Just heard from the folks whose home I completed in December - they sent me six months of electrical bills, mid Dec thru mid June - heating portion is around $230. Thats the total, not monthly. 1500 SF ranch with 1400 SF tempered unfinished basement. R30 walls, R60 flat attic, standard Andersen windows, R33 basement walls, R20 underslab, Airtight - <1 ACH@50 pascals. Heat is geothermal which was overkill, with HRV. This year I'm doing R-38-40 walls & triple glazed windows. AND, no solar panels.

Congratulations.

How did you caulk the framing? Did you caulk everything as you framed or did you caulk seams after the fact?

Posted By Bob I on 28 Jun 2012 12:37 PM
Just heard from the folks whose home I completed in December - they sent me six months of electrical bills, mid Dec thru mid June - heating portion is around $230. Thats the total, not monthly. 1500 SF ranch with 1400 SF tempered unfinished basement. R30 walls, R60 flat attic, standard Andersen windows, R33 basement walls, R20 underslab, Airtight - <1 ACH@50 pascals. Heat is geothermal which was overkill, with HRV. This year I'm doing R-38-40 walls & triple glazed windows. AND, no solar panels.

I'm a bit confused about the solar panels- does the house with the $230 heating bill have/not-have solar panels.  It reads as if the new house with the somewhat lower-loss walls won't have them, implying that the current house did have them.

Mind you this was one of the mildest winters on record for New England, but even at 2x it would still be pretty cheap heating.  I suspect the windows were a pretty big chunk of the total load given the tightness and moderately high-R.

How many tons geo?

Caulk- I used EDPM gaskets at the sill & plates (conservationtechnologies.com) and used my foam gun wherever possible & a few tubes of Geocell caulk. Also ZIP sheathing.
Sorry about the fuzzy solar panel sentence - we did not use any panels. We installed a three ton geo system (my first) but when I finally, belatedly received a copy of the manual J calcs, it was obvious that the installer used "standard" specs, not the ones for this house. Had they figured it correctly it should have been a two ton system. The client had asked for a geo system & spec'd the units he wanted. I would have preferred using minisplits which would have saved considerable upfront costs and probably not affected the cost to heat. We also used a heat pump water heater.

I dunno, if you'd gone with mini-splits it might have cost a whopping $290-300 instead of $230 to heat the place this past winter- you sure the customer could afford the $60-70 uptick in annual operating expense?

Of course if they'd spent the delta in upfront cost of the geo vs. ductless on PV they might be knockin' on net-zero (at least on space heating.)

Good job on getting the heat load down!  It'll be interesting to see if the cooling season load also sufficiently well-bounded.

And the increase in cost is due to...? They're both heat pumps, although the air to air is using lower temps. Would have saved probably 15K in capitol costs, so 15K over 20 years.... and this is exactly where PV makes sense. First step - minimize loads!

The increased operating cost is a reflection of the average efficiency of ground source vs. ductless air-source in a NH climate. In typical installations geo averages a COP of about 3.5. Better-class mini-splits in this climate will average 2.7-ish for COP most winters, but closer to 3.0 this past winter due to the warmer average air temps.

Best in class ground to air geo will be in the 4s, (but I've yet to see any evidence that the local industry average hits that.) If this installation is really averaging 4.0 a mini-split solution would have cost $300-340 to run. That's still peanuts when you consider the difference in capital cost between 2-tons of geo to even 3 tons of mini-split. Whenever I've run real numbers on real projects and the design condition heat load was under 2-tons the mini-split + PV solution is a better deal until Federal subsidy for geo is factored in, and even there it sometimes wins. With PV and geo both heavily subsidised, and subsidized differently in different states it all kind of up in the air- you have to do the real accounting.

Of course geo heating contractors will point out that it's not apples-to-apples, since ducted (or hydronic) geo delivers heat to each room, and that a 8-10 head ductless solution is very expensive, but that feels like a willing ignorance of the fact that homes with extremely low heat loads have very low heat loss from any one zone or room, reducing the room-to-room temperature deltas to inconsequential levels if you design it right, and place the mini-split heads in the highest gain/loss spaces.

At last season's prices $230 would have purchase 50-60 gallons of heating oil. It's EASY to make the argument for geo against propane or oil, but a bit harder against ductless, provided the peak loads are well bounded and you don't have the odd very-lossy room without a ductless head.

