Is Positive Input Ventilation (PIV) the best solution for mould and condensation?

PGL · 30-03-2015 9:51am #1

Hi folks

I have recently moved into a house built approx 15 years ago, and have an issue with mould and condensation in the bay window (north facing) of the master bedroom.

I have cleaned off the mould using HG mould spray, made sure the vent is not blocked, and also put in a B&Q moisture trap (using crystals). While the condensation was not as bad as before, the mould returned.

It appears to me the only solution is to change the air ventilation in the house. I have spoken to a couple of companies that specialise in damp mould solutions. They both have said the relative humidity in the house is too high, and have both recommended installing a Positive Input Ventilation system in the attic, and fitting 3 more filterless vents in the ensuite, bathroom and kitchen. The main issue for me is the cost - they are both quoting approx €2,000.

Does anyone here have experience of these systems? Are they successful? Is there a proven cheaper alternative solution?

Many thanks!

martinr5232 · 30-03-2015 1:43pm

I dont know much about it but do you have issues anywhere else in the house ??
Do you have a shower in the ensuite if so have you a fan on the vent maybe try leaving that on for ten minutes after using the shower.

PGL · 30-03-2015 1:52pm

Hi Martin

The ensuite has a shower, and there is a fan on the vent which only stays on for about a minute after you switch off the light. I'm sure leaving the fan on for longer would make some difference. However as I mentioned, I have been told the relative humidity throughout the house is too high, so I would doubt that leaving the fan on for longer in the ensuite is going to remove the problem??

MicktheMan · 30-03-2015 11:35pm

OP,
PIV is not the best solution for mould and condensation, imo.

MEV would work better as it extracts the moisture rather than forcing it into the building fabric.

Also, 2k seems very high for a PIV system.

PGL · 31-03-2015 2:54pm

Hi Mick

Thanks for your response. I hadn't heard of MEV before. Do you happen to know how much such a system would cost, and can you recommend any companies who install them?

cheers!

SemperFidelis · 31-03-2015 5:57pm

PGL wrote: »

Hi Mick

Thanks for your response. I hadn't heard of MEV before. Do you happen to know how much such a system would cost, and can you recommend any companies who install them?

cheers!

I put in PIV about a 18 months ago. It has made a big difference to our mould issues although we still get some it's very little compared to before we installed it. Used to get mould under beds, on the cot, ceiling corners etc

The units cost about €550 but I managed to get one second hand and fit a new filter. It simply sits in the attic and blows air into the hall and the main bed. The air is cold in winter so it'll effect your heating. I have it set to low because of this.

I'm considering going for hrv to properly ventilate the house and to allow me to fill in the 4 inch holes in every room. The house is nowhere near airtight tho so I need to do some work on that.

also have a look at demand controlled ventilation. Might be what you need.

MicktheMan · 31-03-2015 9:13pm

PGL wrote: »

Hi Mick

Thanks for your response. I hadn't heard of MEV before. Do you happen to know how much such a system would cost, and can you recommend any companies who install them?

cheers!

MEV - Mechanical Extract Ventilation - google is your friend:)
Depending on house layout, cost should be less than 1000.

MicktheMan · 31-03-2015 9:20pm

SemperFidelis wrote: »

I put in PIV about a 18 months ago. It has made a big difference to our mould issues although we still get some it's very little compared to before we installed it. Used to get mould under beds, on the cot, ceiling corners etc

QUOTE]

While a PIV system will improve the ventilation of the property, I don't like it because it forces the moisture laden air out through gaps and cracks in the structure. The moisture will then condense at some point in the structure and may cause unseen damage. This may be more critical in a tf house. MEV, on the other hand, has no such issues.

TSQ · 21-03-2016 1:47pm

I am planning on installing a wall mounted mechanical positive input ventilation unit. All of these units have very low running costs for the ventilation only operation - i.e. when heating of incoming cold air is not activated - but the manufacturers seem to be very coy about publishing the running costs of the heating element (which would be on when outside air temperature is low, to heats the incoming air to 10 degrees and avoid cold drafts).

Anyone know what the running cost of the heating element of these units would tend to be?

CodeJACK · 26-09-2020 10:12am

Did anyone go with PIV in the end? Any thoughts on how it worked and is the heated version a bank breaker?

