We have an older home (built 1939) in Iowa that we purchased a year and a half ago.  The house is poorly insulated and are looking for potential options for heating systems.  Our current heating system is a high efficiency gas as well as gas water heater.   Our house is 3500 sq. feet plus an additional ~ 1000 sq. feet partially finished basement.  We have had our attic insulation upgraded to the 12" depth and received quotes for the wall insulation.  The quotes for our walls  (no insulation currently) were in the $12000 range without repairing the interior walls -- which would likely add an additional $1000 - 2000.   Our highest gas bills were both in Jan. of '07 and '08 at 394 therms (~$415) plus we are spending $200 in electric these months for extra space heating.  Our other highest months have been 260 or less therms.  Our maximum electric bills in the summer are in the $250 range.

Outdoor temperatures range from -15 below on a few days/year to over 100 a few days/year. 

If anyone has any information on whether geothermal heating would make sense in our particular situation, we'd greatly appreciate it.  Thank you!

John

A geothermal system will save you at least 50% - 70% on your heating costs. 30%- 40% on your cooling cost. The better insulated you house, the smaller system you will need. I think that geothermal makes sense in most situations. However site conditions play a factor.

John,

At a trade show I saw a low-expansion foam with a reasonable R-value that can be used on existing walls without blowing them apart.  I do not remember the brand name but maybe someone here or googling the internet can locate the product.  I watched the demo at the home show.  The damage to the interior walls consisted of  one to two small round holes in the sheet rock (drywall) between each set of studs that were easily repaired. 

Thanks for the tip Alton -- I will definitely google that to find some information out. We've looked at two other options for wall insulation that were still fairly destructive, so this sounds like a good option. Also, I talked with one of our local companies that does geothermal installations -- about $4000/ton installed and he estimated a 4 to 5 ton system (over the phone -- but will be coming to evaluation the house).....so a reasonable price I think.

Be very careful,  I have a new 3400 sqft house with  a 4.5 ton heat pump.  The last thing you want is to be undersized.  There have been lots of sad people posting on these forums about how cold their house is after they just paid $10000's to have a geothermal system installed.

It is  sad but true,  some contractors will sell an undersized system because they think that the owner will not pay for a right sized system.   I would almost hire one guy to do the heat loss calcs and then get heat pump system pricing from a different company.  Then make sure the heat pump is big enough to satisfy the heat loss.  Remember that you don't get 4 tons of heat out of a four ton heat pump.

funny I ran into u---I also live in DesMoines Iowa--1898 home NO Insulation I priced Tigerfoam and it will run me about 6 to 7000 to do myself. Its cavity fill spray foam. I also priced GeoThermal but it cost $20000 ( but I will also get A/c with that) curently running 3 Window airs. Last month heat bill was $289 I am tring to figure out if 20000 is to high --everything i read says 2500 per ton unit -- 2 people i talked with said i needed about a 3 ton unit --as u can see that math doesnt add up

I brought a house in 1999 that was built in 1950 had no insulation in the exterior walls, I mean absolutely zero. I hired a company to inject foam insulation into the walls for 3k. The house had absestos shingles on the outside, I drilled enough of the nails holding the shingles to pull them out, two rows, top and bottom completely around the whole house. The contractor then drilled into the walls from the outside and injected the foam insulation in that way. After they were finished, I reused the old shingles where I could, brought replacement shingles from Home Depot (not absestos) for the ones that broke. I was even able to bring a sample of the paint color to the paint store and they matched the color exactly. I repainted the two rows of shingles all around the house and it looked fine without having to repaint the whole house. I did all the work of removing the shingles before the insulation contractor arrived, and put everything back when he was finished. In the end it cost me less than $3,500 to do my 850 sq ft house. The foam was called Icynene I beleive.

From what your saying, you talking about letting the contractor drill the holes from the inside of the house and repair the sheet rock what he's finished. That of course not only involves repairing the walls, but repainting all of them as well. One of the main reason's I opted to go from the outside in was doing it from the inside would have damaged the titled bathroom and tiled kitchen walls redoing the kitchen and bathrooms would have been way too expensive. If you have any questions about putting foam in your walls, Ask me, I did it before. What are you exterior walls made of?

Years later I completely gutted and remodeled the bathroom for $5,500 by doing most of the work myself. When I removed the walls every bay was filled to the top with foam except one that was half way filled up. 

As far as installing a geothermal system goes, I think your wasting your time until you get the insulation problem addressed first. If you can insulate it well enough and replace some of the old drafty windows with some newer high R value stuff, you'll save money on a geothermal by being able to get away with a smaller system.   

Well said

John,

Look at this web site for low-expansion foam:

http://www.fomofoam.com/existing_homes.htm

Thanks for the info! I checked out Fomofoam and Tigerfoam (which I understand is the same product) and did the calculations and would be at minimum $9000 for the amount needed (for supplies alone). Our energy audit and previous insulation quote have approx. 2600 square foot of coverage required. Also, our windows are relatively new -- all put in within the last 5 to 7 years.

