"If you are Dana, you're calculating a significantly faster payback on solar hot water."

I can tell you're not a real mind reader toddm, even if you play one on web forums. :-)

"My version of multifuel is coming in at about $15k after careful buying and as much DIY as possible (not much.)"

$15K is more than the OP wanted to to spend on all of it.

"What you are still missing is why the UK energy code encourages multifuel, and would not penalize my ductless as part of a multifuel system."

What I'm still missing is where the O.P. indicated that he even cares about the letter of UK energy code. But mayhaps you're referring to my critique of the costs of the example system in the UK PassiveHouse (?), and not the O.P.'s aversion to cost. Codes will vary, and while some complexity may have a rationale, that doesn't mean that it has a financial or technical rationale.

"PV/heat pump would not be as comfortable."

That's probably true for your house (and mine), but that assertion flies in the face of experience in homes with near-PassivHouse heating & cooling loads. Wood stoves (even small ones) are more likely to cause roasting overheating discomfort in homes with ~2-4kw design condition heat loads than to provide a cozy spot to toast your feet. A 2kw load is literally an order of magnitude lower heat load that that of typical 1960s US code-min homes, and less than 1/4 the load of typical code-min 2500' homes today. (The paradigm heat load per home used by the state energy analysts in MA is 13kw.)

Mike: Indeed I was aware that manure is used in wattle & daub as well as other mud-based construction methods still used in parts of Iran and south Asia & elsewhere. While not absolutely required for authenticity in adobe, it's a traditional oft used organic fiber additive & binder/sealer there too. It's a standard construction material almost anywhere that dried-manure is used as heating & cooking fuel. A primary benefit of manure in mud construction is that it limits cracking from too-rapid drying. Mud construction has never struck me as a superior way to build, despite it's economy in places where capital is scarce and labor cheap. The 2003 earthquake in Bam, Iran destroyed entire mud-built towns that had been around for more than 2500 years- hopefully the rebuilding effort takes seismic resilience into account. (The mud, sand, straw & manure bricks used there probably qualify as "adobe" even to the technical purists.)

I thought, having agreed with you that multifuel is overkill in a passive house, we could move on to a reasonable discussion of why it is not a kludge as you described it in any earlier post. Once again I underestimated your need to be right. So henceforth you shall be Dana1HW2 (he who's never wrong). All hail Dana1HW2!

OK todd, you win- it's not a kludge, it's a feature. :-)

Make it a feature that improves the efficiency of all its parts, greatly so in the case of heat pumps, is readily adaptable to grid pricing changes and represents a series of small bets on energy policy rather one big one, and we are in agreement.

In Pa, utilities are under orders to install "smart" meters. Imagine meters smart enough to operate a spot market in electricity. Imagiine a bright winter day gutting rates -- and net meter payments. Imagine my smile as your pv array heats my storage tank.

Imagine (as in MA) receiving not only the reduction in billing from net-metered PV (even in a smart-metered environment, as will be the case in my neighborhood by the end of the year), and the smile I'd get receiving a check for ~25 cents/kwh for the entire AC output of the inverter, whether that power is consumed on my side of the (smart) meter or went onto the grid.  At my shading factors I'm not going there, but some of my less shaded neighbors could (and arguably should, from a "Where could you get a better more secure ROI than that?" point of view.)   The subsidy won't last forever, but typical simple-payback is currently running 4-6 years for rooftop installations, 3.5-4 years for ground-mount, driving boom times for local solar installers. With an IRR >> 15% it's worth financing even at significant interest rates.

Yes, these grid-times are a-changin' and the benefits will accrue in many ways. 

Most residential smart metering proposals I've seen going forward would offer lower rates for opting into a demand-response control, where the utility can opt to turn off some of your big loads selectively as a means of controlling grid load during peak demand, but there's no reason you couldn't run your own off-peak turn-on, as described. I don't expect off-peak rates to occur in the middle of a bright winter day anytime soon- you'll still be primarily reaping the benefits of variable rates during hours when the sun doesn't shine- hour at temperatures where a mini-split will still has a COP > 1.5 even in a PA climate.  The COP of heat pumps still has value whether off-peak or the middle of the day.  Until the off-peak rate is less than 1/3 the average rate you'll still get more bang/buck out of mini-splits than storing off-peak energy at a COP less than 1.   The mid-day peak pricing will occur at temperatures and load that get much higher COPs out of the ductless. On that bright sunny winter day the load is near zero due to passive gains, and the COP would be bumping on 4 even at 25F.

