Posted By Amazer98 on 03 Jan 2012 01:26 PM
I'd love to do something more environmentally correct than burn oil. Propane is somewhat better for the environment, but I estimate it would cost us at least $400 and probably more like $500 more per year.

Geothermal sounds great, but I understand these systems are expensive, particularly when being retrofitted. Don't know of anyone local who has one, but I've heard there are a few guys in the area that specialize in installing these systems. Still, $20K+ is a bit out of our range!

There are a couple of coal plants operating in southern NH but the vast majority of fossil-kwh in New England is from natural gas, and a growing fraction of that is from combined cycle plants with ~50% average thermal efficiency. 

Not all fossil-kwh are the same: A  30% efficiency coal plant cranks out 4x the carbon as combined cycle gas plant, and still more than 2x that of an old-school 30% gas plant.

Very little of the power grid in NH is from oil, but surprisingly in CT it's still more than a single-digit percentage.

There's also a moderate amount of nuke in the NH mix for most utilities.

The carbon output of an oil-fired home heating plant is actually LESS per BTU of output than with propane, despite oil being dirtier in other emissions like sulfur & soot and propane has about 2x the carbon footprint of natural gas per BTU-delivered.  Most propane production comes from oil-refining, so price-wise it's going to track oil, but a higher price per BTU for the foreseeable future.

With all environmental aspects factored in, keep the oil burner if it's in good shape, and buy a mini-split (or multi-split) air source heat pump and- use it as a point-source for overheating one room or zone in much the same way as you would use a wood stove.  In southern NH a decent 2-ton (~$5K, installed) will run a COP of 2.5 or better most of the time, and during the spring & fall it'll BEAT geothermal on whole-system efficiency.  At +15F most are still hitting in the mid-2s for COP, but will drop to below 2 somewhere around +5F.  At part load and 35F+ outdoor temps these things are usually rockin' the socks off geo on efficiency, even if they're sub-2 running flat-out on compressor speed at 0F.  (Check out the part-load COP of the Fujistu 12RLS (1-ton) at 30F in this 3rd party testing. See Figure 5 page 10.) 

With an open floor plan or open doors on the first floor a single mini-split can cut your oil use in half or more, even if you still need to fire up the boiler to stay warm when it's -15F outside.  The mean January temp for Manchester or Nashua is ~25F, a temp at which at mid-speed a good mini-split is running a COP of ~3.0. When pumping and air-handler power is factored in, that's about as good as geo gets in the same neighborhood.  If your home's heat load is under 25K @ 25F a 2 ton mini will pretty much carry the whole load.

Marc Rosenbaum (an energy efficiency contractor/consultant) yanked the nearly-new Buderus out of his well insulated house on Martha's Vineyard and has been heating the place almost entirely with a 1-ton minisplit, and writes about it in his blog here-and here-and here- and here.  Being a bit warmer than southern NH his average COP may be north of 3, whereas yours would likely undershoot that a bit due to lower efficiency at your deeper lows, but the overall experience could be similar. 

The cost of mid-winter heating with a mini-split with 15cent electricty and a COP of 2.5 is about half that of heating with$3.50 oil in an 85% burner:

1kwh x 2.5 x 3412BTU/kwh= 8530BTU delivered, for 15 cents, or ~56,8500 BTU/$

0.85 x 138000BTU/gallon= 117,300 BTU for $3.50, or 33,500 BTU/$

During the spring/fall the AFUE  of the boiler falls off, and the COP of the mini-split soars, so your annual heating bill would be something like half, if you idled the boiler except during the coldest days of the year.

Posted By Dana1 on 04 Jan 2012 05:38 PM

The carbon output of an oil-fired home heating plant is actually LESS per BTU of output than with propane, despite oil being dirtier in other emissions like sulfur & soot and propane has about 2x the carbon footprint of natural gas per BTU-delivered.  Most propane production comes from oil-refining, so price-wise it's going to track oil, but a higher price per BTU for the foreseeable future.

With all environmental aspects factored in, keep the oil burner if it's in good shape, and buy a mini-split (or multi-split) air source heat pump and- use it as a point-source for overheating one room or zone in much the same way as you would use a wood stove.  In southern NH a decent 2-ton (~$5K, installed) will run a COP of 2.5 or better most of the time, and during the spring & fall it'll BEAT geothermal on whole-system efficiency.  At +15F most are still hitting in the mid-2s for COP, but will drop to below 2 somewhere around +5F.  At part load and 35F+ outdoor temps these things are usually rockin' the socks off geo on efficiency, even if they're sub-2 running flat-out on compressor speed at 0F.  (Check out the part-load COP of the Fujistu 12RLS (1-ton) at 30F in this 3rd party testing. See Figure 5 page 10.) 


