dMEV vs central MEV

Ay8452 · March 18

Hi all,

I am looking at ventilation options for my renovation/extension project. It's a 1930s single wall house which we are extending to the rear and side as well as a loft conversion. The airtightness of the existing house is probably going to be pretty poor whilst the new part will be better. I have ruled out MVHR for now partly due to cost but also I just don't think we will be airtight enough. I am looking at dMEV or a central MEV with extract for all wet rooms (4 bathrooms, 1 utility, 1 kitchen) and then humidity trickle vents in dry rooms.

- Is there much difference between dMEV vs central MEV in terms of ventilation performance and power use? I prefer central MEV just to avoid making 6 holes in the fabric of the building for 6 dMEV fans however most central units (aside from high end ones) cannot zone areas so if one bathroom is being used, all 6 wetrooms will go into boost mode which seems like over-ventilation/needless heat loss (?).

- Can anyone recommend a central MEV unit, better yet one with zoning? Duco do the DucoBox Focus that can zone but is pricey vs other units especially by the time you add the relevant sensors etc it gets closer to MVHR money.

- The kitchen/living open plan space won't have any trickle vents as the sliding doors are thin frame/we want to avoid them. I am looking at putting in humidity controlled wall vents - anyone have any suggestions of what they have used? Looking at this one at the moment; https://www.bpdstore.co.uk/glidevale-fresh-99hdb-humidity-sensitive-acoustic-wall-ventilator/p/232

- Please see my proposed plans below (loft stairs not shown but they are there!) Does this seem reasonable?

I have looked into dMVHR but not convinced the technology is that great. Heat recovery is pretty low and again a unit in each room is pricey = close to central MVHR money.

Appreciate the help!

Ali