Mid-day off-peak may eventually come in regions where there is a lot of wind resource under development (such as in IA & MN), but I don't forsee PV ever doing more than peak-shaving, and primarily for air-conditioning loads, not heating-season peaks. Could be rong, offen am.  SFAIK neither wind nor PV has much grid-share in PA, and  but it's ~20% of the annual total in IA (and growing), the vast majority of that slice being from wind.

Self-sourced bulk biomass fuel can be pretty cheap if readily available and you have the time, and want to deal with it, but I don't see it as a paradigm that works for most urban dwellers anytime soon.  Even in less-urban circumstances it doesn't always make sense:  My brother lives in a forest, has 3 chain saws & means for skidding logs,  heats primarily with wood w/condensing propane as backup, but he is still is considering adding a ductless before next year.  With ~10 cent electricity (primarily low-carb hydro), average winter temps in the 30s, and a heating design temp north of 15F it's hard to rationalize the annual hours of cutting & splitting wood to offset propane use when a mini-split will average a COP of 3+.  If he cuts down the right trees he could probably make PV pay too, depending on how the changing subsidies in WA work out, but isn't currently planning to.  He has motorcycle enduros to set up & race in, why spend time monkeying around with cord wood when there's fun to be had spewing fossil-hydrocarbon exhaust in the woods!?! 

The flip side of wood heat in an efficient envelope is much less handling than your brother does. What's more, a multifuel heat bank spreads the impact over a longer period and offers more choices. In the US the bigger storage tank the better. In the UK they want overnight capacity and llow morning temperatures that will give solar hot water and/or heat pump a super efficient delta T. Wood heat is a last resort.

That said, forest dwellers such as myself have relatively short leashes. Whether or not it makes sound, a tree falling in the forest makes a mess that requires some manner of cleanup. Solar pv would mean more whacking for me than I am willing to do. Shade is good.

The grid pricing options you mention, interruptible and off-peak, look forward in only one direction, sad to say, toward more of the same capacity constrained, high rate present-day grid. The marcellus shale makes the opposite equally possible. The most likely regulatory response is "never mind" to formerly attractive alternative power deals because, as you note, there is no ground swell of renewable energy in Pa. (Or in MA?) I hold out hope that someone will figure out how to conduct a btu fire sale. If I had a heat pump plumbed to a storage tank, you see, I would want a COP of 4 AND a rate of 4 cents/kwh.

"you note, there is no ground swell of renewable energy in Pa. (Or in MA?) "

Huh? Maybe EXPLOSION would be a better descriptor than "groundswell"- there's a huge BOOM in PV under way in MA, currently on an exponential trajectory! Even though the grid share is still quite small people often have to wait to get a PV system quoted (let alone installed.) It's hard to day when the subsidy-plug will get pulled, but the rate of expansion is breathtaking. See: http://www.olympicroofing.com/news/in-massachusetts-solar-sells/ http://bostonsolar.us/incentives/massachusetts-solar-renewable-energy-certificates/

By 2020 prices may have fallen to where the SREC and direct rebate grants won't be needed to drive it as hard as right now, but I fully expect PV to account for a few percent of the grid share by then, and that share should continue to grow.

The offshore wind potential in MA & RI is significant, but has been held up for a decade mostly by legal wrangling driven by wealthy peops on Cape Cod/Nantucket/Mahtha's Vinya'd pissin' & moanin' about how it'll wreck their views and get in the way of their drunken yachting experience. But they're (almost) out of legal stalls, and wind is likely to hit double-digit fraction of the total grid source locally by 2020. The Cape Wind project (http://www.capewind.org/index.php ) is just the leading edge of what is expected to be serious boom in offshore wind over the next 2 decades extending from the MA cape & islands to NJ & DE.

At current PV prices the lifecycle cost per kwh is already lower than the average residential retail rate in MA & CT, and wind is lower than that. Even low-priced gas in combined cycle generators can't compete on the spot market against fuel-free sources, and the bigger the grid share for those $0.00-bid sources, the lower the average grid price will be. The cheapest fuel-fed sources will set the spot price, but the better profit margin will go to renewables operators- it's a good business!

Dana is hard-wired to the matrix...don't mess with him unless you are fully trained, suited up and have checked with the Oracle first...oh, hehehehehehee peeing my pants! I want to be a PV installer instead of a wet-head!

O.K. he is a little techno-Bohemian, but you gotta love it. hehehehee Buy the way, I have a COP of 4 with my mini-split and a interruptable power rate of $0.04/kW! How cool is that?