BryanF · 26-09-2020 10:46am

Heated version? Do you mean MVHR (Mechanical ventilation (with) Heat Recovery)

CodeJACK · 26-09-2020 11:10am

BryanF wrote: »

Heated version? Do you mean MVHR (Mechanical ventilation (with) Heat Recovery)

Sadly no, as much as I'd love to do MVHR, the cost and work needed is too much to take on at the moment. I also cant seem to locate anyone willing to deal with a DIYer.

PIV units can be got with a heating element in them to temper the air input above 10 degrees etc. I didnt mean to imply it as a "heater" but I figured its better than constant sub zero temps getting forced into the house:

Link: https://fantech.ie/product/sano-ipiv-wall-h/

listermint · 27-09-2020 7:09am

CodeJACK wrote: »

Sadly no, as much as I'd love to do MVHR, the cost and work needed is too much to take on at the moment. I also cant seem to locate anyone willing to deal with a DIYer.

PIV units can be got with a heating element in them to temper the air input above 10 degrees etc. I didnt mean to imply it as a "heater" but I figured its better than constant sub zero temps getting forced into the house:

Link: https://fantech.ie/product/sano-ipiv-wall-h/

I believe there is plenty of threads in renewables forum about MHRV and DIY. But you will need the company to commission.

Calahonda52 · 29-09-2020 8:59am

Not directly relevant to the thread but a useful document, despite being from 2006

mada999 · 22-10-2020 6:18pm

CodeJACK wrote: »

Sadly no, as much as I'd love to do MVHR, the cost and work needed is too much to take on at the moment. I also cant seem to locate anyone willing to deal with a DIYer.

PIV units can be got with a heating element in them to temper the air input above 10 degrees etc. I didnt mean to imply it as a "heater" but I figured its better than constant sub zero temps getting forced into the house:

Link: https://fantech.ie/product/sano-ipiv-wall-h/

Hi there, did you get this unit put in? Just looking to see how much it costs? i have been quoted €900 including installation

ted1 · 22-10-2020 6:33pm

mada999 wrote: »

Hi there, did you get this unit put in? Just looking to see how much it costs? i have been quoted €900 including installation

I got quotes today £375 or £570 with a heater.

Installation wouldn’t be much. I’d do it myself , just cut a hole and run a duct. Bring power up to attic.

Undecided as to what to get. PIV. or demand control

CodeJACK · 22-10-2020 6:44pm

mada999 wrote: »

Hi there, did you get this unit put in? Just looking to see how much it costs? i have been quoted €900 including installation

900 aint too bad. I was quoted 1350. I nearly split my sides laughing at the fella.

I purchased this Nuaire unit and have it installed.
https://drimasterexpress.ie/shop/nuaire-drimaster-eco-heat/

I was skeptical but RH values in the house have dropped 10-15%. Currently maintaining around 52% and going to 55 when its raining out. The weather hasn't got cold enough yet to see how badly it might affect the ability to heat the house but I did get the one with heating element so I hope that helps.
The bathroom extractor fan was never great at clearing the air moisture after showers but when you put the PIV on boost (I also bought the external controls) they work well together and the bathroom clears noticeably faster.

If you have the tools and your attic is easy accessed with a place to put the vent in the hallway, then I'd recommend doing it yourself for the 560ish that I spent on the PIV and controller.

mada999 · 22-10-2020 7:26pm

ted1 wrote: »

I got quotes today £375 or £570 with a heater.

Installation wouldn’t be much. I’d do it myself , just cut a hole and run a duct. Bring power up to attic.

Undecided as to what to get. PIV. or demand control

CodeJACK wrote: »

900 aint too bad. I was quoted 1350. I nearly split my sides laughing at the fella.

I purchased this Nuaire unit and have it installed.
https://drimasterexpress.ie/shop/nuaire-drimaster-eco-heat/

I was skeptical but RH values in the house have dropped 10-15%. Currently maintaining around 52% and going to 55 when its raining out. The weather hasn't got cold enough yet to see how badly it might affect the ability to heat the house but I did get the one with heating element so I hope that helps.
The bathroom extractor fan was never great at clearing the air moisture after showers but when you put the PIV on boost (I also bought the external controls) they work well together and the bathroom clears noticeably faster.

If you have the tools and your attic is easy accessed with a place to put the vent in the hallway, then I'd recommend doing it yourself for the 560ish that I spent on the PIV and controller.

thanks for the info lads..

I'm useless with DIY though so wouldn't be doing it myself lol..

It just seems like a lot of markup on the unit and the install.

