Combined HRV and mini-split ?
GBA Editor
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Are there commercially available units which combine heat-recovery ventilation with an air-to-air heat pump?
I’m imagining something that could transfer heat from the exhaust duct to the supply duct of the HRV as needed during the heating season and vice-versa in the cooling season. Heat transfer within the HRV would be wholly conventional and the additional heating/cooling would be introduced in the duct supplying air from the HRV to the house.
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Replies
Dear Interested,
Many European Passivhaus buildings do what you propose — that is, scavenge heat from the exhaust air stream of a ventilation system, using a heat pump. Although such integrated appliances are available in Europe, they are not yet available in the U.S.
Further discussion can be found here:
http://www.passivehouseca.org/hydronic-heating-through-hrv-supply-air
You might also want to check out this page:
http://www.passivhaustagung.de/Passive_House_E/compact_system_passive_house.htm
Many thanks for a swift and helpful reply at 4:50 a.m. Vermont time - don't you sleep?
There aren't any products that I know of that are applying this concept to cooling applications. The European units don't have it because their clients don't usually need cooling.
In addition, the cooling capacity that you could provide using typical fresh air cfm would be pretty small. For example, in a small house with ~70cfm balanced fresh air/exhaust, you'd only be able to supply about 2,000Btu of cooling (1/6 ton).
My water heater vent runs in a chimney through the MB closet. I am building a passive heat exchange (cold air in from bottom, hot out the top) that will operate in the winter depending on the temperature.
You can buy a Nilan with a heat recovery pump and integrated air filtration (which every HRV should have IMO) through Canada: http://www.nilan.ca/indexen.htm - they ship to the US. Currently they do only carry the VPL-15 (6,500 btu/h heating-5,500 btu/h cooling) and VPL-25 (13,500 btu/h heating-11,500 btu/h cooling), would be nice to see availability of the VP-18 combo unit. This was the choice of HRV/DHW of the wining German Team from the last two Solar Decathlons. Usually any of the integrated heat pump units can do heating and cooling - there are many excellent units in Europe. Unfortunately the Nilan is the only one I know of right know available in our market place. They have a very good reputation in Europe and are one of the bigger players in ventilation...TC
Thorsten,
Thanks for the information on the Nilan — a European "magic box" now available in North America (the distributor is only a few miles north of me). Very interesting.
Hi Thorsten,
I agree with Martin......
This is most interesting.
JB
Thanks, Thorsten. I didn't realize there were models available that offer cooling. Martin - it's close but not quite a "magic box"...the models available in N. America do not include domestic hot water, yet.
I took a quick look at the performance specs from the brochure and am very confused. The heating capacity capacity chart (combined with power usage) indicates that the unit has a higher heating capacity at lower outside air temps, and with a slightly lower power consumption to boot. How does that happen? Perhaps a call to Quebec is in order....
Hello, as John pointed out in his response, some claims made by these machine manufacturers are problematic. We are a Quebec-based non-profit (www.archibio.qc.ca) in the sustainable home field and many of our readers have asked us about these so-called "thermodynamic" ventilation machines, many of which manufactured here in Quebec.
Our answer: none of these machines have had any third-party energy performance verification which opens the door for exaggerated performance claims. Indeed, these may include such head-scratching statements as " through positive pressurizaion, this machine will eliminate shale gas seeping into your basement". One manufacturer was singled out by a provincial consumer protection publication as being corrupt in an article entitled "10,000$ for thin air" (loose translation). Overall, the message is : buyer beware!