heat recovery ventilation systems

roisincorran

Hi. I am building a 2 story house ( its at 1st fixing) and have bought a heat recovery ventilation system..just wondering where people who have such a system put the box for it? And how accessible it realistically needs to be?

fredgalway

Hi Roisin motor usually sited in attic. Company fitting system will usually advise on this. You need access to change filters annually at least .

Phirstclass

The HRV unit should be situated in a central location and as close as possible to your external envelope to minimise duct run lengths. It is a good idea to place both intake & extract on a sheltered side of your home as these should be unaffected by wind pressures.
It is also important to make the unit itself easily accessible in order to check filters and carry out any maintenance required.

Andrew_Doran

They often go in the attic as Fred says but ideally it should be inside the house to ensure that:

- it reaches the manufacturer quoted efficiency. In the attic (cold space) it will lose heat, remember MHVR should pay for itself through heat recovered.
- the condensate drain pipe does not freeze in cold weather.
- it can be easily accessed for maintenance, incl. by older/infirm residents.

fclauson

also I would suggest that all duct work is run inside the thermal envelope as duct runs in loft space need a lot insulation wrapped around them

tred

all recent installs i have seen are putting the unit inside the thermal envelope. I havent seen one in the attic in some time.

blast06

I had to put my one outside the cold envelope so in addition to the insulation wrapping on the pipes, i put a further ~12" of wool around them as well. Not ideal but shouldn't be OK

Barrysham

Hi guys, I'm thinking about installing a heat recovery system in my new build.

I was wondering is their a system that has a heating battery on the air supply into the house?
I was thinking this heating battery could be heated by the main heat sorce e.g oil/gas boiler, controlled with a motorized valve. Like an air handling unit that is commonly use in commercial buildings.

galwaytt

I'd avoid putting it in a cold attic.
Centrally located, inside the thermal envelope.

galwaytt

Barrysham wrote: »

Hi guys, I'm thinking about installing a heat recovery system in my new build.

I was wondering is their a system that has a heating battery on the air supply into the house?
I was thinking this heating battery could be heated by the main heat sorce e.g oil/gas boiler, controlled with a motorized valve. Like an air handling unit that is commonly use in commercial buildings.

Yes, I've been in a house that uses it as sole heat source. Pm me for the name.

893bet

galwaytt wrote: »

I'd avoid putting it in a cold attic.
Centrally located, inside the thermal envelope.

Is a service void created for pipe runs then?

galwaytt

893bet wrote: »

Is a service void created for pipe runs then?

Essentially, yes.

893bet

galwaytt wrote: »

Essentially, yes.

How are these installed? Is there a product that is used? Or some kind of counter batton. Can't see counter battoning working.

galwaytt

893bet wrote: »

How are these installed? Is there a product that is used? Or some kind of counter batton. Can't see counter battoning working.

Depends on method of build. Much easier in a TF or SIP house. Open Web joists make it very easy - no counter battening required. If conc walls or hollow core slabs more difficult. You will have to box out or create a service cavity to accommodate.

galwaytt

Fwiw I was talking to a HRV manufacturer yesterday and they have a combination model in development which would also do heating, cooling and humidity control. In testing now but 2016 is estimated time to market.

BarneyMc

galwaytt wrote: »

I'd avoid putting it in a cold attic.
Centrally located, inside the thermal envelope.

I hope to put the unit in the hot press and the ducts for the first floor into the attic but buried under the insulation.... The ducts come pre insulated also.

Andrew_Doran

BarneyMc wrote: »

I hope to put the unit in the hot press and the ducts for the first floor into the attic but buried under the insulation.... The ducts come pre insulated also.

I was playing around with a duct heat loss calculator a while ago, and it was surprising just how quickly the temperature drops along the duct runs unless you completely bury them in insulation. It seems there's not much heat energy in the ducts to begin with (very little air, moving slowly) so any energy lost really pulls the temp down. The conclusion I drew was best to keep the duct runs short as possible and have somewhere around 300mm insulation around and on top of them.

