it.
 
GeX said:
I've considered PIV for our 1900's house, but as we have suspended timber floor, no carpet downstairs and none of the doors really seal underneath.. I'm not sure it make any difference with pushing air out.

We have the windows open often, keep the house warm - but still get condensation around the windows in the bedrooms. I think the actual fix here is better windows.
Click to expand...
If it's just the lower inch or so I don't think any fix is required. It soon evaporates
 
Hagar said:
Watching a program on television last night with Denise van Outen, she spoke to a German guy who insisted that to remove condensation, open all windows wide for at least three minutes every day before closing them and heating the house again. Apparently it is common practice and the heating is far more effective as the air is dryer.

Note I have not tried this as we don't suffer from condensation so should be treated as hearsay.
Click to expand...
Yup
 
I understand that you do not have trickle vents, noting draughts as a possibility of having them, but I'm not sure how ventilation / draughts can be avoided rather than sealing up a house, to a point.
We tend to leave quite a few of our windows on the open/close locked feature to allow air flow most of the time. There can be exceptions in the day, but the yare then opened up later and locked, if that makes sense.
Basic things like using a Karcher type squeegee thing to totally wipe down the shower area after taking a shower, and lots of air ventilation in the bathroom, helps.
Having a dehumidifier and also raising the temp a little for the central heating, frostguard setting used, to ensure a little warmth in the rooms above that of the otherwise cold they would be, helps. That raises the dew point and makes it easier for the dehumidifier to extract the moisture.
We have some monitoring going on in some of our rooms....

Screenshot-2024-12-09-06-13-27-174-com-govee-home.jpg


kinda allows for a more informed look at the dehumidifier placement and keeps watch on the minimum temps etc, especially in the garage where the boiler is. Trends with temps, humidity and dew point readings etc can be seen for each room.

Overall.................ventilation, heating and habits of extractor fan for the kitchen and squeegee use etc has helped to make the condensation far more manageable than it used to be.
 
Vimes said:
I understand that you do not have trickle vents, noting draughts as a possibility of having them, but I'm not sure how ventilation / draughts can be avoided rather than sealing up a house, to a point.
We tend to leave quite a few of our windows on the open/close locked feature to allow air flow most of the time. There can be exceptions in the day, but the yare then opened up later and locked, if that makes sense.
Basic things like using a Karcher type squeegee thing to totally wipe down the shower area after taking a shower, and lots of air ventilation in the bathroom, helps.
Having a dehumidifier and also raising the temp a little for the central heating, frostguard setting used, to ensure a little warmth in the rooms above that of the otherwise cold they would be, helps. That raises the dew point and makes it easier for the dehumidifier to extract the moisture.
We have some monitoring going on in some of our rooms....

Screenshot-2024-12-09-06-13-27-174-com-govee-home.jpg


kinda allows for a more informed look at the dehumidifier placement and keeps watch on the minimum temps etc, especially in the garage where the boiler is. Trends with temps, humidity and dew point readings etc can be seen for each room.

Overall.................ventilation, heating and habits of extractor fan for the kitchen and squeegee use etc has helped to make the condensation far more manageable than it used to be.
Click to expand...
what sensors are they and can they be put into home assitant??
 
@Welshman



they are "just" Bluetooth and are standalone, with an app for the phone. There are more expensive Wi-Fi type. But those are good enough for our needs. I did a review of them there, under the name "Morgan" if you wanted to read a little more.

At the time of writing the yare 2 for £20 or so, on offer.
 
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