I am building a new custom 4300sq/ft home in Rhode Island. I would like to use geothermal but every builder I speak to is telling me I am insane. Even after the tax breaks. They are all pushing efficient propane systems as I can't get natural gas where I am (sadly). I am looking into a closed loop vertical system. The roof line will be spray foamed with batten+ on walls. (R21). I am concerned about the winter we just had where we measured snow in feet and it seemed to never stop. Is there ANYONE out there that has a similar size home in New England and can share their electric bills. I do NOT want to heat with electricity that is insane to me, as it is the lest efficient cost wise. Wondering if there is a geosystem that would use propane as a backup for heat? (i will have propane for fireplace and cooking).. Thanks in advance.. -Ken

Ken, I am in RI with a GSHP.

All electric, though I would like a propane generator someday.

I am heating 3800 sq ft. Half is a walk out basement and garage, both heated.

I had a couple of $400 per month electric bills this winter, but I still think I am paying less then if I had propane, no natural gas either out here in Foster Glocester.

I think it is more expensive to run a separate propane auxiliary system then to have the electric elements run for what should be $75- $100 a year.

I have a horizontal loop system because room in front of the house was not a problem. Usually they are a little less $ then vertical loops.

I love our system, even though it has been giving me some trouble (I am to blame pretty much, long story.

For the first 3 yrs we were averaging about $175 a month year around, higher in winter low in spring and fall, not too high in summer, a/c was very nice. That was everything, hot water, dryer, stove ,lights.

We did a lot of the building our selves. A lot of things I would have done differently, after reading on this forum and others.

Not sure exactly what you mean by batten in walls, if the is doing fiberglass bats, in the wall, are they putting rigid foam on the exterior?

Chris

rigid foam on exterior as well as interior.. (fiberglass behind it).
I am curious .. what would you have done differently?
How deep is your horizontal loop?
Also how many tons?
and do you use it for hot water? I assume you have electric hot water from your comments.
Radiant heat?

Thanks for feedback.. I am sure I am where you were at, when you started..

-Ken

I have what is called a combination heat pump, water to air and water to water. My main level is air heat and a/c. Radiant in basement and garage.

It's a dual compressor, not single 2 stage compressor. So it has 3 compressor stages and aux toaster strips, 5k watts. Brand is a small name not Waterfurnace or Climatemaster. 4 tons. Loops are 7-8' down. 5 trenches 200' long, 1" HDPE pipe. Hydro-Temp is the company. I was sucked in by "this heat pump does it all" It used to do 100% of my DHW too.

Our well is bad with iron, so I put in an iron filter. The filter media needs to have 7.5 PH water so I also installed a chemical feeder which raises the PH with soda ash.

Problem is I raised it too high corroded the heat exchangers for the radiant and DHW. Have had the radiant one replaced and bypassed the DHW one. In December I added a heatpump hotwater heater( GE Geospring).

For insulation I had open cell spray foam done in my 2 X 6 walls. I should have done more research, air sealing is very important. I could have done exterior foam and something cheaper in the walls.

There is a gentleman on this forum named Dana1 that is very knowledgeable about insulation. I'm sure he would question having foam on the inside and outside, you need to be sure you don't trap moisture in the middle.

Chirs

It is common for builders to advise against geo. They are afraid that it will hold up the building process, they want to get in, out , and make their money, and many of them do not care how much you pay for propane down the road. No need for a propane backup, a small electric heat element built into the unit can fulfill all your back up needs, with out the uproot costs and without the maintenance costs of a backup propane system.

Posted By docjenser on 15 Apr 2015 02:21 PM
It is common for builders to advise against geo. They are afraid that it will hold up the building process, they want to get in, out , and make their money, and many of them do not care how much you pay for propane down the road. No need for a propane backup, a small electric heat element built into the unit can fulfill all your back up needs, with out the uproot costs and without the maintenance costs of a backup propane system.

In Dallas, where it's Christmas in July due to the heat, it's a two step business model.  Step 1 is one hour of the salesperson's time (often the company's owner), to make the sales pitch, size the replacement equipment needed, and get signature on a contract, and get signatures on any financing documents.  Step 2 is max 4 hours for a 2 man crew to get in and out doing whatever's been agreed to in the contract, even including up to a full change out of furnace and outside compressor.

If you ask about who will do the Manual S, J or T, or if you ask about alternately doing geothermal instead of conventional A/C or conventional heat pump, the salesperson will expertly and gracefully exit, convincing you that in fact you suddenly don't need his/hers company's work after all.

In fact, at the moment, I know of no company, located within the city boundaries of Dallas, that will talk to anyone about residential geo.  There's just too much money to be made getting in and out with conventional A/C systems.  And the very sophisticated sizing technique used is to make the tonnage the same as what's present, or, make it larger if customer says that he/she/whole-family is always warm.

It gets better.  Because there's so little heating load, as compared to cooling, it's tough to put in a 5 or 6 ton A/C unit without having to put in a 120 - 140K BTU furnace.  So increasingly these days, two units get put in, so that furnace size can remain at 50 - 65 KBTU.  All the more profit.

It would be suicide to set up a professionally run, pay for what you get type of geo business here, like docjenser, or engineer, or bergy, or joeami, or geopalace do, or a few other names that escape me for the moment.  No one would want to spend the money for 300' vertical holes because of the heat, or getting their air distribution problems fixed.

It's absolutely amazing how in a hot climate, where geo makes clear financial sense, it's only the commercial building owners that buy into the upfront cost of geo. 

