We recently bought a two-story colonial house built in 1964 in suburb of Indianapolis, Indiana. It has about 2855 sqft above ground and close to 1600 sqft unfinished basement. Current heating and cooling is on conventional electric central heating and cooling. The system is about 16 years old and not efficient at all. The windows are original wood windows and drafty but we are planning to change it efficient vinyl windows before winter. The previous owner has also had blow-in insulation about 12 inches deep in the attic. We don't really know what kind of insulation on the walls. We are looking into the geothermal options and so far got three quotes from local HVAC contractors who have good review from angieslist. But we are not sure which one is good option for us.

1. 4 ton tranquility 27 geothermal unit (TTV049), average 6 feet 5 ton geothermal horizontal loop, ECM blower motor (variable speed fan), average 6 feet deep loops,2-stage compressor, options 50 gallon buffer tank (bradford white brand), convas correction to get rid of vibration. 10 years part and labor warranty and lifetime loop warranty. Contractor will use excavation to put loops in. with buffer tank, it is $15,500

2. Waterfurnace 5 series model #NSV070A110NLB with 6 ton capacity, high static ECM blower, 20kw supplemental electric heater, dual stage scroll compressor, convas connectors to adapt to the existing duct system, 5 deep horizontal bores complete with manifolds (4.85 ton capacity), marathon super insulated 85 gallon tank, 1 year warranty on parts and labor from the contractor, 10 years on parts from waterfurnace, 55 year warranty on loop material, it is $18990

3. Install one (1) GeoComfort 5-TON Geothermal System. Install one (1) GXT060 2-Stage variable speed geothermal package unit. Install proper electric backup heat. System comes with factory installed Desuperheater. Install one (1) AGFC2A flow center. Install one (1) 5-TON Horizontal Ground Loop, buffer tank it is $20,100 but we have to pay extra $930 for 10 years parts and labor outdoor and another $541 for 10 years parts and labor indoor.

For quote 2, we are not sure why the contractor will put 6 ton compressor but only 5 ton loop capacity.

For quote 1, we are not sure if 4 ton unit is enough for our house

For quote 3, with extra warranty, we are looking about close to 22k

We'd like to see opinions from others. Thanks

 

Addressing only the sizing...

Even with code-min replacement windows & the foot of fluff in the attic your "after" picture heat load with the new windows could already easily be in the 4-ton range. Six tons would usually be a lot for a house that size, unless you had a LOT of unshaded west-facing window area and you need it for cooling. (With decent low-E heat rejection on the west side and cellulose wall insulation 3 tons cooling might be about right- it depends.)

In 1964 the most common wall insulation in timber framed housing was low density R11 batts. Low density batts are not very infiltration-resistant, and if it hasn't been upgraded it's probably worth blowing in cellulose from the exterior, compressing the R11s and filling in all voids, which would tighten up the walls by quite a bit and increase the R-value slightly. There may be other low hanging fruit in the form of air-sealing & spot insulation, or (if there's room) adding 3-6" of cellulose on top of whatever is in the attic, air-sealing & insulating the foundation-sill/band-joist with a couple inches of closed cell spray foam and putting a couple of inches of foam (rigid or ccSPF) on the foundation walls. On a 2-story house stack effect infiltration pressures are significant, and the foundation sill & band joist is often several times the air leakage as all the windows & doors, and in a most-damaging place: the bottom of the stack. Air sealing both the bottom & top of the house are far more critical than whatever is in-between.

By tightening up the house and going with slightly better than code-min (code-max, really) U-values on the windows, paying attention to solar gain on the west-side windows (need to be low-gain there) it's realistic to get the heat loads down into the 3 ton range on a house that size. Insulating the foundation wall may be the most expensive part of it unless you do it as a DIY, but it's usually more than 10%, and may be as high as 15% of the heat load on a 2 story 2x4 framed house (somewhat more on a 1-story house), not counting the infiltration losses. At the VERY least air-seal the foundation sill & band joist, and any doors/windows/dryer-vents etc that are in the basement. Fully air sealing the basement ceiling is a fools-errand never likely to succeed , but with any plumbing or electrical chases that run from basement to attic it pays to at least TRY to air seal them. Keep the south facing windows higher gain- it's still a heating dominated climate- you can shade the south side effectively with overhangs or awnings, but not the east or west sides.

