Heat Recovery Ventilation Systems
Discussion
Lots of people are down on them, but having lived in a house with one, and knowing someone who did it on a new build, I am a convert.
In a very sealed house (which, as a new build, yours will be), it makes the house less 'stuffy' and regulates temperature very well as a bonus. To me, it's about the airflow keeping the house fresh and not "stale" that's the real benefit. I don't think the energy saving bit is the killer feature, though if used correctly they can be quite efficient.
However there are servicing costs to consider and it is something that can break.
In a very sealed house (which, as a new build, yours will be), it makes the house less 'stuffy' and regulates temperature very well as a bonus. To me, it's about the airflow keeping the house fresh and not "stale" that's the real benefit. I don't think the energy saving bit is the killer feature, though if used correctly they can be quite efficient.
However there are servicing costs to consider and it is something that can break.
We have this in our new build, which is part of an Eco development - 60 houses and 2 apartment blocks.
The air system I think works very well - extracts warm air from kitchen, bathrooms, filters it, adds clean air and pumps to outlets at floor level in the main living areas.
I'm not entirely sure on the energy saving benefits yet, the house being A/A rated, as we've only been here a few months and the electricity co are still working from their estimates, which is >€/month than our previous G rated house!
The air system I think works very well - extracts warm air from kitchen, bathrooms, filters it, adds clean air and pumps to outlets at floor level in the main living areas.
I'm not entirely sure on the energy saving benefits yet, the house being A/A rated, as we've only been here a few months and the electricity co are still working from their estimates, which is >€/month than our previous G rated house!
10 years ago friends bought a flat on the continent built to the highest energy saving standards (at the time). It's so air tight that when you turn on the extractor in the kitchen the barometer in the lounge drops.
It's also fitted with an air exchange system. It seemingly doesn't matter what you cook in the evening; by the next morning the air is neutral. Thus I think they're brilliant. When installed at the build stage.
It's also fitted with an air exchange system. It seemingly doesn't matter what you cook in the evening; by the next morning the air is neutral. Thus I think they're brilliant. When installed at the build stage.
paul.deitch said:
Don't forget to change the filters. One of our friends has a system which, because the feed pipes are just a little too small, hisses gently day and night, Drives them mad. Also make sure that the inlet and outlets don't cause uncomfortable drafts.
I did see a comment elsewhere that they're falling out of favour in Nordic countries as you can never fully eliminate the fan noise. I don't know what they're doing instead - maybe passive stack systems, but they're trickier to design.I installed a heat recovery unit (vent axia 100r) in a drying room. Obviously this is not necessarily what the OP is asking but I found the unit/concept to be excellent. It uses a tiny amount of electricity and despite being a cheap system recovers a lot of exhaust heat whilst removing a lot of moist air. For a bathroom, kitchen or utility room I'd definitely recommend getting one.
Paul seem to the leaders. Ventaxia seem to be the cheapest.
I am seriously considering one for my refurb. The plan is to dry line without removing the existing plaster (and, indeed, repair the plaster where the walls will be stitched). The roof will be sealed with OSB done at the same time as the insulation (but there are problems with the positioning of that) and lots of air sealant tape everywhere. The ground floor will be lifted (suspended timber), and insulated with an air tightness membrane over the top (taped and sealed DPM). The only problem will be my existing double glazing which I don't have the budget to replace.
From what I can gather one of the trickiest aspects is, aside from running the ducts (difficult with if you have traditional joists and they're spanning in the wrong direction), getting the locations of the inlets and extracts right, in relation to each other. I've even read some people suggesting to leave a gap at the bottom of every door so that you can have inlets and outlets in separate rooms. Not sure I like the idea of that...
The downsides to me are:
- the need to replace the filter every year
- getting one with summer bypass (and remembering to use it)
- the archaic interfaces they all seem to have - not wife friendly
- the space that the ducting and the unit itself requires
- availability of spare parts - I mean, the life of the fan will be, what, ten or so years - will the spares still be available then?
- not being able to have an open fire.
I'm thinking about a stack effect natural ventilation approach as an alternative, but that will require:
- trickle vents through the walls at a low level in every ground floor room
- knocking through the ceiling in the stairwell and adding automated skylights
- and big gaps under all the internal doors.
and there's no guarantee that it will work.
And, of course, neither of these strategies will cool below the ambient external temperature.
