Positive input Ventilation units – What is your experience?

Reply to the comment left by Robert Locke at 26/11/2024 – 14:24
Never thought of a 10mm gap under internal doors – great advice, thank you!

Reply to the comment left by Neil P at 26/11/2024 – 14:53
Me neither!

Reply to the comment left by K Anon at 26/11/2024 – 10:03
I’m thinking of getting a dehumidifier. Issue for me is tenants not ventilating properly despite a window in the bathroom and numerous please for them to open it. Its a large but odd long shaped rectangle bathroom but in a G2 Listed property. Window there but probably not the size it needs to be as would be in the case in modern spec new build, but I have to deal with what I have.

Simply wont get permission to get an extractor fitted (wall as thick as the length of your arm) and access to the back of the bathroom wall tricky too as property has no back access and will have to be over other owners ground and to be honest I cant be bothered to pay for the drawings etc and all the paperwork just to explain what would be needed to even just apply for the ‘free’ permission which will inevitably get refused anyway.

PIV not really possible. Loft above yes but very very limited height so difficult to fit and access for any maintenance etc. Then issue of damp air infiltrating the loft space which is actually share and level with bed 2 – that could cause more damp issues in an unseen area.

Going to get a dehumidifier and tell tenants to plug in hallway and then drag into the bathroom after showering etc.

Use in association with the open window being open at the same time or closed?

Reply to the comment left by Reluctant Landlord at 26/11/2024 – 16:56
It won’t get around the listing conundrum, but Manrose offer a vent kit that can be installed from inside without the need to scaffold outside of access. It gets pushed through from the interior and then a seal opens out, before everything is pulled tight. A fan is then installed through the duct. We’ve installed them before in awkward positions, and found them to be very effective.

Reply to the comment left by Robert Locke at 26/11/2024 – 17:00
sounds ideal, but as you say the listing cancels that out.

Reply to the comment left by Reluctant Landlord at 26/11/2024 – 16:56Window closed unless you want to try to dehumidify the world 😉
Looking at the comments it’s definitely a horses for courses approach.
To avoid humid air circulating, which bathroom is #1 cause, I don’t want a door gap or door open but with the vent then I guess it needs to extract the air so I seems you’d need one.

I fitted a PIV into my remaining rental a few years back, works a treat by pushing the air through.

Makes the bathroom and kitchen extracts work more efficiently as well. Think of sucking a straw with your finger restricting the other end, now imagine something was blowing the other end whilst sucking, the difference is amazing.

Also, these things use about as much power as a light bulb (Don’t hold me to that) when in standard mode so constantly changing the air in the house (Providing there are trickle vents or other forms of passive ventilation.)
Depending which unit you get, you can get a boost switch which is great if you need to clear kitchen smoke, overload of moisture or just clear the air if the house has been closed up a while.

However, if I was building new in the UK I would highly recommend whole house heat recovery with a summer bypass, more efficient when installed to suit the house in the first place. These units are difficult to install as a retrofit when not planned into the design unless its a bungalow or the like and you need very good air tightness.

It sounds to me like a contrbutory factor may be that the window wasn’t installed properly

Reply to the comment left by Robert Locke at 26/11/2024 – 14:24
Hi Robert, you are obviously very knowledgeable when it comes to damp issues. I am hoping you can answer a query for me please. I have a property with rising damp in a kitchen and it has a concrete floor and no underfloor access from the lounge due to the segregating wall, so basically no airflow. The front of the house has airbricks but the back of the house does not (old terraced property) Should I install airbricks and try and get some airflow under the concrete in the kitchen or is this not a requirement due to the concrete floor. Thank you
ps actually the whole ground floor has rising damp and Bostik are not honouring a 20 year guarantee for works carried out 7 years ago. I think I need legal advice.

Whole house heat recovery ventilation unit:
We have had installed in four wood framed “Eco” houses the above. No trickle vents required, filters on the out going and incoming fresh air, and heated. Minimum costs. This was 15 years ago and very rarely have a hint of mould. Only when tenants have tried to get involved by either turning it off or reducing the fan speed. A fifth Victorian house had one system fitted, again good results. Plus the air quality is superior. Downside, EPC calls it a negative! EPC regulations need to be updated. We had the same problem 15 years ago – we were advised NOT to install LED lighting. Bit like people who think climate change is rubbish??