Marc Rosenbaum (an energy efficiency contractor/consultant) yanked the nearly-new Buderus out of his well insulated house on Martha's Vineyard and has been heating the place almost entirely with a 1-ton minisplit, and writes about it in his blog here-and here-and here- and here.  Being a bit warmer than southern NH his average COP may be north of 3, whereas yours would likely undershoot that a bit due to lower efficiency at your deeper lows, but the overall experience could be similar. 

The cost of mid-winter heating with a mini-split with 15cent electricty and a COP of 2.5 is about half that of heating with$3.50 oil in an 85% burner:

Dana,

Your post was very illuminating.  I had no idea that oil had less of a carbon footprint than LP gas.  This makes me feel better about burning oil, since I can't get the economics of propane to work, at least with current local fuel pricing. As you know, propane is also derived from natural gas production, so there's the possibility that the current development of gas production in North America will drive down propane prices... but it's an open question whether propane will get within spitting distance of oil prices on a "per BTU" basis.

I spent a good chuck of last evening reading through Marc Rosenbaum's blog.  I hadn't even know what a mini-split was until I saw the photos. Now I know-- you see them in hotel rooms across the country.  Despite their efficiency, I don't think they match our needs.  For one thing, I can't think of a suitable location in our house.  Ideally, we'd put one in our family room, but there really isn't adequate wall space for one, except perhaps behind the TV cabinet... but then the airflow would be impeded.  Anyway, we already have a wood stove in that room, so the final effect would be somewhat like Marc's with a mini-split, baseboard, and wood stove within 8 feet of each other.  I'd never live it down!

I admire what Marc is doing in his quest to eliminate fossil fuel burning and return energy to the grid.  It's interesting reading and a valuable endeavor.

Hey, I have a question: How does "indoor reset" compare with "outdoor reset"?  Some boilers like the Burnham MPO-IQ have an option to add outdoor reset, while other boilers like the PurePro TRIO come with indoor reset (you probably could add outdoor reset to this, right?).  Is one type of reset better than another?  Also, can you use regular programmable thermostats with these reset controls?

Thanks,
Andy

The fraction of propane derived from natural gas is currently a small fraction of the total, and propane is a very small fraction of the BTU content of natural gas, but they extract the heavier molecules from n.g. in order to prevent condensation in the pipelines and distribution equipment. The quantity of propane in raw n.g. will vary by source - coal seam gas has a higher methane content than oil-field & shale sources and almost no propane. Gulf coast gas is "dry", with only ~2% propane, whereas some "wet" shale formations can even have on the order of ~10% propane. In the Marcelles & Utica shale formations of the northeast the fraction of propane is higher than the average when looking at the US gas production as a whole, but still a small fraction of the total BTU content. Since the primary non-industrial uses of propane compete directly with petroleum liquids (mostly heating oil and motor fuels), the price of propane will track oil (and not natural gas) prices for the forseeable future, even if the propane from gas processing should overtake that from oil refining.

In this region the majority of propane on the market still comes from crude oil as a byproduct of oil refining. I don't expect that to change in the near term, but possibly in mid term with the ramping up of shale gas production. But it isn't likely to affect the price of propane, even though shale gas development will puts downward pressure on the price of natural gas. Nearly half the propane produced in the US (all sources) is used in the production of chemicals (mostly plastics)- a total volume greater than that used for heating fuel. (I suffer from having a brother-in-law in the gas exploration biz- too much info perhaps? :-) His current project is assessing coal seams in Zimbabwe- yikes!)

Daikin makes a very efficient air-source heat pump with mini-split type compressors that has hydronic output, but to be able to use that effectively in your house would require putting in low-temp radiation like panel radiators or radiant floors. Even with the cost of retrofit low-temp radiation it would still come in under the price of geo, but it will still be more than 2x, possibly more than 3x the cost of a 1-head minisplit.

They make ceiling-mount interior heads for mini-splits that can be made nearly flush with the ceiling, if you can't find a spot for the wall-wort. They also make multi-head versions that can serve up to 8 heads for micro-zoning, but at ~$1.5K per head (installed) it starts to add up. Simple 2 & 3 head versions are more common. (eg Daikin 3MXS24JVJU, or Mitsubishi MXZ3B24NA & MXZ3B30NA, all of which test well in heating mode with HSPF ratings of 9+.)

"Indoor reset" is usualliy refers to a smart algorithm economizer control that "learns" the as-used characteristics of the system, and adjusts output temps & burner cut-outs to the anticipated load on every burn based on recent and longer term system behavior. It attempt to utilize the thermal mass of the boiler & system for maximum efficiency, varying the temperature-hysteresis, and heat-purging the boiler into the system (or indirect HW heater, if you have one) at both the beginning and end of burns to minimize standby losses by "parking" the boiler at a lower temp at the end of each burn. Outdoor reset varies the output temp of the boiler based on the outdoor temperature (a crude heat-loss model). It cycles the burner on/off during a call for heat keeping the output temp within a temperature band, the center of which varies with outdoor temp.