Divisadero · 22-10-2020 7:54pm

In the meantime one of these should sort anyone out. Certainly in the bathroom or as a secondary unit when you have the new system installed if needed. Instead of relying on the bathroom fan which I find useless I leave this on the landing with the room doors open and windows closed on the middle setting for two hours (timer) after I use the shower. At night I leave it on all night in the bedroom on the lowest setting (it has a thermostat). This sorted out the mould and condensation issues. They were very bad in the bathroom and I had a little mould in the bedroom but the window would be dripping with condensation in the morning. This took care of it. These desiccant type dehumidifiers are more expensive but seem much better than the older style refrigerant option. You should get it for less if you shop around online or you could try a different brand of desiccant dehumidifier.

https://www.meaco-dehumidifiers.ie/meaco-DD8L-junior-dehumidifier

CodeJACK · 22-10-2020 8:02pm

mada999 wrote: »

thanks for the info lads..

I'm useless with DIY though so wouldn't be doing it myself lol..

It just seems like a lot of markup on the unit and the install.

IMO, 900 is not bad having done the job myself. There is a fair bit to it that a pro will knock out fast. I forgot to mention you will need a power point in the attic so if the 900 does not inc wiring, that's an extra cost.

listermint · 22-10-2020 8:52pm

CodeJACK wrote: »

900 aint too bad. I was quoted 1350. I nearly split my sides laughing at the fella.

I purchased this Nuaire unit and have it installed.
https://drimasterexpress.ie/shop/nuaire-drimaster-eco-heat/

I was skeptical but RH values in the house have dropped 10-15%. Currently maintaining around 52% and going to 55 when its raining out. The weather hasn't got cold enough yet to see how badly it might affect the ability to heat the house but I did get the one with heating element so I hope that helps.
The bathroom extractor fan was never great at clearing the air moisture after showers but when you put the PIV on boost (I also bought the external controls) they work well together and the bathroom clears noticeably faster.

If you have the tools and your attic is easy accessed with a place to put the vent in the hallway, then I'd recommend doing it yourself for the 560ish that I spent on the PIV and controller.

Wait, is that unit just putting damp air into your attic space ?

ted1 · 22-10-2020 9:06pm

listermint wrote: »

Wait, is that unit just putting damp air into your attic space ?

No, it’s a PIV. It filters and blows the air from your attic into your house. Which in turn pushes the air out through the existing wall vents.

They work on the basis that the attack is heated , in winter when it’s cold. It has an element to heat the air. In summer you can set a dial do it don’t blow air above x degrees.

Calahonda52 · 22-10-2020 9:07pm

listermint wrote: »

Wait, is that unit just putting damp air into your attic space ?

It blows, not sucks, as suggested by the title of the thread:D

Its a 400 w fan heater supplying free air from the attic

ted1 · 22-10-2020 9:10pm

Divisadero wrote: »

In the meantime one of these should sort anyone out. Certainly in the bathroom or as a secondary unit when you have the new system installed if needed. Instead of relying on the bathroom fan which I find useless I leave this on the landing with the room doors open and windows closed on the middle setting for two hours (timer) after I use the shower. At night I leave it on all night in the bedroom on the lowest setting (it has a thermostat). This sorted out the mould and condensation issues. They were very bad in the bathroom and I had a little mould in the bedroom but the window would be dripping with condensation in the morning. This took care of it. These desiccant type dehumidifiers are more expensive but seem much better than the older style refrigerant option. You should get it for less if you shop around online or you could try a different brand of desiccant dehumidifier.

https://www.meaco-dehumidifiers.ie/meaco-DD8L-junior-dehumidifier

Looks heavy on the juice compared to the alternatives

listermint · 22-10-2020 9:12pm

ted1 wrote: »

No, it’s a PIV. It filters and blows the air from your attic into your house. Which in turn pushes the air out through the existing wall vents.

They work on the basis that the attack is heated , in winter when it’s cold. It has an element to heat the air. In summer you can set a dial do it don’t blow air above x degrees.

Alright cool got it.

Calahonda52 · 22-10-2020 9:19pm

MicktheMan wrote: »

While a PIV system will improve the ventilation of the property, I don't like it because it forces the moisture laden air out through gaps and cracks in the structure. The moisture will then condense at some point in the structure and may cause unseen damage. This may be more critical in a tf house. MEV, on the other hand, has no such issues.

