I am building a house for a couple in VA. They are going to be living completly "off the grid" when the house is complete. There will be no power meter. They were spec'ing a concrete radiant floor system fed by a wood boiler for heating. There is no cooling system included.  Given the climate here I think that the house will be prohibitavly hot in the middle of the summer. I am looking for alternatives to this system that might provide some cooling capacity. The solar system provides 10 -12 KWH of electricity.  I am having trouble tring to work this out. I have looked a GHPs, pasive air, solar, etc... Any help would be appreciated. I am stumped.

1st of all 10 - 12KWH is way too much power, unless that is for an entire day!

A GSHP would be a good method for cooling, but it's pricey. The easiest way to accomplish the cooling task is to Earth Shelter the house. If earth sheltering is unacceptable, you might look a cooling tubes. A series of buried tubes that will return air cooled to ground temperature. No matter what you do, I'd make sure that the house is Super Insulated. That will reduce both heating and cooling loads.

Good Luck!

Consider using a while house fan. It usually has to run at night in order to work well - so they may need to run it off of batteries but it is a very cheap way to cool a house off. Also - suggest they put a number of retractable awnings on the south side of the house - these can be used in the summer so it doesn't heat up to much. www.wholehousefan.com is a good website. airscape 1.7 is also a good model to consider.

GSHP is more costly UPFRONT but over all it is a very cheap way to go. The DOE website has some good data on the payback period for GSHP which is about 5 yrs - and then for the next 15 years of the piece of equipment you are saving much money as your heating and cooling costs will be about half normal.

Hope this helps Todd

We are planning on a 10kw solar electric system and using an evaporative cooler (swamp cooler) as our central A/C. It only uses 1.5 kw a day on energy.

10-12 kWh / day MIGHT supply enough power to run a small minisplit heat pump. By small I mean 1 ton or less.

A swamp cooler is not gonna work real well in any part of Virginia I've been to...

JC might have the best solution with ground tubes. I helped with a project in the early 80's with a two story bld. that was 50 X 100. In Mo. We dug a trench 50 ft out and looped it back six ft. deep. We welded 33 gal drums together for the tube and placed a 4 ft. box fan for the air circulation. This dumped 68 degree temp air into the bld. both winter and summer. For summer you have the cool for winter you only have to raise the temp two degrees, which was done by passive solar hot water that thermo cycled through radiant floor heating. All very low tech and very slick.

This is for Rayan who sent me an e-mail. 

The system discussed above was for a comercial BLd, Ofices and a chapel on the second floor.  They used regular duct work for the trasmission of the air.  At first there was a problem of condensation inside the tubes and it was handled by haveing a dehumidifyer to take out the extra moisture.  Then I believe the system was ran through an air handler so the air went through a set of coils like a big radiator which causes the moisture to condese againt the metal of the coils and be extracted just like any regular HVAC.

The radiant floor heating was a closed system, with a systern of water below ground level and then the pipes in the cemet circling back and fourth bouth in the three walls and the ground that was all poured cement.  The panels are easy enough to make out of a box 3' X 8' X 2".  With foil backed foam on the bottom and then six  rungs of 1/2 " copper tube.   15 gage alluminim was used for the fins that covered the pipe.  Then the bosx had two sheet of plexi glass on top with 1/2 inch spacers between.  All very low tech but this pane will produce 4500 BTU's.  This is what I have for my hot water here in FL.

Try a cool roof type system whereby you spray some water on the roof to let it evaporatively cool the house. Simple, cheap, and somewhat effective. Also if the solar panels are atop the house they should help reduce the heat.