Cohousing-L Mailing List: Re: Heating systems

[David Hungerford (dghungerford]

On Wed, 12 Oct 1994, Stephen Hawthorne wrote:

> Do any of the existing groups have any experince with geothermal heat pumps?
> Our research as we approach retrofitting our recycled homes indicates that
> this may be a viable system despite some additoinal upfront installation 
> costs.  But since it's new technology, we're looking for info from people 
> who've already taken the plunge.
> 
These are also known as Ground Source Heat Pumps.  The EPA recently published 
an evaluation of this and other high efficiency technologies.  
Contact the EPA for 
publication 430-R-93-004, "Space Conditioning: The Next Frontier.  The 
Potential of Advanced Residential Space Conditioning Technologies for 
Reducing Pollution and Saving Consumers Money"  published in April of 
1993.  This is probably avialable through NC State or UNC libraries, in 
their government documents sections.

*IGNORE THE REST OF THIS POST IF YOU'RE NOT INTERESTED IN DETAIL*
A ground source heat pump (compared to a conventional air source heat 
pump) uses a "loop" of tubing circulating a working fluid underground to 
transfer heat from a building to the ground(summer) or from the ground to 
a building (winter).  Because ground temperature is fairly constant year 
round (except very near the surface) the unit can use the phase change 
properties of the working fluid to remove or add heat to the indoor 
air *without supplementary heating or cooling, except in extreme 
weather* since you're only running the pump, this is very efficient.  
According to the EPA they use 40-50% of the quantity of R22 (freon) as 
air source heat pumps, and use as much as 60% LESS energy.  The 
installation costs are higher, however.  If you're serious about these, 
get the pub and do the benefit/cost ratios yourself.  Depending on your 
electricity costs, the payback (in saved energy costs) should be less 
than 10 years.

Of course, before adding heat to your houses, or taking it out, be sure 
to do your homework on passive design.  Proper orientation, shading, and 
insulation can make a huge difference in your energy bill, on the 
environmental (and energy security) impacts of the energy you use, and 
your house will be more comfortable to boot.

David Hungerford
Muir Commons