Positive input ventilation

[Conner]

Hi gents. Hoping I can get some feedback on a PIV system. Have been looking at installing on of these to try and reduce damp in the house. Online reviews look very good so would like some real world experience before shelling out.

[Conner]

Well the lack of replies says it all don’t bother we haven’t heard of this. 
cheers gents il save my cash👍

[Mark Bolam]

I’ve never heard of it tbh mate.

@Big J might know more, his wife is an architect.

[Conner]

It’s one of those things lots of very positive reviews on line not many bad ones except faulty kit. Sounds too good to be true. Fan in loft pushes stale air out of house, no more condensation low running costs. Are the reviews true or is this the best thing since sliced bread no one has heard about?

[carlos]

ive been looking into this sort of thing, hard to find out if it will work well in your own home, i think a lot of it depends on the airtightness of the building.

does the system heat the incoming air? i would of thought air in the loft would be cold( well it is in mine) .

the MHRV systems sound good but require a pretty airtight house to be efficient.

iam just going to start with extractor fans in kitchen and bathroom (  like most people have and i didnt bother fitting.... doh).

carl

[openspaceman]

  On 24/01/2023 at 22:16, Conner said:

Well the lack of replies says it all don’t bother we haven’t heard of this. 
cheers gents il save my cash👍

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Not really as I was unsure of what it was,  Mechanical Heat Recovery Ventilation is what I think @Conner is referring to and in a well sealed house is a good thing as it sucks moist warm air out of the house, it exits via a heat exchanger and warms a similar amount of cold air coming in (this which lowers the relative humidity as it warms, thus effectively drying the air). Water which condenses out drips down a drain. Some even have in built heat pumps that drop the old air temperature below zero  and the warmth this produces goes back in the house.

[Dan Maynard]

I'm sceptical, think the damp cure people are often sharks and most of it is fixed by regular gutter maintenance.

[carlos]

  On 24/01/2023 at 22:40, openspaceman said:

Not really as I was unsure of what it was,  Mechanical Heat Recovery Ventilation is what I think @Conner is referring to and in a well sealed house is a good thing as it sucks moist warm air out of the house, it exits via a heat exchanger and warms a similar amount of cold air coming in (this which lowers the relative humidity as it warms, thus effectively drying the air). Water which condenses out drips down a drain. Some even have in built heat pumps that drop the old air temperature below zero  and the warmth this produces goes back in the house.

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i think positive input ventilation and MHRV are slightly different, i think the PIV just pumps fresh air in.

i think these systems have been developed for the trend towards airtight (passive haus) new builds.

a friend has a MHRV system in his new airtight spec house, he said it was good but he wasnt so sure about the heat recovery side of things being so efficient. 

[openspaceman]

  On 24/01/2023 at 22:40, Dan Maynard said:

I'm sceptical, think the damp cure people are often sharks and most of it is fixed by regular gutter maintenance.

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Yes but condensation becomes a bigger problem as people keep doors and windows shut to prevent expensive heat loss, especially if they dry clothes on radiators as tumble driers (spit) are too expensive to run.

 

Damp tends to occur in cold corners where the temperature drops below the dew point of the air which people are breathing out. This is often at the bottom corner where the cold bridging between walls and floor happens and is often wrongly diagnosed as rising damp.

[openspaceman]

  On 24/01/2023 at 22:50, carlos said:

i think positive input ventilation and MHRV are slightly different, i think the PIV just pumps fresh air in.

i think these systems have been developed for the trend towards airtight (passive haus) new builds.

a friend has a MHRV system in his new airtight spec house, he said it was good but he wasnt so sure about the heat recovery side of things being so efficient. 

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Yes I can see that from what you say, the only advantage in that case would be that the incoming air was likely filtered and because the house was at slightly higher pressure no dust particulates would blow in when a door was opened.