Texas Geothermal for Modest Sized House Questions

Greetings. I am planning on having a new house built later this year and am seriously interested in geothermal heating and cooling. I am almost completely ignorant of the costs associated with such a thing, but I know that I am on a budget so it may not even be monetarily feasible for me. Please forgive me if some of my terms are off. I guess a little information about the dwelling is in order:

I plan on having a MODEST sized home built. Two-storey with 835 square feet on the main floor, and 938 square feet on the second. The house is going to have a heavy steel frame for all load bearing and outer walls and light steel frame for inner walls. (I am dead set against having a wood framed house) The walls will be made of that 'softwall' fiberglass paneling. (I don't like drywall or sheetrock) I want to take advantage of whole-house radiant flooring so the entire home will be covered with ceramic tile (no wall to wall carpeting). This house is also going to have off-grid solar panels to power it. I would be using the heating portion for the radiant flooring only, as I do not want a large tank of water in my home (a water heater). I will be using an on-demand water heater. The house will have a basement...but its a single room-sized basement that does not encompass the entire perimeter of the house. (Basements are unusual in Texas, anyway)

I know my budget for solar is around 15K, but I have been reading some of these threads and these quotes scare me. .22 acres almost guarantees that I am going to need a vertical heat pipe. 14K for drilling alone is seriously making me sit back and wonder if this is even for me. I mean I WANT to be energy efficient, and I really like the idea of underfloor radiant heating, but if it costs that much just to get some holes drilled, I may as well have installed a standard HVAC system and just buy more solar panels to compensate.

I know that I probably am missing some information. Maybe because the house is so small that I do not need as deep of a hole drilled, so it won't cost as much, OR maybe I might be able to combine vertical and horizontal heat pipes to reduce the maximum length that would need to be drilled vertically.

Anyway, I was just wondering what size system would be recommended for a house of this size, and built with those types of materials.

I know that every driller is different, but I'm going to have a 200K budget, that has to cover everything and geothermal is going to be impossible if it is going to take a huge chunk of my budget. I saw some way out there quotes on some of these threads as high as 75K, but not lower than 45K. Even with the tax credit it would still be out of the question.

I am sure that some of you would just tell me to get some local quotes, but I don't want to waste my time if the average price is going to be beyond what I can afford.

Please Advise.

Thank you for your time reading this post. Excuse my ignorance and ranting.

P.S. If you absolutely must comment on my design decisions, go ahead, but I am telling you now that they are set so firm that not even a diamond would be able to scratch. ;-)

 

Where in Texas? I had a geothermal well driller in Oklahoma put in my wells (I'm in Arkansas). He charged me $7/ft to drill, install the loop pipe (I bought the pipe), and grout the wells. Generally, in Texas you would need ~300 ft of borehole per ton of HVAC to deal with the summer time cooling needs. If your home is well insulated (that will be a challenge with steel framing) and you don't have a lot of west facing glass, you could probably get by with ~2 tons of HVAC. Less well insulated or lots of west facing glass and you may need up to 3 tons HVAC.

Back to that steel framing. How do you intend to insulate the wall? It doesn't really matter what you put between the steel studs for insulation, because they have such high thermal conductivity that they effectively short circuit the cavity insulation. You will need a lot of rigid insulation (i.e. foam board) on the exterior of the steel structure to effectively insulate it.

 

Thank you for your reply. I will be building in Lago Vista, Texas.

Hmm. I do not know much about building methods, but i will tell you that I am going to be doing what is appropriate for my specific design decisions. 7USD/foot, you say? That is a lot better than the quotes I've seen in other threads, even if I am forced to get a 3-Ton HVAC. I am new to all of this, so I am not sure what these 'tons' mean. Maybe it is how much water is moved in x amount of time? Maybe it is the actual weight of the HVAC system itself? Maybe it is the amount of air that is moved around? I dunno. Well. My budget for such a geothermal installation would be around 15K. 15 for solar, 15 for Geothermal. I still have to have the 1000 gallon buried propane tank put in.

I guess the bottom line is this: Can such a system be put in with a tight 15K budget?

Sorry, I am a little scatterbrained at the moment. This will be my first home, and I don't have any resources such as friends or family members that all these websites recommend you ask to find a General Contractor who is not going to rip you off. I am going to be doing this all on my own. I am in the information gathering phase at the moment, to find out what I can afford and what I cannot.

I've also noticed that many posters are very concerned with X model made by X company, but as I have mentioned earlier, I am on a tight budget, so I don't care what it is or who makes it so long as it is the proper unit for my situation, is reasonably priced, and has a decent warranty.