Best regards,

Bill

R21 between studs is essentially code-min construction (aka "the crummiest house that's legal to build".) A code-min 4200' house in RI would have typical heat load of 50-65,000 BTU/hr@ +10F (the approximate 99% outside design temp in most RI locations) which would take something like 4-5 tons of GSHP to support (the pros can feel free to correct me if I'm off on those estimates).

In nearby CT under a recent statewide subsidy program the average system size was about 5 tons, at a pre-subsidy cost of about $9KUSD/ton, or about $45K. With the 30% income tax credit that's reduce to about $32K. The actual cost will vary by the actual load and your soil conditions and contractor's competence/hunger-level.

By contrast, mini-split type air source heat pumps (mini-ducted or wall-blobs) run about $3.5-4K/ton and you'd be looking at less than $20K, maybe even a LOT less. A 3/4 ton Fujitsu -9RLS3H has a capacity of about 11,000 BTU/hr at -15F (colder than it's been anywhere in RI since record keeping began, and a capacity of 16,000 BTU/hr @ +10F (your 99th percentile temperature bin), and has a tested HSPF efficiency of 14 (= COP of 4.1, better than the average GSHP installation in New England, but not as high as the best). But it's a wall-coil type, a point-source heater, which would have heat distribution issues in a code-min house.

OTOH a 1-ton mini-ducted version like the Fujitsu 12RLFCD has comparable or better output at +10F (but not the same output at -15F), but at a lower HSPF of +11.5 (~COP= 3.3), and the 1.5 ton 18RLCD delivers even more:

http://www.fujitsugeneral.com/PDF_06/Submittals/12RLFCD%20Submittal.pdf

http://www.fujitsugeneral.com/PDF_06/Submittals/18RLFCD%20Submittal.pdf

(Consult the distributor for extended temperature capacity ratings- it's not published online.)

In your climate these units WILL actually hit their HSPF numbers (unlike northernmost New England), and may even exceed them if optimally oversized (about 1.25-1.5x oversizing capacity at your +10F tempeature & load), since modest oversizing means they modulate at part load nearly all the time, at higher average efficiency than test conditions.

Mistubishi has similar offerings, as well as multi-splits that have specified capacity down to -25C/-13F.

This means you'd be able to deliver the full load at only 3-3.5 tons of mini-split, at a cost of $12-15K. Even at this year's National Grid electricity pricing, the annual heating cost of heating with modulating mini-split heat pumps is comparable to heating with natural gas, but also comparable to the heating costs of GSHP systems, albeit slightly higher than a first-class best practices GSHP system. On a Deep Energy Retrofit project house I was involved with a few years ago (up the Blackstone from you in Worcester MA), with a design heat load of about 30,000 BTU/hr @ +5F, heated solely with older (and lower efficiency with an HSPF less than 11) Mitsubishi FE series mini-splits, the total utilities for this 3 story have yet to exceed $300 in any one month, even at this year's ~25 cents/kwh power rates.

Then there's the issue of the code-min construction. At current fuel & electricity prices and interest rates (subsidized in the tax code, mind you) it's cost effective in a decades long financial analysis to go higher than code min on everything, and in high-cost energy markets (that's us, in southern New England) even going 1.5-2x code min isn't crazy. A good starting point can be found on Table 2, p10 of this document:

http://www.buildingscience.com/documents/bareports/ba-1005-building-america-high-r-value-high-performance-residential-buildings-all-climate-zones

Note, those are "whole assembly" R values, not center cavity. A code-min R20 open cell foam filled 2x6 stud wall with wood batten & board sheathing and 3/4" of blue-board + plaster interior comes in at about R13-R14 after factoring in the thermal bridging of the framing. If it's 3" of closed cell foam in a 2x4 wall it's even worse, at about R11-R12 whole-wall, due to the higher thermal bridging of the shorter path through the studs.

RI is at the warm edge of US zone 5, so look the zone 5 recommendations. The R30 wall is more than 2x code min, but 2x code-min is literally half the heat loss, and much higher wall temperatures during polar vortex events. How do you get there without breaking the bank?

A 2x6 wall air-sealed with caulk and meticulously installed R23 rock wool or high density R24 batts brings the whole-wall R up to about R15.5 if the studs are 16" o.c.. If you can tolerate a somewhat less-flat wall, putting the studs 24" o.c. would bring that just north of R18. To that you can install 3" of exterior rigid rock wool (not too many contractors in RI have dealt with that), or 3" of rigid foil-faced polyiso foam, and you'd be there. The facers get taped for higher air tightness, and held in place with 1x4 furring through-screwed 1.5" into the studs 24" o.c., and the board & batten gets mounted to the furring. There are flashing and housewrap details to get right around the window mounting, but the cost-adder for 3" exterior polyiso is $1.80-2/ square foot, whereas the cost of the cavity insulation is likely to be lower than your spray foam solution (a LOT lower, if you were using closed cell foam), and the exterior insulation keeps the sheathing warm enough that you have HUGE dew point margin, with no need for interior side vapor retarders more powerful than latex paint, which gives it a lot of moisture resilience.

If you build to the Table-2 recommendations your heat load will be under 40,000 BTU/hr, possibly as low as 30,000 BTU/hr, depending on just how much window area you have, and how many corners bump-outs and dormers etc you have. Heat loads increase with greater exterior surface complexity, since all those corners means more exterior surface area per square foot of conditioned space, and the thermal bridging of the corner framing is much higher than mid-wall. A competent architect/engineer would keep careful track of the heat load numbers during the design phase, but every ton of load you shed comes directly off the GSHP sizing. Unfortunately GSHP costs do not fall in direct proportion in system cost. Even a 2-ton GSHP is going to run you ~25-30K in southern New England, based on recent quotes I've seen in MA. Part of the reason is that the amount of engineering it takes to design a 2 ton system is about the same as what it takes for a 5 ton system. Every GSHP system is a custom design (unlike air source heat pumps, which are "systems in can"), and there is nothing more expensive than a cheap rushed GSHP design.

