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birgco
Joined: 01 May 2007
Posts: 302
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 Posted: Sat Jun 16, 2007 8:38 am Post subject: Air Conditioning for ZEH |
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| I am looking for an air conditioning system for a planned ZEH (Zero Energy House) in a mixed climate environment ( generally brief periods of 90 + very humid weather in July & August and winters mostly low teens to 40 degrees). The house will require about 3/4's less energy than standard new construction. I am trying to get away from standard large ducting because the large ducts seem to be at odds with maintaining an energy efficient envelope. The 2" mini duct systems do not seem to be very energy efficient but like the idea of the small ducts. Thought about 4 " PVC as an alternative for ducting but also need a main supply system. The air duct system will also function to supply fresh air into the house from an air to air heat exchanger. Would like to hear input from anyone with thoughts on the subject. thanks |
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joelmckellar
Joined: 31 May 2006
Posts: 86
Location: Charleston, SC
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| Posted: Mon Jun 18, 2007 5:25 am Post subject: |
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It seems like you've looked into this quite extensively, and are fairly far into the design process, but has any consideration been given to radiant floors, chilled beams, etc?
In cooling mode, a laminar flow, displacement ventilation system may work if your ceiling heights are large enough, though I'm not sure what duct sizes would be required for this system, and it would also rely on an underfloor distribution system. This still leaves you with your heating ducting unresolved, but combining with radiant heating could potentially work.
Hope this helps.
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Joel McKellar, LEED AP
http://www.reallifeleed.com/ |
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birgco
Joined: 01 May 2007
Posts: 302
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| Posted: Mon Jun 18, 2007 6:15 am Post subject: Air Conditioning for ZEH |
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| Joel, the house will have full radiant (pex) floor heating and I really like the idea of supplying chilled water to the radiant floor system but a bit concerned about the potential for condensation on the tubing. Not familar with "chilled beams" but would like to hear about them. Also am leaning towards a ground source heat pump to supply heat/ac. I know you have experience with heat pumps so would appreciate your thoughts. The heat pump would be the back-up for the main source of heat, evacuated tubes on the roof. Also, next to the evacuated tubes there will be a 3K or greater Pv bank. Thanks again for your input. |
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birgco
Joined: 01 May 2007
Posts: 302
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| Posted: Mon Jun 18, 2007 6:19 am Post subject: Air Conditioning for ZEH |
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Also forgot to mention, the ceiling heights will be 10' on main floor living space of 2750 sq. ft. Second floor has 2 small bedrooms and bath (about 600 sq. ft.)
Full, unfinished basement w/ radiant floor heat w/ 10' ceiling height. |
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joelmckellar
Joined: 31 May 2006
Posts: 86
Location: Charleston, SC
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| Posted: Mon Jun 18, 2007 8:39 am Post subject: |
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I'm happy to help in any way I can, but you may have overestimated my experience. My posts on geothermal heat pumps are questions more than advice, and your last questions would be better fielded by an engineer than me.
I can help a little with chilled beams. None of the projects I've had have used them, but another branch of our office placed them in a commercial facility. There is a good introductory page from an engineering firm:
http://www.aeieng.com/services/sustainable/chilledbeam.htm
It looks like they are geared more towards cooling higher process and equipment loads than would occur in a house.
Sorry I can't help further.
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Joel McKellar, LEED AP
http://www.reallifeleed.com/ |
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birgco
Joined: 01 May 2007
Posts: 302
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| Posted: Mon Jun 18, 2007 11:43 am Post subject: Air Conditioning for ZEH |
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| Joel, not to worry, I appreciate the input just the same. The page on chilled beam tech is very interesting. As you said, don't know if it will apply to residential applications but I like reading about technologies that could be adapted to another need. I will be talking to a few heat pump technicians next week who may shed some light on potential systems. thanks again. |
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birgco
Joined: 01 May 2007
Posts: 302
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| Posted: Sun Jun 24, 2007 4:57 pm Post subject: solar power heat pump |
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| There is a Sanyo solar powered split system heat pump available in Europe that sounds like a great solution for A/C in a ZEH. Anyone manage to use one here in the U.S. thanks |
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birgco
Joined: 01 May 2007
Posts: 302
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joelmckellar
Joined: 31 May 2006
Posts: 86
Location: Charleston, SC
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| Posted: Mon Jul 16, 2007 5:56 am Post subject: |
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A local elementary school used ice storage. They had problems with it at first, but I understand those have been worked out.
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Joel McKellar, LEED AP
http://www.reallifeleed.com/ |
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csintexas
millennium club
Joined: 06 Feb 2006
Posts: 1860
Location: USA
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| Posted: Mon Jul 16, 2007 6:22 am Post subject: |
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ice storage has been around for a while, I did not realize it saves energy though, I just thought it was used to offset peak demand.
The chilled floor would be an interesting experiment and if you did a search you would find I brought up the subject about trying it last year. As long as the floor temp remains above the dew point condensation would not be a problem and I can't see wanting the floor to be colder than that anyway. You would still need an air handler (at least around here) I would guess.
Chilled water has been used before but they used to run it through a radiator close to the ceiling with a drip pan under it.
I've seen that system that uses mini ducts and I don't like it. (other than they say a different coil design also reduces humidity) a central plenum within conditioned space with low air speeds would be best.
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Chris Stewart
Modern Texas Home Project |
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joelmckellar
Joined: 31 May 2006
Posts: 86
Location: Charleston, SC
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| Posted: Mon Jul 16, 2007 6:26 am Post subject: |
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We're looking at a variable refrigerant volume system (Daikan - SEER at about 20) for a LEED project in place of a geothermal system. Does anyone have any experience with these?
We received a remarkably convincing argument from a sales rep (always a little scary), and are currently scratching our heads wondering why they're not used more extensively. Our MEP guys are on board, but I'm waiting for the other shoe to drop...
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Joel McKellar, LEED AP
http://www.reallifeleed.com/ |
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