This is the problem with the mini split, vrv and ductless conversations around here. Any system's efficiency is greatly impacted by application; so when mis-applied touted efficiencies are wishful thinking.
It is no different with an underducted geo or an under radiated boiler, you put burden's on the system it wasn't designed for and it will under perform.

Posted By jonr on 03 Apr 2013 06:48 PM

The few ducted ASHP systems tested by Ecotope in the NEEA Northwest Ductless program came in under 2.0 for a seasonal COP, compared to a 2.7+ average for the ductless systems

Given that the typical, non super insulated house cannot use a ductless system (although a mixed system might work), higher efficiency ducted ASHPs might be something to encourage with subsidies. I can't believe that it is difficult to change a ductless ASHP into a ducted design.

Actually MANY non-superinsulated houses can use ductless systems (sometimes with a bit of resistance heating to take the edge off design-day extremes) at far lower operating cost &  lower carbon footprint than oil or propane fired systems. But, resistance backup can be a real efficiency-killer if use is unchecked, bringing the net-efficiency to that of a bang/bang ducted ASHP. 

In the NEEA in-situ efficiency monitoring nearly ALL installations were retrofits in existing sub-current-code older housing (like my mother's place, and my uncle's place, both currently heated primarily with single-head mini-splits), most of which had been previously heated with resistance heating only.  (Electric heating was heavily promoted in the NW during the '50s & 60's to soak up the substantial output of the BPA hydro system, which is still the primary source of power in the region.)  The net reduction in heating electricity varied pretty dramatically- clearly those who can tolerate leaving the bedroom doors open had the highest benefit.  IIRC the mid-point of the bell curve on energy reduction was near the 50% point, but the 1-sigma breaks were pretty wide. (In my mother's non-instrumented non-monitored place it appears to about a 65-75% reduction in heating power use, slightly better than I had anticipated.)  But the average temps of the homes in the NEEA monitored houses was also higher- when it's cheaper/affordable to maintain a higher more comfortable winter temp, people generally do.

Very few of the NW Ductless programs were intended to be whole-house solutions, and I would expect that to be the case for sometime to come in homes with existing functioning oil/propane systems. But the affordability factor of offsetting oil use with mini-splits looms large, even as a partial solution.  One bit of analysis done by the utilities in MA estimated the  average 99% condition heat load of existing housing stock in this state is about 14KW, or 48KBTU/hr.  Even in January the binned hourly average heat load on these houses would run only ~25-30KBTU/hr, which is the output capacity of 2-ton mini-splits (~$5K, installed) at +5F.  Even when it's +5F out they're still running at COP of ~2, a cheaper BTU-delivered rate than an 85% efficiency oil burner at current electricity & oil prices. For most of the population in the northeast the outside design temps are +5F or higher, so running mini-splits would be taking the bulk of the load off the oil burners even at the 99% design temp.  When it's +30F outside the COPs are in the 3s, and it's carrying the whole load (or nearly so.) 

From an affordable carbon footprint reduction for heating oil users point of view it's a no-brainer, even in central ME or northern VT climates.  There are currently MANY people in this region spending north of $4000/year on heating oil, even while shivering under the blanket in front of the TV for the colder months.  I've yet to see a credible narrative or analysis projecting a downward trend on heating oil prices over the intermediate or long term- most point the other direction.  Those with wallets/credit fat enough to afford GSHP have an out, but even for them it's a longer term investment. For the rest, there are still heat pump exits, even if they're not always going to be perfect.  Pellet stoves & wood stoves are point-source heating too, and are flying off the shelves. But they are a bigger PITA to operate & maintain than a mini-split, more expensive to run, and there are sometimes local fuel shortages (primarily for pellets, not so much on the cord-wood.) 

High efficiency pellet boilers are about as rare as GSHP in this region, but it's a growing market.  Cheaper outdoor wood boilers are becoming common enough to be a serious air pollution problem in some locations, leading to neighbor complaints, lawsuits, and  regulatory action. (This is potentially correctable by introducing modulating controls, but I'm not holding my breath- though maybe I SHOULD, to avoid inhaling the soot!)   For the money I'd take heat pump solutions over biomass (I say, as I slip another log in the woodstove...  :-) )  When pellet boilers hit the price & efficiency of oil-burners they may be worth considering, but according to the RMI analysis the LVCoE of pellet boilers at this point is substantially higher than GSHP or VRF-ASHP, but still at least slightly cheaper than oil.

Now that Daikin has acquired Goodman they have been marrying some of the variable speed air handler technology to their VRF compressor units. I know of one installation near me, but have no numbers on it's in-situ efficiency.  (SFAIK it's not being instrumented & analyzed, but it was installed as part of a deep energy retrofit on a now pretty-tight way-better than code house.)  Duct design & implementation is critical to getting the efficiency out of it, as well as dialing in the dynamic air-handler speed controls. According to Lawrence Berkeley and PG & E data "typical" duct losses on pre-existing ducted air systems run in the 15-35% range, which does a real number on the net system efficiency. (And that's even before the effects of duct impedance on air handler power is factored in.)  You can retrofit-seal & insulate the ducts to reduce those losses, but even in a perfectly implemented Manual-D design they'll never be as low as refrigerant-line-only losses on mini-split heads.