Every ton you shed in load also comes back to you in higher comfort, since the radiant temperature of the walls & windows at +10F are measurably higher.

Bottom line: Spending the money on a higher performance building envelope buys you more comfort than spending it on higher efficiency heating systems. And in your climate, best-in-class air source heat pump technology yields comparable efficiency to GSHP systems, at a much lower up-front price point, and at a lower overall lifecycle cost. So while GSHP has a good lifecycle financial case vs. best in class propane heating, it's still not as cheap as mini-split technology, which is getting better year-on-year, but not getting more expensive.

Then there's the solar situation...

In any new construction it's useful to consider designing the roof lines a site orientation to be able to take advantage of rooftop photovoltaic panels (PV). At this point in time even without subsidy, at the recent $3.50/watt average installed price for rooftop PV in MA the lifecycle cost of it's output is less than Nat'l Grid's residential retail rates. That includes the cost of financing on a 20-25 year lifecycle basis, with one inverter replacement at year 15, and doesn't include the residual value of the still functional (if not performing to day-1 spec) of the equipment at end of that lifecycle period. The $3.50/watt price point is literally half what it was five years ago, and there are no technical barriers to going lower over time. (In Australia & Germany's mature markets for PV the all-in installed cost is about $2/watt, sometimes as low as $1.50.) At some point (maybe even on day-1 for new construction) it becomes something of a no-brainer type investment, especially if the financing can be rolled into a mortgage. Solar City is currently offering 30 year 4% financing and 30 year warranty on their equipment in a few states (not RI yet, SFAIK). But if you cut up the roof lines too much or orient them sub-optimally it cuts into the value of that roof as a photon farm. On a 4200' house with a heat load of under 40,000 BTU/hr, it's likely that you could come close to net-zero-energy in your location, with a bit of foresight & planning. You could wait 6-10 years for the cost of solar to hit a buck a watt, but if you're paying grid-rates for that period that might not be the right thing to do. Last time I looked most Nat'l Grid customers were paying 25 cents/kwh (about 2x the national average), though there will be some rate relief fairly soon, but I don't expect rates to drop below 18 cents (could be wrong, hope I am...)

Wow, first of all I would to thank you for such great info. Honestly this is the first time I am getting the non-sales pitch real data.. Thank you. On that note if you are a builder please contact me.. I would like to hire you.. Let me make sure I get this straight.. For insulation: 1. ignore the code-min R values, they're trash. 2. Go with R30 for walls 3. To get there on a 2x6 16o.c. wall: air sealed with caulk (suggested products?) R24 high density batten gets you to whole wall of ~15.5. Then on the exterior you add 3" of rigid foil-faced polyiso foam which is about an R factor of 19 (15+19 = R34) so you are there.. is that correct? I was looking for a good image that shows it all together. From the exterior.. to the inside I get this order.. 1. ceder shingles or hardie plank fastened to furring 2. 1x4 furring strips holding on polysio screwed to studs 24 o.c. 2.5 air between the shingles and the polyiso created by furring strips 3. 3" rigid foil-faced polyiso foam taped 4. some air barrier membrane? 5. sheathing 6. 2x6 studs 7. filled with R27 high density fiberglass 8. blueboard 9. plaster 10. paint Did I get that right? It seems it may be difficult to attach shingles to this or the stone veneer? What do you suggest for roof insulation? basement/cement wall insulation? basement slab insulation? for HVAC... considering the above insulation and the insane winter we had with 7 feet of snow laying around. The quotes I have to geothermal are crazy. 78k! includes well and does not count tax credits. Is there a good supplier in the area you can recommend? I gotta ask, how will a mini-split type air source heat pump will work under 7 feet of snow? I am open to other options but I am not a fan of the standard split AC system... seems when you are exchanging heat for cooling it is the hottest outside and via-vera for winter. Also I was worried about the electric heating elements as "backup" for a geo system. Electric direct to heat is the most expensive in my book. Would radiant heat be a better option with geo thermal? for solar... Solar City is in negotiations in my area but not a done deal yet.. FYI they are building a new manufacturing facility to make their own panels. Do you have a recommend installer? Again.. thank you for your excellent feedback. _Ken

Posted By kleach on 16 Apr 2015 05:25 PM
Wow, first of all I would to thank you for such great info. Honestly this is the first time I am getting the non-sales pitch real data.. Thank you. On that note if you are a builder please contact me.. I would like to hire you.. Let me make sure I get this straight.. For insulation: 1. ignore the code-min R values, they're trash. 2. Go with R30 for walls 3. To get there on a 2x6 16o.c. wall: air sealed with caulk (suggested products?) R24 high density batten gets you to whole wall of ~15.5. Then on the exterior you add 3" of rigid foil-faced polyiso foam which is about an R factor of 19 (15+19 = R34) so you are there.. is that correct? I was looking for a good image that shows it all together. From the exterior.. to the inside I get this order.. 1. ceder shingles or hardie plank fastened to furring 2. 1x4 furring strips holding on polysio screwed to studs 24 o.c. 2.5 air between the shingles and the polyiso created by furring strips 3. 3" rigid foil-faced polyiso foam taped 4. some air barrier membrane? 5. sheathing 6. 2x6 studs 7. filled with R27 high density fiberglass 8. blueboard 9. plaster 10. paint Did I get that right? It seems it may be difficult to attach shingles to this or the stone veneer? What do you suggest for roof insulation? basement/cement wall insulation? basement slab insulation? for HVAC... considering the above insulation and the insane winter we had with 7 feet of snow laying around. The quotes I have to geothermal are crazy. 78k! includes well and does not count tax credits. Is there a good supplier in the area you can recommend? I gotta ask, how will a mini-split type air source heat pump will work under 7 feet of snow? I am open to other options but I am not a fan of the standard split AC system... seems when you are exchanging heat for cooling it is the hottest outside and via-vera for winter. Also I was worried about the electric heating elements as "backup" for a geo system. Electric direct to heat is the most expensive in my book. Would radiant heat be a better option with geo thermal? for solar... Solar City is in negotiations in my area but not a done deal yet.. FYI they are building a new manufacturing facility to make their own panels. Do you have a recommend installer? Again.. thank you for your excellent feedback. _Ken

