PIV Unit or dehumdifiers?

  • This topic has 12 replies, 8 voices, and was last updated 3 weeks ago by  eskay.
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  • PIV Unit or dehumdifiers?
  • Premier Icon eskay
    Subscriber

    After having decorated all upstairs rooms in our new house over the summer and replacing the badly leaking seals around the double glazing I have noticed bad condensation on both the windows and surrounding walls (causing some mould already).

    Has anyone had any success with PIV systems? My concern is that during the winter it will be pumping cold air into the house – would dehumidifiers be a better option?

    Premier Icon jam bo
    Subscriber

    installed a NuAir PIV unit ~5yrs ago, haven’t had any damp problems since in what was an old (1880’s) damp house.

    can feel the cold air if you stand directly underneath the vent but nowhere else. not noticed any impact on the electricity bill. I have the version that heats the air if its too cold.

    only issue I’ve had is in the summer when I’ve had to turn it off as its been pumping hot air into the house from the attic. I’m sure there is a setting for an upper temperature cutoff but it was easier just to turn it off for the summer.

    Premier Icon jam bo
    Subscriber

    i should add, i’ve subsequently added better extraction in the kitchen/bathroom and had much better windows/doors fitted.

    but the big step change was the PIV unit. Confirmation bias maybe but I’m pretty sure that before that, the humidity and damp was making the household ill.

    Premier Icon timmys
    Subscriber

    My NuAIR PIV has been very helpful with condensation, but if I was doing it again I would opt for the one that does heat the air as well as is it definitely chills the landing more than I would like.

    toby
    Member

    Am I right that PIV units just[1] blow in air from the loft? If I wanted to try the concept is there anything wrong with replacing the loft hatch with a sheet of plywood with an old computer fan blowing through a hole to see if it helps with the general condition of the house?

    [1] Presumably with filtration, quiet fans and ducting to make them better long-term than my trial bodge…

    Premier Icon lovewookie
    Subscriber

    My NuAIR PIV has been very helpful with condensation, but if I was doing it again I would opt for the one that does heat the air as well as is it definitely chills the landing more than I would like.

    I have this one fitted. The heating doesn’t really make a lot of difference, maybe takes the chill off a little, but I keep mine off. When it’s below freezing overight I’ll switch the PIV off until morning.

    We had dehumidifiers before, they were OK, but the PIV is noticably different.
    Ours is a 1820’s cottage, redeveloped in the 70’s and mid 2000’s with little knowledge of old buildings so pretty much sealed up. We’ve been finding solutions to get the air flowing around the house since. log burner, decent fan in the bathroom etc. Stil need to get room vents fitted as the night vents in the UPVC windows just don’t cut it, and a proper extractor for the kitchen, but getting there.

    Premier Icon lovewookie
    Subscriber

    Am I right that PIV units just[1] blow in air from the loft? If I wanted to try the concept is there anything wrong with replacing the loft hatch with a sheet of plywood with an old computer fan blowing through a hole to see if it helps with the general condition of the house?

    most PIV’s are loft installed, with a filter of sorts at the inlet.

    Mine is one designed for flats, as I don’t have a loft (70’s dormer conversion), so ours sucks from an external vent, through a big box with a filter in it, and blows it into the landing.

    Only slightly rubbish thing is that, it’s OK, until someone has a bbq in the summer, or if one of our neighbours burns stuff they shoudln’t in their woodburners, then it just blows it in.

    I am looking at adding carbon filtration to it anyway.

    Premier Icon eskay
    Subscriber

    Thanks for the answers, sounds promising.

    Any recommended manufacturers?

    Premier Icon lovewookie
    Subscriber

    Nuair seems to be the most common.
    https://www.i-sells.co.uk/ventilation-positive-pressure?ref=mgNav

    Is where I got mine. They’re really helpful too, as are Nuaire

    Premier Icon K
    Subscriber

    We had a PPV System fitted in the last place we rented, it was cheaper than sorting the actual cause of the damp problem… Tile floor with lino over the top to try and hide the problem that was always wet underneath. Don’t know if it it was a leaking pipe, ground water spring or what but the floor needed to come up.

    Yes it did lower the humidity in the house but was quite amusing showing the letting agen when it was really cold the condensation literally drip from the housing of the unit itself as it was drawing in very cold air from the loft space and condensing the damp air. It did cool the house down considerably then it was below freezing outside.

    We had a dehumidifier that if I remember correctly would pull 2l of water out a day.

    We don’t live there anymore.

    PPV or extractor fan with heat recovery would be where I would go depending on the source of the condensation if it really couldn’t be sorted any other way.

    Opening windows is really good and pretty cheap.

    myti
    Member

    Piv totally sorted our condensation and mould. Cooler on landing but don’t hang out there and central heating works less hard to warm dry air than wet.

    fossy
    Member

    A good dehumidifier will pull loads of damp out of the air, and it aids your heating systems – dry air being easier to heat.

    Premier Icon eskay
    Subscriber

    An update after fitting a Nuair PIV unit last Saturday:

    I decided to go for the non-heated version because it did not seem to be enough heating power to make that much of a difference, but it was enough power to make the system expensive to run. The jury seems out on the heating element on most of the reports I read.

    The windows and walls were covered in very heavy condensation (top to bottom) last Saturday morning and the Karcher window vac thing had to be emptied several times when getting rid of the moisture.

    I fitted it to the highest part of the stairwell, very easy to fit and because I have power in my loft all I needed was to fit a 3-pin plug to it.

    I have initially set it to ‘4’ which I think is a slight overkill (3 bed detached with 4 people) but a few people suggested running it high for the first week.

    I have seen a dramatic improvement in the condensation levels. It hasn’t totally eradicated it but it is now at a very acceptable level.

    In the mornings there is a very light dusting of condensation on probably the bottom 1/4 of the windows which clears very quickly when the curtains are opened. I don’t get any on the landing window and most importantly the lintels and window surrounds are no longer wet.

    I think in time better windows will improve things further, but I am very happy with how things are now.

    I would say the stair well is a couple of degrees cooler (will probably be less noticeable when I reduce speed of fan). I turned the thermostats up on the radiators on landing to compensate.

    I cannot hear the fan running (I have it in the hanging configuration in the loft).

    Thanks for the helpful suggestions above!

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