Gotta poke at the geo pros dontcha Dana .
I agree sounds like geo was over kill.
That ductless may not communicate to all corners of the home as well is self evident. Whether or not the home is designed in a way that ducts are unneccessary is case by case.
Whether or not a central minisplit meets code or mortgage requirements for "central heating system" is also going to vary.

Good results on the heating bill, but I think that this is what should be expected for a new house of this size in a predominately heating environment. You prompted me to check my natural gas costs over the past two years that includes heating (~7000 degree days historical avg.), hot water (supplement to solar thermal), and cooking. My house is similar in size (but conditioned crawl space rather than basement) and insulation package to the one you described, although less wall insulation (R27) and leakier (2.35 ACH at 50 Pa). Using a modulating, condensing furnace (Johnson Controls York YP9C060), my natural gas bills were $293 for July 2010 thru June 2011, and $311 (est. for last month) for July 2011 through June 2012, so similar costs to the one you described. (Electric bills are always just the connection fee due to solar PV.)

So heating costs are similar, but I expect that the cost of the natural-gas-fired, hot-air furnace was much less than the geothermal system. You seem to brag that the house had no solar panels, but I propose that your customer would have done much better to choose a cheaper heating system, and use the difference in cost to buy a solar PV and/or solar thermal system. Bob, maybe you were saying this same thing in your second comment.

Dana always suggests using a minisplit, but I propose that if natural gas is available, and if A/C is not required, that a modulating, condensing, natural-gas furnace is as efficient or more efficient than a minisplit, and probably has a considerably longer lifetime. Using Dana's 2.7 COP for a minisplit (which varies with location), and the site-to-source energy delivery ratio of 1/3.340 for generation and delivery of electricity to the house (EPA report "ENERGY STAR Performance Ratings, Methodology for Incorporating Source Energy Use, August, 2009"), the overall efficiency of fuel thermal energy to delivered heating energy is 81%. The furnace referenced above is claimed to have an efficiency of 98% adjusted to a site-to-source ratio for natural gas of 1/1.047 (same EPA report), then the overal efficiency is 94%. So to really go green in a heating only environment... :-)

I used EDPM gaskets at the sill & plates (conservationtechnologies.com)

At only $0.80/linear foot, those are less expensive than I would have thought. I'm sure a lot of builders find it hard to go there because the "alternative" sill seal is only about $0.10/linear foot. How do you handle the caulking during framing? Is there one person responsible for the caulking or does everyone grab the gun before assembly?

Have you ever tried advanced framing?

Posted By Bob I on 28 Jun 2012 12:37 PM
Just heard from the folks whose home I completed in December - they sent me six months of electrical bills, mid Dec thru mid June - heating portion is around $230. Thats the total, not monthly. 1500 SF ranch with 1400 SF tempered unfinished basement. R30 walls, R60 flat attic, standard Andersen windows, R33 basement walls, R20 underslab, Airtight - <1 ACH@50 pascals. Heat is geothermal which was overkill, with HRV. This year I'm doing R-38-40 walls & triple glazed windows. AND, no solar panels.

What framing method & insulation type did you use to get R30 walls & what will you use to get R40 walls?

Posted By Lee Dodge on 30 Jun 2012 11:58 AM
the overall efficiency of fuel thermal energy to delivered heating energy is 81%. The furnace referenced above is claimed to have an efficiency of 98% adjusted to a site-to-source ratio for natural gas of 1/1.047 (same EPA report), then the overal efficiency is 94%. So to really go green in a heating only environment... :-)

I think Dana is a little more even handed than always recommending mini splits........

We enjoy both cheap nat gas and electricity in our area and I think in the type of high performance homes you and OP describe, natural gas would be the way to go here, whoever if in the out skirts and nat gas isn't available air source would be fine.
For larger loads ('round here) with new construction and a 30% tax break geo will save over nat gas in <10 years in most cases where installation includes duct system.

Joe,

I know this is a tricky question, but what would typical costs be for a heating-only system without hot water for a the 1500 sq. ft. one-story ranch described above in New Hampshire (or in your area) for the following:
1. hot-air furnace with ducting
2. minisplit (single outdoor unit, with two or three indoor units?)
3. geothermal

Posted By Lee Dodge on 30 Jun 2012 11:58 AM

Dana always suggests using a minisplit, but I propose that if natural gas is available, and if A/C is not required, that a modulating, condensing, natural-gas furnace is as efficient or more efficient than a minisplit, and probably has a considerably longer lifetime. Using Dana's 2.7 COP for a minisplit (which varies with location), and the site-to-source energy delivery ratio of 1/3.340 for generation and delivery of electricity to the house (EPA report "ENERGY STAR Performance Ratings, Methodology for Incorporating Source Energy Use, August, 2009"), the overall efficiency of fuel thermal energy to delivered heating energy is 81%. The furnace referenced above is claimed to have an efficiency of 98% adjusted to a site-to-source ratio for natural gas of 1/1.047 (same EPA report), then the overal efficiency is 94%. So to really go green in a heating only environment... :-)

The COP average of 2.7 is an appropriate estimate for best-in-class ductless in NH, the location in question here.  (Were it north of the Whites it may not even be that high.)

