Positive input ventilation - does anyone have this?

[danlightbulb]

Ive been using a dehumidifier almost continually since I acquired one. I am still struggling to get the humidity down in the house, and running the dehumidifier is quite expensive. Plus it only really works well in the immediate room that I put it in, and obviously I can't have multiple units spread all around the house.

So Ive been looking at PIV.

The units themselves are not that expensive - circa £350 for one without a heater element or c.£4-500 for one with a heater. I could install the unit in the loft myself regarding the wiring and ducting, but can't do any roof modifications.


I'd like to know if anyone has one and can share their experiences.

How are running costs? Does it make the house cold? How is the heater or unit controlled?

If I do fit one, could I use it with a wifi smart plug to control the unit or run it on a schedule? But this wouldn't control the heater specifically.

 

[Deleted User 298457]

What "problem" are you solving for? Reason I ask is because I used the dehumidifier when drying washing but never any other time, and no chance did anyone else even do that courtesy, and the place was almost 150 years old.

 

[Mysterae_]

They are supposedly good if you have pets as the fresh air from outside pushes the dog farts out through the trickle vents of your windows and other cracks. I'm not kidding!

Not such a good idea if you live close to a sewage treatment plant or your neighbour is running a meth lab. I know the units filter the air but how good would they be?!

 

[danlightbulb]

What "problem" are you solving for? Reason I ask is because I used the dehumidifier when drying washing but never any other time, and no chance did anyone else even do that courtesy, and the place was almost 150 years old.

House is prone to being musty and mould build up in the corners of rooms.

I've been unable to determine the real cause, there isn't any apparent damp anywhere. But if we leave the dehumidifier off, the house gets musty and the humidity rises. It's very hard to get the humidity below 70% in this house.

 

[Buffman]

Do you have trickle vents?

I added one to a previous house and it does work although it does smell a bit "lofty". Possibly as I had a very small loft to put it in.

In hindsight think maybe I should have added trickle vents first.

 

[BUDFORCE]

They are supposedly good if you have pets as the fresh air from outside pushes the dog farts out through the trickle vents of your windows and other cracks. I'm not kidding!

Not such a good idea if you live close to a sewage treatment plant or your neighbour is running a meth lab. I know the units filter the air but how good would they be?!

I was thinking the exact same thing.

 

[danlightbulb]

Do you have trickle vents?

I added one to a previous house and it does work although it does smell a bit "lofty". Possibly as I had a very small loft to put it in.

In hindsight think maybe I should have added trickle vents first.

There are trickle vents on the windows and airbrick vents in some of the rooms.

 

[Orifice]

If you get one with a 400w heater, they are not really that cheap to run.

I have one on a timer running from 22:00 - 06:00, and if the temperature drops below X (You can choose what temperature the heater kicks in, or have it completely off) it can consume 3.2kw a night, so about £27 month at current rates.

Without the heater the draw is tiny, more like 40w night but its pulling in air at whatever the loft temp is. (2.6 degrees last night).

They do work but ultimately installing wall insulation fixed the issue of condensation/mould in room corners.

 

[Paul11]

I have one and its brilliant.

the heating is a swtich on the unit, so on or off so yes i you could put a timer/smart plug to turn it all off and on when you wanted (although the idea is to leave them on all the time to keep the air moving and stop condensation)

 

[danlightbulb]

How would I find out if my loft is sufficiently vented to install one? It's an older house so I imagine the loft is as leaky as the rest of the house but I don't want to have to fit any eaves vents because I don't have any ladders.

 

[SoliD]

PIV are a real good addition to many homes. I used to have one and it solved condensation on windows overnight. You'll feel a draft in the winter but if you're trying to get rid of mould and condensation they'll definitely help. I removed it last year as I had had aircon installed and have now added a filter to one of my extracts to bring in fresh air to the house.

 

[SoliD]

How would I find out if my loft is sufficiently vented to install one? It's an older house so I imagine the loft is as leaky as the rest of the house but I don't want to have to fit any eaves vents because I don't have any ladders.

Can you see light at the eaves. if so it'll be fine.

 

[Paul11]

How would I find out if my loft is sufficiently vented to install one? It's an older house so I imagine the loft is as leaky as the rest of the house but I don't want to have to fit any eaves vents because I don't have any ladders.

So i have fit mine in a flat so not 100% sure about the loft/house installations but i think they just input from the loft but blow air in to the house so it wouldnt matter if your loft was a bit leaky

best thing is to speak to one of the companies that sells them and ask some questions

 

[danlightbulb]

PIV are a real good addition to many homes. I used to have one and it solved condensation on windows overnight. You'll feel a draft in the winter but if you're trying to get rid of mould and condensation they'll definitely help. I removed it last year as I had had aircon installed and have now added a filter to one of my extracts to bring in fresh air to the house.

Well what I actually want is to have lower humidity. We're always in the 70% range no matter what I try, I want it down to within the 50-60% range.

 

[SoliD]

Unlikely to happen with PIV alone but thats mainly because you'll be blowing in 70% humidity air with the UK's typical weather system. You'd need something like MVHR and/or aircon to get down to that level.

 

[danlightbulb]

Unlikely to happen with PIV alone but thats mainly because you'll be blowing in 70% humidity air with the UK's typical weather system. You'd need something like MVHR and/or aircon to get down to that level.

I've said this before and don't have an answer still but my old house never was as high as 70% even in the winter and I dried washing inside and barely opened the windows. I don't understand what is happening physically here for the humidity in this house to be so high.

 

[Nathan]

Get a log burner, our house currently at 38% according to the nest. However, a heated positive system would probably be sufficient. I almost bought one for the last house but sold up.

 

[danlightbulb]

Get a log burner, our house currently at 38% according to the nest. However, a heated positive system would probably be sufficient. I almost bought one for the last house but sold up.

Is that just because of the heat they generate?

There is one place a log burner could go but it would be right next to the TV and would require a through the wall flue.

 

[roboamigo]

1920s solid wall house here. Black mold behind wardrobes, condensation on windows so bad we rolled up towels on the windowledges to catch it!

Fitted a Nuaire Drimaster PIV and it solved literally all of this within 2 days of being installed. Have it set to 3 in the summer and 5-6 this time of year, and it is fantastic. We have it at the top of the stairs. Plus side is it helps dry clothes on the landing as the air is always moving.

Theres a slight hum if you listen out for it, and if you stand directly under you can feel a breeze.

Otherwise I would not be without it. Dont bother with dehumidifiers or anything else imo., this will do the trick.

 

[SoliD]

Are you getting the new place as hot as the old place as obviously most sensors report relative humidity so the warmer it is the lower that number will be despite havnig the same amount of water in the air.