GeoThermal in a TF

[EastMark]

I have done a little reading on the EnergyStar stuff and contacted a certifier here in Maine hoping to learn more.
It refers to all parts of the house,insulation,windows,heating systems,etc...    I will obviously insulate to or above their ratings and am interested in finding info on GeoThermal Heating for my radiant slab. I have looked over some great google results...lots of info out there these days. Im not really interested in the cooling/AC/ductwork values of it although it seems to be significant. The whole concept seems to make so much sense for a SIPS or highly insulated TF.
Question is...Anyone used or researched GeoThermal themselves? In this cold climate it may be a good option and was looking for input.
Mark

[Radar67]

I have done a little research. I found some good info at www.waterfurnace.com

[EastMark]

Good site. Thanks ! Did you do it ? Know anyone who has done the closed water system ?
This stuff looks great but I wonder the drawbacks if any. (other than install cost!) With the effeciency
of a SIPS TF I think it would be great.
Mark

[Radar67]

I have not done it...yet. I am in the process of building a house and plan to use it.

Don't know anyone who used the closed water, but do know a guy who used an open pipe air system. Basically, he buried several hundred feet of 3 inch pipe eight feet deep. Had the intake and exhaust inside the house to create a cross flow of air. The system kept his house about 65-70 degrees year round. Used a small fan, powered by solar, to exchange the air in the house through the pipe.

[Thehardway]

Mark,

I am doing a lot of research on it right now.  I am in touch with WaterFurnace regarding their EW series geo-pump.  In my case it will heat, cool and supply domestic hot water.  I have about 200' of 1-1/4" pipe buried in 2' of #67 gravel going under my 4" radiant slab which will be isolated and insulated.  This will be part of my ground loop.  I am going to see what I can do strictly with ground loop and solar collector on a thermosiphon circulation.  If that doesn't work I will use a circulating pump and if that fails I will go to the EW water to water heat pump.  I am going to be super insulated as well.  I have some passive solar glazing on the south wall.  This will heat in the winter and help prevent condensation on the slab in the summer while in cooling mode.  Will try to post some pics of the gravel bed/pipe as it goes in.

[moonhill]

What is the R-value of super insulated?  50....60....  Check out Hallowell International. They are a Maine based company.  Sorry I don't know how to make the blue lettered link thingy work.   Tim B.

[Thehardway]

I don't know that there is a true standard for the term "Super-insulated" but I could be wrong.  I would say it is more about building design and envelope performance.  I wish we could throw the term R-value out these days as it has so little meaning when it comes to real world performance for energy efficiency.  There are too many other factors that come into play.  Solar gain, thermal mass, air permeabilty, reflectivity, radiated heat, thermal bridging, humidity, condensation and evaporation all need to be factors in energy efficient structures.  A stick and batt home may have a calculated R-value of 19 but in 3-5 years time it may perform as a R-9 home.  A Log home may have a calculated R-value of 9 but is actually "super insulated" due to thermal mass and outperforms an R-19 stick and batt day 1.  SIP and ICF homes far outperform stick and batt so much so that standard blower door tests cannot even be performed on many of them.  R-value really becomes meaningless in te whole performance scheme.

[moonhill]

That is pretty much my thoughts as well.  Tim B.

[Raphael]

  My engineer is using geo to heat his timberframe, he came up with an ingenious second floor design that gives him access to the space between the first and second floors.  He's heating air but it'd work equally well (or better IHMO) with radiant tubing.  Basically any "low temp" tubing layout that will heat your home adequately will work regardless of how the water in the tubes get's heated.

  Hydronic cooling can be a challenge but may not be required in a well insulated home (especially in Maine).  My approach to cooling is a single window/wall mounted AC unit in the office (where the computers generate heat) and a whole house fan to blow out the hot air during the night.

[EastMark]

Seems a big part of the payback/savings annually comes from the A/C part of this system. Im not concerned with A/C so I am starting to think it may not be applicable cost wise for me. I'll keep you posted as I look further into it.
Thanks for all the feedback on this! Great stuff.
Mark

[Thehardway]

Mark,

The biggest savings in geothermal comes from the fact that your base temp from which you gain heat or cooling is the ground temp constant.  It is always the same regardless of which mode you are in.  In Maine you would most likely need to use a well for your loop or have a fairly deep ground loop but your base temp to heat from would be in the 48-58 degree F range which beats -0 to 85 degrees you would have with any type of air based heating system.  Because the temp rang is much smaller it can operate much more efficiently year round, both in both heating and cooling modes.  Think of it as the difference between trying to boil a pan of ice water vs. trying to boil a pan of hot water from your tap. The energy required to acheive the desired temp is much less.  Add to this that water is the most efficient medium for heat transfer and you have a very efficient system.  Have you ever noticed how spring water seems warm to drink in the winter and cold in the summer although its temp is pretty much the same year round?  Don;t forget the saving that can be acheived  using it for domestic hot water as well as your radiant heat.

Bob

[scsmith42]

We have a Geothermal Expert here on the Forum... send a PM to Bruce (Submarinesailor).  He is highly educated in the technology and has overseen the installation of multi-million dollar systems.

Scott

[submarinesailor]

Scott,

Thanks for the complement, but as I'm very fond of saying; I know enough to be dangerous. : : : Most of the comments that have been made in this thread have been right on.  But, I would like to caution those who are thinking about doing this themselves.  There has been several installation problems (errors) that come back and bite you in the a$$. 

One of the early problems with the vertical well type of installations was the lower elbows.  Owners and/or their installation companies were using lower grade (JUNK) elbows and they were blowing out.  Which in turn, was getting the owner in trouble with the local or state EPA because of the leakage of the glycol/treated water into the ground water.  SO, I STRONGLY RECOMMEND that if you are planning on a vertical well installation, use the correct piping and elbows that are designed for this type of installation.

The other problem area has to do with the compaction of the sand and/or soil around the horizontal ground loop(s).  If you do not compact the sand/soil to the correct value (don't ask me what value is, I don't remember it), you can get a build up of condensation on the outside of your loop as you inject or extract heat in and out of the ground.  This condensation can cause an air gap to build around the outside of the piping, thus affecting the efficiency of the system.  You must have good contact between the loops and the ground for these systems to work right.  One job I worked on the vertical well keep closing as soon as they driller pulled the bit.  Soon they had to fill the hole with bentinite(sp)  as they pulled the bit.  The design engineer worried about it drying, separating from the piping and causing problems.  Well, this type did not set up, so it worked great on this site.

Check out these two sites for some more good info.

Bruce

http://www.geoexchange.org/
http://www.geothermal-heat-pump-resource.org/

[Larry]

You might check with your electric company.  When I built our house in north Missouri the power co. did a lot of work for me to determine the best HVAC along with a cost analysis and payback schedule.  At the time geothermal was too new and expensive...we went with a dual fuel system.  A few years later when the technology was a little more mature and cheaper, B-I-L went geothermal using a trench.  He got an installation grant along with a reduced electric rate.  That power company, Platte Clay Electric still overs financial incentives along with demo projects for education.  They even had some hydrogen gen-sets for awhile...that project failed.  I noticed they are supporting WaterFurnace as a supplier now.

Unfortunately our power company here in Arkansas does nothing other than blow hot air.  Trying to get info on a water to air system now, along with a permit to get water out of a Corp lake.