It SHOULD be a great business with the feds and utilities handing you major subsidies. (For the uninitiated, NJ's SREC program sets renewable energy benchmarks for power generators but allows them to meet the goals by buying solar renewable energy certificates from customers who install PV systems. SRECs were fetching $342/ Mwh annual production recently, down from $617 last year. PV customers get no state rebates, but get net metering and fed tax credits.) NJ was the first state to offer SRECs in 2001. Ratepayers foot the bill ultimately. PSEG, the largest NJ utility, is charging 11.45 cents/kwh Across the river in Philly, PECO charges 10 cents.

Incentives that are too good to last tend to sow the seeds of their own destruction, as the Germans are learning at this very moment. Regardless of fuel cost, the grid needs base load generators that work even if the sun doesn't shine and the wind doesn't blow. Natural gas from shale deposits greatly simplifies the balance of base and peak. Essentially jet engines, gas fired generators are both cheap and responsive. The peak load problem SRECs were meant to address may well go away without solar and wind development. Utility and petroleum lobbyists are already at work. The empire will strike back. Sad to say, the empire always strikes back.

Morgan: 4 cent demand-response electricity and a COP of 4 is easy street compared to oil-fired hydronics or splittin' wood, fer sher! :-)

(If your power is off long enough for the house to really heat up it's time to drink-down whatever's in the fridge before it gets warm too, eh? ;-) )

Todd: Sure, subsidies that drive boom times inevitably go bust, but for just as with nukes & heavy-hydro the legacy of the built up infrastructure implemented in boom times lives on for decades, well after the point that the subsidized boom has become a footnote in history. The German ratepayers seem willing to foot the bill for their renewables, and it's not necessarily a mistake on their part. The fraction of the bill that is paying the PV feed in tariff is still quite modest( but measurable)- they're still paying for their soon-to-be-decommissioned nuke fleet. Fuel-free grid sources don't set the price, but they become a damper on the price with marginal costs near zero.

In the US the marginal cost of wind REC to the ratepayer is still less than the fuel & maintenance operating costs of fossil fired generation- the 1.45 cent delta between PECO and PSEG has very little wind component to it. In TX where the wind infrastructure is highest (and some of the cheapest natural gas) wind has smothered peak rates (lowering the fixed-rate residential prices) and become an export resource bringing revenue into the state, despite being only a ~10% grid fraction. Their rates have steadily fallen since 2008, between the natural gas prices (~45% of the TX grid source) and the boom in wind development more than doubling their renewables fraction in that period. RECs aren't proving damaging to ratepayers in TX- the development they're funding puts a lid on prices, just like in IA. YMMV.

In the PNW with the huge legacy hydro in place and a newly-expanded wind resource off-peak curtailment has become a bone of contention, since minimum flows are required through the dams on environmental grounds, and it's cutting into wind operators' business: http://205.254.135.7/electricity/monthly/update/ (Time for an electrified personal transportation fleet to soak up the excess into batteries when it's cheap, mayhaps? ) Methinks the mid-Atlantic and New England have a lot of infrastructure to build before it gets to that point.

Regionally in New England gas-fired peakers sure look good compared to where it was a decade ago, but even low-cost gas has marginal cost well above zero, and the cost of building gas-fired peakers running at a low capacity factor isn't as cheap as you might think relative to their capacity factor. As national & state policies get more serious about atmospheric carbon issues the renewables will continue to be subsidized in favor of any gas-fired generation. In MA as of 2010 statistics from the EIA gas accounts for about 60% of today's grid-source, and the state has the 4th most expensive electricity among the US states at about 15-16cent/kwh residential-retail-delivered. The crash in gas prices has taken a few cents off the rates from the 2008 peak, but at existing rates & sources wind is still a pretty good deal and state policies on greenhouse gases is pushing the efficiency & renewables buttons hard. Total renewables are still in single digit percentages, but wind/PV/biomass combined had already pulled ahead of hydro in 2010, and that was just as PV was starting to take off like a rocket, and the Cape Wind project has yet to produce a single kwh (but it will!) (See table 5, right column for fraction of grid-source: http://www.eia.gov/electricity/state/massachusetts/pdf/massachusetts.pdf )

Wind is proving to be a more reliable baseload source than naysayers would have you to believe, and output is fairly predictable 24 hours ahead making it easy for grid operators to manage. In places like IA it's essentially "backed up" by the pre-existing grid sources, resulting in fossil plants taking substantial hits to their capacity factor as more wind generators come on line. Even though individual turbines can stop, the distributed output of wind in IA or TX is never zero, and has a surprisingly good capacity factor (typically 30-40% for land-based wind- higher for off-shore). Coal plants have typical capacity-factors of about 70%, nukes run about 90% capacity factor but can't be ramped up and down in a day like thermal coal plants can ( and as such are $0.00 bidders just like wind- they don't set the price, they just reap, even if they're taking a loss some days, making it back on others.)

