Discussion
Yes.
They need regular maintenance, filter changes and heat exchanger to be cleaned.
Ours is in the loft and in very cold weather it tends to get condensation on the outside of the unit which then drips everywhere, so that's worth considering.
Getting some sort of smart controls that can be linked up to humidity sensors to control boost periods is worthwhile. I've done mine with a bit of aftermarket DIY, but no doubt you can also specify this when buying and installing.
They need regular maintenance, filter changes and heat exchanger to be cleaned.
Ours is in the loft and in very cold weather it tends to get condensation on the outside of the unit which then drips everywhere, so that's worth considering.
Getting some sort of smart controls that can be linked up to humidity sensors to control boost periods is worthwhile. I've done mine with a bit of aftermarket DIY, but no doubt you can also specify this when buying and installing.
Yes, we've got one (and find it excellent) but as it was a retrofit I expect most of my advice from first-hand experience would be from that perspective which may not apply in your new-build situation (a situation I'd view with some envy given how hard a decent retrofit can be!).
Like the previous poster our unit is in a cold loft however we've never had any of the condensation issues they've had. It is insulated though, but I would assume all are and with ours not being particularly top of the range (just a relatively basic Titon unit, albeit with more advanced DIY'd controls bolted to it) I wouldn't expect it to have anything special in that regard. Given this insulation I wouldn't expect the outside surface of the unit to be any colder than the ambient temperature of the loft even when the exhaust temperature drops below that of the intake when recovering heat.
Maintenance-wise I just change the filters every six months (cutting my own from filter cloth roll so very cheap). The filters remove the need for heat exchanger cleaning, or at least have done for the five or so years it's been in - I couldn't rule out action being required in, say, 10 or 15 years when things might look different.
Like the previous poster our unit is in a cold loft however we've never had any of the condensation issues they've had. It is insulated though, but I would assume all are and with ours not being particularly top of the range (just a relatively basic Titon unit, albeit with more advanced DIY'd controls bolted to it) I wouldn't expect it to have anything special in that regard. Given this insulation I wouldn't expect the outside surface of the unit to be any colder than the ambient temperature of the loft even when the exhaust temperature drops below that of the intake when recovering heat.
Maintenance-wise I just change the filters every six months (cutting my own from filter cloth roll so very cheap). The filters remove the need for heat exchanger cleaning, or at least have done for the five or so years it's been in - I couldn't rule out action being required in, say, 10 or 15 years when things might look different.
Edited by tux850 on Tuesday 16th April 14:38
I installed one as part of a full house refurb. Ours is in the utility room but was fairly straight forward to run the upstairs ducting in a stud wall & then keep it under the loft insulation.
I used a company called BPC who were also helpful in terms of design - IIRC they offered a free service.
Ours ends up off a lot of the time as my wife prefers to open windows in the summer & we're mostly not there in the winter. Still, it saved me having to have trickle vents on the new windows
I used a company called BPC who were also helpful in terms of design - IIRC they offered a free service.
Ours ends up off a lot of the time as my wife prefers to open windows in the summer & we're mostly not there in the winter. Still, it saved me having to have trickle vents on the new windows
Last time I looked into fitting one, in our climate it wasn't worth it, compared to a simple extractor fan or Drymaster.
The electricity it uses pushing air through heat exchangers outweighed the heat recovered except perhaps in February.
These things make a lot more sense in a Siberian or Nordic climate.
The other thing is, when it's really damp outside they won't be a substitute for a dehumdifier.
It would be interesting to see any updated proper analysis of cost and perfromance.
The electricity it uses pushing air through heat exchangers outweighed the heat recovered except perhaps in February.
These things make a lot more sense in a Siberian or Nordic climate.
The other thing is, when it's really damp outside they won't be a substitute for a dehumdifier.
It would be interesting to see any updated proper analysis of cost and perfromance.
OutInTheShed said:
Last time I looked into fitting one, in our climate it wasn't worth it, compared to a simple extractor fan or Drymaster.
The electricity it uses pushing air through heat exchangers outweighed the heat recovered except perhaps in February.
Do you recall what sort of figures you were envisaging?The electricity it uses pushing air through heat exchangers outweighed the heat recovered except perhaps in February.
tux850 said:
OutInTheShed said:
Last time I looked into fitting one, in our climate it wasn't worth it, compared to a simple extractor fan or Drymaster.
The electricity it uses pushing air through heat exchangers outweighed the heat recovered except perhaps in February.
Do you recall what sort of figures you were envisaging?The electricity it uses pushing air through heat exchangers outweighed the heat recovered except perhaps in February.
Gas heating being about 1/3 the cost of electricity.
I don't have the figures i used to hand, but SW UK climate, where it's often not ever so coid outdoors, for instance our average daily Low in Feb is about 8degC IIRC so the delta T you're working with is pretty small.
It maybe looks different for the half an hour each day that there's pots simmering on the stove and the kitchen extractor draws quite hot air.
The maths could look different in Yorkshire, or if you assume cheap electricity from solar or battery perhaps.
