Condensation issues, I have been recommend to fit a PIV ( Positive Input Ventilation) Unit

justwondering25

Has anyone had any past experience with a PIV unit to help combat condensation?
My tenant of the past 4 years is about to leave, one thing he has done and it can be seen on the estate agents inspection reports, is that they have been drying clothes on radiators etc.
Which has caused condensation which has led to black mould.
The double glazing does not have any inlet vents, so unless the tenant opens the window, or turns on the fan in bathroom, then there is little airflow in the building, other than a couple of building brick vents two of the bedrooms.
I was reading up about condensation fixes and I watched a couple of Youtube videos and a lot of people seemed very positive about using a PIV unit, the unit is fitted in the loft and actively circulate the air in the house, low powered and quite too.
The reviews for the various units available online via the various big main online shopping venues, seem very positive and so did the comments on the youtube videos of people that have used them.
The house is a centrally heated doubled glazed 1930's semi.

princeofpounds

Yeah not having trickle vents (or similar ventilation) is always going to give you problems. Of course the tenant shouldn't be drying clothes on radiators (do they have anywhere else to do so?) and should open windows, but the way you have things set up it wouldn't take much for problems to recur, even if people live reasonably.

I haven't used PIV myself, but I've mainly heard good things about them. But often just having simple ventilation may be enough, so I'd see if there were easier options first. 

justwondering25

princeofpounds said:

Yeah not having trickle vents (or similar ventilation) is always going to give you problems. Of course the tenant shouldn't be drying clothes on radiators (do they have anywhere else to do so?) and should open windows, but the way you have things set up it wouldn't take much for problems to recur, even if people live reasonably.

I haven't used PIV myself, but I've mainly heard good things about them. But often just having simple ventilation may be enough, so I'd see if there were easier options first. 

The problem I have found over the years, the tenants do not like to open the windows during the winter, due to heating the house, they see it as a waster of money, the PIV unit is something that would run all the time and take out the need for the tenant to be play their part, which sadly they generally do not.

A PIV unit appears to automate the process of bringing the air into the house to help fight condensation.

greatcrested

Whether you deduct from the tenant's deposit for causing condensation and mould is of course your choice. Even if there is no express prohibition in the tenancy agreement, tenants are implicitly required to act in a 'tenant-like manner', and drying clothes on a radiator without opening windows or otherwise ventilating fails in this duty.

I've no idea about PIVs - do they just 'circulate the air' or do they extract moisture as well? If just circulate I don't see the benefit - the moisture remains and will end up somewhere.....

justwondering25

greatcrested said:

Whether you deduct from the tenant's deposit for causing condensation and mould is of course your choice. Even if there is no express prohibition in the tenancy agreement, tenants are implicitly required to act in a 'tenant-like manner', and drying clothes on a radiator without opening windows or otherwise ventilating fails in this duty.

I've no idea about PIVs - do they just 'circulate the air' or do they extract moisture as well? If just circulate I don't see the benefit - the moisture remains and will end up somewhere.....

I am a complete novice to PIV units, I have watched the youtube fitting guides and reviews.
Below is a cut and paste on how they work.
"PIV works by continually diluting, displacing and replacing indoor air with filtered, low moisture content external air from either the loft of an external source. This air is delivered to a central point in a property and, in turn, each room off this central point benefits."
https://www.fixmyroof.co.uk/videos-and-guides/condensation-cure/piv-unit-system/

princeofpounds

greatcrested said:

I've no idea about PIVs - do they just 'circulate the air' or do they extract moisture as well? If just circulate I don't see the benefit - the moisture remains and will end up somewhere.....

They basically push in new air, which continually displaces old moist air. It's like an active version of what happens passively with things like trickle vents, there's nothing mysterious about it despite the acronym. It's high and consistent volume, low speed. It's used a lot in commercial buildings, although often as part of a general air con system.

justwondering25 said:

The problem I have found over the years, the tenants do not like to open the windows during the winter, due to heating the house, they see it as a waster of money, the PIV unit is something that would run all the time and take out the need for the tenant to be play their part, which sadly they generally do not.

It is sad, but it should be recognised that a lot of British homes are designed very badly for moisture management too. Drying clothes on radiators is one thing, but when cooking, showering or just plain breathing are enough to cause condensation damp, there is a problem with the structure. 

[Deleted User]

Is it worth putting trickle vents in some windows?  If you look on Youtube, it can be done.  I don't know if that will be cheaper than a PIV system.  I had one of those in the ground floor hallway of a three storey maisonette.  It made the ground floor really really cold but didn't have enough power to push air into any of the upper stories.  It didn't stop the mould problem at all (putting insulating wallpaper on the walls did as cold external walls was the cause of the problem.., you touched the affected mouldy walls and could feel they were colder than other walls).  It was a very easy fix.  BTW I never dried clothes on radiators.

The lack of vents in the windows/drying of clothes on radiators may be the cause, but to be honest, most houses should cope with this unless the tenant was running a professional laundry business (or has masses of clothes to wash and dry).  I'd check for other problems as well.

Unfortunately a person's lifestyle is often blamed for condensation (like, "stop breathing in your house, did you realise you are breathing out four cups of moisture each and every day, you monster?").  I agree with POP that a house should be able to cope with humans living in them without having open windows dripping icicles onto its inhabitants.

ProDave

You already know the cause of the condensation and mould, drying clothes indoors.  I am willing to be he under heated the property, never opened a window, turned the bathroom fan off etc.

We had one tenant like that who managed to cause condensation and mould where no tenant before or after did,

Top tip. NEVER have a fan isolator switch in a rental property so the tenant cannot disable the bathroom fan.

FreeBear

deannatrois said: The lack of vents in the windows/drying of clothes on radiators may be the cause, but to be honest, most houses should cope with this unless the tenant was running a professional laundry business (or has masses of clothes to wash and dry).  I'd check for other problems as well.

Similar age property here. No extractor in the (small) bathroom, and we regularly dry clothes over radiators & banisters. The windows are generally kept firmly shut during the winter, and condensation hasn't been a problem. I try to maintain the temperature above 18/19°C, and it has been ~24°C in a couple of rooms this past winter.

If I were to fit a PIV system, it would have to be combined with a heat recovery unit - No point in keeping the place warm if half the heat is being pumped outside.

hb2

OP, if you do fit a PIV, will the next tenant be able to switch it off? If they can, they will, cos they will argue that it 'costs too much to run' . . .

justwondering25

hb2 said:

OP, if you do fit a PIV, will the next tenant be able to switch it off? If they can, they will, cos they will argue that it 'costs too much to run' . . .

Well no, as it costs around £1 a month to run, I will be happy to set the rent accordingly, to cover that cost.