Here is is, it's a bit unfriendly:

http://www.remak.eu/en/support/calculations/thermal-insulation-and-ductwork-heat-loss-calculation/

Superdaddy

galwaytt wrote: »

Fwiw I was talking to a HRV manufacturer yesterday and they have a combination model in development which would also do heating, cooling and humidity control. In testing now but 2016 is estimated time to market.

That's great but if I tell the wife the house won't be finished till 2016 I'll get some looks.:)

There two threads going on this subject at the moment, here's what I just posted in the other one.

Does anybody know what the story is with the "breathable window"? I have been considering this. It seems like a perfect solution. Albeit very new. It would have to come with a very serious guarantee.
Here's a bit copied from the website, it's an irish based company known for passive houses.

Quote:
Game-changing ventilation technology for low energy houses. Saves €500/annum in a 200m2 house, paying for itself in 4 years. Available Feb 2014.

World's most efficient HRV (heat recovery ventilation).
No ducts anymore.
No filters anymore.
Fans automatically speed-up or slow-down depending on indoor air quality.
95% lower running costs than always on ducted HRV.
50% lower ventilation heat losses than ducted HRV, only occupied areas are ventilated.
4 year payback compared with 40 years for a ducted system.
CO2, Humidity monitors and automatic balancing fitted as standard.
Fits discreetly into the external wall creating zones within the house with external air quality.
4.2W/l/sec fan consumption puts it on top of the SAP list.
Very quiet - 25dB @50m3/hr and 30dB @100m3/hr.
Uses the world's best fine-wire heat exchanger, it's 15 times more efficient than a plate heat exchanger.
The fans constantly adjust to maintain equal airflows through the heat exchanger improving efficiency by 10%.
The smart siphon system automatically dumps condensation water externally without freezing.

BarneyMc

I saw these (or similar) windows at a self build show recently. The sales rep said they would be useful if putting on an extension. I really can't see how they would be cost effective on a whole house situation - it's like a mini HRV system in every window of your house.

Old Jim

BarneyMc wrote: »

I saw these (or similar) windows at a self build show recently. The sales rep said they would be useful if putting on an extension. I really can't see how they would be cost effective on a whole house situation - it's like a mini HRV system in every window of your house.

Usually only need 1 on each floor level. Works out cheaper than a ducted HRV.
Problems I have with them is the lack of documentation and certification on the units. How effective are they at removing bathroom condensation for example if the unit is located 20m away?
Would be great if they did work as they claim as eliminating the need for ducts removes a lot of the risks around bacterial growth and filter replacements etc.

Superdaddy

I was thinking of putting them in the bathrooms upstairs and downstairs. I spoke to the lad selling them and they seem sound. I neglected to quiz him on the certification though. It would be great if they work.

fclauson

Old Jim wrote: »

Usually only need 1 on each floor level. Works out cheaper than a ducted HRV.
Problems I have with them is the lack of documentation and certification on the units. How effective are they at removing bathroom condensation for example if the unit is located 20m away?
Would be great if they did work as they claim as eliminating the need for ducts removes a lot of the risks around bacterial growth and filter replacements etc.

Remember to read Part F

Every rooms needs ventilation

fclauson

Superdaddy wrote: »

I was thinking of putting them in the bathrooms upstairs and downstairs. I spoke to the lad selling them and they seem sound. I neglected to quiz him on the certification though. It would be great if they work.

And how will you ventilate all the other spaces ?

Superdaddy

According to what I was told, you are meant to have a specified space around internal door or perhaps internal vents to allow the air to disperse. Apparently there is some science to this and they use the analogy of the dispersal of smoke and steam( water vapour). It was an interesting conversation/ sales pitch. While I say I was thinking of putting the in the bathrooms, I don't know if that is what is recommended.

fclauson

Superdaddy wrote: »

According to what I was told, you are meant to have a specified space around internal door or perhaps internal vents to allow the air to disperse. Apparently there is some science to this and they use the analogy of the dispersal of smoke and steam( water vapour). It was an interesting conversation/ sales pitch. While I say I was thinking of putting the in the bathrooms, I don't know if that is what is recommended.

