Recommendations on HRV system

BoozyBabe

Hi all,
I’ve touched on this here before, but I’m hoping someone who has it installed or who has experience of installing it, or has just done lots of research on it & has experience of it in operation can comment.
I’m very interested in installing a HRV system in my new build.
The architect doesn’t seem to think he needs to be concerned about it in relation to the drawings. Is this correct?
If I go for precast concrete slabs upstairs, will this still work ok? Will it add an awful lot to the thickness of the floor between ground / 1st floor?
I’m doing a block build. Will I be able to seal my house enough using this method to make HRV viable?
A biggy:- I want to use my attic as a 3rd floor. Can the HRV system be designed & installed for me in such a way so that it doesn’t take up a huge amount of my attic space?
I will have 2 open flue fireplaces. Although obviously not ideal, will a door to close up the flue when not in use be acceptable enough to make the HRV worthwhile? Obviously I plan on putting extra money into the insulation & window spec also to make the system worthwhile.
So, they were overall issues I wanted to raise. I’d appreciate your input.

I’ve went to view 2 showhouses with this installed recently, but I couldn’t get into the attic to view. I’d be eager to hear your opinions on these installations.
House A:- HRV system combined with Solar Power. Every room in house had an input vent, where air was blown into room. Kitchen, utility, bathrooms also had a 2nd extractor vent to remove moist air.
There were NO radiators. These vents were solely incharge of heating the house.
There was an open fireplace with trap door to close off flue.
There was 1 thermostat in the house set at a specific temp. The sensor for this was in the attic measuring the temp of the outgoing air. If this air was less than that set on the thermostat, the solar panel kicked in to boost the incoming air to the required temp. (i.e. the temp set on the thermostat, not the temp the exchanger could take from the outgoing air)
There was an oil condensing boiler as a backup.
The solar was also used for the hot water. If there was not enough solar energy to raise the space heating enough, or heat the water enough, only then would the oil burner kick in.
A 70% reduction in energy bill was stated for this house.
What are your feelings on this system?
The house was certainly very warm, maybe too warm, but it was also a reasonably warm day, so maybe not a real indication?

It was definitely recommended to implement solar along with the HRV system regardless as solar is more suited to space heating than water heating. What’s your opinions on this?
What about the fact there are no radiators in the house? Do you really feel such a system could adequately & comfortably heat a house without radiators especially say in the winter?
Wouldn’t you get a small area of each room with a blast of warm air hitting you?

House B also had solar incorporated into the HRV system (in the same way as above), but the kitchen, utility & bathrooms only had extractor vents because this house had radiators. Also had chimney & trap door on flue.


In both cases, I was told the attice was pretty much taken up with this system, between the exchanger & the ducting, so wouldn't be much use for storage. This is why I'm concerned about installing it in my house. Would this mean I couldn't then use the 3rd floor, or have ye experince of this being done?

Sorry this is SO long.
I’m finding it SO hard to get info. I’m sending my drawings to some installers shortly to see what they can come up with for me, but I’d really love some of your opinions on what is the best was to install this to gain most benefit in terms of reduced energy bills. Which of th above would be best, or would you do something completely different? In your opinion, are some of the ideas about fundamentally wrong, & if so, why?
Also, if you could answer my more general questions at the start.

I had been thinking of UFH downstairs & rads upstairs. It’s a 2600sq ft 2 storey block house.
Really appreciate you help, hopefully a lot of you will have experience of this now to guide me.
Thanks,
BB

sydthebeat

In the House A situation, did you ask what the oil boiler heats?? If its a purely air heated system, and knowing oil burnes at high temps, that makes an oil based water to air heating system highly inefficient..... your heating water to heat air to heat air....

gman2k

Hi, I'm building a 2800 sq foot 'passive' house at the moment, and am about to embark on the HRV route. My understanding is that the box is not that large, but the pipework can take up a good amount of space. If you have solid conc FF floors, you will have to box out below ceilings for the pipework - not ideal - and avoided if you use timber frame engineered joists like me!
Back to your house - block house? Not a problem making it airtight, just carful detailing around opes. unfortunatley in Ireland, builders seem to think that a few cans of no-more gaps around window frames will make you airtight. You might as well have nothing there!
I wouldn't rely on a HRV system to heat your house, as they are not really meant to do this. I feel you would be left with an uncomfortable type of air heating, as opposed to a classic radiant heat from rads/ underfloor etc. (Think of the type of heat from a convector heater)
There are numerous companies in the HRV market at the moment - have a looka the Construct Ireland magazine. Be wary of very high (98%) efficiency figures, as these are probably only attainable in lab conditions, not real life.

galwaytt

gman2k wrote: »

If you have solid conc FF floors, you will have to box out below ceilings for the pipework

...also known as suspended ceilings - your architect will have needed to have allowed for this in your ceiling heights, as you are talking about losing 50-75mm on this alone. And drilling 100mm holes through hollowcore is not a job for the light hearted......