This is worth repeating.
PIV should never be seen as an alternative to removing damp air from the places where its produced on mass such as bathrooms kitchens etc.
Plenty steamy windows in bedrooms as well but over a longer so the PIV would be useful there

mada999 · 22-10-2020 10:00pm

Calahonda52 wrote: »

This is worth repeating.
PIV should never be seen as an alternative to removing damp air from the places where its produced on mass such as bathrooms kitchens etc.
Plenty steamy windows in bedrooms as well but over a longer so the PIV would be useful there

We got a survey done and was recommended this along with some other things.

Yeah the bedroom we sleep in is very stuffy in the mornings with condensation on the windows. Some of the bedrooms rooms are musty sometimes also

coathanger · 22-10-2020 10:29pm

mada999 wrote: »

We got a survey done and was recommended this along with some other things.

Yeah the bedroom we sleep in is very stuffy in the mornings with condensation on the windows. Some of the bedrooms rooms are musty sometimes also

Who did your survey & was it expensive? Thanks

Calahonda52 · 23-10-2020 12:10pm

coathanger wrote: »

Who did your survey & was it expensive? Thanks

If the surveyor is not independent, then you will always get them writing a report to support their products: eg the modern version of the tap water testing model.

Dacelonid · 25-11-2020 10:41pm

I just started looking for a solution to my steamy windows and the first thing I came across was a crowd called home and dry that quoted me ~€900 to install a PIV system and they guarantee that it will work.

However I am both sceptical and ignorant of what exactly all this entails, or even what I should be looking for.

Is there companies that would do an (independent) survey of my house and tell me what I do or don't need to address in order to fix my problems.

The problem being, when we get up in the morning we have to clean the windows at the front of the house (master bedroom, box room and sitting room) as they are constantly dripping wet with condensation. The back of the house seems ok, or at least not anything that I am concerned about.

Lumen · 26-11-2020 10:21am

Surely mechanical extract is fundamentally better for mould and condensation?

Think about the airflow.

Assuming the building fabric is leaky (otherwise you'd get HRV) then if you pressurise a room with PIV some of the air is going to leave via the hole in the wall, and some of it via leaks in the building fabric. Those leaks will take moist, warm air and condense it in the building fabric.

Alternatively, if you're depressurising a room with MEV, then that same leaky fabric is going to be pulling fresh air in, which won't cause condensation because it carries less moisture and is being warmed up as it enters.

I know this is all theoretical but I just can't see how PIV makes sense over MEV.

CodeJACK · 26-11-2020 10:56am

Lumen wrote: »

Surely mechanical extract is fundamentally better for mould and condensation?

Think about the airflow.

Assuming the building fabric is leaky (otherwise you'd get HRV) then if you pressurize a room with PIV some of the air is going to leave via the hole in the wall, and some of it via leaks in the building fabric. Those leaks will take moist, warm air and condense it in the building fabric.

Alternatively, if you're depressurising a room with MEV, then that same leaky fabric is going to be pulling fresh air in, which won't cause condensation because it carries less moisture and is being warmed up as it enters.

I know this is all theoretical but I just can't see how PIV makes sense over MEV.

It makes sense because it s a cheap and quick fix. Hence companies selling it to cure your damp.

I like your explanation and you might be right, but in my case the fabric is brick/concrete so the volume of damp that's going to build up, will have little effect... i hope.
The "damp" in a house that condenses on the cold surfaces is initially relative humidity. My understanding is that its key to reduce RH as much as possible, to prevent it condensing and turning to moisture/damp. Air and its RH will exit via the easiest path, especially with the sort of pressure being put in by the PIV... its next to nothing. So PIV must be coupled with trickle venting and open windows or background vents drilled through walls. Without these, PIV will not work well..IMO.

The RH outside my house right now is ~65%. Before we had the PIV, inside would match and exceed this, 70%++.
We have trickle vents permanently open and the heating controlled via smart thermostat. The house has so far stayed warm and thankfully no sign of the damp we saw last year. Granted, we both now WFH so maybe the heating on more regular has helped too. We are getting the house wrapped next month so that will seal up more of the gaps in our fabric. I'll be watching the RH and increasing the trickle vent size if it starts to go up as a result.

PIV is worth a shot, if you can do it yourself its cheap as chips.