PV output is similarly predicable and manageable 24 hours in advance, but unlike wind PV output is NEVER during off peak hours- there is ALWAYS a market for it's output. The fact that PV output peaks just slightly ahead of air conditioning peaks during the day means that PV a summertime peak-shaver, well worth the investment, and delivering cheap power when pricing is at premium. The fact that it's lifecycle per-kwh cost has yet to hit grid-parity with fossil sources hardly matters- it's per-kwh cost is well under spot market on air conditioning peak rates, and is at parity with the average residential retail rates in MA (even without subsidy.) The trajectory on PV costs is still strongly downward, and most analysts (even the nay-sayers) assume it'll cross the fossil-grid parity at retail almost every before 2020 (2015 is the common estimate), but it's widely expected to hit even the wholesale grid parity by 2030 in many places (even without taxing carbon), a point at which any type of subsidy would be absurd.

Back from sailing in the Chesapeake. Wound up using the iron genoa. Consarned unreliable wind. Where were we? Oh yes...
You seem fixated on wood heat while the heart of the British multifuel approach is a heat storage tank good for the 24-hour diurnal cycle, and a grabbag of fuels that make sense, including air/water heat pumps. My hypothetical would play out differently than badger boiler's if renewables took off to the point that grid pricing incentivized storage in peak production times. Towit: 4-cent power, COP of 4 AND perfect comfort -- no sacrifice required. That said, this EIA chart's breakdown of renewable energy production in 2010 shows 1,986 trillion btus in the wood column, 924 by wind and 109 by solar (pv and hot water.) http://www.eia.gov/totalenergy/data/annual/pdf/sec10_3.pdf Not too outlandish would you say?

Even so, only trees would stop me from jumping on solar pv if pa had a srec program. NJ's certificate program is based on actual production so shade and cloud cover are significant income liabilities.I would raise a caution about historic prices paid for certificates (by commercial power generators who are under orders to increase renewable production but can meet their responsibilities by buying certificates from pv households instead.) Once PV is commercially viable these companies will build their own and the auction market for SRECs ultimately will go away. In NJ, pv households are promised 15 years and minimum guaranteed payments -- IIRC $200/certificate -- so you want to base your decision on some middle ground mix of of high market prices and guarantees. $200/yr/MW production is certainly better than treasury bills. The economist in me dislikes the perverse incentive. (Got my collectors on the roof and my certificates in my pocket; man, I hope PV never takes off.) But I'd go for the bucks if I hadn't moved to the forest for a reason.

Naturally water storage is the key to comfort serving various multi-fuel scenarios for various climates but no one has convincingly overcome the challenge of where to put the tank! When working on solar systems in New Mexiico and Colorado back in the 80's and early 90's it was usually an outbuilding in NM and a basement in CO but you have to pay taxes on both. Dare I say high-mass?



Given that the English are not known for the size of their homes I am still leaning on efficiency leaving load management to the power suppliers. Personally, energy independence starts at home, but for people living on an Island cooperation is a given.

http://news.bbc.co.uk/2/hi/8201900.stm

Future construction standards - including the following - will be a key feature but dehumudification and ventilation will continue to be a challenge in renovations. http://web.ebscohost.com/ehost/detail?sid=6d273f80-281a-4ec1-922f-698db4f5f14b%40sessionmgr14&vid=1&hid=8&bdata=JmF1dGh0eXBlPWdlbyZnZW9jdXN0aWQ9czM2MTM5MDQmc2l0ZT1laG9zdC1saXZl#db=keh&AN=21489915

toddm: Yes, the installed infrastructure for burning wood is well ahead of wind or PV power as of 2010 (and now), and some of it is even decently efficient compared to what it was in 1980, but it's still a bulk fuel that needs to be lugged & stored, which most urban-dwellers are loathe to deal with.

And yes, the SRECs are going away as the price of PV falls, no doubt, and it's only the early-adopters that are going to get their systems paid-for-pronto by tax & SREC subsidy.

Morgan: That UK house size statistic seems almost hard to believe- 76 meters as the AVERAGE size of new construction? (The O.P. was looking at a ~250m house!). A house that size is even smaller than my mother's tiny place (that is currently heated & cooled with a 1.5 ton mini-split) IIRC they measure it differently than the way it's stated by the US real estate industry- only from the interior-paint inward rather than from the exterior paint as here. But that's still a pretty small house for more than 1-2 people, still less than 1000 square feet using US methods. OTOH back in 1950 US houses averaged 1200' for 4-5 person households- it's all a matter of what you're used to, and how efficiently the space is used.