If you use overnight setbacks the smart-economizer will be far preferable to outdoor reset from a functional point of view since it shortens the recovery ramp. It will also outperform outdoor reset if you have enough heat emitters that the output temperatures never NEED to be over 160F even on design day, since the minimum return-water temp for an oil boiler to prevent condensation damage to the boiler is ~140F, and the min-output temp would have to be on the order of 20F above that, making the output temp curve a constant. (With the heat-purging smart economizer the boiler temp can be driven lower than 140F during the heat purge without damage, since the burner isn't firing.) Outdoor reset can be somewhat more comfortable though, since it will limit overshoots/undershoots from the thermostat setpoint better under some conditions, but it will have a higher average boiler temp (=more standby loss), and result in a greater total number of burns (=greater ignition and flue-purge losses.)

Smart heat purging economizers have been around for awhile as retrofit items (Intellicon 3250 HW+, Beckett Heat Manager, etc.), and they really DO work. The more dramatic savings occur when the boiler is more than 2x oversized for the load (which is most boilers in New England and nearly ALL oil boilers, since the smallest burners available are already nearly 2x the design day heat load of a reasonably tight code-min insulated ~2500' house with U0.35 or lower windows.) By reducing the boiler's standby loss an minimizing the number of burns it moves the knee in the part-load efficiency curves well to the left, with a longer flatter plateau. Newer-better triple pass boilers have a very slight edge on combustion efficiency, but bigger efficiency gains due to better insulation. But at 2x or higher oversizing there is still a great deal of efficiency to be recovered via heat purge control (as is heavily marketed with the EK System 2000 steel boilers.) If you're into pondering all this with new boilers, read this:

http://www.nora-oilheat.org/site20/uploads/BNL%20Integrated%20Hydronic%20System%20Report.pdf

Note the part load efficiency curves for the various systems tested in the appendices. The steel boiler w/purge control (system 3, or Appendix 3) was an EK System 2000 boiler, but a $200 Intellicon retrofit economizer can improve performance similarly on many existing oversized heating boilers.

Dana1 said: "The carbon output of an oil-fired home heating plant is actually LESS per BTU of output than with propane, despite oil being dirtier in other emissions like sulfur & soot and propane... "

This statement looks suspicious without even going through the numbers. Hydrocarbon fuels are made up of hydrogen and carbon with some minor impurities (coal can have lots of impurities, but it is not in this discussion). When the hydrogen burns, it combines with oxygen to make water vapor, and when carbon burns it mostly goes to CO2. Therefore, the higher the hydrogen-to-carbon ratio of the fuel, the more water vapor and less CO2 is created. Burn hydrogen, and you get no CO2. Propane is C3H8, so the molar hydrogen/carbon ratio is 8/3 = 2.67. The only hydrocarbon fuels with higher hydrogen/carbon ratios are methane and ethane. In contrast No. 2 diesel fuel (and therefore No. 2 fuel oil) has a chemical formula of approximately CnH1.8n (Heywood, Internal Combustion Engine Fundamentals, Table D.4). "n" is approximately 13 for the mid-range of a No. 2 oil. So the only fuels likely to have lower greenhouse gas emissions than propane are methane and ethane. However, any unburned methane is about 25 times worse than CO2 as a greenhouse gas, and because methane is a very stable molecule, significant amounts often survive combustion, so let's leave methane out for now. Comparing propane and No. 2 fuel oil, we would have to say, that just based on hydrogen/carbon ratio your statement is highly unlikely unless there is something else hiding in the details.

It is easy enough to go into more detail. Propane is C3H8, so a molecular wt. of 44, and when it burns it makes 3 molecules (or moles) of CO2 per molecule (or mole) of propane. Since both propane and CO2 have a molcular wt. of 44, the weight ratio of CO2/propane is 3.00. Heywood gives an average molecular wt. of No. 2 diesel fuel as ~170, so let's construct a typical molecule of C13H23.4 (preserving the critical hydrogen/carbon ratio and haviing a molecular wt. of 179.4), and when it burns it makes 13 CO2 molecules (or moles) per molecule (or mole) of oil burned. The weight ratio of CO2/oil = 13*44/179.4 = 3.19, higher than the ratio for propane combustion. So on a molar basis, oil makes more CO2 per unit fuel mass than propane. How about on an energy basis?

