Since you are exploring all options, your basement is unfinished and you are energy and environmentally conscious, may I suggest that you consider a combinational approach that would include one geothermal heat pump unit that would provide force air heating and cooling, radiant in-floor heating (for your 1st floor since the basement is unfinished) and domestic hot water. Another option would be a regular geothermal HP without the radiant in-floor heating option.

One of these options would provide the highest installation costs, however, this would be offset by the lowest operating and maintenance costs, highest comfort levels, greatest satisfaction and life-cycle level & lowest GHG emissions (according to the EPA) and greatest increase to the resale value of your home. You may also benefit by the largest rebate incentive programs for the reduction GHG emissions (not to mention eye and noise pollution). You may also be eligible for a lower interest rate, should the money have to be borrowed, for having done the project GreenÂ; just food for thought.

SR

Fsq4cw, thanks for the info. I have not looked into geothermal at all, so I have no idea about it. I will do some research. But can you please tell me about how much this sort of thing would cost in relation to installing a traditional forced air system? In both cases, we'd be starting from scratch and would have to deal with our "old house" issues.

Well, after doing some research on this forum, I'm thinking a geothermal retrofit might be way outside of our budget, though most of the posts I read had more to do with new construction rather than a retrofit. We've saved for this cooling project and aren't willing to take on debt for it. But I have some calls into a few places to explore the option, just in case.

Does anyone have any thoughts on my questions in my original post?

It would be difficult to give any kind of estimate. I will say that a retrofit geothermal project is just as doable as what you are already planning, especially since you are planning to convert to forced air. The biggest increase in price would likely be the cost of drilling, which seems to vary regionally.

I would suggest examining the cost differential between the project you are planning and what it would cost to do it with geothermal and balance it against the likely operational savings in heating, cooling, hot water, maintenance costs and financial incentives. Crunch the numbers for a 10-year period even at todays energy price. In our case the payback has been years shorter than we ever imagined do to the rebates and the large increases in energy costs since we installed our retrofit. Its also interesting to keep in mind that unlike virtually all other systems, geothermal requires no annual or semi-annual maintenance beyond the regular changing of an air filter that you can do yourself. Its like having another fridge; how often does that need to be serviced?

SR

Check out this thread in the "Old House" forum here - it's specifically about installing geothermal in old houses. I have a posting in there which shows the drilling of the borehole for the retrofit we did. Our house sounds similar to yours except we don't have an attic. The cost was not prohibitive, even allowing for the drilling. Our annual energy bill is now only 1/3 of what it was previously and we're extremely happy with the comfort the system provides. SR is correct about the maintenance aspect - just a $50 a year media filter change.

Paul in Montreal.

Thanks for the encouragement about geothermal. I am making several appointments for comparative estimates. I've already been warned by one to brace myself for the cost to be in the "prohibitive" range, but I am hoping that he is just projecting the worst case scenario before actually seeing our house.

Keep your fingers crossed for good luck for us! And stay tuned, I might end up having more questions for you.

Well I'm back, after having consulted with 2 geothermal installers. One is doing a complete load calculation and evaluation for geothermal versus an air-source heat pump, for us to compare against the quotes we have for just doing a/c. The other guy won't do a full analysis, including potential cost savings based on our individual usage patterns, without us paying a large fee for that service (US$700), but he was definitely there to try and sell it.

Both gave a ballpark of the cost being about 3x (at least) of our a/c-only quotes, and both said that we'd have to have a split system (two systems?)--one in the basement going up to the first floor, and the split being in the attic coming down to the second floor. And because of that, the cost goes up. The first says we have enough room to trench, while the other says he prefers drilling vertically, saving horizontal loops for unlandscaped/non-lawn areas (like for brand-new construction). Both did say that our access in our unfinished basement and attic are generally good.

We have one more home visit by another geo person, but I can already tell that my husband thinks it's way out of reach, though he loves the idea of geothermal. He's now back to thinking that we should just buy window a/c units, as the easiest and cheapest option (he also thinks it would be more energy-efficient if we only get 2 for the hottest 2 rooms).