Bottom line- if it's not under 4 tons for both heating and cooling even with code-min windows, it probably COULD be brought that low or even lower for less money than the cost delta between that quote and the others. Unlike another ton or so of geo, insulation & air sealing have no operating or maintenance costs- only higher comfort.

A real Manual-J load calculation is in order, and that would require inspecting to see what really IS in the walls. Short of a Manual-J, if you have a mid-winter power bill with meter-reading dates, a zip code, and a power bill from May when the heating & cooling portion is fairly light to subtract out a baseline, it's possible to use that information against heating degree-day data for your zip code to come up with a pretty good idea of what the "before" picture heat load looks like based on how many kwh/HDD were used. That's easily converted to BTU per heating-degree, then multiplying the degree difference between the 99% outside design condition (+3F for Indianapolis) against the base/balance point (65F). That's about 62 heating-degrees for Indianapolis, which is probably close enough, given the inherent error in any one billing period from random varations in monthly power use or random time-of-day meter reading. But you'll know if it's 4 tons vs. 5-6 right away. If the "before" picture is already around 4 tons, even that quote is probably oversized for the new-windows in a tightened up house "after" picture.

If you want to run the calc yourself, find a weather station near you and download a base-65F spreadsheet spanning the wintertime billing period, and add up the HDD between the meter-reading dates. Use a shoulder-season bill to subtract out the kwh/day baseline from the power use. One kwh =3412 BTU, so once you've come up with a kwh/HDD from the mid-winter bill with the baseline use subracted out, divide by 24 hours in a day, multiply by 3412 for the BTU/heating-degree, then multiply by 62F- that'll usually be within 10% of your actual heat load at +3F. If you had used deep overnight setbacks it might have saved 7-10%, but if you had been heating your domestic hot water with electricity that's going to more than compensate for those savings, so the combined number is a wash. If you didn't use setbacks at all it would be a slight overestimate of the real heat load.

Size-wise 4 tons is probably on the high side, and definitely NOT undersized.

If you're pulling the siding it's DEFINITELY time to pound cellulose into the wall cavities from the exterior (unless that's already been done). And don't stop there- this is an opportunity moment for upgrading the thermal performance of the house that won't come along again for another century, given the longevity of fiber-cement siding! You don't have to knock yourself out, but there's a huge wintertime comfort difference in the interior-surface temp of the exterior walls if you add some exterior insulating foam, and it'll knock something on the order of half a ton or more off the heating & cooling loads!

If pre-existing batts have foil facers or there's a poly vapor barrier between the gypsum & studs there are some limitations (dig in there and find out- a 1/4" hole drilled from the interior and a wire hook can tell you a lot. But even with interior side vapor retarders you can put at least SOME insulating foam between the sheathing and the siding, and it makes a HUGE difference:

A 2x4 studwall 16" o.c. with cellulose or high density fiberglass cavity fill comes in at about R10 whole-wall average after factoring in the thermal bridging of the framing.

Add 1" of XPS (blue, pink, green, whaddevah) and that wall is now R15.

Add 2" of XPS and it's R20 (which you've cut the wall losses literally in HALF!)

If there is no interior side foil or poly, only kraft type facers on the pre-existing batts (or if those batts can easily be removed, including the facer) you can go with foil-faced poly iso which runs ~R6/inch of thickness, and a 2" layer would give you a whole-wall performance of about R22.

At only 2" of foam on a 2x4 wall you have the standard wall thickness of a 2x6 framed wall- it's not bad.

With any thickness of foam, use 1x furring through-screwed to the studs with pancake-head timber screws (eg FastenMaster HeadLok, which is carried by some of the box-store chains) to limit the thermal bridging of the fasteners, and mount the fiber-cement to the furring only.

Be sure to properly lap the window & door flashing to the housewrap or felt while you have it open too. If you're using replacement window inserts the housewrap goes between the foam and the sheathing, but if you're going with new-construction windows you have the option of moving the plane of the window outward and putting both the housewrap & flashing outside the foam.

If you can use foil-faced goods with a 3/4" gap to the siding it'll peel something extra off the cooling loads too due to the radiant-barrier effect by letting the siding run a bit hotter in the sun with less heat transfered to the rest of the wall structure. There's a smaller benefit during the heating season, but on average it's adding about R2 (or about 10%) to the whole-wall performance.

A lot of tips on mounting & sealing exterior foam can be found here:

http://www.greenbuildingadvisor.com/blogs/dept/musings/how-install-rigid-foam-sheathing (Click on the various links on that page for more detail.)