Calahonda52 · 26-11-2020 3:46pm

RH values without the dry bulb temp and the dew point temp is not that useful.

https://en.wikipedia.org/wiki/Dew_point#/media/File:Dewpoint-RH.svg

listermint · 26-11-2020 4:06pm

Calahonda52 wrote: »

RH values without the dry bulb temp and the dew point temp is not that useful.

https://en.wikipedia.org/wiki/Dew_point#/media/File:Dewpoint-RH.svg

Dry bulb ?

Calahonda52 · 26-11-2020 6:10pm

listermint wrote: »

Dry bulb ?

Not a dry bulb in the house

The Dry Bulb Temperature refers basically to the ambient air temperature. It is called "Dry Bulb" because the air temperature is indicated by a thermometer not affected by the moisture of the air.

CodeJACK · 26-11-2020 6:14pm

Calahonda52 wrote: »

RH values without the dry bulb temp and the dew point temp is not that useful.

https://en.wikipedia.org/wiki/Dew_point#/media/File:Dewpoint-RH.svg

So dry bulb=Ambient temp indoors= 18-20degrees always for me. The damp guy we had assess our place said to keep temps above 17 degrees always.

zoom_cool · 29-11-2020 1:01am

If you install PIV do you close some of your wall vents?

CodeJACK · 29-11-2020 1:46am

zoom_cool wrote: »

If you install PIV do you close some of your wall vents?

Absolutely not, the PIV needs to have something to push air out of. Wall vent or trickle vents on the windows are still needed.

Calahonda52 · 30-11-2020 11:48am

CodeJACK wrote: »

So dry bulb=Ambient temp indoors= 18-20degrees always for me. The damp guy we had assess our place said to keep temps above 17 degrees always.

17 will allow a higher RH
http://www.dpcalc.org/

jellybeans · 28-12-2020 12:21am

I am having a serious issue with damp in the main bedroom in our apartment which has an en suite. I dont even know where to begin to solve this issue. Can anyone recommend an independent surveyor that can recommend and carry out works necessary to solve the problem? Thanks

MicktheMan · 29-12-2020 12:06pm

Pm sent

moon2 · 31-12-2020 3:11pm

jellybeans wrote: »

I am having a serious issue with damp in the main bedroom in our apartment which has an en suite. I dont even know where to begin to solve this issue. Can anyone recommend an independent surveyor that can recommend and carry out works necessary to solve the problem? Thanks

I've got the same issue so would appreciate if someone could pass on a recommendation.

The window glass and frame is literally dripping wet on cold mornings even though it's triple glazed. This is causing mould on the sill, all around the window frame and on the ceiling in the bedroom as I just can't keep it dry enough.

whizbang · 31-12-2020 4:07pm

Thats a major problem with way too much water in your house.

Even a sealed up house with 20 people living in it shouldnt be that bad.

listermint · 31-12-2020 4:45pm

moon2 wrote: »

I've got the same issue so would appreciate if someone could pass on a recommendation.

The window glass and frame is literally dripping wet on cold mornings even though it's triple glazed. This is causing mould on the sill, all around the window frame and on the ceiling in the bedroom as I just can't keep it dry enough.

That would imply that your window and frame are the coldest of all surfaces in the room. The mould on the ceiling means that location is missing insulation in the attic above. Easily fixed

It also implies that you have far to much moisture in your home generally referred to as humidity levels.

The moisture can be any number of sources but it is only ever dealt with via proper ventilation.

Check your sources of moisture such as drying clothes, showers, even leaks. But even more importantly check the ventilation in that room and the house in general.

Getting triple glazing and closing all vents for example won't solve your problems it creates mould.

suritlbgrand · 21-11-2021 10:05pm

hi All. Our build is well on but I’m sweating now after seeing this tread- wish I seen it last year.

We hav no trickle vents in our windows (and our windows are taped/airtight etc)

we do have mechanical extract fans are in the kitchen/ bathrooms.

we are planning on getting PIV system. Drymaster or similiar

would this suffice for ventilation etc??

Lumen · 21-11-2021 11:23pm

@suritlbgrand wrote

would this suffice for ventilation etc??

No. As described earlier in the thread you need permanently open wall vents to let the moist air out.

How do you have a new build underway without a ventilation strategy? What does the architect say?

Ryan davis · 26-10-2022 8:54pm

https://www.boards.ie/discussion/comment/115022367#Comment_115022367

Hi just read this , I'm seriously considering buying one to reduce condensation and help with my sons asthma. Just wondering how are you getting on with it did it reduce condensation? And does it use much electricity. Thanks

Is Positive Input Ventilation (PIV) the best solution for mould and condensation?

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