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Ventilation heating and cooling a PH

A Passive House requires a mechanical ventilation system and a heating/cooling system (Zone 5A).
What is the most cost effective method of achieving this? Since we will be putting in ductwork for the ERV/HRV system, it only makes sense to use this system to distribute warm and cool dry air, as opposed to having the ductwork and mini splits hanging on the wall. Also, we would have to condition (de-humidify or heat) the incoming air before it hits the heat exchanger anyway.
Zehnder ComfoFond (http://zehnderamerica.com/our_products_categories/geothermal-heat-exchan... ) , or something like this (perhaps an air to air heat pump instead of geothermal) appears to be the solution. Are there other manufacturers that have similar systems? Are they as efficient or more affordable? Will this pre-conditioning of the incoming air be enough to keep the house comfortable year round? Therefore, no other heating or cooling would be needed?
My Passive House consultant directed me to a “black box” (CERV) manufacturer in Central Illinois. http://buildequinox.com/products/cerv/ . Has anyone used one of these? How do these compare in cost? This sounds like a complete system for heating, cooling and ventilation.
Earth tubes to pre-condition incoming air sure sounds like a good idea on paper – really simple, cheap to install, and cheap to run - but that pesky mold potential has me thinking of using a different solution.
Given that the black box and the Zehnder systems are probably quite costly, it might make economic sense to use a less expensive heat exchanger and mini-splits. This seems to be the solution for many of the North American passive houses. Is that because of costs? Product availability? Familiarity with the products installed?

Asked by Steve Young
Posted May 5, 2014 4:53 PM ET


7 Answers

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Steve, most of what you ask has been answered by yourself and here at GBA via blogs on PH homes. Visit more actual PH homes, and contact some of the more experienced PH builders direct if you really want to dig deep into PH.


Answered by aj builder, Upstate NY Zone 6a
Posted May 6, 2014 7:03 AM ET


There is no advantage to combining the ventilation with the heating &/or cooling systems, since ventilation needs occur with or without heating or cooling loads. In a super-high-R house with super-performance windows, ducted heating & cooling have little benefit, making mini-splits a good solution, using some other approach for ventilation.

In a zone 5A location cold-climate mini-splits (Either the Mitsubishi M-series " -FHxxNA" or the Fujitsu Halcyon XLTH series "-xxRLS2-H" ) make sense, since they are purpose-designed to work well at sub-zero F temps, and have rated output even at -13F/-25C and lower. Other heat pumps can have ice accumulation issues (and pathetic output & efficiency) at low temps below +5F/-15C.

Answered by Dana Dorsett
Posted May 6, 2014 4:28 PM ET


Dana - Thank you for clearing up the mechanical system issues that I am grappling with. It looks like I will have to find a HRV or ERV (I am still not too sure which is more appropriate for 5A) and a mini split system. If I insulate and seal well enough, I hope to get away with one unit in a 1850 sq ft house.
My brother, in Ottawa ON, will be interested to see the models that you recommend for cold weather, too.

AJ - I have spent many many hours on the GBA website, and purchased every Passive House book that I can find, GBA is far better for acquiring knowledge. Most of the books have been next to useless with regard to building details and systems used - more like architect showcases.
I realize that PH cannot be "cookie-cutter-ed" but it would be nice if PHIUS would put together a distilled and detailed summery of what is being used in North America. I see that they have started with window manufacturers, but I would like to see more on how folks insulated under foundations/slabs, wall construction, window and door installation, mechanical systems, and barriers (tapes, membranes, foams and the like).
The two or three good PH books that do go into some detail are still quite limited. That is why I have been spending my time at this website and posing a question or two. I have too much to learn and no nearby examples of PH or PH groups (I am currently south of Houston, TX), although I have been on a tour of such houses in Urbana several years ago, well before I knew what to ask.

Answered by Steve Young
Posted May 7, 2014 5:58 PM ET


South of Houston. Well that makes a difference. Humidity? Heat? Cooling season? Minor heating season?

PH US, has no one including the boss Katrin Klingenberg willing to set you on your path?????

Steve. get on the phone my man and get Katrin on board.

Answered by aj builder, Upstate NY Zone 6a
Posted May 7, 2014 9:54 PM ET


Sorry AJ. I guess that I was not clear. I live in Texas now, but will retire to Ohio in a few years where we will build a mostly DIY PH. That DIY-factor is why I am trying to learn as much about all aspects of the PH.
I have a PH consultant in IL but I am trying not to bother her too much until I have a satisfactory preliminary design, including floor plan, mechanical ideas, construction details and the like.
I have no intentions of building anything down here where the next hurricane could take it all away. Plus it is too hot for this Canadian boy ;-)

Answered by Steve Young
Posted May 8, 2014 10:53 AM ET


Urbana west 5 hours thee place to be passive for hockey puck lovin Canadians... As to this site.... Spend many hours under the green homes tab... Along with here Kevin.
:) aj

Answered by aj builder, Upstate NY Zone 6a
Posted May 8, 2014 11:29 AM ET


As Dana pointed out, there is no advantage to combining the ventilation with the heating/cooling system. For your size house the Renewaire EV90P should handle the ventilation quite well and consume under 45 watts doing it. For lower ventilation rate and power use, use the percentage on timer type of controls. I plan on using one and drawing air into it from 2 bathrooms and returning the fresh air output to a common hallway. Mini splits are actually intended to only heat/cool a single room. Even with passive house insulation and sealing, "private" rooms will have noticeable temperature differences with a "point source" heating/cooling system such as a mini split. My solution is to locate the mini split's indoor unit in a "closet" along with 5 "Whispergreen" fans that collect the output of the mini split and move it, via simple ducts under the floor, to the perimeter of the building whenever the mini split is on, with a return air path via "jump ducts" and open grill work around the top of the "closet". The "Whispergreen" fans are very quiet, very efficient and smart in that they move a selectable amount of air, independent of duct back pressure. However the fans and controls add about 50 watts to the heating/cooling power use.

Answered by Jerry Liebler
Posted May 16, 2014 11:51 PM ET

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