Vent position relative to radiators

[Barnacles]

Hi Again,

 

I am am now we’ll under with my MVHR project. Something that I have been giving a lot of thought to is about how to position vents in the rooms. However, what I haven’t seen is any mention of how to position them with regard to central heating radiators.

 

Is it wise to position vents directly above a radiator so that the convection current mixes with the incoming fresh air and warms it? Or, is it better to position it on the opposite side of the room? In a couple of my rooms that would mean siting the vent close to the doorway which I don’t want to do (unless there’s a good argument for doing so).

[Bitpipe]

Not sure as I've only ever seen them in relatively airtight houses that have minimal heating requirements or just UFH.

 

MVHR flow rates are fairly low - they are there to provide fresh air while minimising heat loss (i.e. compared to a window trickle vent).

 

Normally you position them in a room to maximise airflow from their location to where the nearest extract is (usually bathroom or kitchen) so in the corner of the room diagonally opposite the door (which needs to have 7600mm2 gap at the bottom to facilitate air movement.

 

Is this a new build or a retro fit? If the latter, how airtight is your house? It's not that MVHR won't help but below 2 ACH the heat recovery part won't be that effective as you'll be getting a lot of heat draining inherent ventilation anyway.

Edited October 18, 2019 by Bitpipe

[Barnacles]

This is a retrofit to an 1850s stone-built house which currently leaks like a sieve. However, I am working to remedy that as far as is practicable. My primary reason for installing the MVHR (at least in the short to medium term) is to keep air moving through the house. The house has some damp areas and I am working my way around troubleshooting but it’ll be an ongoing process. In the meantime I want to try and make the house a bit drier and hopefully a bit healthier to live in.

 

I’m prepared for the fact that the heat recovery aspect may not be hugely effective as long as the system moves air around the place and extracts damp air from bathrooms etc.

 

Going forward I intend to install new windows and doors, dry-line some of the walls (when they are dried out etc) and go nuts with insulation. I envisage 2 to 3 years to complete the works.

[Bitpipe]

Got it - suggest you sketch out your floor plan and then put an extract in each loo / bathroom and one in the kitchen (near the hob).

 

Then choose a supply point in each room that's as far away from each extract as possible, preferably diagonal to the door as that's where the extracts will pull air from.

 

Again, you're just trying to maximise cross airflow in each room - it's far from an exact science and usually you need to compromise around where you can actually fit the vents (joists etc).

 

Best practice is to have the MVHR unit roughly in the middle so supply runs are roughly the same length - this makes it easier to balance.However in my case, the unit is in the basement on one side of the house and there are vents everywhere so  again, not critical. You also need to think on where to put the external in/out as these are larger bore ducts (sometimes steel if moving between floors) and need insulated so you don't want them too long.