Back to your house - block house? Not a problem making it airtight, just carful detailing around opes. unfortunatley in Ireland, builders seem to think that a few cans of no-more gaps around window frames will make you airtight. You might as well have nothing there!

I think you will have great difficulty getting an airtight house with concrete build - even with perfect joints (:rolleyes:), and fantastic detailing...........conc block walls are as airtight as a block of cheese...... add in around window boards, socket and pipe chases, holes, etc. and you're on the back foot the whole time.

I wouldn't rely on a HRV system to heat your house, as they are not really meant to do this. I feel you would be left with an uncomfortable type of air heating, as opposed to a classic radiant heat from rads/ underfloor etc. (Think of the type of heat from a convector heater)

....not quite true. I've been in a pukka passive house with an air system, and it was very good. Again, it's down to details etc etc, but there are systems designed and capable for home heating. Don't ever see it working in a concrete house, though......I hope you have included an airtightness test as part of your building spec, otherwise the builder won't have to build to any standard, and no matter what you put into it, you can't rectify anything he did, or didn't, do.........without enormous expense, at any rate.......+1 on the UFH, 0/-1 on traditional rads, imho......

There are numerous companies in the HRV market at the moment - have a looka the Construct Ireland magazine. Be wary of very high (98%) efficiency figures, as these are probably only attainable in lab conditions, not real life.

so true. Putting in a HR system into a house doesn't necessarily save you any money - it can, but that's not it's primary goal. It's a ventilation system, with heat recovery capabilities. A 100mm hole in the wall (the alternative), is neither, really.

OP - Are you drylining the house?

BoozyBabe

Hi,

Thanks for the replies.
I'm not sure all the questions I was asked.

Yes, we'll be building it with blocks. I know this isn't as efficient as timber, but himself won't have it any other way!!!

No, we're not tied to precast concrete slabs upstairs, HRV aside, lots of people were recommending it, but we hadn't made a final decision on it yet.

The attic space is being drawn up in the way a dormers roof would be done. Sorry, I haven't a clue on technical terms, but there won't be any beams in the way of walking.

I've no idea about dryliningor what have you. Don't even really understand what it means:o

The chimney issue:- again, can't get himself to back down.

In house A, the boiler would heat water if surplus hot water was needed. Beisdes that, it would boost the air temperature if the solar panel couldn't reach that temperature on its own.
Or that's what I believe he was saying anyway.

Thanks guys.
Much appreciated.

BoozyBabe

Just thinking over the whole thing last night.

So, HRV is really worthwhile in a timber frame & can help reduce heating bills quite a bit.

BUT:-
Are you saying that its benefits in a block house, financial benefits that is, will not be that great?
Or would you still recommend putting it in?

I.e., puttinga HRV system combined with solar as described in my first post, backed up with a condensing boiler, with UFH downstairs, rads upstairs, do you think this system could even save me 50% a year on heating / energy bills (running costs) over a traditional radiator / oil burner system?

Thanks again,
BB

Obviously if I ask these type questions to the people hoping to install it for me, they will tell me whatever in order to seal the deal, whereas here I know I'm getting unbiased opinions, so I greatly appreciate you taking the time to answer me.

muffler

Moved to the renewable energies sub forum

BoozyBabe

Sorry Muffler!
I wonder are you now going to get a slap on the wrist for moving an oil boiler to Renewable energies!!!

I wasn't sure which section to put this in.

Sorry again

muffler

BoozyBabe wrote: »

Sorry Muffler!
I wonder are you now going to get a slap on the wrist for moving an oil boiler to Renewable energies!!!

I wasn't sure which section to put this in.

Sorry again

Hah. That was smashey who moved that. :rolleyes:

I think Im safe with the HRV

AckwelFoley

Im always amused when i see ppl saying timber frame is more energy efficent than concret homes. This is not the case. A concret built home is every bit as efficent if the house is well insulated.

Your architect want a smack in the head.

Yes it is important to plan for HRV in the house. You may choose the "suspended ceiling" route which in my opinion is the ideal route to take.