Heywood gives a lower heating value for propane of 46.4 MJ/kg, and for No. 2 diesel fuel of 43.2 MJ/kg. Taking the values above of 3.00 kg CO2/kg propane and 3.19 kg CO2/kg oil, and dividing by the heating values, this comes out to 64.7 kg CO2/GJ with propane and 73.8 kg CO2/GJ with oil. If you liked mixed units, this is 68.2 kg CO2/MMBtu for propane, and 77.9 kg CO2/MMBtu for oil.

The DOE GREET model is widely used to evaluate greenhouse gases, and it comes to a similar conclusion with an even greater advantage for propane, but I am suspicous of the results since the propane industry appears to have sponsored some of the work.

I would say that propane may have some disadvantages compared to oil, safety and maybe cost among them, but greenhousse gas emissions are not a problem with propane.

Let me rephrase my last statement to say: "I would say that propane may have some disadvantages compared to oil, safety and maybe cost among them, but greenhousse gas emissions should be lower with propane than with oil."

FWIW, from the EIA:

http://www.epa.gov/climatechange/emissions/ind_assumptions.html

Yes, the green house gas numbers from EIA for propane and fuel oil are the same as the numbers that I gave (different units) except that I used the lower heating values for the fuels, while EIA used the higher heating values. Lower heating values mean that the water vapor from combustion is assumed to be exhausted as vapor, while the higher heating values assume water is exhausted as a liquid. The convention in combustion engineering and research is to use the lower heating values. That difference in heating values is the main reason condensing furnaces are attractive -- they make use of the higher heating value of the fuel. They often also make use of the exhaust heat by preheating the inlet air with co-annular inlet and exhaust pipes.

I see that they now make condensing furnaces fueled with fuel oil. That surprises me in that any unburned fuel or heavy hydrocarbons would condense in the exhaust system while they are condensing the water. Does anyone here have experience with fuel-oil fired condensing furnaces? Is the exhaust stack clean?

The document I had only recently been looking at when making that statement also included the greenhouse gas potential of all processing/refining/transportation etc, not just the combustion product releases from burning it in a boiler. (So couching it as "carbon output" was imprecise.) But said document is also pretty thin on source-references, so I was remiss in relying on it as a reference. Good estimates of those other factors are hard to come by, and rarely measured directly.

The greenhouse gases released is in production & processing will vary a lot by source & processing requirements, and even natural gas isn't as comparatively carbon-benign as the raw combustion products would suggest- particularly from coal-seam sources, where the major "contaminants" of the goods are CO2 and CO, some of which is released in processing along with some of the methane itself. Lower CO2 content increases the value of a coal seam gas field when it's low enough to pipeline directly without processing, and too high a CO2 content will render it commercially nonviable.

There's a lot of discussion about the quantity if methane leakage on shale gas, but not a lot of data. Some are suggesting that the greenhouse impact per BTU of shale derived fuels from the Marcellus formation are on a par with (or even exceeding) that of coal, but that is currently a highly politicized hotly contested discussion, with many less than well substantiated assumptions & claims. This bit of analysis is oft cited by opponents of shale gas development, and has created quite a splash:

http://thehill.com/images/stories/blogs/energy/howarth.pdf

But there are clearly some very squishy numbers that are hard to nail definitively.

Even if shale fuels prove to be on a par with coal per BTU, gas burned in a combined-cycle gas plant will have half the greenhouse impact of a typical coal plant (but well over the 1/4-1/3 often cited.)

Heat pump technology breaks even on carbon footprint with condensing gas at a COP of 2 with a grid run primarily on combined-cycle gas fired generation. The grid in New England as a whole there is an increasing share of combined-cycle gas, but in NH fossil fuels (all types) account for less than that supplied by nukes (low carb, other issues notwithstanding) and the fraction supplied by renewables (all types) is rising, but still less than 1/4 of the mix. See:

http://www.instituteforenergyresearch.org/states/new-hampshire/

It's fair to say that a mini-split or geothermal solution in NH would have lower greenhouse impact than oil or propane at any efficiency.

I have no direct experience with condensing oil burners, but local boiler-tech scuttlebutt has it that US heating oil isn't up to snuff compared to the lower-sulfur standards available in Europe.

Concerning fuel effects on greenhouse gas emissions, we can follow the example given by folks doing automotive research, and compute emissions based on well-to-pump, and pump-to-wheel, with the whole process being termed well-to-wheel. In the case of furnaces, we can talk about well-to-furnace, and furnace-to-heat (combustion process for fuels). Now the well-to-furnace emissions can be the result of some subjective decisions, but the furnace-to-heat is mostly straightforward. For the amount of CO2 created per unit energy content of the fuel, the CO2 footprint scales with the carbon-to-hydrogen ratio. Fuels with lots of carbon make lots of CO2 and visa versa. The heating value of fuels (energy/mass) also tends to slightly decrease with increasing carbon-to-hydrogen ratio. So, from a combustion standpoint, hopefully we agree that choosing a fuel with a higher hydrogen-to-carbon ratio is desirable to reduce greenhouse gases. The good-to-bad order would be methane (H/C=4), propane (H/C = 2.67), fuel oil (H/C ≈ 1.82, Heywood, ref. prev.), and then coal (H/C ~ 1, http://www.enotes.com/fuels-fuel-chemistry-reference/fuels-fuel-chemistry).

