doubled cooling load? > GreenBuildingTalk - Green Building Forums on Insulating Concrete Forms (ICF), Structural Insulated Panels (SIP), Radiant Heating, Geothermal Heat Pumps, Solar Power

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catsrevil

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Posts:1

04/21/2008 10:49 PM
Hello all, I am new to this fourm, and i have a question about SIPS for the roof. My wife and I are planning to build a new home in Northern La. later this year. I have read on this fourm and others that it is desirable to place al the heat and cooling equipment inside the conditioned space. so now i am wondering why? it stands to reason that a simple square house that that is 2000sf with a ceiling height of 9ft takes "X" tonnage of cooling to keep it comfortable. then take that same house and build it out of SIPS and put all the equipment in the overhaed space. haven't you just increased the amount of cubic area that need to be cooled all because you hve put the roof insulation directly under the decking istead of directly above the 9 foot mark as with traditional stick built houses? I hope that i am explaining this correctly for some to answer my question. Also, i would like to poin out that i am not arguing the fact that SIPS would be great for the exterior walls, just questioning the roof part. If you know then plz type slowly so i can understand...

Jelly

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Posts:295

04/22/2008 4:41 AM
There is a lot of information about your questions at: http://www.buildingscience.com/index_html Look for unvented attic or conditioned attic.

cmkavala

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Posts:859

04/22/2008 1:48 PM
It is most efficient to place the HVAC airhandler and ducts all within conditioned space envelope. It does not necessarily need to go overhead , we prefer an easily accessable closet for future maintenance and replacement. While the dropped areas in SIPs house will get conditioned thru duct leakage you are not fully conditioning the overhead space. While it may be pleasantly comfortable up there. Your supply ducts and return air will keep most of the air flow where it needs to be. In a conventional system you ducts and air handler are fighting hot humid air greatly reducing efficiency. A reason why your HVAC in a SIP house must be downsized and properly designed.

Chris Kavala chris@southernsips.com 1-877-321-SIPS

trigem1

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Posts:50

04/22/2008 8:05 PM
If I understand your question correctly, I think the place to start is, are you planning on a vaulted ceiling, or a flat 9 ft ceiling? A vaulted ceiling is nice in that it makes the house feel much bigger, and gives you options for beams, lighting and ceiling fans. If you are planning on a vaulted ceiling, lean towards a SIP roof and if not, lean towards ceiling with joists with batt or blown-in insulation. I think that even with the added area to heat and cool, the extra insulation value of SIP’s for the roof would offset the need for a larger HVAC unit. Best thing might be to go to a HVAC business, and let them calculate your two options. I’m not sure if the attic is place to have your heating and cooling unit. Should it ever need repair or replacement, the attic would be a difficult place to work or lift a furnace-evaporator. Also, you would have to run a hose to the outside from the air conditioning unit to drain water that condenses on the coils, and if that leaked, it would damage the ceiling. I would suggest putting a heat pump on an outside wall, with the compressor right outside that wall. Steve GrandCountySIPs.com

GeorgiaTom User is Offline

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Posts:132

04/22/2008 8:13 PM
I think most HVAC contactors would like to see equipment closer to the center of the home for balanced distribution rather than an outside wall

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