I'm trying to decide whether to invest in geothermal or not, and the issue I think is comfort not price. I have done research, got 3 bids on closed loop (all similar priced, but won't quote numbers on this website). The proposed specs varied between bidders - 2.5 ton versus 3 ton versus 4 ton. The 4 ton proposal included a summary of Manual J with Elite software. But out of the 3 bids I received for geothermal, the contractor whom I believe has the most experience with retrofits said that I *might not* be as comfortable with geothermal heating, compared to how I have not had any problems with comfort in the past using my oil forced air furnace (that furnace was replaced in 2003). He said that he cannot guarantee the comfort level, and so must caveat his bid that I might need modifications - either ductwork or insulation. He is being honest and says he does not want to lead a customer to spend money if he doesn't think it is the best idea. Meanwhile, I tend to trust his judgement as he has done quite a few retrofits of homes that are better insulated and have better return air ducts, compared to my home. To be sure, I am going to call 3 references once he gives me the phone numbers of previous customers who have had his company do a geothermal retrofit.
I live in S.E. PA near a small town where the heating degree days annually are roughly 5000 to 5600. Based on his measurements, he said my ductwork sizing is good for airflow for a 2.5 ton geothermal heating, and up to 3 tons max would be just fine. The house never had central air and A/C is not the issue here for me, just heating is where I am concerned about saving the cost of oil over the long haul. (I have run calculations on this and no matter if oil prices escalate relative to electric slowly or rapidly, I will still save money eventually if I own the house 10 or more years, even including a 10 year home equity loan into the return on investment calculation).
Given that the issue he said is comfort, I am reluctant to spend the large total investment cost if the net outcome might make the house very uncomfortable and then I end up spending 5 or 10 grand more on insulation or windows or both. Or worse yet, realizing I need more ductwork and in order to effectively utilize the increased airflow I would have to upsize the geothermal model to one with more tonnage.
Last year I used 666 gallons of oil for a home living area of 1890 square foot (main floor plus upper floor two bedrooms) cape cod-style house. The basement is only used occasionally for exercise but is where the furnace is located. I really don't care if the heating of the basement is good enough since it isn't a daily living space. There is NO separate ductwork for heating the basement, just a small vent off the main trunk in the furnace room. I say this because including the basement in the Manual J would add 1200 sq ft to the area of the house.
In the winter, my oil furnace which is probably 82% efficient and 105,000 BTUH, runs at most only 5 minutes, then shuts off for a while. My main floor thermostat is usually set at 69 deg overnight and 70-71 daytime. In the winter there are not any cool spots in the room near the walls, even though when I remodeled main floor bathroom I found NO insulation in the main floor walls. About 6 years ago I added heavy thermal drapes to all the main floor windows, which really made a difference in comfort because they are kept closed or partway open in the middle of winter. The second floor has a cape cod style sloped ceiling that has limited insulation, but with an oil-fired furnace the two ducts, one leading to each 13 x 13 size (plus alcoves) bedroom, was more than adequate for comfort. One bedroom is vertically above the basement furnace on the second floor, while other bedroom involves a 32 foot horizontal run of ductwork in the basement, then running upwards to the second floor.
One contractor ran a Manual J based on including the basement, and the summary is as follows:
"Total building supply CFM = 1837"
"Sq Ft of Room area (including basement) = 3164"
"CFM per sq ft = 0.581"
"Sq Ft per ton = 723"
"Total heating required with outside air = 77200 BTUH"
"Total sensible gain = 40400 BTUH"
"Main trunk size 12x28"
"Room load summary:"
"1st floor -- 875 sqft -- 36300 sens BTUH -- 342 htg nom CFM -- 4-8 run duct size -- 542 run duct vel -- 757 Air sys CFM"
"1st floor addition -- 384 sqft -- 22500 sens BTUH -- 292 htg nom CFM -- 3-8 run duct size -- 480 run duct vel -- 503 Air sys CFM"
"2nd floor -- 630 sqft -- 21300 sens BTUH -- 276 htg nom CFM -- 3-8 run duct size -- 522 run duct vel -- 546 Air sys CFM"
"Basement -- 1270 sqft -- 7200 sens BTUH -- 93 htg nom CFM -- 1-4 run duct size -- 359 run duct vel -- 31 Air sys CFM"
So I would think that these Manual J results should have allowed the second contractor to judge if my ductwork is undersized or if I needed more insulation, yet he did not suggest either, and meanwhile proposed a 4 ton system.
The first contractor, who proposed a 3 ton system, said that I might need either larger ductwork or better insulation to be comfortable.
Who is correct?
Does anyone have experience with an older home (1950s to 1960s) that does not have ductwork or insulation equivalent to a new home, but was able to have adequate geothermal performance in the midatlantic area during the winter?