Now wood has an H/C ~ 0.1 (http://phe.rockefeller.edu/PDF_FILES/Wood_HC_Ratio.pdf), but since wood removes CO2 from the air to make cellulose, and then liberates it on combustion, and since trees can replenish the wood supply in a human lifetime, wood is considered to add nothing to the CO2 load during combustion, assuming that it is replaced. The same argument is made for ethanol from crops, biodiesel, and other bio-derived fuels.

Interestingly, the amount of soot (particulates) produced also is related to hydrogen-to-carbon ratio, with higher hydrogen content fuels producing less soot (lots of papers document this, especially for gas turbine combustion). Therefore, for petroleum-derived fuels and coal, the high hydrogen-to-carbon ratio fuels are good from both a greenhouse gas and soot standpoint, with coal ranking poorly in both cases. Wood is good from a greenhouse gas standpoint, but poor to very poor from a particulate matter view.

Considering acid rain, the sulfur in fuels is the predominate contributor. Refined fuels have little sulfur except for heavy residuals like heavy diesel fuels, and coal can have high levels of sulfur. Similarly for heavy metals like mercury, coal is by far the worst problem.

So from a combustion viewpoint, we can label fuels pretty easily in terms of their greenhouse gas potential and their other environmental problem potential. Since electricity makes no greenhouse gases at its end use for heating applications, it has been left out of this discussion. Do we all agree with this end-use ordering of fuels?

The wood fuel carbon thing is also very squishy and a matter of some debate, since it all depends on the forestry practices, and whether that carbon would have otherwise been sequestered in soil/peat etc on the forest floor rather than a "catch and release" policy.

To be sure it's better than taking long sequestered oil-carbon that was last seen in the atmosphere even before the invention of trees, or coal-carbon that came somewhat later.

The lowest carb "fuel" for most homes is still the nega-btus: Improving the thermal efficiency of the building envelope. But even there you can go backwards if your idea of greening up the house is encasing it with 6" of closed cell spray foam, with blowing agents with a lifecycle greenhouse potential in excess of what could have been gained by the lower source-fuel combustion. (Hitting the same R with cellulose would semi-sequester the carbon in the cellulose, with very little processing overhead.)

Then leaving wood out, do we agree on the ordering of the other fuels in terms of their greenhouse gas contribution during the end-use (combustion) process?

Amazer98
I'm not a heating expert so I won't comment on your boiler selection. There is another issue here, though and that is your heat loss. From what you say about heating the house (can't get it over 66 on a cold day) you are an excellent candidate for a complete energy analysis by a certified Energy Auditor. There are many good ones in your area - google them or go to their professional web site at www.REPA-NH.org (Full disclosure - I'm an associate member but not an energy auditor) Even with 2x4 walls, the house should heat much better than it is doing. I suspect that you may have some significant air leaks and heat loss areas in the basement rim joist area (very common) and possibly in the knee wall (extremely common in capes). Fixes of this type may be relatively inexpensive, and will save you $$ & increase comfort . You might also call your electric utility - PSNH and other utilities have energy audit/ weatherization programs which are well worth looking into & may save you costs over hiring your own auditor. Good luck.
Bob Irving

Thanks Bob, you're singing our song:

"The lowest carb "fuel" for most homes is still the nega-btus: Improving the thermal efficiency of the building envelope."

Before dropping ten grand on replacing a currently functional boiler with a latest-greatest mod-con, calculate the fuel reductions you'd see by spending the same amount on envelope upgrades. Most existing housing stock in New England is abysmally leaky, well over the recent (and quite modest) introduction of a 7ACH/50 standard into the IRC code. Almost any house can be cost-effectively air sealed to meet or exceed that low hurdle.

A high efficiency boiler might cut fuel use 35% over what an aging beastie boiler running at 70-75% AFUE is doing. But it's often possible to reduce the heat load by that much or more than that for less than the cost of a replacement boiler, and that would be a better long-term investment. Recommissioning and retrofitting a functional aging beastie boiler with heat purging economizer controls like the Heat Manager or Intellicon 3250 HW+ can also be worthwhile, a sub $1000 investment that cuts fuel use by double-digits, with payback in under 2 years (often under one heating season, at current oil prices.)