Sorry - but read part F!!

Moisture will condense on the first below dew point temp surface it comes into contact.

Unless your house is a Passive House and hence the internal surfaces are ALL above the frsi limit of 0.75 as calculated on page 61 of Part L then the first place moist air passes which is below condensation point will become wet from condensation.

fclauson

If you want to learn about the maths then read http://www.ohio.edu/mechanical/thermo/Applied/Chapt.7_11/Chapter10b.html

ferryman35

Possibly a really 'rookie' question but anyway....

Any of the HRV systems I have seen extract from kitchens / bathrooms & distribute to bedrooms & living rooms and then depend on the movement of air within the house to replenish 'fresh' air back to the kitchen & bathrooms.

So if I'm understanding this right the heat recovery part of the system only actually recovers heat at the 'peak' times after cooking / showers.

Then the 'fresh' air replenishing the kitchen & bathrooms at other times is actually going to be the 'stale' air carried from other rooms.

I'm wondering that if someone in the house has the flu for example, is the stale air from their bedroom is going to be carried into the bathroom to be shared by everyone else (after being heated in a moist warm environment) before it gets exhausted.

Am I missing something obvious?

fclauson

ferryman35 wrote: »

Possibly a really 'rookie' question but anyway....

Any of the HRV systems I have seen extract from kitchens / bathrooms & distribute to bedrooms & living rooms and then depend on the movement of air within the house to replenish 'fresh' air back to the kitchen & bathrooms.

So if I'm understanding this right the heat recovery part of the system only actually recovers heat at the 'peak' times after cooking / showers.

Then the 'fresh' air replenishing the kitchen & bathrooms at other times is actually going to be the 'stale' air carried from other rooms.

I'm wondering that if someone in the house has the flu for example, is the stale air from their bedroom is going to be carried into the bathroom to be shared by everyone else (after being heated in a moist warm environment) before it gets exhausted.

Am I missing something obvious?

Ferryman - sort of - typical airchanges are once every 2.5 hrs for the volume of the building. Having lived in a build for 1.5 years now all I can say is its fantastic (other than my Christmas Candle fiasco - see https://www.facebook.com/photo.php?fbid=194972617374517&set=a.163708813834231.1073741828.154344008104045&type=1&stream_ref=10)

One of the benefits of ventilation is the air is much dryer than otherwise and mr cold bug and ms flue bug doesn't like it dry - it kills them

ferryman35

But you are depending on air circulation within the house to replenish the air that is extracted from the 'wet' rooms ??

In our build downstairs is relatively open plan, but what happens upstairs if the bedroom doors are closed? Do you need to make provisions like mentioned in an earlier post to allow the air to circulate?

Whatever about the kitchen ( our downstairs is relatively open plan so I can see how it would work there) I'd have thought a utility / bathroom would benefit from a more dedicated fresh air supply?

fclauson

Unfortunately the Irish regs have not caught up but you undercut the doors with a 10mm gap to allow for ventilation

Superdaddy

So what's the difference then between the ducted and duct less. If both are pulling air from wet areas, both require spaces under doors. Isn't there always the risk of condensation in the ducts too? I understand the need to eliminate cold bridging to eliminate condensation, I'll be putting in a passive slab. Still deciding what type wall to go with but it will be near passive at least.

hexosan

What are you considering to be a passive slab and can you define a near passive wall.

Superdaddy

hexosan wrote: »

What are you considering to be a passive slab and can you define a near passive wall.

Basically a raft foundation which eliminates all cold bridging and meets passive house standard. Same applies to the wall, haven't settled on a wall type yet but that's what I am aiming for. Could be wide cavity pumped, could be precast concrete insulated sandwich panel or could be wooden SIPs. Cost is a major consideration and will make the decisions for me in the end. Such a job to get quotes from people, waiting weeks for prices. I'll know better what i'm doing then.

