Can my 30 year old home use Geothermal?
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  1. #1
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    Can my 30 year old home use Geothermal?

    I have a 30 year house that currently has oil heat and no air conditioner. I'm considering going to a Geothermal HVAC system.

    My 2-story house is 1400 square feet, not including the basement. I live on 5 acres in Southeast Michigan. My water table is about 7 feet below the surface.

    My wife wants a pond in the low-lying area in my front yard, so I'm thinking I can combine her pond with a Geothermal system.

    Two rooms have ducts that run on the outside of the house. I've been told that Geothermal systems need special insulated ducts.

    My attic has 2 ft of blown insulation, but the walls feel cold in the winter. The walls are 4 inches thick with fiberglass insulation, but there is no Tyvak and no styrofoam insulation sheets below my aluminum siding. I think I'm getting air infiltration.

    Is it reasonable to explore a Geothermal HVAC system with a house such as mine? Or is Geothermal more for a new house that's designed for Geo?


    Any recommendations of a particular brand?

    Thanks in advance for any advice!

  2. #2
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    Quote Originally Posted by Nim Chimpsky View Post
    I have a 30 year house that currently has oil heat and no air conditioner. I'm considering going to a Geothermal HVAC system.

    My 2-story house is 1400 square feet, not including the basement. I live on 5 acres in Southeast Michigan. My water table is about 7 feet below the surface.

    My wife wants a pond in the low-lying area in my front yard, so I'm thinking I can combine her pond with a Geothermal system.

    Two rooms have ducts that run on the outside of the house. I've been told that Geothermal systems need special insulated ducts.

    My attic has 2 ft of blown insulation, but the walls feel cold in the winter. The walls are 4 inches thick with fiberglass insulation, but there is no Tyvak and no styrofoam insulation sheets below my aluminum siding. I think I'm getting air infiltration.

    Is it reasonable to explore a Geothermal HVAC system with a house such as mine? Or is Geothermal more for a new house that's designed for Geo?


    Any recommendations of a particular brand?

    Thanks in advance for any advice!
    I do a lot of geo installs, old and new homes. First, your pond will need to be sized for the load on the home, It may be bigger then you think. As with any install the tighter your home, the more cost effective it will be to heat and cool it. Properly installed geo systems are probably the most energy effecient systems out there. Find some contractors that specialize in geo and seek them out. Ask for refrences from previous projects so you can ask home owners about their experiance with the contractor. Check out www.igshpa.okstate this is a great website for info on loops and geothermal. It would not make sense to put in a high end system without addressing the whole building envelope. Look for a contractor that will do this and not just try to sell you a system. CHECK THEIR REFRENCES!
    Genius = The guy who can do anything...except make a living!

  3. #3
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    A geothermal's going to be expensive. The heating/cooling bills will be cheap, but the pay-back will take a long time.

    Another thing to consider is maintenance; depending on brand, they can need a fair amount. If you use a pond you'll need to use a closed loop system. There are formulas for how large a pond you'll need.

    You also need enough surface run-off to keep the pond full. As a general rule of thumb, you'll need 10 inches of rainfall per year with run-off from 10 acres to keep a 1 acre pond full. This doesn't take into account drought conditions. Don't count on your high water table keeping the pond full.

    Call a local geothermal contractor and ask them for a price.

  4. #4
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    I would agree with the pond comments. You need a fairly large pond to support your heating needs. Good news is that you have a high water table. You would most likely have the basis for a horizontal closed loop system. You certainly have enough land (1 or so acres) and the fact that the water table is high should greatly increase the capacity you can get from the ground.

    I have a 20 year old, well built house, with a horizontal loop that is about 500' long, covering about an acre in area (loop around the the perimeter of that area. Works well. A horizontal loop is one of the cheaper systems to put in, mostly digging costs for the trench.

    paul

  5. #5
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    Quote Originally Posted by tecman View Post
    I would agree with the pond comments. You need a fairly large pond to support your heating needs. Good news is that you have a high water table. You would most likely have the basis for a horizontal closed loop system. You certainly have enough land (1 or so acres) and the fact that the water table is high should greatly increase the capacity you can get from the ground.

    I have a 20 year old, well built house, with a horizontal loop that is about 500' long, covering about an acre in area (loop around the the perimeter of that area. Works well. A horizontal loop is one of the cheaper systems to put in, mostly digging costs for the trench.

    paul
    I have two ponds, a high water table, and an average rainfall of about 30 inches. One pond is about 1 acre and fills with surface water from about 5 acres. The other is about 2 acres in a stream, and receives water from thousands of acres. They have both gone down 3 to 4 ft. in droughts. Because the banks are sloped, they contain a lot less water during a drought. If the pond isnt on level ground, a natural liner like clay or something should be installed to stop animals from digging through the bank and draining it.

    Building a pond isnt as simple as some people might think. It can get pretty technical. All the information on ponds can be obtained from the US Dept. of Agriculture Soil Conservation Service.

    Im not saying a pond loop isnt a good idea, Im just saying that care must be taken when building one.