 

I would be hard pressed to see a 3ton closed loop vertical system going in for 15K. Especially if ducting or radiant piping is part of that total. There are possibly a few compromises one could make to fit that budget, but then you have a geo system built on a bunch of compromises.

 

Oops, I am sorry that I wasn't more clear. No, the radiant flooring is separately budgeted with the ceramic tile installation. HVAC ducting goes in with the normal costs of building a house, so that is completely covered. My main concern is the cost of the drilling and the unit itself.

 

One refrigeration/HVAC ton is equal to 12,000 BTUs per hour. You need to know the heat loss/gain in BTU/hr of your home (typically calculated using ACCA Manual J) to determine the size heating/cooling unit you will need.

How do you intend to heat water for radiant heating in winter and then cool the air in the ducts in the summer? It can be done, but the system is more complicated and costly than a more typical fan forced air heating/cooling system. If you don't go with geothermal, how were you intending to heat the water for the radiant floors?

What is the proposed source of power for your on-demand water heater? Do you have natural gas available? Or were you intending to use electric to heat your water? If so, do you realize that in-line tank-less electric water heaters consume huge quantities of electricity? I doubt that that is something that could be powered by off-grid PV panels unless you had a huge array and significant battery storage capacity.

Do you really need radiant heated floors in Texas? I agree there are benefits, but those will likely be limited in your environment. Is it worth the additional cost?

 

Again, thanks for the reply.

The source of power for the on demand water heater will be from the solar and battery backup. I will have a propane tank, but that is to be used for ONLY the drop in cooktop, in-wall double oven and the clothes drier. There are efficient on demand heaters available that will suit my needs, since I will be the only person living in this home.

You are confusing me. I thought that this geothermal system can be used for both heating and cooling, and can be used with radiant flooring. Please correct me if I am wrong.

I really want radiant floors and for me, it is worth the extra expense. Texas gets colder than you think in the winter. And even if it didn't, that only means the geothermal system won't have to work as hard to heat the home

If I do not go with geothermal, then there is no reason for the radiant flooring and will probably use standard HVAC heating and cooling, all powered by off-grid solar.

Not sure if it makes any difference, but my home will have a wood burning fireplace in the living room.

I plan on having 30 panel, 325W pole-mounted solar array, equaling ~9425W total.

...I think I have answered all of your questions. If I missed anything please let me know

Edit:

After further consideration of the issues you have presented, I may consider using the geothermal to preheat the water to a hot water tank, so long as the tank itself is heavily insulated and efficient.

 

Hi:

I am sure I could think up a design to do what you want.

I do not think I can stay in budget. Even if you priced loops and manifolds for the radiant, the water will not just jump around the house.

Mark

 

Well, how far out of budget are we talking here? 5K 10K? 50K? And what exactly would you be pricing out? The Geothermal unit? The drilling? I don't know how much those units cost as it is generally VERY difficult to get prices on-line. With that being said, I am in the planning/budget/information gathering phase of my home building plans, so it is a good idea for me to know these things now.

Like I said, if I have to, I can just wash my hands of th geothermal setup and just put the budget toward a cheap standard HVAC setup, more (or higher wattage) solar panels.

I just do not have any experience with any of this. I just know what kind of house that I want. Off grid solar, modest square footage with a simple design (cheaper to build), steel frame, fiberglass panels in place of Sheetrock, ceramic tile flooring throughout the home, room-sized basement, fireplace, etc etc etc.

I am getting the impression that geothermal very expensive and just not possible for anyone on a budget.

 

I do not know until I know what you need to be comfortable, in BTUH heating and cooling.

Show me your tool box and work bench and we might bring it in at or under budget.

Mark

 

Hey, you lot are the professionals. That is exactly why I am here. I do know that too much A/C in the summer sets off my asthma, so I definitely don't need any cooling beyond ~21C. I plan on using my fireplace in the winter when it gets too cold, and I know that ~18C is my absolute limit in the winter. Getting close to 27C is far too hot for me.

What do you mean by 'show me your toolbox'? Are you talking about my do-it-yourself skills? I mean, I can put anything together so long as there are instructions, but I don't want to work on anything where liabilities are an issue. That's why subs are insured in case something goes wrong. If I do it and make a mistake, its all my fault.

 

Not sure how the calculations will go in Texas. But Geothermal was a incredibly shorter return of investment over adding more solar panels up here in Wisconsin.

I would imagine your more cooling dominated in Texas so this may not be the case for you.

When debating Geo vs solar, Return of investment is how I would be making my decision.