Some white-space between paragraphs help. Sometimes it requires using a different web-browser for line breaks to work on this site. (I've settled on FireFox as the best compromize for me on this site, YMMV.)

In Climate zone 5 you can't rely on the labeled R-value of polyiso in an exterior-foam application.  The material is tested for labeling at a mean temperature of 75F, and a 30F delta. (The hot side is 90F, the cold side is 60F.)  As you shift the mean temp of polyiso colder it improves for awhile, peaking at mean-temp of about 60F (cold-size 45F, hot side 75F) for a few degrees cooler, but then it's performance begins to slide fast from there.   In your stackup at +10F on the cold side of the 3" of foam and 40-something F on the warm side it's actually performing at about R10, but at your average winter temp it's performance not bad. From a heating energy use point of view it's safe to de-rate it to R5/inch or maybe even R5.5/inch.   If you were to do it in 2 layers of 1.5" polyiso next to the sheathing, and 1.5" of EPS next to the siding, the EPS will outperform it's labeled R4.2/inch during cold weather, and it would keep the polyiso warm enough to operate at higher performance. But it's up to you if the added complexity of dual-foam types is going to be "worth it" in this application. 

With simply 3" of polyiso it's operating at R25-ish whole-wall R during your 99% design condition, but more like R30 during the winter average, and during the shoulder seasons it's doing better than R30.  The difference in peak heat load between an R30 wall and an R25 wall is negligible, and it's the average performance that determines energy use. From strictly an energy use point of view it's hard to make that case for the walls, but if you were insulating at your roof deck, with some of the insulation above the roof deck, dual-foam stackup is often "worth it." 

For clarity I'm going to copy & paste your wall stackup with line-breaks:

1. ceder shingles or hardie plank fastened to furring

2. 1x4 furring strips holding on polysio screwed to studs 24 o.c. 2.5 air between the shingles and the polyiso created by furring strips

3. 3" rigid foil-faced polyiso foam taped

4. some air barrier membrane?

5. sheathing

6. 2x6 studs

7. filled with R27 high density fiberglass

8. blueboard

9. plaster

10. paint

That's almost right. Some clarifications:

Regarding #2,  1x4 furring only makes a 3/4" air gap, often referred to as a "rainscreen".  This air space functions as a capillary break between the siding and the inner layers, so even wet siding can't wick moisture into the assembly. It also functions as quick drying path for the back side of the siding.  To keep critters from setting up condos in there it's good practice to install Cor-A-Vent and a strip of the roll polyolefin mesh commonly used under ridge vents both at the bottom and top of those cavities.  For best effect it needs to be vented at the top of the rainscreen cavity, to allow convection purging of that air, but it's not absolutely necessary- bottom venting only can work fine, especially if the roof overhangs are deep enough to keep the siding from rain-wetting most of the time.

For 3 & 4, it needs to have a weather resistant barrier (housewrap, or #15 felt), but the order of the stackup depends on how you intend to install the windows.  If the window glass is going to be roughly co-planar with the structural sheathing (aka "innie mounted window") the WRB needs to be between the foam and the sheathing, and the window flashing needs to be lapped so that it dumps the bulk moisture on the exterior side of the WRB.  The best material to use for that layer in an innie mount is a crinkly type housewrap (eg. Tyvek Drainwrap), since that provides some amount of drain space and some amount of capillary break, so that any rain that finds it's way in there gets out before it permeates through the housewrap into the  sheathing.   If the glass is going to be roughly co-planar with the siding (an "outie window mount"), the WRB goes on the outside of the foam layer, facing the rainscreen gap (with the proper lapping of the window flashing, etc.) In outie mounts using flat goods is fine.

The WRB can be detailed as an air barrier, but it's more reliable over the long term if you make the structural your sheathing your PRIMARY air barrier, by caulking the framing to it everywhere, an sealing it's seams from the exterior.   Huber ZIP sheathing is pre-coated with a WRB material, and is designed for the seamse to be sealed well on the exterior using their proprietary tape. But you still need to caulk the framing (including the stud plates) to the sheathing on the interior side, and caulk the bottom plate of the studwall to the subflooring, etc. etc.   The traditional "gold standard" for this is Tremco Acoustic Sealant, which never fully hardens. But several of the fiberglass batt vendors now have very good purpose-made caulks for sealing framing to sheating.

Regarding #7, I think the best you're going to do in a 2x6 cavity is R24 batts, not R27, and R24 will need to be special ordered. (They're pretty standard in parts of Canada-never seen them in the US.) R21 fiberglass is more readily available in the US, as is R23 rock wool. Either are pretty good products if installed obsessively for fit & compressions. Rock wool is more fire resistant- it doesn't melt even in direct hot flame conditions- whereas glass can.