Or if your alternative involves shifting a lot of air anyway?
But the heat exchanger alone costs North of £500 and our heating bill is 'only' about £1000 a year.
One of the things which made me interested was the desire for a really quiet kitchen extractor, so that might justify the capital cost.
If I were designing a fantasy house foir here, I'd probably have some sort of whole house ventilation and dehumidifer type system.
I don't have the figures i used to hand, but SW UK climate, where it's often not ever so coid outdoors, for instance our average daily Low in Feb is about 8degC IIRC so the delta T you're working with is pretty small.
It maybe looks different for the half an hour each day that there's pots simmering on the stove and the kitchen extractor draws quite hot air.
The maths could look different in Yorkshire, or if you assume cheap electricity from solar or battery perhaps.
Or if your alternative involves shifting a lot of air anyway?
But the heat exchanger alone costs North of £500 and our heating bill is 'only' about £1000 a year.
One of the things which made me interested was the desire for a really quiet kitchen extractor, so that might justify the capital cost.
If I were designing a fantasy house foir here, I'd probably have some sort of whole house ventilation and dehumidifer type system.
I doubt they're ever worth it from the purely economic point of view, but if you're designing a very airtight house as the OP seems to be doing, you don't have much choice with the current building regs.
Our house is also built from a type of SIP, has a very good result on the air-tightness test, so we have relatively lower gas bills, and the MVHR on it's lowest setting works well for keeping it ventilated efficiently without the draughts or noise associated with trickle vents.
When the weather's better, obviously you can just open windows.
outnumbered said:
I doubt they're ever worth it from the purely economic point of view, but if you're designing a very airtight house as the OP seems to be doing, you don't have much choice with the current building regs.
Our house is also built from a type of SIP, has a very good result on the air-tightness test, so we have relatively lower gas bills, and the MVHR on it's lowest setting works well for keeping it ventilated efficiently without the draughts or noise associated with trickle vents.
When the weather's better, obviously you can just open windows.
I used the vent axia heat recovery (through the wall) extract in kitchen and bathroom at the old house, seemed to be a decent and cheap compromiseOur house is also built from a type of SIP, has a very good result on the air-tightness test, so we have relatively lower gas bills, and the MVHR on it's lowest setting works well for keeping it ventilated efficiently without the draughts or noise associated with trickle vents.
When the weather's better, obviously you can just open windows.
OutInTheShed said:
One of the things which made me interested was the desire for a really quiet kitchen extractor, so that might justify the capital cost.
Yeah, and I think you've touched on a key point for me there. My motivation wasn't saving money (i.e. through the heat recovery aspects) but rather the admittedly subjective but never the less perceptible benefits such as near-noiseless operation (I am thinking particularly in terms of comparison to intermittent extractors or trickle vents), a good base level of air quality year-round that isn't reliant on people opening windows, not shutting trickle vents etc but also that it didn't negatively impact comfort in any way which I was concerned about going down the cheaper and easier PIV route. There has also been a benefit to my hay fever (which I get around late-Spring and so still plenty of indoor-only living still going on hence the filtered air being beneficial) and speeding up indoor clothes drying (albeit not as quickly a dedicated dehumidifier would surely do) which I wasn't necessarily expecting.All that said, whilst operational money saving wasn't our motivator we were still heavily motivated by the desire to minimise capital costs and so opted to buy a practically new MVHR unit off eBay (for £350) and undertake all the design and installation work ourselves. Total cost was still nearly £1500 though once absolutely everything was factored in and of course there is the ongoing running cost for power (ours uses ~125kWh/yr so ~£40/yr which whilst not ridiculous is still non-zero). That said, it did directly negate the need for trickle vents in our sliding doors which knocked £400 off their cost so that could be factored in, and also avoided the need for a cooker hood which can all too often be extremely pricey purchases too.
Edited by tux850 on Tuesday 16th April 22:44
wyson said:
Always wondered about the comfort cooling option that seems optional on MVHR systems, sort of cost effective semi AC? Like if its swelteringly hot, you can shut all your windows, keep the hot air outside and still have some airflow.
Ours (Airflow, with a bypass feature when it's warm) does that, although we get a lot of solar gain in the summer so still need to open windows. It's in a modern, very well insulated house so, as others have said, it'd probably get very stuffy without it in the winter. I can't comment on whether it costs or saves money as I haven't done the calcs, plus coming from a Victorian house to this there's no like for like comparison I can make.Ours is in a spare cupboard on the first floor & I haven't noticed any issues with condensation at all.
Thank you for the replies.
I've got a plant room behind the garage where the electricity main fuse box is coming into including storage of the batteries and solar set up.
There will also be a SAHP water tank , so im assuming the temp in that room will be warm.
This is where I will hope to grab some of the recirculated heated air from .
As its a new build im just trying to go the least painful route with the ducting and future proof it.
The windows are triple glazed,
if I do get an over heat scenario in the summer it will go off and I will open the windows for a flush through
So its just recommended companies from the collective and nothing better that a recommendation
thanks again
I've got a plant room behind the garage where the electricity main fuse box is coming into including storage of the batteries and solar set up.
