Can anyone comment on the common types of heating and cooling systems installed in their region in high performance homes? More and more, I see designers and builders turning away from forced air and towards radiant hydronic or point-source systems (like mini-splits). Reasons include mismatch between load and size of forced air furnaces, zoning control, lower pumping energy, distribution system takes up less space, better integration with solar thermal, etc. Granted my scope is mostly California. Can people comment from other regions about trends in conditioning systems in high performance homes? Cheers!
Mini-splits are excellent for homes with open floor plans. If a home has a lot of smaller rooms mini-splits don't do so well. Getting contractors to believe you can cool a 2,000 sq ft house with a 2ton central A/C unit can be a challenge.
Combi-systems for forced air is what we have been exploring in MN. It is a compelling alternative to a separate furnace and water heater especially when the loads are low because you can add the heating load with the water heating load. We obviously have much higher heating loads in MN, but I know that Dan and Gavin from Balance Point have been using this approach for low load homes in CA. We have been mostly using a sealed combustion water heater combined with a hydronic air handler within the existing ductwork. It would be much better with an appropriately sized/sealed duct system, but we are making it work in our existing since most of our ductwork is within the thermal boundary in MN. Since we are using the water heater as the combustion unit, there is potential to hook up to a solar thermal array in certain products. Let me know if you want any more info on this approach. (Get my email from Iain).
In California geothermal heat pump systems and air handlers with evaporative cooling. In some instances, you can do with evaporative cooling alone without requiring mechanical cooling. If you are in northern California, air side economizers are a must. But I would say a lot of homes are going the geothermal heat pumps route because of federal rebates and when you purchase one it the price can be fixed into your mortgage instead of paying for the whole system at once.
You know I thought one day I would get a chance to share this story. A while back I worked for a buddy of mine on a big job for him putting in wall paper on a really nice 9 K sq. ft. home. The owner was very nice and obviously had retired well. He asked me what I did full time and said I,m trying to get an energy audit buisness off the ground. He informed me he retired from a regional sales buisness selling HVAC equipment. So I asked what he thought of any new trends in the industry. He told me to look outside and see the heat pumps...NINE ! outdoor units,they were in their own 4 ft deep concrete pits so they wouldn't be seen at eye level,split systems for 9K sq. ft......I came back in the house and told him " they look great!" and never spoke of matter again..Who am I to tell a guy with 30 yrs in the buisness and a 10mil. dollar home to show for it what he should do with his money. My point is 'know your market" in this situation.