well, the continued availability of the geo credit makes it worth to atleast consider.

I agree, you don't need propane. Propane is expensive. Only downside to airsource is that it goes to into defrost when snowy and icy or cold and rainy.

If you do decide geo - make sure the ground loops are sized right cause I hear people who have not such amazing success and I assume its from loops not sized good or they are unable to pull the nice heat from the ground.

I would rather stage slightly bigger and have a 2 stage unit as a side note.

$12k seems like a lot. As a point of comparison, NG and a/c 2 units for 7.5 tons in new construction was budgeted at $13k. Not what I did and your equipment will obviously be better but $12k seems like a lot for 2 tons. A really good install costs money, that just seems like a lot.

Second, $.04 is not going to last 15 years. Dereg in Ohio is already getting away from that as talked about in another thread. It makes zero sense from an environmental and energy prospective to have a reverse rate tier structure. Not having geo in Iowa with no NG is going to hurt resale in 15 years also. To illustrate how bad of a policy $.04 is, it is encouraging a efficiency minded builder like yourself to not do geothermal in what I am guessing is one of the most brutal climates in the US.

I'd be really curious to see the highlights of your Man J. I'd like to see what your window loss vs. wall loss is. I still can't wrap my hands around just 2 tons unless your window area is small. I assume your summer needs are pretty small.

My guess about man J's is that they assume no window covering and I would guess that insulated window treatments are pretty common in Iowa. That could cut your heating needs in half.

In 15 years, you might run through your ASHP. That would eat up at least 1/2 the difference in cost between ASHP and GSHP.

Propane would be crazy unless you wanted it for fireplace or cooking.

Some devils advocate questions to ask:

It's very important to make sure your load calcs is correct. (for either system)

Have they accounted for the entire lower level as conditioned space, especially since you are north facing as it relates to heating needs. Any skylights?

Since you are doing horizontal loops, do you have the land to do so? Could they do 3 tons if needed, or are they telling you 2 tons because there is not sufficient space to place the loops for more tonnage?

Just asking....

If your house is air tight and super insulated, you're HVAC requirements are going to be smaller. Maybe I'm short sighted, but if I were you I would get a bid on a dual fuel system with good air source heat pumps and a backup propane furnace. Lots of postings on this forum talk about the need to really weatherize a home before using geothermal, but they always fail to bring up the point that once you've done the weatherization the "traditional" HVAC systems benefit as well and become even more cost effective.

At $.04 - why would you ever use propane. Shouldn't be too hard to add later if electric rates change. A quick check shows electric strips to be 1/3 the cost of propane.

If it's not hard to add later, then sure, go with heat strips instead of propane backup. But $0.04 is pretty low and I can't see it staying that way for long, so I thought you should at least look at the costs of a dual fuel system.

thanks for the replies.

I will try to touch on some of the questions:
I am getting about 4 different load calcs, along with my own which include loading my Revit model into Autodeck Green Studio which analyzes everything and produces costs and loads. So once those start to get in, we can compare everything for similarities.

For wells, we are building on about 1 acre. However we also need a septic in that space, so that eats up some. The house is modest size, with a footprint of around 58'x36'. There should be space for 2-3 tons worth of horizontal. THe guy digging my basement and septic can also dig trenches for the ground loops. However vertical wells cost around $2k in my area, depending on the depth of course. Most like to size up .5-1 tons worth of well around here.

all windows will have coverings on them. I am toying with making the north glass triple pane. it would be roughly 800 for that upgrade for the north windows. According to the cost vs savings, that is a pay off of around 11 years....over high performance duel pane. not sure its worth it at all. I am way ahead to put in some nicer insulated shades instead of the glass. Looks nicer and is more efficient.

Any thoughts on the more "DIY" approach? Meaning supply the products and just hire out the install? I have subs that can do vertical wells, grouting and hooking them up to the system for about $2k per well. I am not sure how many I need just yet, depending on the depth obviously. It looks like I can buy everything I need for 8k or less. Plus wells and install costs, I am probably around 15k or less, maybe.

well, if you plan to contract each part out, you should make sure you atleast have the geo hvac contractor involved to make sure things are up to his standards and set for him the way he thinks is appropriate.