Uncharacteristically, off the point. If it is true, or not, we in the US are loathe to give up any living space. I have found that an "average" room in the US is just about right for the "average" storage tank which most practically goes in the conditioned space. These things have to be addressed, more especially if artificial markets - gov't. subsidies will end.

One theory goes that the size of the US living space expands to fit the heating & maintenance budgets, so as incomes rice, U-values drop, air tightness improves, and HVAC efficiencies climb we discover that we can afford ever larger dwellings. I'm not sure I buy into that completely, but there's a thread of truth to the theory, at least in some cases.

I have been designing and in installing smaller systems and additions and have seen a trend in basement remodels, so the total fuel bill does affect the size of the conditioned space, but I think the big box, big glass days are over for most.

You shouldn't assume that the British multifuel model requires a US style mega tank. To the contrary you want a small enough tank that the btus are pretty much spent when the solar collectors heat up in the morning or the ambient temp turns favorable for heat pump so as to maximize the efficiency of either. A 1k liter tank (250 gallons) is roughly 40 inches in diameter and 80 inches tall. This would be the first tank in the average British home, which uses a combi boiler (heat and DHW on demand) rather than a US style hot water tank. A selling point of heat banks in the UK is abundant hot water, typically via a flat plate heat exchanger. While a 1k liter tank is too wide to fit into most existing homes, this company will sell you a stainless steel liner tank plus insulation that collapses to 19 inches wide. http://www.stsscoinc.com/?page_id=96

I crammed all of the mechanicals in my house into a vertical tower that its 4.5'x4.5'x22'. That would be an air isolating surround for the stove (aka "fireplace"), a 200 gal heat tank, a 65-gal solar tank, a 30-gal well-water pressure tank, an ERV, a Merv 12 fliter and continuous air flow fan, two hydronic floor plumbing sets, a solar plumbing set and a Manublock (home run plumbing manifold.) OK I couldn't fit in the inside ductless HP unit. (The tower is also a plenum that moves air between floors.)

The heat tank is 2'x3'x6' with an extra eight inches of insulation in each dimension. It was custom made because of the space, and cost $1,600 including a pair of 120', 3/4 inch copper heat exchanging coils, the bottom one being heat in from the wood stove, the top one being heat out for the hydronic floors. As I wrote earlier, solar hot water btus, when available, are captured by drain back in tanks that are mounted literally one on top of the other. I worried initially that the drain back pump would mess up tank thermodynamics, but decided that it has plenty of time to restratify between 6 p;m and 6 am. Stratification (hot water rises) means that storage itself improves efficiency.

The Brits pay top dollar for fossil fuels and, as opposed to us, they have learned how to make every btu count.

I crammed all of the mechanicals in my house into a vertical tower that its 4.5'x4.5'x22'

OK, that sounds like a chimney chase. So, did you do that because you had the space, or was there another reason for constructing it like that?

The Brits are paying bottom-pound, not top dollar for natural gas. They have some of the lowest residential retail natural gas prices in Europe (mostly 'cuz they produce about half of what they use domestically, unlike most European countries who rely heavily on imports.) They have some of the lowest prices in Europe for heating oil too. See: http://www.energy.eu/

With gas at about € 0.04/kwh- source-fuel energy it works out to ~$1.45/therm at the current exchange rate. While that's more than the US residential retail average, but not even close to 2x- it's less than I was paying a handful of years back during the mid-decade peak, and only ~33% more than I'm paying now.

Home heating fuel for this year in the UK averaged € 0.846/liter, which is ~$4.00/gallon, a bit less than some of my neighbors paid.

I'm not sure that's really "paying through the nose", even if UK n.g. is running 2x what people smack the middle of US shale gas fields pay. In European terms it's a bargain- only a few eastern European countries are paying less. The Scandinavians are all paying 2-3x as much as the Brits, which feels a bit more like "paying through the nose" to me.

The chase started as a design element in my homage to frank lloyd wright's Usonian small house designs. FLW put "shoulders" on his designs so they looked less long and skinny. But, lacking a basement, I needed the space. My success is praise to bond beams, anchor bolts and structural steel. As an energy design, it greatly reduces waste heat, because chase air is circulated continuously by a 120 CFM fan. I should note here that the mechanical code specifies minimum distances between wood stoves and return registers. I maintain that the fireplace surround isolates the stove from the house and from the chase and features zero returns, but your code official, as always, has the last word.

Your ability to circumnavigate the point is estimable , Dana.