In Indianapolis (warm edge of climate zone 5) an inch of foam does a lot for protecting the integrity of the structural sheathing from rot by keeping it above the dew-point of the interior air.

On the basement walls you need at least an inch of foam between the concrete and any interior studwall. If there is no sill-gasket or capillary break between the foundation and the foundation sill it's somewhat safer to use unfaced EPS or XPS than anything with a foil facer. A inch of XPS and a studwall with UNFACED rock-wool batts (avoid cellulose or cotton below grade) in a 2x4 studwall brings it up to about R15, which is fine. Put an inch of XPS or EPS (but not iso) under the bottom plate of the studwall to keep it from wicking up moisture. Don't put up poly or even kraft-facers on the interior side of the studwall- bare-wallboard or latex paint, at most, to keep groundwater humidity from accumulating to mold-levels in the stud bays. With an inch of exterior foam wintertime moisture drives won't condense often on the foam/fiber contact even at the above-grade section, and when does, it won't run down and be absorbed by the stud plate, since the bottom of the bottom of the studbay is much warmer than the above-grade section. Both the foam and rock-wool will dry quickly as the temp rises, and neither are harmed by the modest amounts of fog-film moisture you'd be seeing during condensation events.

If there's a sill gasket and/or you have good overhangs & drainage, no moisture issues with the foundation you could use fire-rated iso held in place with plastic fasteners. Tips for that approach can be found here:

http://blog.energysmiths.com/2011/08/basement-insulation-part-3.html

BTW: I live in a comparable sized (~2400' + 1500' basement, ~ 20% smaller) 1.5 story 1920s bungalow with retrofit cellulose in most stud-bays ( a few known gaps totaling about 100 square feet) and much crummier roof R still to be rectified. It's currently glazed with 19 original antique double-hung windows (+ clear-pane storms) plus 12 ~U0.5 double-panes and two ~U0.5 skylights. (31 windows total, not counting the handful of basement windows.) You probably have more wall area, less window area, and less roof area than I do. After some amount of tightening and R18 on the basement walls the measured heat load is in the 3-ton range @ 0F outdoor temps, and the heating system is radiation limited to about 3.5 tons at the water temps I'm running. It got through a -8F overnight low a couple of years back without losing any ground- I'm pretty sure about the load numbers.

Your house might have a heat load of about 4 tons maybe even 5 as-if the windows are leaky single-panes sans-storms, but it probably won't be much more than 3 tons with modest tightening and better windows, even without exterior foam. With exterior foam you're probably in the 2.5 ton range, maybe a hair under, depending on the windows and foam-R.

But do the math using utility billing data to rough-out where you are.

I have included the load calculation that first contractor gave to me (4 ton transquility 27 quote). But those numbers don't really make much sense to me as I am pretty amateur in the geothermal world. Given the load calculation, do you think first option is good option?

That Wrightsoft analysis looks....jiggered.

Gotta love those ground loop quotes - "5 ton ground loop", like that means anything. I would get the pipe length, layout, and depth and then use software to check the expected annual operating cost for each quote.

Could you specify why the analysis looks jiggered. We are so new to the geothermal and we are not sure what else to do rather than getting quotes from local contractors that have relatively good reputations from Angie list.

According to DOE's Oak Ridge National Laboratory, Indiana is one of the few developed geo markets in the country (i.e. contractors are competent and competitive.) If you can get it done for $15k and can claim federal tax credits expeditiously, you aren't paying a whole lot more than conventional hvac replacement. I'd use it as a placeholder: control costs this winter and decide later what else makes sense.

I have no idea how you could possibly be getting anything like 22,000 BTU/hr of heat loss out of the floors unless you leave the basement doors and windows open and run a fan.

If it's even remotely air-tight it'll be under 15K, might be around 10K. But for sure air-sealing & insulating the band joist & foundation sill with 2" of closed cell foam and putting the 1" rigid + unfaced batt studwall would cut whatever the real number is down to 5K or less. To lose 22K/hr out of 1900' of floor the floor temps would have to feel seriously cold to bare feet- well under 60F in a 70F room. Even if an uninsulated basement coasts along at 55F the air films at basement ceiling would be much warmer from stratifcation, and with a 70F room above you'd be looking at the low-60sF fora floor temp. If you insulate the basement walls it probably won't drop below 65F in the basement as long as it isn't leaking massive air, and the floor temp on the first floor would be but a couple degrees below the average room temp.