Don't undersize the wells. Don't skimp on the grout. You want maximum heat transfer. When it is below twenty degree's outside you want the water coming from those wells to be like in the upper 40's or more I imagine. If your not pulling the heat from the wells properly its barely better than air-sourse.

I don't think you can get the 30% tax credit as DIY.

As far as triple pane - how do you figure 11 years? I only ask because it really matters if you do geo or not. I can't imagine anything paying off if you do geo at $.04.

In my more modest climate with NG, each window costs about $7 a year (for heating). Geo at $.04 is about 1/2 or 1/3 NG cost so that same window would cost at most $3 a year. I'd assume your climate has 3 times the heating need - so we are at $9 for a 2'6"x6' window. These are basic low-e wood double pane. I'd expect high performance to be more like $7 a window and triple pane to be $4 a window. So for that payback you are looking at more than 20 windows. Is my math off?

Do you have 6500 HDD b/c I am at 2700 so not quite 3 times the heating need (however flawed that concept is).

my HDD is about 7200, however my estimates on windows were done some time ago with a lesser system, prior to knowing about the .04. Regardless, we know it doesnt pay off, which is the bottom line.

I wouldn't expect it to pay off easily but 11 years wouldn't be bad. Did you do the same calculations on your walls? Because I wouldn't expect that to pay off in less than 11 years but of course it depends on what you are comparing to. I would think a standard 2x6 wall, with 1 in XPS is where the sweet point would be as far as payback.

I know it doesnt seem like it, but the 2x8 sills and staggered stud design with 1.5" XPS is cheaper then a similar advanced framing 2x6 w/ 2" XPS on the exterior. 1" XPS is really still not as much insulation as I would like to see in our area. It is really only around an r25, clear around r-21 range. Adding the 2" makes it closer to an r26-27 clear, but costs about $700 more for materials then the one I am using, and has about 6 less clear R. It costs about 1k for materials more then a similar standard 2x6, 16" oc w/ ZIP sheathing, but is nearly 2x as efficient. Payoff is less then 2 years for the walls.

In other news, I have recieved a 3 ton 2 stage geo quote (climamaster) quote, isntalled for around 13,500. Does not include ducting or HRV. but includes horizontal wells. Add the other items, and I am close to 19k. Minus the tax rebate, it comes in about 2k higher then the "standard" hvac unit...a no brainer for sure.

You know how they say architects have no idea what things cost.... Not saying that would be you. The thicker walls cost a decent amount in trim/jambs for every opening. In my area, it cost $2000 to go from 2x4 to 2x6 in wood and jambs. Every window sill is more expensive, every window and every door. I would imagine using a non standard 8 inch would be even more expensive. But - there may be ways of doing things without spending that much money, I am just surprised by your totals.

I'd give your costs at $.04 and geo to be comparable to NG in my climate. That is, the geo is about 1/3 the cost of NG but the climate is 3x as cold. My standard (below code in your area) 2/4 walls cost $200 a year and that is what the same walls would cost in your setup. 2x6 would get that down to $130 or so. Add 1 in XPS and you would probably be $90. (all very rough math).

The reality is the savings comes from needing 3 tons of geo rather than 4 tons but not really from ongoing energy use. Here in a/c land, the tonnage is based on cooling which isn't helped much by wall insulation. I think the walls cost about $50 in cooling costs

Again I commend you on the focus on efficiency. Too bad that thinking isn't standard in the industry.

the wall is expensive as you let it be. window jamb extensions are some of the highest cost, most wasted cost IMO of a construction project. As you stated, they add considerable amounts to the window. I avoid these by 2 ways: use standard 2x4 jambs and add the wood jambs myself with trimming, or in the case of the 2x8 walls, I will do gyp returns with wood sills. Obviously there is more labor in the mudding, but when its DIY, it doesnt cost all that much, especially since most of the gyp in the returns will be scrap pieces anyway. The detail around the 8" walls will be a double 2x4 at the exterior face for solid nailing for both the window and trim, then a single 2x4 on the interior side for the gyp to screw too. I was planning on boxing out the RO with scrap 1/2 OSB so I have a nice solid opening to set the window and the gyp returns.

I thought you might have a less expensive answer.