The best way to keep a mini-split working in 7' of snow is to not treat it as if it were an air conditioner, mounting it on the ground somewhere out in the open.  The best practice (rarely followed) is to bracket mount them on the wall protected by the overhang of the roof (under the rake of a gable is better than under eaves), with the bottom above the snow pack.  In Worcester, MA (which has thus far topped the list of snowfall for all US cities over 100,000 people this year) mounting them 3' above grade has always seemed to work, but I've been recommending 4'.  Even though I had 6-7' drifts in my yard, it never got that deep under the roof overhangs.  People are often wary about vibration issues when wall-mounting them, but the blowers are low-speed, and the compressors are all very quiet scroll compressors. I've NEVER been able to feel or hear the vibe without sticking my ear to the window near the mount. YMMV.  This 1.5ton mini-split compressor is on the back side of a house in Cambridge NY (north of Albany):




I would have advised bumping it a foot higher, and mounted it under the rake of the roof rather than under the eaves, where it can't get buried in the roof avalanche that you KNOW is coming, with steep metal roof like that! (Not my project, don't know those people...)

It's clearly not a thing of beauty, but then, neither is a gas meter or propane tank. There are places to install them where they still work, and are not sticking out like a hairy wart.

Mini-splits do not come with resistance heaters for backup. But the better ones have VERY good cold temperature capacity.  For example, a 1.25 ton Fujitsu 15RLS3H can deliver about 16,000 BTU/hr @-15F, and about 18,000 BTU/hr @ +10F, and will beat most geothermal systems on efficiency. The mini-ducted 1.5 ton -18RLFCD is good for about 20,000 BTU/hr @ -5F.  How much margin do you need?  If you build your house to the rough parameters in that Building Science Corp document your heat load at +10F is going to be under 10 BTU/hr per square foot of space, unless you make it some crazy thing with a gazillion dormers & bump-outs, and max out on total window area or something. 

It's pretty common to install one mini-split per floor so that it's naturally zoned, and oversize the capacity at your outside design temp by 25% or so, which means it will modulate at highest efficiency & comfort most of the season, only cycling on/off when it's already pretty comfortable out. (The house in the picture has only 1 mini-split for the whole house, but it's a PassiveHouse, with R50-ish whole-walls and some VERY high performance windows, and I'll bet there are some seasonal comfort issues from stratification between the upstairs and basement. I would have suggested two 3/4 tonners there, one per floor.)

If you go geothermal radiant heat is nice, it boosts comfort and the efficiency slightly better too. But it boosts the price tag even more. And, you still have to deal with the air conditioning issues. Although the 1% outside design temps in RI are pretty tepid, and in a high-R house with very little west facing window the sensible cooling loads are low, the LATENT cooling loads are still pretty real. You can't just ignore it- you have to dehumidify, if not actively cool.  With a geo system set up for radiant that means chilled water wall coils (looks like mini-split wall-blobs) or a ducted delivery system, either of which adds yet another layer of cost.  Most people opt for ducted-air only, since that deals with both the heating & cooling distribution.  Radiant cooling doesn't cut it in New England either- the dew-points are too high. Mechanical dehumidification of a high performance home (or even an IRC 2012 code-min home) is a requirement, not a luxury.

Until and unless you have the house designed and heat load calculated, you can't get a realistic quote on any system.  The high-R house sketched out needs maybe 3-tons geo to manage the heat load, less if you opt for resistance strip-heating as backup, but the real numbers aren't knowable before you do a careful and aggressive Manual-J calculation, or simulate the house with something like BeOpt/DOE2.  Anybody giving you a quote now before those calculations either has a lot of caveats built into the wording or is a total hack willing to build you something 2-3x oversized for your actual loads. Don't expect to get out for under $40K even for a 3 ton system (even if you might).  It's those kind of local/regional cost numbers that has driven me into the mini-split camp, since the mini-split technology has gotten SO much better in the past 10-15 years, and is getting more efficient with every model release from the bigger vendors (Fujitsu, Mitsubishi, Daikin.  Daikin mini-split offerings are a bit marginal for cold climate use, they have a pretty good air-to-water heat pump that does OK in low-load situations in New England.)

I'm aware that SolarCity bought a high-efficiency panel maker in CA last year, and are building  a high throughput mega-plant somewhere in the Buffalo NY area to serve the NE/NY region.  Their board chairman is Elon Musk, the CEO of Tesla, which is itself building a gia-normous battery factory outside of Reno together with Panasonic to serve both SolarCity's grid-attached solar & battery applications, and Tesla's electric car battery. (SolarCity's CEO Lyndon Rive is Elon Musk's first cousin- heluva family biz they have going there, eh? ) These guys are going to put vertically integrated utilities out of business in some places, and sooner than you might think.

Ahh.. this is better in firefox.. chrome would not let me format.. sorry..

On insulation..
Are you saying that the setup we have outlined, in your opinion, is the best cost/value option?
In the walls it seem like we would end up with R25 acting like R30 in the winter.
and you are suggesting the same but dual stack ridged foam for the roof?
The windows will have a trim kit around them (anderson 400).. I assume that means the glass is coplanar with the siding?  not sure.. seems like an "outie" mount is cheaper? 
I would be happy to send you a copy of the plans if you don't mind looking at them.  I would be willing to pay you for your time to get a real rating and recommendation. 

I had a question on this...
"...make the structural your sheathing your PRIMARY air barrier, by caulking the framing to it everywhere, an sealing it's seams from the exterior."
Are you saying to do what these images show?
http://www.kimjordanbuilders.com/qualityconstruction.htm
By saying " But you still need to caulk the framing (including the stud plates) to the sheathing on the interior side"
does that mean in the last picture on that page you would caulk the particle board to the studs?

