[Greenbuilding] [BULK] Re: Ground-source heat pumps

[RONALD CASCIO]

Just some personal information to share regarding geothermal/groundwater 
heat pumps and this discussion.

When we decided to build our own new home a few years ago a geothermal unit 
was our clear choice. With A/C being a must here in our hot/humid climate 
going with some sort of heat pump (for heating) makes sense because we could 
utilize the existing duct work for an A/C unit and the shared mechanics of 
heat pumps. We went with a GWHP over a high efficient ambient air system for 
aesthetic reasons (no outside equipment to see or generate noise) and 
superior efficiency. Payback was not as much of an issue as the attempt to 
reduce our overall energy use, costs be damned.

Here in Maryland closed loop systems are the only ones permitted, and we 
wouldn't even consider an open loop one anyway. The lines are charged with a 
refrigerant, friendly to the systems innards to reduce potentially adverse 
mechanical problems.

Obviously the first order of business is to build a very efficient envelope 
to reduce losses/gains, then take advantage of any available winter passive 
solar gains. When presenting the plans initially to the HVAC contractor they 
spec'd 6 tons with 6 closed loop wells, which is the standard size unit for 
our house's interior square footage. When pointing out to the engineer all 
of the measures we took to reduce heat gain/loss the system size was reduced 
to 2.5 tons and we opted for three wells to make the system even more 
efficient. The price went from $30,000 to $20,000 with the resizing, 
realizing an immediate $10,000 payback for all the insulation/shading 
measures we invested in. I calculate the upgrades in windows and insulation 
costs us about the $10K savings making the difference a trade off. Now it's 
a matter of realizing the cost difference of the GWHP vs. a high efficiency 
ambient air heat pump over time, if monetary savings are your bag.

So far, with only six months of use under our belt the performance of the 
entire home systems are extraordinary by industry standards and the comfort 
level is perfect with the temperature set at 72* in summer and 70* in 
winter. Paying our utility bills are a pleasure, as crazy as that sounds. We 
are happy to have invested in both a very efficient structure and an 
extremely efficient HVAC system to go along with it. When energy costs 
double and triple we will be even more happy with our choices.

Right now though, the wood stove is toasting the house on this chilly night, 
fueled with wood scraps from the project I am presently working on that 
would have gone to the chipper if we didn't have the stove. We're squeezing 
every BTU out of everything we can around here in the Land of Pleasant 
Living, Maryland's Eastern Shore.


Ron Cascio
Chestnut Creek
Design/Build/Consut/Develop
Maryland's Eastern Shore



----- Original Message ----- 
From: "Keith Winston" <keith at earthsunenergy.com>
To: "Greenbuilder list" <greenbuilding at listserv.repp.org>
Sent: Thursday, January 11, 2007 8:44 PM
Subject: Re: [Greenbuilding] [BULK] Re: Ground-source heat pumps


> Reading between the lines, several of the comments here have been about
> open-loop systems. We should always make this distinction explicitly
> when talking about geothermal, since it's an entirely different
> arrangement. The closed loop is generally more expensive to install and
> a little less efficient to operate, but the most responsible way to do
> it IMHO, and perhaps the only legal way in some places. It would be
> helpful for people to make this distinction as they wrote about specific
> geothermal systems.
>
> Keith
>
>