The advantage of the MVHR is, of course, the heat recovery in winter. And while you don't need the air tightness for natural ventilation you would not want to use it in the winter...
I am seriously considering one for my refurb. The plan is to dry line without removing the existing plaster (and, indeed, repair the plaster where the walls will be stitched). The roof will be sealed with OSB done at the same time as the insulation (but there are problems with the positioning of that) and lots of air sealant tape everywhere. The ground floor will be lifted (suspended timber), and insulated with an air tightness membrane over the top (taped and sealed DPM). The only problem will be my existing double glazing which I don't have the budget to replace.
From what I can gather one of the trickiest aspects is, aside from running the ducts (difficult with if you have traditional joists and they're spanning in the wrong direction), getting the locations of the inlets and extracts right, in relation to each other. I've even read some people suggesting to leave a gap at the bottom of every door so that you can have inlets and outlets in separate rooms. Not sure I like the idea of that...
The downsides to me are:
- the need to replace the filter every year
- getting one with summer bypass (and remembering to use it)
- the archaic interfaces they all seem to have - not wife friendly
- the space that the ducting and the unit itself requires
- availability of spare parts - I mean, the life of the fan will be, what, ten or so years - will the spares still be available then?
- not being able to have an open fire.
I'm thinking about a stack effect natural ventilation approach as an alternative, but that will require:
- trickle vents through the walls at a low level in every ground floor room
- knocking through the ceiling in the stairwell and adding automated skylights
- and big gaps under all the internal doors.
and there's no guarantee that it will work.
And, of course, neither of these strategies will cool below the ambient external temperature.
The advantage of the MVHR is, of course, the heat recovery in winter. And while you don't need the air tightness for natural ventilation you would not want to use it in the winter...
Edited by dxg on Friday 25th April 18:04
Following the passivhaus conference on twitter - #iPHC18
This looks *very* interesting for reducing the ductwork and space required. But, for my intended location, it's external terminals would on a party wall...
https://twitter.com/AR_Clarke/status/4600385126001...
This looks *very* interesting for reducing the ductwork and space required. But, for my intended location, it's external terminals would on a party wall...
https://twitter.com/AR_Clarke/status/4600385126001...
We have one, now about 4 years old. It's a Vortice Prometeo. The only downside to that unit is the wireless remote eats batteries.
As above, no point at all if your house isn't airtight. No catflaps, no trickle vents, and serious attention to detail if you plan on 'traditional' build methods. We went the easy route and have SIPs panels, so the house went up airtight.
Routing ducts is a pain. Pay attention to the direction of joists to make life easier. Metal web joists would possibly make things easier, but check the clearance. As the ducts are relatively large, cutting through joists may be very difficult.
The main unit will make noise - stud walling is a bad plan, and transmitted vibration is hard to eliminate. It's not that bad, but you are aware of it in a silent house. We find our vents make very little noise though - it all comes down to not introducing tight gaps so the air can flow freely.
If you've sealed your house, you can't have an open fire (regs require a certain volume of incoming air for the room with a fire in it), as opening up a vent for the fire will completely destroy any value of the HRV. On the other hand, you can get room sealed stoves (we have one) which give you a nice centerpiece and don't wreck the ventilation system.
Cleaning filters is a pain because it happens infrequently enough that you easily forget to do it. Which reminds me....
As above, no point at all if your house isn't airtight. No catflaps, no trickle vents, and serious attention to detail if you plan on 'traditional' build methods. We went the easy route and have SIPs panels, so the house went up airtight.
Routing ducts is a pain. Pay attention to the direction of joists to make life easier. Metal web joists would possibly make things easier, but check the clearance. As the ducts are relatively large, cutting through joists may be very difficult.
The main unit will make noise - stud walling is a bad plan, and transmitted vibration is hard to eliminate. It's not that bad, but you are aware of it in a silent house. We find our vents make very little noise though - it all comes down to not introducing tight gaps so the air can flow freely.
If you've sealed your house, you can't have an open fire (regs require a certain volume of incoming air for the room with a fire in it), as opening up a vent for the fire will completely destroy any value of the HRV. On the other hand, you can get room sealed stoves (we have one) which give you a nice centerpiece and don't wreck the ventilation system.
Cleaning filters is a pain because it happens infrequently enough that you easily forget to do it. Which reminds me....
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