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Geo-Thermal

by Thomas last modified Oct 24, 2009 09:21 AM
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Geo-Thermal

Posted by Thomas at September 12. 2009

My wife and I are going to soon start a modern build from scratch.  I am very interested in renewanle energy concepts and reducing utility cost.  I have enjoyed the posts I have found here but have not seen Geo-Thermal as a topic.  I have a very general understanding of it and was hoping we could have a discussion.  Esentially here is my summary of Geo-Thermal in talking to a couple of people about it:

 

--  Basically the system will revolve around 250 foot deep holes that are drilled under house.  At that depth air that is 65 ish degrees can be constantly pumped to the surface through pipes which should reduce expenses greatly in Summer and Winter.

--  There can be a component to also heat water.

--  Cost is heftfy.  10-20K more than conventional systems.  Have heard 50K total cost estimates...but others think far less.

--  There is a 30% tax write-off capability with no $1500 cap like other green features.

 

Here are pros/cons as I see them so far:

 

Pros:

 

--  Greatly reduced bills.  one person I spoke to said in a 5000 sq ft home, the bills were $200 through the Texas Summer.  That sounds GREAT!

--  Greener living.

 

Cons: 

--  Lots of $$$$.  Have to live in house long-term to re-coop investment.

--  Newer concept without clear idea of future maintenance.  (IE: what if pipes fail?)

 

 

Re: Geo-Thermal

Posted by Thomas at September 24. 2009

guess no takers on the Geo-Thermal talk.  found this forum that answered many of my questions if you are interested: 

 

http://forum.geoexchange.org/

 

take care.

Re: Geo-Thermal

Posted by Jason at October 04. 2009

Thomas - I wouldn't do geothermal unless you plan on spending 15 years in your house. I have never priced one myself but I hear they are REALLY expensive.

Have you considered foam insulation instead? I had foam insulation on my last house along with commercial grade windows, 16 SEER variable speed HVAC units my energy bills were 40% less than similar sized houses I have lived in the past.

Re: Geo-Thermal

Posted by Thomas at October 04. 2009

Hey Jason, Thanks for the input.  My wife and I (and 2 very young sons) do plan to be here for the long term.  We hope this is the last house we build...but stuff happens...though I don't expect it.  I have progressed a bit in my research but will continue to weigh the benefits of conventional vs geo-thermal systems.  I have gotten some arguments for geo-thermal that are pretty compelling.  I have to use a vertical system on my lot and I was given a ball-park estimate of 5-7K per ton of HVACsystem.  I had one builder tell me we would need 5-6 tons of HVAC system...while another said 3-4.  comes down to the energy efficiency.  with the government write-off, I think it might be 10K or so over conventional.

 

Our home will be a bit shy of 3500 sq ft.  The design is pretty simple.  2 story.  an atrium in the middle.  bottom floor esentially shaped like a square with the atrium cutting out the middle of the square.  the second floor is still in design process...with some nice banter between my wife and I.

 

I value any opinions for conventional or otherwise.  these forums have been quite useful.  I am meeting a builder tonight I met from these forums.

 

Re: Geo-Thermal

Posted by Paul Vetter at October 24. 2009

Previously Thomas wrote:


Hey Jason, Thanks for the input.  My wife and I (and 2 very young sons) do plan to be here for the long term.  We hope this is the last house we build...but stuff happens...though I don't expect it.  I have progressed a bit in my research but will continue to weigh the benefits of conventional vs geo-thermal systems.  I have gotten some arguments for geo-thermal that are pretty compelling.  I have to use a vertical system on my lot and I was given a ball-park estimate of 5-7K per ton of HVACsystem.  I had one builder tell me we would need 5-6 tons of HVAC system...while another said 3-4.  comes down to the energy efficiency.  with the government write-off, I think it might be 10K or so over conventional.


 


Our home will be a bit shy of 3500 sq ft.  The design is pretty simple.  2 story.  an atrium in the middle.  bottom floor esentially shaped like a square with the atrium cutting out the middle of the square.  the second floor is still in design process...with some nice banter between my wife and I.


 


I value any opinions for conventional or otherwise.  these forums have been quite useful.  I am meeting a builder tonight I met from these forums.


 Thomas,

If you're wanting to do an energy-efficient home; geo-thermal may be just one of the pieces.  As efficient as geo-thermal is: it really doesnt' do any good if a lot of other items are neglected.  I'd concentrate on energy conservation measures first.

Quick checklist:

1. proper orientation with minimum fenestration along the west side, and decent overhangs along the south

2. good envelope design...no need for 2x6 walls, but 2x4 conventional framing with open-cell spray foam insulation including (and most important) the underside of the roof deck

3. good windows...double pane, insulated with southern low e glass

4. pay attention to lighting (a huge heat load to combat with AC)...much use of fluorescent or CFLs

5...and then mechanical systems:  you'd be surprised if you do the other items a conventional system would work extremely well.  Geo-thermal would be even more efficient giving you a quicker pay-back...they are also quiet systems with no need for the compressor outside

6. other energy producing items:  PV and wind.  Now with PV, if you're in the Oncor service area, you can have a good rebate to do PV.  Typically it costs about $6-7 per Watt and the rebate is $2.46 per Watt.  You can also take advantage of the Federal tax credit (30%).

Hope this helps.

 


 

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