893bet

Superdaddy wrote: »

Basically a raft foundation which eliminates all cold bridging and meets passive house standard. Same applies to the wall, haven't settled on a wall type yet but that's what I am aiming for. Could be wide cavity pumped, could be precast concrete insulated sandwich panel or could be wooden SIPs. Cost is a major consideration and will make the decisions for me in the end. Such a job to get quotes from people, waiting weeks for prices. I'll know better what i'm doing then.

You need get a provisional BER and spec done. This will tell you what values you need to achieve for floors walls etc. You cannot consider each on their own rather a holistic perspective must be taken.

hexosan

There are cheaper ways of attaining the required floor u-values without having to go to the expense of a fully insulated raft system.

I think you need to do more research considering the whole build rather than getting bogged down on each individual area

Superdaddy

hexosan wrote: »

There are cheaper ways of attaining the required floor u-values without having to go to the expense of a fully insulated raft system.

I think you need to do more research considering the whole build rather than getting bogged down on each individual area

I seem to do nothing but research, answers are hard to find. You think you've the right way to proceed and then someone tells you there's a better way. What are you suggesting? Any information is most welcome.

Do I not need some idea of a preferred structure before I go to a BER consultant? Would seem wasteful to do that work and then when the prices come in find that it is too expensive.

fclauson

Superdaddy wrote: »

...

Do I not need some idea of a preferred structure before I go to a BER consultant? ...

Which came first chicken or egg ?

You are right to do your research and it will seem to go around in circles. You can down load DEAP from the SEAI website and run your house through the maths - this is a good learning process and allows you to play with options. DEAP is flawed in its maths in places and after a while you will realise you will need a copy of PHPP to do this properly

galwaytt

ferryman35 wrote: »

Possibly a really 'rookie' question but anyway....

Any of the HRV systems I have seen extract from kitchens / bathrooms & distribute to bedrooms & living rooms and then depend on the movement of air within the house to replenish 'fresh' air back to the kitchen & bathrooms.

So if I'm understanding this right the heat recovery part of the system only actually recovers heat at the 'peak' times after cooking / showers.

Then the 'fresh' air replenishing the kitchen & bathrooms at other times is actually going to be the 'stale' air carried from other rooms.

I'm wondering that if someone in the house has the flu for example, is the stale air from their bedroom is going to be carried into the bathroom to be shared by everyone else (after being heated in a moist warm environment) before it gets exhausted.

Am I missing something obvious?

You are missing something: the air extracted is NOT recirculated- it is vented outside. However, before it leaves the house it passes through a heat exchanger. The heat captured as it leaves the building is transfers to the - fresh - incoming air. That's the only transfer, not the air itself.

ferryman35

That part I understand.....but it is the air supplied to the wet rooms that I was trying to figure out.

Take a typical upstairs - fresh air is supplied to the bedrooms via the heat exchanger. and cascades to the hallway & bathroom through the undercut doors (Thanks FC!). So in the morning the air in the bathroom (when its at it's busiest?) is the 'stale' air from the bedrooms.

So if someone has a cold / flu or something nasty, does everyone not get to share it? Notwithstanding that the systems seem to work and maybe this effect isn't enough to cause a problem - but I'm thinking of a situation like a plane cabin...

I read more about it today and it was specifically mentioned that the 'supplied-air' was used twice in one brochure that I saw.

I'm wondering would it be a better system if the fresh air was delivered to the hallway / landing for example and extracted through the adjoining bedrooms & bathrooms - that way the air still gets used twice but is alot less polluted coming from the hallway / landing into the living / sleeping spaces?? Not that I have seen it suggested in any brochure I've studied...

We're trying to get a handle on this for our own imminent build before any blocks are laid and in conjunction with the heating (which seems to be another quagmire!). Many people I've spoken with regard the HRV as an optional extra which I can't understand at all. I've recently been in one highly insulated new build and was shocked at how uncomfortable the sitting room was because of the heat build up.