I think we are at...
1. Cedar shingles/hardie plank or stone veeneer fastened to furring
2. 1x4 furring strips holding on polysio screwed to studs 24 o.c. 2.5 air between the shingles and the polyiso created by furring strips with Cor-A-Vent with roll polyolefin mesh at the base and cap (would like to see a picture of that one)
3. WRB on
4. 3" rigid foil-faced polyiso foam taped
5. sheathing  (is the Huber ZIP product cheaper than 1/2" ply and wrap?)
6. 2x6 studs (caulked on inside)
7. filled with  R23 rock wool
8. Membrain
8. blueboard
9. plaster
10. paint

This guy is suggesting to use rock wool on both the inside with a membrain and to replace the pluiso foam on the outside.  One point he makes is that thick (3" polyiso) will form a vapor barrier and so will the membrain.. now you have an issue..
http://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/mineral-wool-insulation-isn-t-fiberglass
Thoughts?

One question is the cost factor... that is a lot of material to purchase and install.  In the end would spray foam be simpler/cheaper.. less layers?

Great discussion..

on HVAC
Again.. I can sen you the plans but the living space sq/ft is different than the house envelope.   If we spray foam the roof rafters and count the basement (to be finished later). then the sq/footage is much larger and is over 5000 sq/ft (not counting attic).  If you use your 10BTU/hr per sq ft (max) we are looking at 50,000BTU/hr 
How can I expect to heat/cool that much space without ducts?

-Ken


-Ken

In my AO where no nat gas is available, propane heat is aout a wash with electric baseboard. ASHPs are second best with or without propane back up and GSHPs are best (in the context of operating cost. In the context of first cost (to purchase and install a system) cost v benefit does not always favor geo.
It would suggest if you haven't found a builder yet who's suggested anything other than propane that you keep looking for a more evolved builder.

Innie window mount:

 

Outie window mount:



It can be done either way.  From the interior side an outie window has deeper sills for your cats to nap on,  for an innie window you have to build deeper window bucks. With only 3" of foam it's not a big deal to do it either way.  In very fat walls there are both interior and exterior aesthetic issues to think about.

BTW: You have to specify the glazing to get U0.24-U0.25 windows in the Anderson 400 series, and it might not be a super-expensive upgrade to go with a U0.18-U0.20 triple-pane from Harvey or Paradigm.  In an ~R30 whole-wall R house the windows become an ever bigger fraction of the total heat loss.  It's worth shopping it around, getting quotes.

The 3" foam + 2x6/fiber option is a cheap way to hit R30-ish whole wall.  With the derating curves of polyiso factored in the R25 performance only happens during the coldest hours of the winter, the average performance will be about R30. The R25 performance at the 99% outside design temp adds about 2.3 BTU/hr per square foot of insulated wall area to the peak heat load over what it would be if the wall performed at a rock-steady R30- maybe about a 5000BTU/hr uptick in peak load for a 4000' 2-story house.  It's not insane to go with 4" foam, especially if you are up for building with reclaimed roofing foam (used-once pretty-good condition roofing iso or factory seconds with cosmetic dings cost about 1/4-1/2 of virgin stock, available from multiple vendors in southern NE.)

On the roof IRC 2012 code min is R49.  To do a vented cathedralized ceiling at R49 requires rafters deeper than 2x12s. To do an unvented roof splitting the R between above-deck foam with fiber in between requires that at least 40% of the total R be on the exterior.  That means at the ~R50 code-min you need at least R20 on the exterior, which with all EPS would be 5" of foam- which is doable.   You could do it in 3.5" with polyiso if polyiso didn't have the de-rating problem.    But if you put 2" of polyiso next to the roof deck (labeled at R12) , with   2" of EPS (R8-8.4) between the polyiso and a nailer deck you're a bit over R20 from a labled perspective, but unlike 3" of polyiso, it still performs at R20 when it's +10F outside.  This is because EPS performance increases somewhat as the mean temp of the foam drops, and the EPS keeps the polyiso warm enough to stay in it's decent performance temperature range.  With that stackup you can use R28-R30 rock wool tight to the roof deck with 2x8 rafters (or 8" of half pound open cell foam in a trussed roof, which installs in 2- passes.)

For cathedralized ceilings aka "compact roof" in the ba-1005 document they're suggesting that R50 is the approximate financial balance point. Bear in mind, that's not the center cavity R-value the way code minimums are defined- it includes the thermal bridging of the rafters.  To get there you're really looking at about R60 center cavity, and R25 exterior foam  which adds an inch to the exterior stacup.  But that's still cheap if you're using reclaimed foam.  Taking it to R60-R65 would pretty much guarantees you NEVER see ice dams on your house, even in a winter like we just had.

Even though it was targeted at high performance retrofits, the Mass Save Deep Energy Retrofits Guide has a lot of relevant information on how to do new construction builds of high performance houses. It's worth downloading and studying. Some things are easier & cheaper to do as new construction. For instance, insulating the foundation can be done with insulating concrete forms in one schedule-time saving step.  Or, putting insulation under the basement slab is cost-prohibitive in a retrofit, dead-cheap in new construction, but you have plan for the 2-3" of EPS before pouring the footings to ensure you have the right depth, etc.  (The slab foam is important for keeping the summertime mold factor down, since the deep subsoil temps are well below the summertime air dew points. If you store something in a cardboard box on an uninsulated unheated slab in RI it's almost guaranteed to get moldy, even if there is a vapor barrier under the slab.)

