Without natural gas, is there a better option than electric baseboard heat?
I am currently designing a home to build, that is to be the best compromise of sustainability and affordability. This home is 800 s/f and will have a passive solar heat design, and a wood stove to use our local biomass resource of beetle kill pine, however I need a third heat system for the house (what the City considers to be the primary system). Although natural gas is very cheap in CO, we decided we would rather put the money to run a gas line and install a furnace toward a net metering PV system, since we have the optimal climate for this. Without natural gas, is there a better option than electric baseboard heat? The city boosts our electric fee $1000 to put in a 200 amp line, to use electric resistive heating.
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Curt,
Q. "Without natural gas, is there a better option than electric baseboard heat?"
A. Yes. It will cost you about $3,000 to $4,000 to install a ductless minisplit heat pump.
For more information, see:
Just Two Minisplits Heat and Cool the Whole House
Will Minisplits Replace Forced-Air Heating and Cooling Systems?
Two Years With a Minisplit Heat Pump
Report on Our Ductless Minisplit Heat Pump
And with a mini-split you wouldn't need a 200A service either. A high-R 800' house would likely have a heat load at the 99% outside design temp (http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/Outdoor_Design_Conditions_508.pdf) of -10F lower than the ~9000BTU/hr output of a Fujitsu AOU-9RLS2-H or Mitsubishi MSZ- FH09NA, both of which have a rated output at -13F or lower. Where you are in CO matters too, the outdoor design temp in Leadville is considerably below that in Colorado Springs or Boulder- enough to make a difference in mini-split sizing.
That's also a low enough heat load that any EPA rated cast iron or steel wood stove would be prone to turning the place in to a sauna before reaching it's higher-efficiency/lower-polluting operating temperature & firing rate.
If it's more of a code-min design with a lot of glass you could be looking at the 1.25 ton versions (-15RLS2H or -FH15NA) rather than a 3/4tonners. As with any heating system, a careful heat load calculation would be in order. But know that even at subzero temps a cold-climate mini-split would only be using about half the instantaneous power that resistance heating would (even the 1.25 tonners work fine on a 20A 230VAC breaker) and during the shoulder seasons the average power use would be about 1/4 that of resistance heating or less.
http://news.mehvac.com/Bulletins/FH_Product_Guide.pdf
http://smartgreenbuild.com/pdf/Fujitsu-RLS2H.pdf
Curt, Have you had an electrician do a load calculation? It is quite common for conventionally built houses under 1500 Sq ft to use a 100 amp service and still have baseboard heat. Unless you have other unusual power needs, there is every chance that your better insulated structure can be serviced by the smaller panel.
I know this doesn't conform to the prevailing orthodoxy here but think baseboard heaters are a very good back up to a wood heated house. You can zone the rooms and use them sparingly. They are without costly up-front installation expenses - and they are maintenance-free
Better than baseboards at a similar upfront cost would be radiant cover heaters, operating under both occupancy sensor and thermostat control. Even cool rooms can be comfortable as it's coming up to temp using radiant coves, unlike baseboards which are convection heaters, and transfer the heat to the air rather than radiating it at the humans & other objects in the room.
Controlling a radiant cove heater via an occupancy sensor in series with a line-voltage thermostat it remains off when the room is unoccupied, then limits the room temp with the thermostat when someone IS using the room. With baseboards it takes much longer for the comfort to kick in, since the average radiant temp of the room stays cold until there has been sufficient convective heat transfer to heat up the objects in the room.
But a passive solar home in CO is likely to have substantial sensible cooling loads too, making a mini-split a better overall solution, with lower overall peak power draw issues to boot.
I'm still not convinced that a wood-burner won't cook you out of the place too, unless it's a high-mass masonry or stone "Russian fireplace" or at least a smallest-in-class soapstone stove that can be intermittently fired at high-burn rates to still get the efficiency and clean burn without the sauna effect.
Thank you Dana, Malcolm, and Martin. To be clear, our city, Ft. Collins, automatically makes anyone using resistive heating up-size their service to 200 amps, regardless of energy used. I have been reading all the suggested articles regarding mini-splits, and must admit I am intrigued. Two questions, 1) how noisy are mini splits? For ex. is the noise equivalent to a forced air furnace? 2) Ft. Collins building dept. told me " the 2012 IRC says you need to be able to maintain a minimum room temperature of 68°F at a point 3 feet above the floor and 2 feet from exterior walls in all habitable rooms at a winter design temperature of +6°F." So I have to assume a mini split will do this. How is that determined, since I know they are not going to wait for a 6 deg. day to give me a CO. I know this is blasphemy on the GBA, but we are looking into less expensive, more primitive ventilation systems than HRVs as well.
Regarding the "being cooked out, with a wood stove," although not a passive house, we are a little concerned about this, but for multiple reasons we really enjoy our wood heat. Jotul has a 28K/btu/hr stove.
A Mitsubishi M-series 3/4 ton mini split at low speed is 20dbA- which is literally quieter than a whisper at 1 meter. At high speed it's 42dbA , which is about as loud as the quietest refrigerators out there. (50dbA @ 1 meter is typical for refrigerators.)
The Fujitsu RLS2s and RLS2-H are similar, low 20s dbA at low speed, low to mid 40s at high speed. The noise specs are in the short-sheet pages:
http://news.mehvac.com/Bulletins/FH_Product_Guide.pdf
http://smartgreenbuild.com/pdf/Fujitsu-RLS2H.pdf
To compare what those numbers mean see:
http://www.seattle.gov/dpd/cs/groups/pan/@pan/documents/web_informational/p2081596.pdf
You have to run a heat load calculation (Manual-J or I=B=R methods are fine) for the heat loss at 68F indoors / +6F outdoors (delta-T= 62F) on your house, then be sure that the BTU/hour output of the unit at +6F will cover that load. The 3/4 ton XLTH is good for ~15,000BTU/hr @ +6F , the 3/4ton M-series Mitsubishi is good for ~11,000 BTU/hr @ +6F.
Typical heat loads of code-min house at +6F come in around 11-15 BTU per square foot of conditioned space (with lots of exceptions to prove the rule of thumb), and most passive solar houses are designed for higher-R, and will come in lower than that. An 800' better-than-code house should easily come in under 11,000 BTU/hr @ +6F, but you have to run the heat load calculations to know for sure. And if it's still being designed/constructed you can pretty easily make SURE it's that low, by-design.
The 28K BTU/hr Jøtul F 602 has a couple of strikes against it:
A: It's cast-iron, which heats up and cools down quickly, with a high peak surface temp
...and...
B: it has no provision for ducted combustion air hooked up directly to the fire box, which means you'd have to install a (much larger) makeup-air duct somewhere near the stove. The tighter the house, the more you have to be concerned about drafting (and back-drafting), and making the conditioned space part of the combustion-air path isn't necessarily a great idea.
Morsø has quite a selection of tiny ~30K cast iron stoves ( http://www.morsona.com/Classic-stoves-527.aspx ) that at least have the direct-ducted combustion air kit options, but still have the hot-flash/cool-down issue of cast iron. I have no direct experience with them, but have read third hand issues of getting them to draft properly in super tight houses (they are a popular back-up heat for PassiveHouse folks in some places.)
Although it has a higher firing rate, a tiny soapstone unit like the 36K Hearthstone Tribute has the thermal mass of the soapstone to average out heat delivery from intermittent firing, and has a 3" combustion air kit for ducting combustion air directly to the firebox, with the door gaskets limiting the rate of combustion-product spillage that can be drawn into the conditioned space.
If your house is super-tight you may have to crack a window to get any of them to draft well on a cold-start, but I know from first-hand experience that the outdoor combustion air kits for the Hearthstones work just fine, and that series burns VERY cleanly even at ~1/3 of full-fire. (Even the viewing window rarely has to be cleaned unless you throttle it all the way back with a full load of not-so-dry wood.)
Woodstock Soapstone stoves all have ducted combustion air options, but the smallest start a 45,000BTU/hr-max. which is almost surely going to be bigger than you really want.
Dana ... I learn a lot from reading your posts. But on the issue of stove drafts, we need to defer to the experts. I posted this elsewhere on this site; you might have missed it:
Folks interested in how and why stoves work should read this twice:
http://www.woodheat.org/
Most all models of stoves will get enough makeup air from the normal inside -envelope atmosphere with normal venting if properly located. They need 15 cfm; that is equal to one humans make up air rate.
Stoves underperform because they are not installed right. We can’t rely on consumer reviews to evaluate stove performance; they mis-install and then complain.
If the chimney design, height, location relative to wind pressure and surrounding wind interferences (just like a wind generator), and the stove and chimney are put into the (1) negative pressure zone and (2) cold chimney zone they will not work. Period. That has little to do with stove box and baffle design or make-up/combustion air and all to do with stove location and installation.
Most people don’t want an interior, penetrating-at-the-ridge chimney; they want an after-market, exterior wall chimney. That immediately misplaces the stove and the chimney. Instead we need to learn how to seal the through ceiling penetrations to allow chimneys to be in the envelope and stoves to be located where there is positive pressure.
The Jotul F100 will deliver the hear you are talking about and its cast iron.
Fitch
You can see photos of the F100 and what appears to be proper placement relative to the ridge on this GBA blog:
Going High-Tech With an Induction Cooktop
While I agree that stove performance issues while burning are primarily chimney design issue and that the actual combustion air cfm is pretty tiny, PassiveHouse-tight homes have a history of having cold-start draft problems and backdrafting/spillage issues while running exhaust ventilation. See the paragraphs under "Wood stove woes" on this PassiveHouse with a tiny Morsø:
https://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/two-single-family-passivhaus-projects-maine
(Note that in that blog piece they state the Morsø combustion air kit are proximity air only,, not sealed to the firebox, so from my point of view they really are no better than the Jøtul.)
It doesn't take much to de-pressurize a very tight house to the point of interacting with a stove, and having a stove as close to "sealed combustion" as possible limits the rate of spillage into the house when the wind gusts change the pressure equations temporarily, or when both the kitchen & bath exhaust are running when they turn on the clothes dryer, etc.
There's nothing magic about wood stoves that make them any less susceptible to the spillage issues than any other atmospheric drafted combustion appliances in tight houses. If it makes sense for a gas/propane burning appliance to have sealed-ducted combustion air (and it does), it surely must make sense for wood stoves.