Similarly, in our current home every room is vented with a 4" hole and those hideous plastic grilles. The house is well insulated, warms quickly, but is very draughty. Depending on the wind direction there can be a gale in some rooms, and you get to hear every sound!!

I think the benefit if a hrv system is wrapped up between the recovery of the excess heat, the distribution of the air around the house and the control that it allows, but I still come back to my first question. In an older house you might just open the window and sod the efficiency and maybe that's just what we should do in this case as well (even with underfloor? , )

BarneyMc

ferryman35 wrote: »

So if someone has a cold / flu or something nasty, does everyone not get to share it? Notwithstanding that the systems seem to work and maybe this effect isn't enough to cause a problem - but I'm thinking of a situation like a plane cabin...

I read more about it today and it was specifically mentioned that the 'supplied-air' was used twice in one brochure that I saw.

I don't think you understand the previous post. The airs do not mix. If someone has a cold then the germs are extracted and exit the house. They will never contaminate the fresh, incoming air.

ferryman35

Isn't it the case that:

Incoming fresh air is drawn into the heat exchanger, warmed and then distributed to the living / sleeping rooms.

That air is then drawn, via the doors from those rooms into the 'wet' rooms ie. kitchen / utility & bathrooms, and is extracted from the house from there.

The air streams are kept separate withing the system, but within the house the air has to travel between the inlet ports in the living spaces and the extraction ports in the 'wet' spaces

BarneyMc

ferryman35 wrote: »

Isn't it the case that:

Incoming fresh air is drawn into the heat exchanger, warmed and then distributed to the living / sleeping rooms.

That air is then drawn, via the doors from those rooms into the 'wet' rooms ie. kitchen / utility & bathrooms, and is extracted from the house from there.

The air streams are kept separate withing the system, but within the house the air has to travel between the inlet ports in the living spaces and the extraction ports in the 'wet' spaces

Yes but once the air gets into the extract duct it's never going to return. If people are sneezing in the house then of course germs will spread around the house as normal. The incoming air will always be fresh however and the extract will actually help remove germs in the air (good ventilation).

BarneyMc

Remember it's a one way system so incoming air will always be fresh and the outgoing air will always be less fresh than the incoming. It will never reverse.

galwaytt

ferryman35 wrote: »

That part I understand.....but it is the air supplied to the wet rooms that I was trying to figure out.

Take a typical upstairs - fresh air is supplied to the bedrooms via the heat exchanger. and cascades to the hallway & bathroom through the undercut doors (Thanks FC!). So in the morning the air in the bathroom (when its at it's busiest?) is the 'stale' air from the bedrooms.

So if someone has a cold / flu or something nasty, does everyone not get to share it? Notwithstanding that the systems seem to work and maybe this effect isn't enough to cause a problem - but I'm thinking of a situation like a plane cabin...

I read more about it today and it was specifically mentioned that the 'supplied-air' was used twice in one brochure that I saw.

I'm wondering would it be a better system if the fresh air was delivered to the hallway / landing for example and extracted through the adjoining bedrooms & bathrooms - that way the air still gets used twice but is alot less polluted coming from the hallway / landing into the living / sleeping spaces?? Not that I have seen it suggested in any brochure I've studied...

We're trying to get a handle on this for our own imminent build before any blocks are laid and in conjunction with the heating (which seems to be another quagmire!). Many people I've spoken with regard the HRV as an optional extra which I can't understand at all. I've recently been in one highly insulated new build and was shocked at how uncomfortable the sitting room was because of the heat build up.

Similarly, in our current home every room is vented with a 4" hole and those hideous plastic grilles. The house is well insulated, warms quickly, but is very draughty. Depending on the wind direction there can be a gale in some rooms, and you get to hear every sound!!