While the net efficiency of the grid makes gives the theoretical ductless a net source-fuel efficiency of ~81% if the NH grid was all gas-fired sources, and running at the US average grid efficiency (rather than combined-cycle).

In the real NH the grid is only about 30% from gas, with about 47% of the total kwh from carbon-free sources (~30% nuke, ~12% hydro, ~5% other renewables) according to EIA data.

The net carbon footprint of a heat pump in NH is well below that of condensing natural gas heating, even at an average COP of 2.7  But cost-wise it's still somewhat cheaper to heat with 80% gas in those parts of the state on the gas grid.  About half the homes in NH are currently heated with oil & propane at an average as-used AFUE under 80%.

In even slightly warmer climates the average COP climbs to about 3, making the source-fuel-efficiency something of a wash compared to condensing natural gas.  But the grid-sources and carbon footprints will vary- on a mostly coal-fired local grid you'd need to average a COP better than 5 to break even on carbon emissions with condensing gas.

When looking at ultra-low heat loads and the costs of the geo to support that load running the numbers on how much PV the cost delta between geo & ductless buys can be instructive.  It's not always clear which one will win the financial analysis, but any renewable power both sourced and used on your side of the meter has a very low carbon footprint indeed.

Posted By Dana1 on 02 Jul 2012 12:47 PM
...snip...

In the real NH the grid is only about 30% from gas, with about 47% of the total kwh from carbon-free sources (~30% nuke, ~12% hydro, ~5% other renewables) according to EIA data.

...snip...

I would suggest that we really do not know what the carbon footprint of nuclear energy is at this point.  We in the U.S. have refused to agree to a solution to the nuclear waste problem.  Currently we are simply abandoning the nuclear waste at the generating plants.  Therefore, should we assume that we simply lose that land, plus sites for future nuclear generating plants, for the next 10,000 to 1,000,000 years, so that the land cannot be used for trees that can help in carbon capture?  How about the energy costs to maintain barriers (fences, concrete entombment, signs in whatever language is in use at the time, or whatever) to keep people from accessing the radioactive waste either accidently or on purpose for 10,000 years or more?

I am not suggesting that storage of waste at nuclear generating plants is a good idea, and the Fukushima disaster suggests that it is not, but that is the current approach being used in the U.S.

I would say that you cannot claim that nuclear energy is a low carbon footprint approach until you come to a technical and political solution to the nuclear waste problem, and then you can evaluate the carbon contibution.  If we end up using rockets to send nuclear waste to the sun, we need to account for that energy requirement.   

The physical volume of spent nuclear fuel is so remarkably small relative to he energy output that to argue that it's storage/disposal carbon footprint would be substantial is absurd. The bigger lifecycle carbon footprint in nukes is the volume of concrete baked into the plant itself, and a smaller amount for the enrichment centrifuges. The fact that the Seabrook powerplant has already been built means whether you turned it off today or re-licensed it for another 50 years the construction carbon has already been spent. The marginal carbon cost per kwh is quite low and many orders of magnitude behind condensing natural gas. Nukes are at least as "carbon free" as most "fat-free" foods are truly sans-fat, if not exactly zero-carb, it's low enough to be considered zero for any practical comparative purpose.

While there are many valid concerns & criticism to be leveled around the environmental impact and managment costs of nukes, carbon isn't really one of them. If you're going to bring all of it to the table you can't ignore the other environmental issues per BTU surrounding natural gas production. (My biggest issue with nukes is that rather than being "too cheap to meter", for any nukes that aren't already built the lifecycle cost per kwh is "too expensive to MATTER".)

The bad about heat pumps is that they all rely to some degree on inefficient (relative to condensing burners) thermal grid sources. But the good thing is that (for the most part) the grid is getting greener and less reliant on thermal power plant generators over time, which greens-up the heat pump in the process.

