Balanced ventilation with heat recovery

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blackjack17

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#249130 26-Apr-2019 21:29

Hi all

Similar to my other thread about Hydronic heating, we are looking at building in Auckland in the next year and we are interested in the option of using a balanced ventilation with heat recovery.

Has any one put one in? If so do you mind sharing details? What make and model, up front cost, running cost. Any issues?

Cheers

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#2225876 26-Apr-2019 22:03

We put a Zehnder Q350 Comfo Air into a 2 story new build (236m2), in Auckland. Our setup has 7 supply air vents and 6 exhaust vents. They are the only extraction source in the bathrooms and so far have worked fine. You do need to trigger the boost function before showering for best effect, else it will take a while to sense and ramp up.

Haven't had any issues with the system after 14 months. We got the optional LAN kit, which allows controlling most functions via the phone app. My only gripe is that in winter, it does reduce the house temperature a decent amount due to the cooler source air. While the heat recovery system on average can take sub-5-degree source air up to 15-18 degrees on average, it's still cold air entering the house when we try and keep temps as close to 22c all year round. Am playing around with schedules to see if this can be mitigated somewhat. But this does result in us using heat pumps more often to raise the temps back to 22 than we would if we didn't have the system or have it turned off during peak winter. Could argue there is less energy required to heat back up to 22 due to less humid/stale air in the house, but I have no means of validating this and believe it would be immaterial cost savings at best.

According to the app, total power consumption for those 14 months is 251kWh. It estimates we've had total energy savings of 1536kWh, all from avoided heating. I would take that with a grain of salt if you're hoping to offset the install cost somewhat with future energy savings. I don't believe it's accurate.

Total install once everything was said and done c.$18k. Given the amount of pipework required, it would cost significantly more, assuming it's even possible, to retrofit the system. So speccing and installing before lining is highly advised. Only ongoing cost after the first 14 months is replacing filters every 180 days, at about $100 incl GST.

Kickinbac

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#2226037 27-Apr-2019 09:41

I had a Mitsubishi Electric lossnay system in my last house and put one in my parents house, that they still have. Mine was installed in a 60’s house which would be far from airtight. It worked well for ventilation but probably wasn’t necessary due to the air leaks. It worked well.

Zendher is the ‘BMW’ of ventilation systems but I wouldnt spend that sort of money unless building a passivhaus.

Offtopic but things that you should consider before you finalise your build...
Look at passivhaus principles and design.
Insulate your house beyond building code minimum requirements.
Invest in good double glazed windows - look at thermal breaks.
Look at the air tightness of the construction.

I strongly reconmmend you get your plans Homestar rated before you finalise your build.
https://www.nzgbc.org.nz/homestar

My mind still boggles at the state of new builds in NZ considering the building science.

timmmay

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#2226286 27-Apr-2019 13:08

Consider Cleanaire, I had a quote from them a while back but didn't purchase. Even with a heat recovery ventilation system you don't have to run it all the time, and when it is on you don't have to run it at 100%. It's still going to lose some heat and work your heat pump harder. That's why I have my old positive pressure system run 9am - 3pm in winter, plus 20 minutes in the evening and 20 minutes before the heating comes on in the morning. I'd rather have heat recovery, but it's not worth it for this place.

Jase2985

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#2226351 27-Apr-2019 14:56

@timmmay running it like that kind of defeats the purpose of the positive pressure system. to prevent moisture buildup on windows, overnight.

@blackjack17 it really depends on what you want from the home and what sort of "standard" you are building too, a system like cleanair will likley have less larger vents where as a zehender will have lots of smaller vents in every room.

timmmay

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#2226402 27-Apr-2019 15:28

Jase2985:

@timmmay running it like that kind of defeats the purpose of the positive pressure system. to prevent moisture buildup on windows, overnight.

Reducing window condensation is only one benefit of a PPV system. It's not one we particularly need, as we have double glazed windows we only get condensation when it's very cold out or very moist inside - like when we had the carpets cleaned. Regarding condensation though, I think it's the build up of moisture that does that, so if you keep the humidity down during the day it doesn't happen as much at night. To use PPV to reduce condensation on windows you'd have to have an outlet in each bedroom, blowing cold outside air into each bedroom, increasing your heating needs significantly and making the room less comfortable. I don't think PPV should really be used primarily for that, and if it is it really needs to be turned down to a very low speed at night and heating considered.

The way we use PPV, with a bit of air pumped in evening and night, we get little condensation on the double glazing. If it builds up more in winter I might turn it on a bit more, but whoever put the system in only put outlets in the hallway and kitchen.

We use it to push out the stale, damp air, to ensure we have fresh air. We have a bit of moisture come up from under the house, not much since we did a lot of work to prevent it, but still some. It pushes out cooking smells, which happen even though we have an extractor in the kitchen and bathroom.

Opening windows is fine, but despite its reputation Wellington is often fairly still and windows don't do much on the latch position.

Ragnor

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#2232516 7-May-2019 21:55

Kickinbac: I had a Mitsubishi Electric lossnay system in my last house and put one in my parents house, that they still have. Mine was installed in a 60’s house which would be far from airtight. It worked well for ventilation but probably wasn’t necessary due to the air leaks. It worked well.