I think the benefit if a hrv system is wrapped up between the recovery of the excess heat, the distribution of the air around the house and the control that it allows, but I still come back to my first question. In an older house you might just open the window and sod the efficiency and maybe that's just what we should do in this case as well (even with underfloor? , )

Look at the alternative: no fresh air, or not enough fresh air: where do all the bugs go then ?
Or, if you were to put a fresh air input into the shower, air would come in, travel across the ceiling, and straight back out - at ceiling level - so the room wouldn't be refreshed at all.
Ditto the bedrooms. You can't put an intake and exhaust in the same room - other wise you will set up a form of 'eddy' current from one nozzle to the next, and the rooms themselves get bypassed.

Brave Harvey

ferryman35 wrote: »

So if someone has a cold / flu or something nasty, does everyone not get to share it? Notwithstanding that the systems seem to work and maybe this effect isn't enough to cause a problem - but I'm thinking of a situation like a plane cabin...

The alternative is natural ventilation which does not work. The HRV provides regular proven air changes that will omit stale air in an efficient manner that works quite well. I haven't seen any better systems yet.

cb7

We have this in our house and I think it is a total waste of money.
It is very noisy. Upstair rooms all have a pipe running up one corner. This is blocked off.

Brave Harvey

With regards HRV what would be recommended regarding the following:

1. Grade of Filters for extracts and the grade of filter for the intake air
2. I was at the see the light conference where Mark Sidell recommended Frost Protection for HRV very adamantly. What would you say to an installer, or what aggreement could be made such as a guarantee for the system to be protected below a temperature of -10?
3. 25mm of insulation to the Fresh air ducts wrapped in that silver vapour resistant material
4. I was told sound absorbers are not necessary by the installer, however I have been told by a few people now that they are a must?
5. Do all systems come with a 3 mode. Boost, Summer Bypass, Normal. And does an HRV come with an Off switch for holidays?

Brave Harvey

cb7 wrote: »

We have this in our house and I think it is a total waste of money.
It is very noisy. Upstair rooms all have a pipe running up one corner. This is blocked off.

Yeah but in a well managed build, these systems have proven to be the sole heating which will become more pertinent moving forward in a fuel poverished future. Natural Ventilation has been proven not to work. These systems have been installed very poorly in Ireland. Pipes should not be running to corners as a lot of installers recommend as the heat has dissapated already in the longer runs which may not be insulated in any case. Houses that are being built to the passive standard are light years to the way we are used to building in Ireland. The tradesmen are way behind, well the vast majority of them anyway, which is a major shame. They are not being trained to for energy efficiency. In the whole of their training its something like 2 hours they are trained about passive type building. Thats the major stumbling block in Irish construction as I see it.

galwaytt

cb7 wrote: »

We have this in our house and I think it is a total waste of money.
It is very noisy. Upstair rooms all have a pipe running up one corner. This is blocked off.

That's not a HRV problem - that's an installer problem.

I can stand under my vents and can't hear a single thing.

Like so much in modern building, buying stand-alone technology is pointless unless quality-of-installation, system design, and commissioning matches it.

ferryman35

But that's not much good to the householder!!

It's one thing if you cut corners, you get what you pay for...but paying top dollar doesn't necessarily guarantee the best results either...and mistakes are expensive to learn by!

Brave Harvey

ferryman35 wrote: »

But that's not much good to the householder!!

It's one thing if you cut corners, you get what you pay for...but paying top dollar doesn't necessarily guarantee the best results either...and mistakes are expensive to learn by!

You need to be in consultation with people in the know, this area is growing, to ensure you get the best possible installation. Not good enough to go by what a lot of installers are telling you and you will always need to do your own research so you may be confident in what you are doing in any case. A HRV to provide heating to a house on it own accord also depends upon other factors such as the other passive principles, superinsulation, airtightness, thermal bridge free, triple glazing etc and a precisely calculated peak loading for the house of below 10w/m2 from optimising the different parameters. Won't see the maximum benefit of HRV without these. Its only with this level of a build you will see the much talked about benefits of heating the house solely through body heat, appliances etc. Heed all the poor installation stories because they are continually happening, misunderstanding of what can be achieved with differing builds etc but you will develop your own understanding and then look to maximise what best results you may achieve in your own particular case.