In NH most gas-fired thermal generators built in the past 15-20 years are combined cycle units, with burner-to-load efficiencies more than 1.5x (nearly 2x at full-fire on a cold winter day) that of the conventional thermal plant average, but I don't know what fraction of the of NH total that represents. Between just the Newington & Granite Ridge plants it's a substantial amount of juice (over a gigawatt of output in just two plants), so it may be a decent fraction of the gas-fired slice of the pie. In an all combined-cycle gas fired grid the source fuel efficiency with a COP=2.7 heat pump would be over 120%, an efficiency unattainable with condensing gas furnaces & boilers.

Bottom line, when assessing the relative efficiency or verde-tude of heat pumps the particulars of the local grid matter more than national average numbers. NH is both lower-carb than the nat'l average, and trending in the right direction.

I should have mentioned that the house has a number of south facing windows which contribute to the heat gain. This house was 2x6 walls with cellulose and 2" of XPS on the exterior. Cap is a flat attic with R-60 cellulose. Basement has 2" closed cell spray foam and R-21 fiberglass on the walls and R-20 under the slab. the slab is completely thermally broken. My next generation of homes will have double 2x4 walls with cellulose, the same basement setup and either an R-60 flat attic or R-60 slopes using TJI rafters and triple glazed windows. The majority of the air leakage (<1.0) seems to have been the (standard) Therma True doors so we're going to multi point lock system as a tighter alternative.

I've used direct vent high performance gas (propane) boilers and furnaces for thirty years; good product. The difference is that in a very tight superinsulated house the temps are consistent throughout the house, so you really do not need ductwork. The ideal would be a minisplit and enough PV to run it. (and at $500 per year you wouldn't need a very big system.) A ducted FHA system would run 12-15K; a minisplit 5K. The owner had been dreaming of a geo system for years, so that's what we installed. Bottom line: get the heat loss - and air tightness down first, then decide on the heat source, then how to power it.

The real issue with sill seal is that you spend $.10/LF, you get an effective value of between -0- and .01. It's junk. Accept that and move on. I design the houses to be built by good, average framers. They tape the ZIP sheathing which I can see; I handle all the other air sealing issues.

I think it would be accurate to say that we do not know what the full environmental impact of nuclear energy is at this point. There is a lot more to "green" than just carbon footprint.

The talk from Hydro-Quebec is that NH will be taking more hydro power as well, displacing gas, but that carbon footprint is pretty big too.

Posted By jonr on 02 Jul 2012 03:16 PM
I think it would be accurate to say that we do not know what the full environmental impact of nuclear energy is at this point. There is a lot more to "green" than just carbon footprint.

Most of the environmental impact of the Seabrook NH nuclear plant is already written in stone (or concrete), barring a Fukushima type event, the likelihood of which is small,  but non-zero.  The marginal/incremental environmental damage per kwh is also small, but non-zero, but less per kwh of natural gas, once the plant has already been built.

The incremental environmental damage of condensing natural gas space heating is multi-fold, the easiest of which to quantify being the atmospheric carbon output. It is by no means limited to carbon or methane release issues, even if it's about as green as it gets in the fossil-fuel biz.

Space heating loads peak at night, during off-peak hours, and when nukes are such a large fraction of the base load generation (~30% in the case of NH), they get forced into in power-dumping mode when the output exceeds the total grid load, sending the excess  up the cooling towers/rivers/ocean as heat.  Under those conditions the environmental hit of the excess is being taken (even increased) without any energy use benefit.  This is done because very slow turn-on ramp is days rather than hours long, so while they might be able to turn them down during the low-demand hours, they don't, in order to meet the anticipated demand of the following day. (This is why France's heavily nuclear grid is so screwed up- importing peak-power at a premium, and selling off-peak at a loss every night to Spain & Italy.)  Using the off-peak output of a nuke to heat houses as opposed to heating coastal ocean water (the NH case) seems like a greener way to use the grid that exists, rather than some idealized grid of our dreams.

But the NH grid is growing greener over time.  As recently as 2000 coal and oil together accounted for nearly 40% of their grid-source kwh, now less than 25%, the difference being picked up primarily by (predominantly combined-cycle) gas fired generation.  Between the lower-carbon (and other emissions) fuel and the higher thermal efficiency the difference is pretty significant.  NH has committed to a Renewables Portfolio Standard of a ~24% renewable sourced grid by 2025.  They've already over 15%, and they may hit 24% the target early.