So to describe the building as being ‘sealed’ is a bit of a misnoma then.
I have seen the VMC systems offered for sale in the Brico stores, and have known folks who have lived in homes equipped with them. The general consensus of opinion is that they do little apart from create noise and consume electricity, the solution being to turn the thing off and install a conventional extractor fan in the bathroom and kitchen. Admittedly these were older systems that were for extraction only.
However, I see from the diagram kindly supplied by @Flocreen that two sets of ducting are needed for the newer systems, and that presumably there are 2 fans running all the time meaning twice the electricity consumption.
I know from my own practical experience that fan blades become dirty over time, and as the dirt accumulates, so the fan becomes noisier and less efficient. I assume therefore that probably an annual maintenance would be required to clean both the fans and the ducting, which would clearly add substantially to the annual running cost.
The need for two sets of ducting would surely make this system unsuitable for retro-fitting into an older multi storey building. A bungalow or other single floor structure could of course accommodate the ducting in the roof space.
With a new build, no doubt the ducting problem can be overcome by designing in an interstitial space between the ceiling and the floor above.
My understanding, backed up by having lived in HVAC equipped homes in the US, is that the longer the duct runs, then the less efficient the system, and the bigger are the fans needed to make it work at all.
Also, with two fans, a heat exchanger, and two sets of ducting, there is obviously going to be a considerable purchase and installation cost, and no doubt a substantial carbon footprint during manufacture.
So in summation, and even disregarding the initial purchase / installation cost, there are two electric fans to run 24/7 plus an annual maintenance charge.
I think that overall I would favour a more traditional timer controlled extractor fan system with a PIR switch to automatically activate it upon entering the room, and which continues to run for 10 minutes or so after leaving the room. We have such a setup in our bathroom / wc that works very well indeed. (There is never any mold or residual unpleasant odours, nor any need for continual repainting.)
Additionally I would be interested to know how this VMC Double Flux system works in the summer. Is it still churning away to extract heat from the stale air being expelled, and then blowing the heated incoming fresh air into the room. Surely that would be the last thing one would need during a heatwave.
I think that overall I am with @Stella on this one.
These are a completely different generation of homes Stella. Complete airtightness is needed for a fully passive home (one that needs no heating system) but that doesn’t mean you can’t open a window. We have done our best to make sure ours leaks as little as possible, but we know that there is air seepage everywhere.
To me it is technology doing what technology should do - improving people’s lives without requiring an effort. Especially now, imagine the difference if people didn’t have to pay heating costs? Even in the coldest climates they work with v little heat input.
I can understand in especially built homes… and they will presumably have solar power or some such for their electrical needs rather than “the grid/EDF”.
Total crap for those that understand them but as usual fuckwits dismiss tech as they cant grasp the point. You cannot get a passivhaus cert for a leaky old fossil fuel consuming box for good reason. New construction turns a corner and for the betterment of all.
Again a total misunderstanding of the low energy carbon neutral passivhaus tech.
That’s OK. No problem.
Please know that I’m not against new technological things just for the sake of it, but sometimes these new things do seem to fly in the face of traditional practices, and at times seem to have a somewhat limited usage for the average person in the street.
When it comes to house building, I am aware that it is possible to construct a dwelling that is so well insulated that it requires very little additional heating. A house such as this was built some years ago in the departement in which I live. Unfortunately the new technology and methodology seems to come at an additional price of construction which makes it less affordable for the average person.
Also, I think that such new methods will also require many people to change the habits of a lifetime, such as airing their duvet by hanging it out the bedroom window for some hours every morning.
I also have to admit that my own experience of living in houses with forced air heating and ventilation is that it is quite an unpleasant environment in which to live. The air is so dry that one wakes up in the night desperately in need of a drink of water, and the dryness of the air seems to create static electricity shocks when touching anything metal. The only answer is to open the windows, which rather defeats the object of having the heating on.
Personally I would never buy a house that has forced air HVAC. I find that traditional radiators are much nicer to live with.
To be honest I find the concept of the building / room being airtight rather worrying. After the New York 9/11 tragedy, there was a family who were so worried about a possible gas attack that they sealed all around their windows and doors with Duct Tape, and then were subsequently found dead in the morning from asphyxiation. An extreme incident I know, but it does validate the need for ventilation.
You mentioned earlier that this new type of system also controls humidity and CO2 levels as well as temperature. Presumably, this would require a number of strategically placed electronic sensors in the building, connected by some means (Wi-Fi ?), to the central (effectively computerised) unit. I’m left wondering what the cost is of such an array of electronic bits and pieces. Perhaps you can advise on this point ?
Sorry this has been such a long post with so many questions, but I really do have a genuine interest.
You can open windows in a passive house!! Whenever you want. They don’t have forced air heating and ventilation as the whole point is to require no, or very minimal, heat. I have sadly never lived in one, but have spent quite a bit of time in them and a perfectly pleasant living environment. It’s a bit like having a house in a place where it is always 21 degrees.
I would suspect very strongly that relatively economical Passivhaus kits are available from a few German manufacturers and that they come literally with all the bits (No, not like IKEA ) for a local architect to manage the various tradesmen to install.
Depending how far your site is from Germany, personally if I was in a position to look at new build I’d look into this. Transport costs would be a one-off and (assuming you’d picked a style your mairie was fine with) the house should be comfortable to live in, with low energy usage and extremely easy to sell on if you needed to.
When we bought this house, which has a VMC-A, the unit had not been cleaned once, and it was 8 years old. When I opened the unit the dust was solid and up to 1cm thick on all the blades and the inside walls of the unit. I’m surprised it hadn’t seized up. I clean it out once a year now which is more than sufficient and very easy to do yourself. The most difficult part is getting into the attic. I think that a lot of the bad press that VMCs get about starting fires is down to the fact that many people don’t clean them and they then seize and overheat.
Houses without dfrafts can be far more comfortable at lower temperatures around 18c saving more money and CO2.
For my next home insulation will be a major drive and either full external insulation and under floor also or might go to a factory made insulated panel house following the passivhaus theme but there are many factories now doing this.
) for a local architect to manage the various tradesmen to install.