  6. #6
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    Quote Originally Posted by bobb25 View Post
    Because the banks are sloped, they contain a lot less water during a drought.
    The bigger problem with ponds is during heating season. Depth is a critical factor. In a cold winter, a small or shallow pond can freeze, and with the heat being extracted from the geo system you can freeze it solid. Once you freeze the water surrounding the geo pipes, your advantage of geo is mostly gone.

    paul

  7. #7
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    Geodude, thanks for the link for Geothermal installers. I've contacted a few in my area and they are going to come to my house to talk about their systems.

    As you know, one system uses copper pipe with the refrigerant with only one heat exchange (which is good). Another one uses PVC with water/anti freeze with two heat exchanges (not as good). Without knowing anything else, I'm thinking that the copper pipe system may eventually leak refrigerant. So, I'm leaning toward the PVC pipe system.
    Last edited by Nim Chimpsky; 02-11-2008 at 04:26 PM.

  8. #8
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    PE pipe, not PVC!

  9. #9
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    I must have misunderstood him on the phone. I thought he said PVC. What's "PE""?

  10. #10
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    Quote Originally Posted by Nim Chimpsky View Post
    Geodude, thanks for the link for Geothermal installers. I've contacted a few in my area and they are going to come to my house to talk about their systems.

    As you know, one system uses copper pipe with the refrigerant with only one heat exchange (which is good). Another one uses PVC with water/anti freeze with two heat exchanges (not as good). Without knowing anything else, I'm thinking that the copper pipe system may eventually leak refrigerant. So, I'm leaning toward the PVC pipe system.
    The pipe you are referring to is polyethelyne not pvc, HUGE difference. The direct exchange copper tubing installs around here have a very high failure rate. I will only install PE pipe. Do you really want that much refgrigerant in the ground? I looked into this system, but was kind of reluctant to get into DX systems. When was the last time you saw a bunch of copper tubing buried in the ground, welded together that never leaked. Around here, they haven't worked well. So I did not get into that system. In your area maybe they are having better luck. It is a lot newer concept then poly pipe. Good luck!
    Genius = The guy who can do anything...except make a living!

  11. #11
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    Quote Originally Posted by geodude View Post
    The pipe you are referring to is polyethelyne not pvc, HUGE difference. The direct exchange copper tubing installs around here have a very high failure rate. I will only install PE pipe. Do you really want that much refgrigerant in the ground? I looked into this system, but was kind of reluctant to get into DX systems. When was the last time you saw a bunch of copper tubing buried in the ground, welded together that never leaked. Around here, they haven't worked well. So I did not get into that system. In your area maybe they are having better luck. It is a lot newer concept then poly pipe. Good luck!
    There is nothing wrong with DX systems when they are PROPERLY installed. Who cares how much refrigerant you have in the ground when you have a closed loop system that is properly installed and doesnt leak?

    The 1400sq ft house about which this thread is about may well be an excellent candidate for a DX installation. Consider this, boreholes half the diameter of that of a liquid system, 40% less drilling, no secondary heat exchanger, no circulating fluid with antifreeze and no flow center circulating pump to purchase, install, power or otherwise worry about.

    Any variety of GSHP system could be a good choice providing its properly designed and installed!

    SR

  12. #12
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    Quote Originally Posted by Nim Chimpsky View Post
    Geodude, thanks for the link for Geothermal installers. I've contacted a few in my area and they are going to come to my house to talk about their systems.

    As you know, one system uses copper pipe with the refrigerant with only one heat exchange (which is good). Another one uses PVC with water/anti freeze with two heat exchanges (not as good). Without knowing anything else, I'm thinking that the copper pipe system may eventually leak refrigerant. So, I'm leaning toward the PVC pipe system.
    Do NOT use the geothermal system with copper / refrigerant in the ground. A large company around me put a lot of these in and lost a ton of money. They had to constantly dig up and repair the copper. A few times they would dig up the customer's entire lawn and replace the copper. They eventually ended up installing air source heat pumps for the customer at "no charge" LOL.

  13. #13
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    Quote Originally Posted by bobb25 View Post
    Another thing to consider is maintenance; depending on brand, they can need a fair amount.
    I'm not sure what you mean here - what difference does the brand make to the required maintenance? For a closed loop system, the maintenance is minimal - nothing much more than changing the air filters at the appropriate interval. What else is there?

    As for putting geothermal into an old house, we put it in a 110 year old house. Payback was immediate - our energy bills went down from somewhere north of $4000 a year to $1500. Since the old oil furnace and tank (and brick chimney) were at the end of their lives, we had to replace everything anyway, plus there had been no central air. The differential cost was really just the drilling - the equipment cost isn't much different from a furnace+A/C anyway. We were cash flow positive (if you count the extra that the drilling cost) immediately - plus there were some government grants (this is Canada) that pretty much covered the cost of the drilling. Since we installed (in 2005) the grant programs are even more generous now.

    All that said, the first thing to do before everything else is to fix any problems in your house such as air leakage. This will have the biggest bang for the buck no matter what heating system you use. But with the price of fossil fuels continuing to increase (and no sign of them ever really coming down again) I would think you'd be hard pressed to find a more cost effective system for a climate that has a heavy heating need plus is hot enough in the summer to need A/C.

    Paul in Montreal.

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