Most utilities offer free but fairly limited audits, very few subsidize blower door & thermal imaging testing (typically ~$400-600 in my neighborhood), but $500 worth of testing followed by $1-2K of air sealing & spot insulation is usually cost-effective (even on brand new homes), independently of fuel type and system efficiency. Often $1000 worth of air sealing reduces the design day heat load sufficiently to take $1000 off the boiler size requirements, if we're talking modulating-condensing units.
Fix all the air leaks that you know about (concentrating on the basement and the attic, to lower the stacke-effect drives), the call in the pros. Foundation sills & band joists are notoriously leaky, often uninsulated (or stuffed with fiberglass batting without benefit of interior air barriers, creating condensation mold & rot issues.) Take all the low hanging fruit (subsidized or not) on the building envelope that you can before replacing the boiler. It's better for your pocketbook, better for comfort, and better for the planet.

Posted By Bob I on 12 Jan 2012 10:03 AM
Amazer98
I'm not a heating expert so I won't comment on your boiler selection. There is another issue here, though and that is your heat loss. From what you say about heating the house (can't get it over 66 on a cold day) you are an excellent candidate for a complete energy analysis by a certified Energy Auditor. There are many good ones in your area - google them or go to their professional web site at www.REPA-NH.org (Full disclosure - I'm an associate member but not an energy auditor) Even with 2x4 walls, the house should heat much better than it is doing. I suspect that you may have some significant air leaks and heat loss areas in the basement rim joist area (very common) and possibly in the knee wall (extremely common in capes). Fixes of this type may be relatively inexpensive, and will save you $$ & increase comfort . You might also call your electric utility - PSNH and other utilities have energy audit/ weatherization programs which are well worth looking into & may save you costs over hiring your own auditor. Good luck.
Bob Irving

Thanks for the good advice, Bob-- I actually followed it a day before you sent that email!  Yesterday I had my rim joists and sills foamed.  The insulation guy said that he noticed a number of small leaks to the outside, but commented that he had also seen much worse on other jobs.  Hopefully plugging up those air leaks will help mitigate heat loss.

I've also sent in an application to the NHsaves program, which is run by PSNH.  They will arrange to have someone do an energy audit on our house. The fee is just $100, but that's refundable if you do any remediation, including replacing the heating system. I've already blown extra insulation in the attic, foamed the rim joists, replaced two exterior doors and about 1/3 of our windows.  PSNH also has a program that provides interest-free loans for new heating systems, which is too good a deal to pass up.

I've noticed one issue that, when fixed, will help our heating meet demand on cold days:  there's a condenser "radiator" in our kitchen behind the toekick-- I think it's called a "kicker."  The fan inside the unit was disconnected, and so the 5000+ BTUs were not getting pushed into the kitchen area (which is open to the family room).  I went to the basement below the kitchen and saw the wires to the unit were dis-attached.  When I connected them the fan started up, but made a loud buzzing noise as if the bearings had worn out.  I had to turn the fan off-- the noise was too annoying.  But I'll get it fixed, and with the extra BTUs, we should be OK.

I've also decided to stay with oil and install a System 2000 boiler.  By and large the reviews are very good for this unit.  The people who've had problems seem to have had bad installations.  Our local oil company has installed quite a few of these systems, and I think that this product will probably deliver the biggest fuel savings to us.  If propane were cheaper or if we had 50% more baseboard or cast iron radiators or baseboard, then I probably would have chosen a LP modcon.  I know oil is not green, but I'm doing what I can to minimize how much I burn.

The System 2K performs well, and gets around the oversizing factor problem by utilizing it's own heat-purging controls (similar to the Intellicon HW+ retrofit economizer), purging the boiler heat either into the zone or the indirect tank (or both) a the end of each burn. It's still worth getting the smallest in the line to reduce the oversizing factor though, despite excellent part-load performance for a high-mass boiler. But many of the triple-pass units from their compititors have similar economizer control these days.

Depending on how much longer your old boiler could hang on a retrofit control + a mini-split might cost less, and have lower net operating cost, but if you're committed to ridding yourself of the beast, you can do a lot worse than a system 2K. (Just yesterday I found out that my uncle has yet to fire up his propane burner after installing a mini-split 2.5 years ago, and was wondering if he needs to do anything to mothball it so that it will be sure to work should he ever need it. It cut his heating costs by nearly 2/3, but he has 12 cent electricity and lives on the cool edge of US zone 4 where his average efficiency out of the mini-split would be a bit higher than yours, since you're on the cool edge of zone 5.)

Now that you've sealed & insulated the band joist and done some other air sealing it may be time to do a blower door test and nail down the last of the easy bits. It's usually easier to air seal the attic before blowing in more insulation, but not impossible. Fixing the air leaks in the basement and the attic are the most critical, since stack effect drives infiltration far more than wind, but there's no such thing as "too tight", and retrofitting to tightness that would require a lot of mechanical ventilation is usually quite difficult to achieve.

If your basement walls are not insulated, that might be the next-most critical bigger project to tackle. As a DIY it's not all that tough to put 2" of unfaced EPS or 1.5" of XPS against the wall and seal it to your foundation sill foam with 1-part spray foam, which would let you then put up an interior studwall with unfaced batts to fatten out the R-values for relatively short money (especially if you use reclaimed roofing foam, of which there are several vendors withing driving distance from any southern NH location. Search craigslist for "rigid foam" or "rigid insulation" and you'll find a number of them in MA, the biggest being The Insulation Depot in Framingham, but there's a smaller operation just over the line from Jaffrey, NH in Winchendon who advertises there too.) You can use fiber-faced roofing iso (polyisocyanurate) too, since it's permeable enough to keep the moisture content of the foundation from rising to rot-levels a the sill, as long as you avoid impermeable layers in the studwall. You can to an all foam (no studwall) solution too, using 1x furring through screwed to the foundation, mounting the inteiror gypsum on the furring. If you take a studwall approach, putting some foam between the bottom plate and the slab as a capillary break is a good idea too. The studwall isn't structural, single-plates and 24" o.c. spacing is fine. Just be sure to fit the batts snugly with a minimum of compressions, no gaps. With 2" EPS + R11/13 batts in a studwall you'll be at ~R19 for a whole-wall R, which is GREAT (better than your upper floor values). With reclaimed foam an all foam solution can be cheaper though, but going deeper than 3" gets awkward. At 3" of iso would deliver R18, 3" of EPS would be ~ R12. All are better than the R1 you're getting out of a bare foundation. Seal all the seams with either duct-mastic or 1-part foam, paying particular attention to the top & bottom edges, to prevent convection behind the foam.

Insulating the walls with 3" iso and sealing/insulating the band joist & foundation sill took between 15-20% off the heating fuel use in my 1-1/2 story bungalow in Worcester, MA. YMMV. The slab still runs cool and is now the major heat loss out of the basement, but I don't have the headroom to insulate over the slab, and digging down & pouring a new slab isn't cost effective at current natural gas rates. I have bigger heat losses to treat elsewhere too, with better bang/buck. ( Who said houses are ever done? :-) )

Good post Dana! I want to emphasize that it is critical to get the foam tight against the foundation wall without any wood "breaks", and to spray foam (with cans)the top and bottom of the sheets to keep air from getting behind the foam.(which might negate the insulation value). You can glue the sheets to the wall & screw or nail strapping to help hold them on. A stud wall works well also, but should be used inside the foam sheets. Pushing the stud wall tight against the foam is an alternate to the strapping.

Interesting points, Dana.  Now that I've foamed the basement though, I think I'll hold off doing the wall insulation down there.  I don't care if the basement is cool, so long as outside freezing air can't infiltrate the house.  Our budget will be a bit impacted by the new boiler and chimney liner we're planning to install.  The perimeter of the basement is close to 170 feet, so that would be an awful lot of wall to insulate.

I heard back from PSNH and they've accepted our app for an energy audit, which includes a door fan test (or whatever it's called).  Quality Insulation is the company they contract with to do the audit, which does strike me as somewhat of a conflict of interest, but go figure.  I'm expecting that they will suggest upgrading our boiler, which will then make me eligible for a $500 rebate on the System 2K, plus 6 years of interest-free financing.

We are planning to install the smallest System 2000 EK-1 boiler that puts out 85,000 BTUs with a .7 gph nozzle.  That's 33% smaller than our current Burnham boiler (124K w/ a 1.05 gph nozzle).  Can't wait to get the new system up and running, but I have to go through the audit process first.

The concept of insulating the basement walls isn't to warm up the basement, but rather to cut the (very substantial) heat loss out of the basement, particularly from the frost-line up to the foundation sill. Poured concrete or fieldstone, you're looking at R 1 or less, and even if the basement is a cool 50F, the delta-T against your ~20-25F mean January temp is at least 25F, which is a background mid-winter heat load of about (25F/1=) 25 BTU/hr per square foot of concrete from about the frost line up. If you have 2' of the foundation above grade, and it's 2' down to the frost line for a total of 4', and your house is 30x30' (120' perimeter), that 480 square feet x 25 btu/rrft represents a 12,000BTU/hr average background load for 1.5-2 months, less but still substantial during the shoulder seasons.

