"Nate Weber" wrote in message ...
"PhysicsGenius" wrote in message
...
If you want to be really "ultimate" what about a geothermal heatpump?
For a shop-sized building, it'd probably be just pennies to run per month.

Are they really that efficient? I was under the impression that since a
heat pump uses
the same systems as a air conditioner, it would cost the same to run.

Geothermal systems are the most efficient system available today. It
always takes less energy to move heat than to generate it. Air source
heat pumps get into trouble when the outside air gets below 32F or
above 90F (for AC). Using ground source, the temp stays in the 32-55F
range. Wells give you a more constant temp, but pumping tens of
thousands of gallons of water out of an aquifer for heating does not
seem like a good use of resources to me. I put in a ground loop
geothermal system for my house. There's about 3600 ft of pipe in the
ground loop buried around 6 foot down. When running in winter, the
loop will probably get down to 32F (which is why they fill it with
glycol). That will take care of AC, heat and, to some extent, hot
water. I have talked to a number of people in the area (Michigan) who
have done this and their January and Feburary heating bills tend to be
in the $20 range. Yes, that's _twenty_ dollars. Of course, they are
well insulated houses and our local utility gives you a special rate
for geothermal. I'm still under construction and won't be running it
until next winter. For me though, the choices were geothermal,
propane or oil and the latter two for a primary source were not very
attractive.

AC tends to be very efficient because you're dumping the heat into a
cold sink, rather than 90+ F air.

The downside is the capital investment. Water source heat pumps large
enough to handle a house are not cheap. Waterfurnace is one make,
there are a couple of others.

I wonder if you could cobble something up to let an ordinary air heat
pump work with a ground source? Seems like you'd just have to do
something clever with the heat exchanger and you can probably get
those for next to nothing.

I had a contractor do mine, but there's nothing in the installation
that a reasonably handy person couldn't do, particulary if you have or
can rent or borrow a backhoe. The units are sealed, so there's no
handling of refrigerant. The hardest thing to do is to weld the
ground loop so it's leak tight and then fill it and purge the air out
of it. If you can get a unit, you could probably install it yourself
for less than half of what a contractor would charge you. Still
wouldn't be cheap though.

Although I did this for my house, I used radiant heat with a propane
fired tankless 87%+ efficient hot water heater for the shop - block
building with foamed insulation in the cores and 1.5 inches of
styrofoam under the external sheathing. I should end up with an R12
wall if you believe the literature from the foam company. I built it
that way because I was worried about fire. Doing it over though, I
would probably use SIP construction. Masons have been consistently
the worst group of contractors I have had to deal with.

One thing I did do right is to use scissor trusses for the roof. That
gives a significant boost to the ceiling height in the center. I also
put in a couple of skylights as well as a row of windows.

Another option, is a geothermal/radiant heat pump. I didn't
investigate these, but they may be significantly cheaper than the
geothermal/forced air unit I put in the house. Then again, maybe not
:-)

Paul