Air tightness (gues)stimation

[timhowes]

Noob here - please be patient!

 

We are renovating an already-modernised 1949 rendered brick construction bungalow, adding 4 bedrooms and a bathroom upstairs. Timber construction first floor. Cold tiled roof. New windows. Major job.

 

We had originally hoped to install MVHR, but I doubt we will be better than 3m³/m².h - however, I have no idea really and this is purely guesswork. We aren't enveloping in a membrane and don't have PH ambitions (though will be generally attentive to minimising leaks).

 

My latest plan is dMEV with humidity-actuated wall inlets, which will save money and, I imagine, perform adequately given the likely level of air-tightness. Our builder has suggested we can't assess this until the build has got to a point at which it can actually be measured - however, at this point I imagine it would be very difficult/impossible to re-design for MVHR if we found we were better than expected.

 

I suspect dMEV is the best option, but please contribute if you think I've got this wrong!

 

Many thanks

Edited 4 hours ago by timhowes

[JohnMo]

If you don't need to airtest I wouldn't, you end up boxing your self into a corner. Especially if you live in Scotland?

 

I would progress the way you are planning. Tried a couple of dMEV fans in our summer house - Greenwood were head and shoulders better than other fans I tried. And cheap enough on eBay.

 

Remember you need to have all internal door under cut at the bottom for dMEV to work correctly. I would add a co2 sensor to main bedroom as well so you can fine tune your system.

[Night Owl]

Plus 1 for the Greenwood fan.  I'm pretty sure they can be installed in either a wall or ceiling.  Fitted mine in a bathroom ceiling and vented it out through the roof tiles.  A reasonably easy job even with the addition of a condensate type drain as the ducting was vertical.  Only issue I had with the fan and I'm probably being over cautious was that there are 3 or 4 very thin sensor wires that are taped to the body of the fan that's inserted into your ducting.  I found this fit to be quite tight and was concerned these wires would potentially get damaged during fitment / removal despite the insulating tape on them.  In the end, I cut a small channel in the ducting where these wires would sit and sealed the channel up.  No risk now of wire damage.  Fan looks nice on the ceiling too.  Not powered it up yet so can't comment on it's performance but will hopefully save me all of the hassle and expense of a MVHR install.

[timhowes]

Thanks both. I shall continue in the same vein.

 

@JohnMo I have read your many supportive posts regarding the Greenwood (made by Zehnder) fans and have earmarked these, plus some inlets you've recommended. Extremely helpful!

[JohnMo]

I have also found these through wall inlets look a bit nicer.

 

https://store.beamcentralsystems.com/collections/mechanical-ventilation/products/dcv-intake-air-valves