I guess I won't discount geo until I see a hard number from the first guy and compare it to the air-source heat pump option (which I had not considered, either). But there's the update, anyway.

I'm very envious, Pyropaul, that your cost did not end up being prohibitive for your old house retrofit! Do you have a split system, too?

We have a single system. Our old house doesn't really have an attic as such so we had to be creative in thinking how to run the ductwork on the second floor.

As luck would have it, the old oil furnace in the basement was towards the centre of the house. As the chimney was in bad state after an inept contractor ruined it by pointing with portland cement mortar rather than lime based, it needed demolishing. So we demo-ed all the way through the house to the basement. The space created was just the right size to run supply and return trunks from the basement to the second floor. We ran the ducts along the original ceiling (which at 9', was kind of high for bedrooms) and so we just installed a new ceiling about 8" below the original one in the rooms where the ducts were run. As there were no supporting walls at all in the basement, running the main ducts down there was no trouble either as we only ever intend to use it as storage space since there's only 74" of headroom.

So, to cut a long story short, we only have a single system. It's cheap enough to run that there's no need to have any zoning - the house is a uniform 69F in winter throughout.

Paul in Montreal.

I'm assuming you talked with the contractors about how you would get the ducts to the first floor. Maybe using closets? Are you ok with those solutions?
You could put a unit in just for the 2nd floor. You would have a couple of issues you would have to consider. You most likely would be happy May, June, & Sept. In July & Aug it simply would be too hot for an upstairs unit to cool the house satisfactorily. In July & Aug you would also have to hang a curtain or something in your stairway to keep the hot air from the first floor rising up and overwhelming the second floor unit. You also have to make sure it is feasible to put a unit in the basement to feed the 1st floor thru floor registers. That way you can put the 1st floor unit in the future or the next homeowner could.
I'm also in SE Pa.

-Funnycide: yes, we'd use closets to get the ducts down from the attic to the ground floor. Our closets are deeper than one would expect in an old house, so we'd be fine with it. Thanks for your thoughts on doing the 2nd floor only. I think we've talked ourselves out of it for exactly the reasons you mention. Yes, a unit can go in the basement to feed the ground floor via floor registers, which is what the geothermal people have been proposing. They want to do two systems; one in the attic and one in the basement. They say the ductwork would be relatively easy in our situation, but the cost of two systems (split) is something we're balking at. Then again, we'd like to get it right the first time.

-Pyropaul: that's great that you can get away with one system! I think the ductwork would be challenging for us to get to the 2nd floor the way you describe. Every geothermal installer has assessed our access from above and below as being good, and none of them has proposed anything other than doing the two/split systems. Thanks for your thoughts.

The alternative to doing two complete systems would be to do a single water-to-water system in the basement. Then you'd need two fan-coil units, one in the basement for the ground floor and one in the attic for the upstairs. You'd then just run the water lines from the water-to-water unit in the basement to fan-coil unit in the attic. A two-stage water-to-water unit would provide the equivalent of two separate systems - you'd be in "low stage" if, say, just the upstairs was calling for cooling. If both fan-coils were running, you'd run in "high stage".

This would also be the way to go if you wanted underfloor heating as well as air conditioning.

Just a thought,

Paul.

Paul, that might be what they've been trying to explain to me. The "main" unit would be in the basement, but there'd be something running off of it in the attic. I have a lot to learn in terms of terminology.

I am heartened that you are satisfied with the comfort in wintertime. We are often cold in the winter with our natural gas radiators (converted from oil), because we keep the temp setting down, for reasons of economy. You wrote that your home is a uniform 69F in winter, and that would be a huge improvement for us (we keep it set at between 62-64, and I'd be happy to have it even at 66!).

Blueiris, I pulled up one of your old threads on the Porches/Deck forum. We have a similar problem with spilled Anchorseal. Figured you weren't posting over there anymore, so I hope you don't mind that I tracked you down over here.

To natal: you found me! I posted a reply for you on the Porches and Decks forum.