Who knows about Positive Pressure Units? (something to do with damp)

JonathanRyan

JonathanRyan

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So I'm buying a house. Surveyor says it may be damp, get an expert. Got an expert. Expert says it's damp :facepalm:

It need a new DPC 'natch and he wants to fit a bigger extractor in the shower room which seems wise.

However, the biggest item on the estimate is a Positive Pressure Unit. Apparently this will make sure that I am never troubled by black mould or anything else ever again. Is that even remotely true? It looks like they are the very latest in 21st century damp proofing technology but I don't really want to pay 650 quid for the latest fad.

Anybody know what these are and if they are any good?
 
Basically its a fan that draws in fresh air from outside, filters it and then blows it into your room - this forces stale/moisture laden air out through trickle vents. They do work we have one in a couple of our properties but £650 seems a tad OTT (google would suggest about half that - unless the 650 also includes fitting etc of course) - also as you are in essence creating a draught they arent great for the heating bills.

see here for an example http://www.xpelair.co.uk/positive-pressure-ventilation.html in addition to xpelair the other principle manfacturer is ventaxia (of course there are a range of others)
 
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Oh yeah - didn't think about heating bills with the draft. There's something in the spec about it being thermally efficient and so forth. But I bet you'd want the thermostat up.

Quote is £640 + vat supply and fit. Which seems a bit toppy since Amazon will sell me one for £235 and I can't see it being more than half a day's work to fit.
 
It depends on type and spec but yes that is a bit high - you can get units that also heat the air they are putting in, but these are a) more expensive, and b) more expensive to run. Personally I'd say so long as you have a decent heat source, a well ventaliated house, and a good dpc you don't need one (where we've fitted them its in holiday cottages that are left closed up an unheated for large expanses of time)
 
I looked in to them a little while back but it was hard to get a proper opinion - there are lots of negative reviews out there, and all the positive reviews sound more like sales pitches.
The negative points seemed to be about it creating an uncomfortable draft.

I decided that the layout of my house would work against the unit (as the stairs are at one end of a long corridor so the unit wouldn't circulate air well at all). In the one room where mould was particularly bad I built a stud wall to create a small cavity away from the house's solid walls - the new wall is noticably warmer to the touch and the amount of space I lost is insignificant really.
Having a tumbledrier in an outside utility room so that clothes aren't dried in the house has also made a huge difference (probably the biggest difference possible).
 
I tend to think that they should not be needed but you could see how the new house performs without the unit (if you are moving in soon, it is likely to get a good test given the current weather) or consider a dehumidifier before shelling out for one of the units. They don't look too difficult to fit at a later date.

Dave
 
Thanks for the comments.

This is actually going to be a tenanted house. So from a purely mercenary point of view

1. I won't be paying for the heating
2. I won't be able to insist they keep it properly heated/ventilated
3. I will have to pay if there's a future damp issue :)

Currently I'm thinking it would be overkill and see how we go with a new DPC and extractor fan. But I'd be interested to hear more opinions.
 
4 - they will complain about the noise (although thats quite negligible) and the draft - theres a reason why we don't fit these in the long term part of the let estate unless the tenants specifically request them . In the holiday cottages they are wired so that they can be switched on and off at the wall and the caretaker usually turns them off when the renters are in, and only leaves them on when the property is vacant
 
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