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Positive Input Ventilation

E

Enfield boy

pfm Member
I have a bungalow built in 1960. We've owned it for years, replaced the central heating, put decent double glazing in, had cavity wall insulation installed etc. The property has always had a bit of a condensation problem but since we retired and spend more time in it, it seems worse in spite of what we've done. My health hasn't been great the last few years and redecoration is increasingly hard, mould is appearing in a few corners and is getting me down, frankly.
I've seen a fair bit online about PIV's and wonder if anyone has installed one. I also wonder if it's 80-90% humidity outside how drawing air from a cold, well ventilated loft will help.
 
If you have a bungalow with a decent roof space, MVHR would be a (by the standards of these things) fairly easy fit. Ours keeps the humidity below 62% even when it is very wet outside.
 
Thanks for the suggestion which I will investigate. Most of the bungalow has a proper loft but one bedroom and the "office" are flat roof, these are two of the worst parts of course! MHVR looks pretty radical and at first glance potentially quite expensive.
 
It is, but it has made a big difference here. For example, washing dries overnight indoors pretty much all the time without causing damp problems which means we haven't had to use a tumble dryer since it was installed.
 
+1 MVHR is the way to go - the reclamation of 75-85% of the heat energy in the air exchange is a huge reason these things, even as retrofit, pay for themselves quickly - even when you've done the right thing, like deal with airtightness and better windows/draughtstripping etc. (which are also quite likely contributory to your condensation issue)

Just adding positive pressure to inject untempered outside air, is a total waste in comparison

Does not have to be that expensive - there are companies that supply off-the-shelf kits that are relatively easy to install/ have installed.(heck 25yrs ago Wickes used to do a DIY kit in a box for £150 - even that would typically pay for itself in a year or less, then.)


The trick is to work out where the box can live, where to extract vitiated air from (warm + wet spaces like the kitchen first, then the bathroom/most used shower etc) and ..where to supply the tempered, not cold but not that warm incoming air to - like a hallway, so it percolates into the warmer areas or provide a buffer; or is used to directly address cooler spaces where you have the problem, by moving pre-warmed, slightly drier air through them first. If that sounds daunting - it isn't. HTH.


ETA: the other partial but cheap &effective / seasonal solution, is to consider a dehumidifier, to simply remove the excess water vapour / keep local relative humidity % high enough that condesntion cannot occur, and mould will not grow.
 
I used to live in a place with this, it was in France and a porous limestone building with no cavity. No problem, as others have said it goes through a HX and ventilates the space. Without it the stonework turns green, I'm told.
 
stevec67 said:
I used to live in a place with this, it was in France and a porous limestone building with no cavity. No problem, as others have said it goes through a HX and ventilates the space. Without it the stonework turns green, I'm told.
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op cit: most of the Cotswolds .. ;)
 
As Martin above states - MVHR really is the way to go!
Fitted it myself to the workplace, looking to do the same at home now.
Plenty of choices.
Hardest part for the OP will be boxing in the extract / feed pipes, and possibly getting the 'flow' correct.
Being a bungalow should make it a pretty easy task comparatively, (depending on size of unit v size of loft access opening)
Some units are sized to fit within a standard kitchen cupboard as well now.
 
Enfield boy said:
Thanks for the suggestion which I will investigate. Most of the bungalow has a proper loft but one bedroom and the "office" are flat roof, these are two of the worst parts of course! MHVR looks pretty radical and at first glance potentially quite expensive.
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We had a couple of houses with these and it was a simple job to remove the PB ceiling and fill the joist spaces with wool; iirc they were 8" deep so pretty effective.

Got a local guy in to skim the new ceiling but you can tape the joints if that'll do aesthetically.

Would a basic dehumidifier help? Once the house is dried a few hours each night on cheap electricity is usually enough.
 
We've got some minor mould issues in corners and external walls. We've been taking some extra care with ventilation, airflow & have a good home-dehumidifier - things have improved. Old style double glazing with no venting is an issue here so we have it on the 'slightly open' setting in the day. Showers, cooking and drying laundry inside are the problems at the moment.
Have you got a good capacity dehumidifier? We've got one but I'm trying to buy another (obviously popular at the moment - Meaco site seems to be totally sold out)
 
Not sure where we're going wrong here. 1962 detached, d/glazed, cav. wall insulation, full c/h but we don't get visible condensation. When we bought the place 21 years ago there was condensation mould everywhere, but the young things never opened windows. I decorated once; that'll do for life ! ;)

O'p., I do wonder where all that moisture comes from to cause those problems. Our house is usually under-heated (i.e. pretty cold) most of each winter day, which I thought would increase condensation. However, compass direction of property may be a factor. Our only non-aperture wall is north and sheltered. Other 3 facings get light and sun when shining.
 
In the 40 years we have lived in our 1960s bungalow there has always been a problem with black mould despite cavity wall insulation and double glazed windows. Last winter I bought a Meaco Aret One dehumidifier which they claim is a whole house device. Instructions say open all doors and close windows.

This has made a tremendous improvement, reducing mould at least 80% or more. Only downside is it can at times be a bit noisy.
 
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