The unit itself is about the size of a large suitcase, there are units about the size of an ameican fridge.. but these units are used for heating aswell as ventilation but are more suitable imo for small apartment type situations.

The unit you require is small, the duct work comes in different sizes depending on the design, from 300mm to 100mm.

Please make note.. Its absolutely imperative that you use rigid stainless steel ducting.. NOT flexi duct or in some cases Wavin pipe!

The latter 2 are not designed for HRV and you will have heat loss problems, noise issues and and a few others i can mention.

daveoc16

snyper wrote: »

Im always amused when i see ppl saying timber frame is more energy efficent than concret homes. This is not the case. A concret built home is every bit as efficent if the house is well insulated.

Your architect want a smack in the head.

Yes it is important to plan for HRV in the house. You may choose the "suspended ceiling" route which in my opinion is the ideal route to take.

The unit itself is about the size of a large suitcase, there are units about the size of an ameican fridge.. but these units are used for heating aswell as ventilation but are more suitable imo for small apartment type situations.

The unit you require is small, the duct work comes in different sizes depending on the design, from 300mm to 100mm.

Please make note.. Its absolutely imperative that you use rigid stainless steel ducting.. NOT flexi duct or in some cases Wavin pipe!

The latter 2 are not designed for HRV and you will have heat loss problems, noise issues and and a few others i can mention.

I've been told to stay away from flexi pipe work due to poor airflow. Just wondering what's wrong with using wavin pipework if it's well insulated?
I would have thought that it's main advantages would be that it's solid, with a smooth interior.
Just looking into the whole HRV thing myself at the moment.

beyondpassive

Polyethelene is the rigid duct of choice, with flush compression fittings.

I've specified egeplast http://www.egeplast.ie/pepipe.php, sorry to post a product link, but in this case generic descriptions aren't enough. (Sorry Mods if this may be an issue)

The pipes come in different colours which is useful in seperating flow and return duct runs. Its well worth getting a duct schematic done as early as possible in the build.

At the moment, we're noticing some issues with how MHRV was set up in the near Passive and low energy houses, which were celtic tiger type one off's where we applied a low energy spec. The upstairs overheats as the heat rises and stratifies due to the low levels of heat loss through the roof (good ol softboard). This has led to us coming up with a new solution, where we go for two seperate ventilation units, for upstairs and down and connect the ventilation to a simple Building management system linked to thermostats to keep the bedrooms below 20 degrees (better sleep) even if the living areas are 24 degrees. Its all about comfort really.

gears

I just looked at the site for the egeplast piping. Seems like fairly serious piping for air flow do you really feel thats necessary?

beyondpassive

Its fairly serious is right, says I, but these pipes are very efficient to push air through, as its slippery and has no internal baffles. Nowhere for dust or condensation to hide.

CJhaughey

I would differ, I think the spiral wrap galvanised steel pipe is the best available.
regarding the attic mounted units, you have to change filters and the best way of ensuring that they are changed on a regular basis is to have handy access to the HRV unit itself.
Putting the unit in an attic space will make it harder and less likely that they will be changed on time.
Out of sight = out of mind.

gizmo555

CJhaughey wrote: »

you have to change filters and the best way of ensuring that they are changed on a regular basis is to have handy access to the HRV unit itself.

"Regular" does not equal "frequent". My attic installed HRV system needs a filter change annually. The filters need cleaning at quarterly intervals, so that's just four visits to the attic per annum.

CJhaughey wrote: »

Putting the unit in an attic space will make it harder and less likely that they will be changed on time.
Out of sight = out of mind.

This is often raised in this forum as a drawback, but in my experience is a complete non-issue. Personally, I just make a note in my diary to remind myself. You could more usefully make the point that not putting it in the attic wastes valuable habitable space.

CJhaughey

I don't see the HRV taking a whole lot of habitable space in my utility room.
the footprint is 60x40cm and the same height as a fridge.
If you are designing a house to have HRV then it should be a simple matter to have the HRV unit designed in to the room for convenience.
You sound organised with regards to filter maintenance, but many others won't be as diligent and may also have mobility problems that prevent them from accessing the attic on a regular basis.

At the end of the day an HRV unit that is at ground level is going to be simpler to maintain and service than an attic mounted unit.

homewardbound11

I have mine in the attic an stupidly so. In hindsight it should have been in in the larger hotpress.

Fenor

Hi
Sorry for butting in on this thread but wondering can any of you give me names of companies that do the airtight wrap.
I'm putting in HRV but having trouble finding out about the airtight wrap or who can do it for me.
Thanks