That was what first struck me about the system Mr BuildingBoxes has been installing these past nights. Our Zehnder system runs off less than fifty watts. A traditional light bulb runs off 60 watts.
This is the piece of the puzzle we haven’t yet talked about in the Air Tightness, Insulation, Ventilation trifecta that we’re hoping will make our house one lean green efficient…well, house. Simply put, this combination of construction principles (as opposed to design principles) are the kernel of passive house design (says Mr BuildingBoxes). In a passive house, once it’s air tight and insulated, you need to guarantee a minimum number of air changes per hour to distribute air throughout the house and keep it dry. The Zehnder is purpose built to do just that.
The thing that looks more like a Tardis than I expected, takes hot, wet air from kitchens, bathrooms and the laundry and exhausts it outside. Fresh air from outside is supplied to the living areas and on its way there, it picks up the heat that was extracted from those hot, wet environments, but without the moisture.
Moreover, some of our rooms have a lot of solar gain because of our massive heat sink (the concrete midfloor), so they hold a bunch of heat. Other rooms, like the ones downstairs don’t, so we need a way of sharing all that great free heat energy throughout the house.
Zehnder does this with individual ducts, radiating from a central heat exchange unit, supplying each room individually. AND it has one massive sound deadening attenuator box (that’s Mr BuildingBoxes speak for that Tardis I was talking about). It also filters the air as it goes.
The difference between this and what Kiwi’s would associate with a Heat Recovery System is:
· It’s super quiet – no sound travels between the rooms because they have their own ducts and because of that massive Tardis downstairs.
· Really importantly for the long term health of your house, it balances the pressure between supply and extraction. That means hot, wet air from inside the house won’t be forced into your wall cavities creating leaky building syndrome Mark Two.
· And the biggy for us is that it’s fresh air moving around the house. Fresh air that’s been heated by the unit with those clever, super efficient German fans, taking everything we make through solar gain and transferring it into what goes back into the house. Not the same air, just being pushed around room to room.
· For us too, the ducts are smaller and go through the wall cavities – important when you don’t have a ceiling space.
Oh and I’ve changed my mind about it looking like a Tardis, it’s more like a Dalek. Or maybe a cross between the two…
Also, if you were looking for me on stuff.co.nz this week, sorry, they’re having a shuffle around. I’ll be back, but it might not be on Tuesdays, still, the end is in sight so all is well!
It's been a while in the making, but once the ducts were in the walls back some months ago. The Air Tightness membrane went on and the GIB covered the whole thing up nice and neatly, it was time to get those ducts into the mighty Tardis-Dalek...
A family of four: writer, scientist, lego engineer and destruction specialist. Our previous home is featured in New Zealand Interior Style and this new project promises to provide plenty of great, green, smart and maybe madcap solutions to new building in New Zealand.