On your revised wall stackup, the MemBrain behind the blue-board isn't absolutely necessary, since you have a sufficient R-ratio of foam/fiber for walls to be just fine without it.  It doesn't hurt anything though, and it may be easier to detail for air tightness than the gypsum board. It comes in 100' rolls of different widths, starting at 8'. (An 800' roll is about $100 USD from the rare retail outlets that carry it, you may find distributors carrying the 10' rolls for about the same money.)  You can think of it as cheap insurance.

Rigid rock wool is a great alternative to rigid foam, but would require 2 layers to hit R15, and it's quite a bit more expensive than polyiso, WAY more expensive than reclaimed polyiso.  But it's completely fireproof- can't knock it.  The fact that rigid rock wool is far more compressible than rigid foam is another factor to keep in mind- it takes an experienced installer to make truly flat walls using the stuff.  But since you're putting R15-ish foam on the exterior you don't really care about the ability of the sheathing to dry toward the exterior, since it will always be above the dew point of the interior conditioned space air, you can make the interior fairly vapor open without risk of wintertime moisture accumulation, and let the sheathing dry toward the interior. If you were only going for R5 or less on the exterior it would matter quite a bit, since you'd need at least R7.5-R8 with R23 cavity fill to keep the sheathing warm enough to not load up. With the exterior R that low the MemBrain becomes far more important too.

Huper ZIP is more expensive than 1/2" CDX ply + housewrap, but it's a labor saver.  If your construction labor is undocumented people from the Azores who only speak Portuguese that might not matter as much as if they are union-scale carpenters. But the cost of the interpreters necessary to get the detailing information across adequately adds up too...  It's fine to build with CDX or cheaper OSB and housewrap, but it's quicker to build tight houses with ZIP, which is why from a "time is money" scheduling point of view builders in MA are trending toward greater use of ZIP.   Note- with a foam-over build like this you'd still want to use a crinkle housewrap with innie-windows even if using  ZIP sheathing.  ZIP makes the exterior side air sealing detailing pretty quick & straightforward compared to CDX or standard OSB.

The 10BTU/ft number is an extremely crude rule of thumb of where the  likely worst case upper bound would on a house with R30-whole wall house, U0.24 windows, and an R50 (whole-assembl-R) roof.  IRC 2012 code-min houses come in at ~12 BTU/ft these days- higher-R houses often come in under 7BTU/ft.  (My sub-code 2x4 framed 1.5 story 1920s bungalow comes in at about 15 BTU/ft after some retrofit air sealing and foundation insulation, and that's with walls 3x as lossy as what we're talking about.)  Not all conditioned space floor area footage is the same from a heat load point of view either.  The heat loads of below-grade or partially below grade square footage is also quite a bit lower than  fully above-grade floors, since a large fraction of the wall area is not exposed to the 10F minimum temp. The soil even a foot below grade never drops below the weekly average outdoor temp, which is quite a bit warmer than +10F, even during polar vortex weeks, and below that it's warmer still.  With an R15 (IRC code min) to R22 (typical ICF) foundation and a 2-3" of foam under the slab the below-grade losses are truly miniscule.  The basement would want to be it's own heating/cooling zone though, since it's heat loss characteristics have weekly/monthly variable related the the slowly changing soil temps, and while the outdoor temp is still the driving factor, the basement's loads don't swing nearly as far as the above grade floors.  Most basements (even walk-outs) don't need more than a 3/4 ton mini-split to heat, even in a code-min house.

But that's why the load numbers need to be updated with any design changes on the house, and have to be known pretty solidly before picking a heating & cooling solution as expensive as geothermal.  With mini-splits the cost of oversizing by 50% is pretty small in the grand scheme of things, but oversizing geo by 50% is an insanely expensive proposition, which is why most are intentionally undersized a bit, letting the resistance heater strips cover the shortfall from the ~95th percentile temperature bin or colder.

Posted By joe.ami on 17 Apr 2015 10:34 AM
In my AO where no nat gas is available, propane heat is aout a wash with electric baseboard. ASHPs are second best with or without propane back up and GSHPs are best (in the context of operating cost. In the context of first cost (to purchase and install a system) cost v benefit does not always favor geo.
It would suggest if you haven't found a builder yet who's suggested anything other than propane that you keep looking for a more evolved builder.

In the context of  lifecycle cost , at RI/MA/CT type geo pricing GSHP doesn't come close to even standard split system heat pumps, let alone high efficiency mini-splits.

And the mini-splits are getting better with every product release.  In an RI climate the new Fujitsu _ _RLS3H series wall-blob types will be hitting a COP of  4 or better for the all-in power use. Even the mini-ducted _ _RLFCD casettes will be hitting around 3.3-3.5 (and still have the capacity at -5F, which is 15F colder than his 99th percentile temp bin)- better efficeincy in a ducted mini-split than the ubiquitous and well regarded Mitsubish FE_ _NA wall-blobs.  The mini-split solutions are more expensive than a standard ducted split system, but it's nowhere near the cost of geo in this region, and the efficiencies of the new stuff is comparable to "typical" (if not "absolute best practices") GSHP systems.    There is at best marginal, if any efficiency advantage at the warm edge of climate zone 5 (that used to be the warm edge of zone 4 only 5 years ago), so rather than spending (the quoted) $78K or even $40K on GSHP, it's better to spend the real money on a way-better-than code building envelope.

In colder climates, and in locations where a 4-5 ton GSHP system can be had for under $30K the financial balance points will be different.  I wish geo was cheaper and better around here, but there's no recent evidence to support a rosier view. YMMV (and I hope it does!)  I don't know if it's a matter of low competition, gold plating by contractors, drilling through granite, or something else, but the quotes here are ridiculous compared to what comparable capacity geo systems are alleged to cost in other places.