There will also be a SAHP water tank , so im assuming the temp in that room will be warm.
This is where I will hope to grab some of the recirculated heated air from .
As its a new build im just trying to go the least painful route with the ducting and future proof it.
The windows are triple glazed,
if I do get an over heat scenario in the summer it will go off and I will open the windows for a flush through
So its just recommended companies from the collective and nothing better that a recommendation
thanks again
My parents have one in their late 80's build 4 bed semi.
Its a Villavent unit (previously Flebu, now SystemAir) and has been faultless for the past 35 years.
- The box is well insulated, and has its own condensate drain, which rarely flows anything. Located in the loft.
- The filters are fairly basis aluminium mesh type washable units which just get a rinse once a year.
- The heat exchange is a square semi-cross flow (perpendicular flow) type unit.
- Two fans, each of which is a large well balanced slow running centrifugal type, which lasted 25 years and where replaced ten years ago.
- Ducting taking air from each bathroom, utility room, and kitchen in expanded aluminium ducts, and ejecting out of the gable end wall.
- Ducting taking fresh air to each living room and bedroom is the same, save for a 1m of perforated acoustically silenced pipe just before each room.
- Fresh air is drawn from the loft space. Outlets are typically placed towards the windows, including hidden in alcoves.
They run the system on the lowest of three levels 24/7 365 days a year so its on about 1/3 million hours use now.
Gets turned up to full occasionally when entertaining large numbers and or cooking the Christmas meal or the like.
They don't ever have to open an window, basically never get any condensation on windows, and certainly no mouldy behind the wardrobes etc!
Makes a very nice house to live in,
Running costs are negligible compared to the fact the house is heated with underfloor electric night storage heating!
On low mode, you cant hear or feel it in any of the rooms, even in the middle of night, lying in bed directly under it, home alone, very rural location.
You can just about hear the unit if you stand directly below it in the hallway, by the loft hatch, and keep very still for a moment.
Retrofitting the ducting to reach the ground floor would take some doing, but is pretty easy to design in to a new build or major renovation without any obvious boxes.
Its a Villavent unit (previously Flebu, now SystemAir) and has been faultless for the past 35 years.
- The box is well insulated, and has its own condensate drain, which rarely flows anything. Located in the loft.
- The filters are fairly basis aluminium mesh type washable units which just get a rinse once a year.
- The heat exchange is a square semi-cross flow (perpendicular flow) type unit.
- Two fans, each of which is a large well balanced slow running centrifugal type, which lasted 25 years and where replaced ten years ago.
- Ducting taking air from each bathroom, utility room, and kitchen in expanded aluminium ducts, and ejecting out of the gable end wall.
- Ducting taking fresh air to each living room and bedroom is the same, save for a 1m of perforated acoustically silenced pipe just before each room.
- Fresh air is drawn from the loft space. Outlets are typically placed towards the windows, including hidden in alcoves.
They run the system on the lowest of three levels 24/7 365 days a year so its on about 1/3 million hours use now.
Gets turned up to full occasionally when entertaining large numbers and or cooking the Christmas meal or the like.
They don't ever have to open an window, basically never get any condensation on windows, and certainly no mouldy behind the wardrobes etc!
Makes a very nice house to live in,
Running costs are negligible compared to the fact the house is heated with underfloor electric night storage heating!
On low mode, you cant hear or feel it in any of the rooms, even in the middle of night, lying in bed directly under it, home alone, very rural location.
You can just about hear the unit if you stand directly below it in the hallway, by the loft hatch, and keep very still for a moment.
Retrofitting the ducting to reach the ground floor would take some doing, but is pretty easy to design in to a new build or major renovation without any obvious boxes.
wyson said:
Always wondered about the comfort cooling option that seems optional on MVHR systems, sort of cost effective semi AC?
The low flow rate coupled with the low heat capacity of air means it operates very poorly to cool a house down. Objectively speaking at least - I think there's still something to be said for the psychological benefit of knowing that the air being pumped in is a few degrees cooler than what is outside!wyson said:
Like if its swelteringly hot, you can shut all your windows, keep the hot air outside and still have some airflow.
Yes, one particular benefit we do find in the summer is that it does help to keep the air 'fresher' (even if not cooler) than is otherwise the case with typical summer evenings/nights when there is often little or no wind.Edited by tux850 on Wednesday 17th April 18:08
steveamv8 said:
So its just recommended companies from the collective and nothing better that a recommendation
thanks again
I don't know if it is considered bad form to link to other forums, but I would highly recommend checking out the MVHR section at the BuildHub forum as there are loads of people there that have trodden the same path you are heading on and the archive alone will be a worth a trawl through.thanks again
tux850 said:
I don't know if it is considered bad form to link to other forums, but I would highly recommend checking out the MVHR section at the BuildHub forum as there are loads of people there that have trodden the same path you are heading on and the archive alone will be a worth a trawl through.
thanks or the heads upGassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff