PIV units, anyone with real life experience?

I appreciate that they seem to just sit there chuntering away doing their stuff with very low running costs and no user input. We’ve recently moved into a small 4 bed detached and have seen some window condensation popping up; no evidence of any damp/mould though. The gaff is 20yrs old. I’ve seen a unit for around £500, plus fitting/electrics. Worth it?

We’ve got one. Works really well. It’s in an old 1860s chapel that has had huge amounts of historical damp. Much less condensation and doesn’t smell musty like it used to.

Was a bit under £300 for the unit and is a piece of cake to fit. Cut a hole for the vent, connect it to the mains.

That said I know exactly why our place is damp. I wouldn’t expect the same thing in a 20 year old building and it’s probably worth finding the actual cause before working on the symptoms

Had one installed in a previous house. The place was mouldy damp, mushrooms on the skirting boards etc. We did a lot to dry the place and insulate it, this included a PIV unit in the loft. It ran faultlessly for 12 years (until we sold the house). It wasn’t solely responsible for drying the place but I believe it made a significant contribution. We had a dry, warm house with very little condensation, and my bronchial problems cleared up!

Yep, where’s the moisture coming from?

We fitted one earlier this year and it’s definitely reduced codensation.
Hoping it helps to prevent mould on the really cold external walls this winter.
Ours was £375  (Nuaire drimster).  Easy to fit yourself if you’re relatively handy.
No complaints so far.

In a modern house like that I’m not convinced it would make much difference.

Do you dry clothes on radiators and boil water all day long ?

I had one I installed in a 1920’s stone house that did its job very well

We have one in a 1950s house.

House was designed to breathe.

We fitted double glazing and lots of insulation.

Started to get condensation on bits that cannot be insulated.

PIV cured the condensation. Ours is just a boggo vent axia

Had them in 2 houses. (1940’s and 60’s) They are brilliant. Stopped black mould growing in cold corners of rooms. Stopped condensation running down windows.

and have seen some window condensation popping up

How much.  A small amount is relatively normal especially with a high temperature differential.

Is there much difference between a PIV unit and dehumidifier?

Very disappointing thread, the title promised so much more.

@sharkbait. Loads of difference. Much quieter and cheaper to run and you don’t have to keep emptying them. Also they clear the whole house of damp air not just one room

@trailrat

Small amount, on a couple of bedroom windows in the morning, slight misting on the conservatory downstairs. Noticeable to us because we didn’t experience it at all in our previous  much bigger house of 25yrs.

@Funkydunc

Nope, two showers in the morning, madam’s bath at night. Kitchen is well extracted. Probably not worth bothering about tbh, but as I said, we’re not used to seeing it.

The double glazed bedroom and bathroom windows are left open (on their locks) all the time. Heating is set at a comfortable 17° early evening for a few hours, gas fire maybe on early morning then late evening for an hour.

Maybe nothing, certainly no evidence of previous problems.

Contrary to what others have said above, I’ve found they are not liked at all by the householders after I’ve fitted them. They suck cold air out of the attic, and pump it into the upstairs , generally above the stairwell. So all they are doing is pumping cold air into the house, increasing ventilation. It’s like having a window open upstairs all of the time. If they have the additional heater fitted, then it is warm dry air entering the property, which is far better, but expensive to heat that air.
Ventilation is key, if we seal up a house more, we will get damp problems, the typical human emits something like half a litre of water each day, add in kettle use, boiling foods, showering, drying the towel on a radiator etc, and you can see there is easily 5 litres of water emitted into a typical family house a day. This condenses on the walls/ceiling/floor, and starts the mould process.
PIV units will work, in that they will increase the amount of fresh air getting into the house, but so will a good extractor fan, or leaving a window open.

I have a flat master piv in my 1820’s cottage. Only have it on overnight and it makes a lot of difference to the levels of moisture in the place. It smells far less musty than it used to.

Most modern houses should be better ventilated but even the posh house next door that was built a few years ago had condensation halfway up the upstairs windows this week as the temperature started to drop significantly, so it may well be that yours is ok. But a piv will do something for minimal investment.

PIV units will work, in that they will increase the amount of fresh air getting into the house, but so will a good extractor fan, or leaving a window open

Except it’s nothing like either if you live in an area with wind.

The only thing I’d change my PIV for is a whole house MHRV but I can’t make.the ducting routes work.

Sounds like your customers didn’t know what they were getting. Won’t deny their is a cooler air movement on my stairs  …. But I have mine at the bottom of the stairs and it carries the heat up to upstairs nicely.

*Edit Although then I remember that down south they build roofs weird and your roofspace is basically outside which means it would be considerably colder than my roof space – my attics currently  at 12.6c on account of controlled airflow a  solar inverter and solar thermal pipework thats been running all day –  Outside is at -1.5

So YMMV but mine like ronseal does what it says on the tin

Thanks lads, I think I’ll crack on with one. I like the idea of constant, passive ventilation. It can only protect the fabric of the house, which, as previously said, for minimal investment, can only be a good thing.

PIV units will work, in that they will increase the amount of fresh air getting into the house, but so will a good extractor fan, or leaving a window open.

It’s not the same at all. Our place was ridiculously draughty when we got it, loads of damp. Slowly fixed the draughts, still loads of damp. Fitted a PIV and the damp is substantially reduced. It is specifically taking air from the attic space to replace the air in the living spaces that makes them work. They are not perfect but in the right circumstances they work well.

Ours made a huge improvement to our early 1700’s stone house. No more taking the condensation off the windows with a bucket, far less black mould (needs doing maybe 6 monthly instead of 6 weekly). Also, although it is adding colder air, that air is pretty dry and pushes out the damp air in the house. Dry air is quicker and cheaper to heat (you don’t also have to warm the moisture held in the air) so it actually makes the place feel warmer overall, and so the oil usage dropped noticeably.

easily

Very disappointing thread, the title promised so much more.

You’ve been on Mumsnet haven’t you?