 

Oh I completely agree about the return of investment bit, but I am looking at this at a (starting) monetary angle. There won't be a return of investment if I can't afford the equipment and installation in the first place.

 

What I was getting at is your budgeting 15k for solar and 15k for geo.

Maybe if geo is a better R.O.I.
You could spend 20 -30k on geo. Or if solar is better spend the 30k on solar.

 

I see. But 30k is much too much for solar. Solar doesn't cost nearly as much to get a decent, adequate system set up, unless you had a large, multi person house or ridiculous energy demands. No, 15K will do just fine. But I am not as concerned with my ROI as I am of multi-utility independence. If water wasn't so cheap, I'd have half a mind to have a well dug so I wouldn't have a water bill, for example.

I'm just trying to find out how much a basic geothermal setup costs. Apparently I will need a 3-ton system and 3-300ft vertical holes dug, so that is a good place to start as any so I can start calling around and asking for flat rates. I just don't like wasting mine or anyone else's time. I don't want to have people coming to the site or me going to their office, have them draw up plans or whatever they do, only for me to find out that I can't afford it and me tell them that it's too expensive.

BUT, this might be doable if I can find a cheap driller, so that's the only good thing I am seeing out of this.

 

You are asking for a Mercedes for a Chevy price. Radiant is the best thing in HVAC, but if you are on a budget it usually is not for you. Geo is more an uphill battle in cooling dominated climate, when you ground is already warmer, decreasing the cooling efficiency, and the need for longer loops.

If you don't invest money in the floors to ensure very good heat transfer, and low supply temperatures, geo will be less efficient in heating as well. Plus hydronic cooling via chilled water air handlers is less efficient than forced air (water to air geo, so called packaged) units. By a factor of 50%.

In other words you are facing some uphill battles due to your ground, climate and desired installation. Now you are on an unrealistic budget. Don't do it!

Get a water-air unit which does heating and cooling at the same time, or get an high efficiency air source heat pump, which will fit your budget.

 

You are close to understanding what I was asking.

I'm more akin to someone appearing with a budget not knowing the cost of either a Chevy or a Mercedes. I have this idea in my head of what I WANT, not knowing that is necessarily appropriate for my particular situation. I already know that hydronic cooling is less efficient than forced air, which is why I only wanted radiant flooring for heating.

So to be clear, you are still saying that I might still be able to do geothermal if I nix the radiant flooring? I already had the radiant flooring budgeted with the ceramic tile installation though.

I am so confused. Maybe it would be better if I just called around so I can get some actual quotes.

 

"If you absolutely must comment on my design decisions, go ahead, but I am telling you now that they are set so firm that not even a diamond would be able to scratch. ;-)"

Sorry Sabotender, I must comment on off-grid solar.

From what I hear, Electricity in Texas is pretty cheap, Probably half what I pay up here in New England (17.6 cents per KWH)

You can purchase many years of electricity for $15000.

Depending on how well you can maintain your battery bank, they will have to be replaced every 4-6 years at thousands of dollars each time.

You will have to have a generator to charge the batteries when the sun can't, of course you will have a 1000 gal tank of propane to run the gene.

Off-grid is not just buy some panels & batteries and your done. Do some reading on Solar panel talk forum.

ChrisJ

 

The batteries I am getting have a 10 year warranty. They are extremely long-lasting. There is absolutely nothing that will turn my head away from solar, because I simply do not want an electric bill. I don't want to have to worry about paying Oncor for using their power lines. I don't want to have to worry about having to pay a flat surcharge if I do not use enough energy in the the billing cycle. I do not want to frown at the fee increase in kw/h when my contract expires. I have done lots of research, on solar. You can say what you like, but again, its not going to sway me from my off grid plans. The only reason I mentioned that I am going to be using solar in this forum in the first place was so people would know where my source of energy would be coming from.

You must not know how much sun Texas gets on average and how many cloudy days there are. Lots of sun, few clouds. You don't need a generator. How about you alter your energy usage and lifestyle to the amount of energy your panels are providing? How about you set an energy array that provides more energy you will use so that there is a buffer during these cloudy periods? You are aware that the panels will still generate power on cloudy days, right?

For you to say for me to purchase 15K of electricity from an energy provider instead of doing the wise thing and investing in solar sounds like you are in an energy provider's pocket. I don't mean to sound cross, but I am THAT firm when it comes to my off grid decision.

Thanks for reading and your response!

 

I wish you the best.

Sometimes GSHP's are not the best fit. Especially in Texas.

There is a air to water heat pump that could provide you hot and cold water, take a look at http://www.chiltrix.com/documents/

Good Luck Sir, ChrisJ