The wall-loss numbers also seem a bit high- a 2x4 wall with R11 batts comes in at ~R9.5 average, and the heat loss per square foot would be ~0.1BTU/hr per degree, so that should be closer to 7 BTU/ft, at a 66F temperature delta, not 9.5 BTU/ft- that's about a 35% overestimate on that factor. Call it 14-15K tops, not 18-19K.

Not sure how much they mucked with the rest of it, but 30% here, 18% there, with thumbs on the scale it really adds up up.

On the bright side, the 4F heating design temp is credible.

Assuming it was bumped 30-35% everywhere, not just the basement & walls, that 66K number is really a 50K number, and there's room to knock maybe 12-15K off that at reasonable cost just on basement insulation and air-sealing. With cellulose in the walls the infiltration number comes down, and an inch of exterior iso with taped seams and edges sealed when you re-side would knock another 4K or more off the wall losses.

From wintertime power bills (with specific meter reading dates to look up heating degree-day data ) and a May time frame bill from which to subtract the daily background usage the actual heat load could be calculated with reasonable precision.

There are people/companies that will do an energy audit and give you cost effective options for lowering energy usage. But I'd be cautious if they are trying to sell you anything more (like doing the work).

I also just checked with the contractor from Quote 1 and the following is from the contractor "The loops will be about 6 feet deep and there will be 3600 linear feet of 3/4 inch HDPE geothermal pipe. The loop will be 600 feet long wrapping around the back of the yard and will be a 4 ft wide trench". Any opinion on that? I think I am leaning towards the first quote but really like to get experienced people here opinions as well.

sounds like more than enough for a 4 ton heatpump. 900 ft of pipe/ton, 6 ft deep, should be more than fine. 600 ft circuits should keep the pressure drop down. Sounds like he knows hat he is doing. Check previous installs.

Posted By ICFHybrid on 04 Oct 2012 08:37 AM
That Wrightsoft analysis looks....jiggered.

Looks like a comprehensive loss calc to me.
Design seems fine as well.

I've not use Wrightsoft, but the loss numbers look more padded than other tools would give for that type of construction. But even if they're dead-on it's probably cheaper to insulate the basement than to buy the extra ton of geo (and it would provide more comfort too.) For the wall heat loss to hit 9.5BTU/ft with a 66F deltal-T the whole-wall R would have to be about 7, which implies a center-cavity R-value of R8.

There is such a thing as 2.5 thick R8 "econobatts" were sometimes used in 2x4 framing back then, but that would represent an energy-emergency. If that's what's in there you 'd be INSANE not to blow in more insulation to pack out the cavity before putting money into a heating system. Blowing it full of cellulose would take the center-cavity R up to ~R13, and the whole-wall R up to ~R10, which would deliver (66F/R10=) 6.6BTU/ft, down from 9.5BTU/ft.

I don't agree with a cooling setpoint of 70. Our Code (Florida) calls for designing to 75

Odd that 2x4 walls are shown with just R5 exterior board - NO insulation in studbays...has that been verified?

I agree with Dana that losses through floors into basement seem very high...22k Btuh...1/3 total load. I don't buy it.

Posted By engineer on 05 Oct 2012 10:03 PM
I don't agree with a cooling setpoint of 70. Our Code (Florida) calls for designing to 75

Code matters little to someone who is uncomfortable. Some folks are not happy at 75. Not sure OP specified 70. I actually design at 72 unless told of greater demands.

In our area where mid 90s to 100*+ are uncommon, it still happens. Were I to design for 75* and design temp is 91* not hard to guess the outcome.....

Of course we don't have a cooling requirement at all in our code.

Posted By engineer on 05 Oct 2012 10:03 PM
I don't agree with a cooling setpoint of 70. Our Code (Florida) calls for designing to 75

Odd that 2x4 walls are shown with just R5 exterior board - NO insulation in studbays...has that been verified?

I agree with Dana that losses through floors into basement seem very high...22k Btuh...1/3 total load. I don't buy it.

Dang! You must have read past the first page!  (Why would anybody do that? ) The first page numbers already had me looking askance- didn't seem worth digging all the way down to page 5, but there it is!

And there is no sane reason to design and install geo on the ""before" picture loads if the house is truly uninsulated in the cavities- that's extremely low-hanging fruit for a retrofit insulation treatment to bring the load down. (Was that even legal in IN then? It sure wasn't in WA where I was living at that time- R11/R13 batts were pretty standard for 2x4 construction in the mid-1960s.)