If we went with a larger geothermal tonnage -- any idea of what difference that would be in terms of electrical use/efficiency? Can an additional loop be installed but not used initially-- in case of renovating an above garage space for living space? Sorry for all the questions but this has been a great help! In addition, our current gas furnace is nearing 20 years old but has a 90% efficiency rating -- so I fiigure better to make an informative decision now versus waiting for the furnace to crash and burn so to speak. Thanks again for the info! John

John,

If you purchase a larger HVAC system without insulating the walls, then I am concerned that your comfort level will not be as high as it could be.  A larger unit will heat and cool your home, but the temperature in the home will start to vary as soon as the unit shuts off.  With the proper amount of insulation, the temperature inside the home will change very slowly thus giving your body time to adjust.  As people get older, the body seems to resent quick temperature changes.

Another way to look at this is that you will pay for the insulation only once, but without the extra insulation you will pay forever for the extra energy to run a larger HVAC.  In summary, if you plan to live for a long time in this house, then be as comfortable as you can be and still save on energy.

Using my Heat Loss Software, I went back to an 1800 sqft house and took all of the insulation out of the walls. The heat loss through the walls increased from 10,404 btuh to 28,031 btuh. An increase of 14,000 btuh. This on a house that is 1/2 the size of yours. So if we assume that your heat loss through uninsulated walls would be 28,0000 btuh, then you are looking at an additional 3 tons of heat pump capacity.

By the time you drill for the additional loops and buy the equipment, your costs could be equal to or more than $9,000.

You can certainly oversize your loop now in anticipation of adding more heat pump later.

Hope this helps.

I have plugged some preliminary numbers into a heat loss calculator and the BTU/hr drops significantly with adding wall insulation up to R11 value (up to 50,000 BTU/hr savings based on this calculation). With our walls being plaster, the only feasible option seems to be in the blow in foam such as listed above. After doing some research online, a few concerns I've noticed -- one being asbestos in plaster walls built in the era of our house. Since many holes would need to be drilled through the walls for this foam type insulation -- 1" was the smallest hole size I saw -- this seems to be a legitimate concern from different sites I looked at. Another concerns was older electrical wiring if any cracks exist in the fabric of the older wiring. We have about half the house with newer electrical lines versus the old wiring. I'm assuming once the foam has been sprayed in, there is little to no chance of being able to replace previous wiring through the foam. Anyone heard of this as being an issue?? Just another few things to add to this complicated equation!

If we do still install geothermal........Our current furnace is a 132000 BTU/hr furnace which has been adeqaute for heating and there is a 5.5 ton AC unit which is more than adequate for cooling. When trying to determine the size of a geothermal unit, for the coldest average day temp for winter, do you usually want the pump to reach that BTU/hr heat loss or do you also want to include the secondary heating from the unit as well to reach that number? When I plugged in some numbers on the heat loss calculators, there is a big difference for outdoo temps from -10 to -5 to 0 on BTU/hr heat loss. Just curious since i'm reading that you do not want to oversize your system -- especially here in Iowa with the high humidity in the summers. Thanks again for the help!

A lot of this depends on the difference between the heating and cooling loads.  If the heating load is large compared to the cooling load,  most designers size the heat pump to take care of approx 90% of the heating load and let the backup heat make up the difference.  This saves some of the initial cost by  reducing the size of the equipment and  ground loop, the ground loop  being the most expensive part of any system.

Since the advent of two stage heat pumps, being oversized on heating is not as much of a problem.  When in cooling, the heat pump operates on the first stage most of the time which allows for the longer run times needed for dehumidification.

I can't speak to the insulation / asbestos questions as I have no expertise in that area.

Having done this before I can tell you it is. The Form will expand into the smallest openings filling all available space. I had many outlet boxes that filled with foam to the point of foam coming out of the electrical plugs. These all had to be replaced and the foam in the box removed before replacing the plug. The foam is fairly easy to remove from the outlets, you just have to be careful not to damage the wires in the box. When I did my insualtion project I had the forethought of installing a PVC pipe from the basement to the attic along the chimmey, this way is I wanted to add additional wiring in the future, I would have a path for the wire. It came in handy a few years later when I had to replace the temperostat line because the old wire didnt have enough conductors in it to do both heating and cooling for the central air I was adding. The outlets are easy enough to replace, if possible, try and add some PVC pipe to get from the basement to the attic to future use, remember to put a pull string in the pipe to make fishing future wiring easier. Any electrical changes you want to make should really happen before installing the foam insulation. I wouldn't be concerned about the foam getting into the wiring, it's not conductive, I shouldnt hurt the existing wiring at all.    

As far as asbestos is concerned, wear a mask when drilling those holes and vacuum up and dust caused by the drilling right away. Asbestos is only danergous what it get into the air, perhaps a good vac / filiter vacuuming while drilling will minimize any dust particials getting into the air. I can't say I'm a asbestos expert either, but I wouldnt get any asbestos cleanup companies involved, that will greatly compound your costs.