The Mitsubishi lossnay solution with ventilation and ducted heat pump is a really good option for a new build. Best of both worlds and designed to work together effectively.

http://www.mitsubishi-electric.co.nz/ventilation/solution.aspx

akmodi

26 posts

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#2232580 8-May-2019 06:16

We have just built a new house.

We installed a Zehnder system and then used heat pump in 3 areas.

The Zehnder system is 96% efficient at heat recovery. Combine this with individual heat pump means that it will automatically transfer the heating or cooling throughout the house.

Works brilliantly.

AliExpress

Shop now on AliExpress (affiliate link).

nickb800

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#2232581 8-May-2019 06:35

Worth bearing in mind that efficiency ratings are usually for the heat exchanger, but you also loose heat through the ducting, even if insulated, if it sits above your ceiling insulation

akmodi

26 posts

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#2232584 8-May-2019 06:43

nickb800: Worth bearing in mind that efficiency ratings are usually for the heat exchanger, but you also loose heat through the ducting, even if insulated, if it sits above your ceiling insulation

Absolutely, couldn't agree more.

That's the problem with most of the units : they are outside the thermal envelope and are inherently inefficient. Holes through the insulation to install the ducting will reduce the efficiency of the current insulation.

Our roof space is insulated, so the efficiency will apply 😀

Jase2985

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#2233110 8-May-2019 15:58

real world you wont see 96% efficiency even if its inside the thermal layer and you have insulated ducting, more like 70-80 odd %. still better than most though.

kinnadian

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#2239303 16-May-2019 16:19

I've been through the research phase of installing a balanced heat recovery ventilation system.

I ended up going out for quotes from 3 companies (Condensation.co.nz, Smartvent, Cleanaire) and condensation.co.nz didn't bother replying. I developed a system for my house with both Smartvent and Cleanaire customer support agents, but ultimately the quality of the documentation, components and the design led me to chose Cleanaire over Smartvent.

For a 3 bedroom, 1 office, 1 bathroom house with 3 extraction points and 5 delivery points the shipped price was $3800 for DIY installation (about $2500 of this was just the heat exchanger/fans and the rest was all the other bits that could potentially be picked up locally cheaper from an electrical wholesaler but it didn't seem to be much cheaper). I received the package last week and intend to start installing it this weekend. I just went with the barebones setup which has no smarts in the controller, just on/off and 1-10 fan speed. I intend to install aftermarket controls for scheduling the controller on/off (thermostat controllers on Aliexpress are around $50), maybe later I will get thermostat control to bedrooms.

We only intend on running the ventilation during the day when we are not home (to remove moisture) and in the evening when the lounge fire is on (to heat the end bedrooms and drive out moisture) but otherwise turn it off overnight/weekends as it will cool down the house too much with no active heat source - hence I will be installing an aftermarket programmable schedule controller.

The quality of the build of the heat exchanger/fans is top notch (I frigged the wiring to turn the fans on and put them on full power and was very impressed with the fan suction/delivery), all the ducting is 6" insulated with big 6" diffusers.

I'll post an update in a few weeks after I've installed it, if you haven't made a decision already, but I'm very happy so far.

Positive pressure systems we immediately disregarded because I've had them in the past and they were mostly useless, plus due to the inherent dust/etc in the roof cavity you can't even install these anymore in new houses as it doesn't meet the minimum standards for air quality (unless you spend a fortune on expensive filters and replace these regularly). And we have a bad moisture issue due to two fish tanks totalling ~1400 Litres in the lounge and positive pressure systems "forcing air out of the cracks" in your house sounds like total bollocks to me.

neb

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#2239578 16-May-2019 22:57

Kickinbac: I had a Mitsubishi Electric lossnay system in my last house and put one in my parents house.

Friend of mine has what I'm pretty sure is a Lossnay and recently had the whole heat exchanger replaced (under warranty) because they used the wrong adhesive and it broke down over time, leading to not so much an exchanger as an air interchange. Apparently this is affecting a number of units from that time period. I wasn't paying full attention at the time but can get full details if it's of interest.

Kickinbac

427 posts

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#2240000 17-May-2019 16:31

Yes, would be interested. Lossnay is Mitsubishi Electric's brand of heat recovery. I hadn't heard that there were issues with their cores.

Their cores are 'permeable', they are made from a waxed paper to allow moisture to pass between the supply and return airflows. They are not suitable for extracting moist air direct from bathrooms so they now have a specific version that allows this with a different core material, probably plastic.

neb

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#2240008 17-May-2019 16:56

nickb800: Worth bearing in mind that efficiency ratings are usually for the heat exchanger, but you also loose heat through the ducting, even if insulated, if it sits above your ceiling insulation

You can get higher-R ducting (2.0 rather than the default 1.0) but it's a special request and special order.

neb

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#2240010 17-May-2019 17:00

Kickinbac:
Yes, would be interested. Lossnay is Mitsubishi Electric's brand of heat recovery. I hadn't heard that there were issues with their cores.

It was actually a DVS, the Lossnay was in a previous house. What happened was that the adhesive in the casing for the heat exchanger failed so that incoming and outgoing air was mixing, and attic air and dust got into the heat exchanger. He detected it by spraying cheap perfume into the exhaust inlet inside the house and could smell it in other rooms due to it mixing with incoming air in the heat exchanger.

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