Mind you that's cut somewhat by heat from the ground coming up through the slab when the basement is that cold, but say it's cut in half, 6KBTU/hr. In 50 days (1200 hours) that adds up to 7.3MBTU of heat that your burner needs to supply. At 85% efficiency you only get 117300BTU out of every gallon of oil, so that load is costing you (7,300,000/117,300=) ~60gallons of oil for just the middle part of the winter. The load will be lower during the shoulder seasons, something like half that over a 100 days of shoulder season, but it's costing you ~100-120gallons/year, and it could easily be pushing 200gallons if your basement is much warmer than that. At $3.50/gallon it adds up fast.

If you insulate the wall to R15 (an inch of EPS + 2x4 studwall w/unfaced batts) the basement temp will be higher- say it averages 65F in January rather than 50F, for a 40F delta-T. Now you're looking at only (40/15=) 2.67BTU//hr per square foot, about 1/10th that of previously. But a 65F the room is always going to be warmer than the slab, so you're getting no earth-coupling heat benefit. So instead of 1/10th the fuel use it'll be closer to 1/5 the fuel use. But 1/5 the fuel use will be 20-25 gallons, at most 40, and you will have saved at least 80 gallons/year. @ $3.50/gallon that's an after-tax savings of at least $280/year, AND your floors will be warmer, more comfortable, AND the standby loss of the boiler will accrue to the house rather than losing it out the basement walls, the relative humidity in the basement will be lower. It's the right thing to do if you plan to live there, even if you have no intention of finishing out the basement as living space. If you have the time to do it as a DIY the payback on material cost is pretty quick (if you do it with reclaimed roofing foam at ~3cents per square foot per R, or ~50 cents per square foot for R15.) The low end numbers are pretty conservative- the actual annual savings could be as high as 2x that. I haven't counted the heat loss to ~50F subsoil out the lower half of the foundation.

An uninsulated basement foundation wall is a big hole in the thermal envelope, sucking money out of your wallet in this climate. How much would you have to invest in other instruments to return $280+/year after taxes for as long as you live in the house? The lifespan of insulation is probably 5x that of a new boiler, with low/no maintenance costs.

It's not a direct conflict of interest to have the insulation company do the audit unless you're obligated to use THEM for the insulation and air-sealing services. As a practical matter it's tough to find people who have the equipment and expertise for blower-door tests who aren't in the air-sealing business, and almost all air-sealing is a service offered by insulation companies.

An uninsulated basement foundation wall is a big hole in the thermal envelope, sucking money out of your wallet in this climate. How much would you have to invest in other instruments to return $280+/year after taxes for as long as you live in the house? The lifespan of insulation is probably 5x that of a new boiler, with low/no maintenance costs.

Dana,
Thanks for your interesting and detailed reply. I didn't fully appreciate how an uninsulated basement can act as a heat sink for the entire house. I will consider insulating down there, in addition to foaming the box sills by the rim joists (which we just did). I'm also curious to hear what the energy auditor says about that when he comes in the near future.

Certainly putting up foamboard on all our basement walls and then tacking up 2x4's and insulating between them would be a big and expensive project. 180 feet of wall x 8 feet tall = 1,440 square feet X 50 cents= $720 for the foam board alone.

By the way, how do you attach foamboard to concrete walls?-- glue them?

I've been researching basement insulation, and came across an interesting document by the Building Science Consortium:

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&ved=0CJwBEBYwBQ&url=http%3A%2F%2Fwww.eere.energy.gov%2Fbuildings%2Fbuilding_america%2Fpdfs%2Fdb%2F35017.pdf&ei=o2sUT_P0Ncr40gG-6IyEAw&usg=AFQjCNECQntX_aj3z91IpvP5tD059dznWg&sig2=C2miEHq-IahYJ3bKFOUuXw

They said this about how to best insulate an existing basement interior to avoid water damage:

"The fastest and most cost effective way to provide insulation is covering the upper half of the foundation wall with foil-faced polyisocyanurate foam sheathing that is fire-rated for exposed use (Figure 11). This will eliminate the greatest source of heat transfer through the foundation wall while still allowing the lower half of the wall to dry to the interior. The joints between pieces of foam sheathing must sealed using foil tape to prevent air leakage that could result in condensation on the cold foundation wall."

The group said that if you insulated the top half of the interior wall, you would cut basement heat loss by 50%. They also stated that if you insulate the entire interior basement wall, you cut basement heat loss by 70 percent. One advantage of leaving the bottom half of the wall uninsulated was that the lower portion of the wall would be able to dry into the interior.

On balance, it seems like insulating the top 4 feet of the basement concrete wall would be a cost-efffective solution. However, I am not sure how to do this. I uncovered one of Dana's old posts in which he said to use a foamboard adhesive. Do I just squirt some on the polyiso boards and press for a minute? I know I need to use foil tape or spray foam to cover the gaps between the foamboard, but do I need to install furring at all?

Thanks,
Andy