Decentralised MVHR to solve damp stuffy room and corridor

[lurker66]

Hi all - my first post so be gentle!

Planning on putting a decentralised mvhr system in our master bedroom (basically a fancy pants extraction fan that recovers some of the heat from exhausted air and uses it to heat incoming air). The reason behind this plan is that the layout of the house (a bungalow) is a bit weird having been added to over the years.

The master bedroom is at one end of a corridor and tends to suffer from what I’d describe as ‘dead air’ – even with the window open (not ideal in winter as the house is already pretty cold) – and is normally quite stuffy. It is also at a fairly permanent state of high humidity – there are (seemingly) no obvious leaks in any plumbing or wet patches so I’m assuming it’s because there are two adults (and a toddler depending how the night goes!) sleeping in there. Currently run a dehumidifer in there which has stopped any mould but is fairly noisy.

I’m hoping the dMVHR system will make the room less stuffy and less humid. The system I’m thinking of is a Prana one from ecostream (https://ecostream.org.uk/recuperator-prana-210g-erp-pro-mini/). Ecostream will install for a few hundred quid (whilst I could do this, I’m not keen on drilling at 21cm dia hole in my wall and ensuring that it’s slightly sloping.

Anyone have experience of doing this kind of thing? Good idea / terrible idea?

In my mind I’d ideally install a PIV system near the room but there is a storage room in the loft above that prohibits this. I’m reluctant to drop 6k on a full MVHR system. I’ve contacted ecostream but they don’t seem great at recommending solutions / answering questions.

House layout below - not particularly airtight, tho i've done what i can. Concrete floors with cavity insulated walls.

[JohnMo]

I would be tempted to install a small MVHR unit upstairs and not go dMVHR. You need an external supply and extract terminal also, that's the only issue.

 

Have an air supply in the master bedroom and extract in the bathroom. Have the supply in the corner of the bedroom as from the door as possible, same in bathroom have to extract as far from door as possible.

 

Your flow would be, comes in to bedroom, would then pass through bedroom, out the corridor and into bathroom, refreshing the whole hall also.

 

Your existing extract in the bathroom could be dumped and the holes blocked up.

 

Mitsubishi make a small MVHR unit, which come up on eBay quite often for cheap prices.

 

The other option would be to set up a cascade ventilation scheme. You could use a couple of dMEV fans, which are almost silent, to get the air from one place to the other. First extract air out of the bedroom into playroom above, then extract air down into the bathroom. No ducts are required. Remove the extract fan in the bathroom and install a dMVHR unit. This way set up a big circulation of air and heat is recovered in a space where noise isn't an issue. Make sure your bedroom door has a space at the bottom for air movement.

Edited September 22, 2023 by JohnMo

[lurker66]

As I understood it the prana unit did extract and input of air - which removed the need for two units? I thought there would be little downside to it even if later I installed a 'proper' mvhr system.

 

Pulling the air from the bedroom into the playroom (more of an attic storage room really - the estate agents plans are very much overselling it!) then down into the bathroom is an interesting idea. Where would the 'new' air come from - the dMVHR in the bathroom?

 

Currently the extraction fan in the bath room goes up above the shower then across the loft a bit and out of a tile - not sure if I could retrofit a dmvhr into that set up (they seem to be all through wall things) Going through the wall would be problematic in the bathroom as it's all tiled.

 

Also your idea of a small MVHR system is interesting. The extract in the bathroom is currently directly above the shower (so as far as from the door as possible) could I reuse that? I guess the input to the bedroom would then be need to be a new hole in the ceiling but not the end of the world. How would a small system feel about a duct run of 15-20m (i.e. from the unit where the bathroom extraction fan is at the moment to the input in the bedroom)?

 

Thank you for you input!