I think we would go outie then... the admiral wants the sill for the cat...
with a 2x6 wall I doubt you would have much of a sill anyway..maybe a few inches at best?

That changes my wall stack then I guess..

Thank you so much for the links to the reclaimed polyiso.. is there anything I need to be concerned about.. smell? mold? etc?

For siding we may be using cedar shingles (not planks).. so I see that as an issue with the wall design.... how are you to attach each shingle? It seems like this wall design only allows for planks?

I will inquire to the special Anderson glazing.. I did see the hardy 3 pane windows, but they are quite darker and harder to see through... so we skipped them.

for the walls...
I am at the point where I need to turn this conversation into a materials purchase.
So.. it seems like 3" polysio on the outside.. rock wool on the inside with a membrain.. with an "outie" window..
for the roof it is the same except I would use spray foam in the rafters instead of rock wool and maybe 2 3" polyiso?

I still have not found a decent geo thermal person that isn't milking the higher fees.. AND knows their stuff... 78K is crazy..
-Ken

"In the context of lifecycle cost , at RI/MA/CT type geo pricing GSHP doesn't come close to even standard split system heat pumps, let alone high efficiency mini-splits."

That may be true, which is why I learned awhile ago to preface things with "in my A.O." and such.

"I still have not found a decent geo thermal person that isn't milking the higher fees.. AND knows their stuff... 78K is crazy.."

Context means a lot. 78K would be uncommon in my AO, yet I've had 3 different bids with higher price tags lately. While most of our systems are 3-4 ton WTA in the 20K +- range, these clients wanted very sophisticated water to water and water to air systems, some with pool heat two with radiant, some with ice melt. You would be suprised how many people try to pile everything on to geo and then say, "I can't afford that so I just went with a propane furnace". If they just went with a WTA system in my AO it is often less than 5k more after tax credits to go with geo vs a high end propane furnace and high seer AC.

We have built residential geo systems from $20K to $300K. Calling $78K milking higher fee and crazy without knowing what is included is not very objective.

Used foam sometimes has damage, and used roofing foam sometime has some variable thickness issues due long-term shrinkage/aging under ballasted roofs, etc., but that's usually not a wall-flatness issue if you keep it to 1-2 layers of foam.

I've seen reclaimed foam that looked perfecte and measured true to factory dimensional tolerances, and I've seen stuff that had been under a leaking roof long enough to sustain ice & insect damage (priced accordingly.) Expect some amount of scrappage, but it's usually less than 10%. If you're pre-buying, don't leave it out in the sun & rain- put tarps over it to protect it. Polyiso can soak up a lot of water if you leave it the open or floating in puddles, EPS and XPS are degraded by UV if sun-drenched for the summer.

The exterior roof foam has to be at least 40% of the total roof-R to be able to use open cell foam on the interior. From a total value proposition it's worth going with 5-6" of exterior rigid foam to be able use much cheaper (and greener) open cell foam on the interior. If going with reclaimed rigid foam that's even more true. It's worth seeking out a GC or roofing contractor familiar with thick foam on the roof exterior. That's fairly common in commercial roofing (where often all of the insulation is exterior foam, but is still a bit rare in residential work.  At 6" it's still pretty easy to hit the rafters with the pancake-head timber screws that tie the nailer deck & foam to the structure, but it takes a real artist to do that at with thicker foam.  The screws have to penetrate 1.5" into the rafters, and need to be at least 24" o.c. . Those are some pretty long screws, and the hardware budget adds up too.

That is fair..

3400sq/foot home  with the insulation talked about here.  R30+ on walls, R50+ on roof with open cell spray foam on rafters.   MemBrain seal on interior.
Dual Pane windows from Anderson 400 series.  There is a 1000 extra sq/feet for a walkout basement that will not be finished to begin with but will have to be factored into HVAC. Four zones...
We are looking at raident heating at least in the basement floor..
The 78K included (before gov discount)
Vertical closed loop – Two borings with drilling.
They speced out TWO heat pumps.. one for basement and 1st floor , another for 2nd floor.

I just feel these specs were high..

Basement, First and Second Floors

• Area to be conditioned: approx. 4,270 sq. ft.
• Conditioned space Basement – one zone; 1st Floor – two zones and 2nd
• Floor – one zone
• Building construction: New, well insulated
• Estimated heating load: 70,900 Btu/hr
• Estimated cooling load: 30,400 Btu/hr

With the rigid foam on the outside (3" on walls, 6" on roofline) I would think that would impact the BTU/hr calc?

Comments?

I was very concerned about the electricity bill for this system.. and like most were thinking basic propane was cheaper?

-Ken

Once you start adding in radiant price rises rapidly. I had a similar job recently that the geo was about 30K more than the propane system, but more than 30 of that was brought back by the tax credit.
When you do geo hydronic, you often back up with propane meaning you buy both systems which adds up very quickly. radiant floors can add $6-10SF depending on who's buying the insulation and how controls are cost in.
Geo hydronic is also extremely uncommon work so you will pay a premium for some one who knows how or even more for someone who doesn't.
Tell us what the quote is for the high end (not code minimum) propane system with radiant and that will be something we can compare to.

Geo usually beats any source of fuel by price, with the exception of someone chopping wood for free. Given the higher costs of propane, geo usually is a no brainer.

High quality radiant floors usually double the upfront costs, but they also reduce the geo operating costs up to 50% compared to radiant which requires higher supply temperatures. There is no free lunch in this world, you pay now or you pay later.