I have a room (corner room, typical 20 year old insulation levels) with the duct vents closed and the door open. In mild weather it is fine. In cold weather, it is uncomfortable. With cold weather and the door closed, it is very uncomfortable. As I recall, hot weather is also uncomfortable, even with the door open.

How can I use a ductless heat pump in this not atypical case?

"According to Lawrence Berkeley and PG & E data "typical" duct losses on pre-existing ducted air systems run in the 15-35% range, which does a real number on the net system efficiency. (And that's even before the effects of duct impedance on air handler power is factored in.) You can retrofit-seal & insulate the ducts to reduce those losses, but even in a perfectly implemented Manual-D design they'll never be as low as refrigerant-line-only losses on mini-split heads."

That is most important if the duct is out of the envelope. Heat energy lost from the duct work to the conditioned space may not hurt efficiency at all.

Dana,
I agree that splits are better than some solutions and more affordable than others and of all the mini-split or airsource advocates here I find you most even handed and reasonable about application. It remains unfortunate that there is not an air source thread to post these discussions in since coincidentaly most of the pros here at the geo forum are geo advocates. Many of the visitors are geo interested as well or looking for help with a geo.
I occasionally dabble at the radiant forum and don't tout forced air as the better solution (even though a very high percentage of the interested on lookers run away once they discover the cost). I figure people are there to discuss radiant.

Posted By jonr on 04 Apr 2013 12:08 PM
I have a room (corner room, typical 20 year old insulation levels) with the duct vents closed and the door open. In mild weather it is fine. In cold weather, it is uncomfortable. With cold weather and the door closed, it is very uncomfortable. As I recall, hot weather is also uncomfortable, even with the door open.

How can I use a ductless heat pump in this not atypical case?

Separate head/zone for that room.

Resistance radiant cove heater, used when occupied.

Posted By joe.ami on 04 Apr 2013 12:14 PM
"According to Lawrence Berkeley and PG & E data "typical" duct losses on pre-existing ducted air systems run in the 15-35% range, which does a real number on the net system efficiency. (And that's even before the effects of duct impedance on air handler power is factored in.) You can retrofit-seal & insulate the ducts to reduce those losses, but even in a perfectly implemented Manual-D design they'll never be as low as refrigerant-line-only losses on mini-split heads."

That is most important if the duct is out of the envelope. Heat energy lost from the duct work to the conditioned space may not hurt efficiency at all.

Dana,
I agree that splits are better than some solutions and more affordable than others and of all the mini-split or airsource advocates here I find you most even handed and reasonable about application. It remains unfortunate that there is not an air source thread to post these discussions in since coincidentaly most of the pros here at the geo forum are geo advocates. Many of the visitors are geo interested as well or looking for help with a geo.
I occasionally dabble at the radiant forum and don't tout forced air as the better solution (even though a very high percentage of the interested on lookers run away once they discover the cost). I figure people are there to discuss radiant.

The typical NY/New England pre-existing duct setup is uninsulated not-so-sealed ducts in semi-conditioned not directly heated (often uninsulated) basement, and duct losses are pretty much true losses.  Even if those losses accrue to the basement raising the temp from 55F to 58F, putting that heat into the fully conditioned space rather than the basement would result in lower energy use.  Retrofitting heat pumps onto most pre-1990 duct systems here would be a system-efficiency disaster.  The majority of oil-burners in New England are either pumped hydronic or steam boilers, not hot air furnaces, and any ducted output heat pump retrofit would require sometimes awkward new ductwork implementations. (Most of the hydronic systems wouldn't have sufficient pre-existing radiation to work well with hydronic heat pump output either, even though many could still work fine at 140F AWT on design day, due to typical 3x oversizing of the original system.)

I hear what you're saying- but the topic being heat pumps (all types, not just GSHP) displacing heating oil use, this forum seemed the most-appropriate.  Like all heating systems GSHP & mini-split solutions live in a context, and it's still appropriate to consider the different options for different applications.  Discussing the financial crossover points of building envelope upgrades relative to up-sized GSHP is also completely relevant on this forum, IMHO.

Lots of folks chime in on the radiant forum with hydronic heating system issues that have nothing to do with radiant heating, but I don't recall anybody trying to shoo them away for being off-topic.  It's not as if there's another "hydronic heating" forum that would be more appropriate.  If we try to slice & dice it too narrowly, something is lost. "Green building" requires treating the whole house as a system rather than isolating the mechanicals separately from the building envelope.  GSHP doesn't deserve an automatic "Green-Pass" in isolation any more than radiant floors do, even though both can be among the lowest carb and long-term cost-effect solutions in the right context.  Call me crazy, but I trend toward the "Do the math"  approach on both carbon and cash.

OK, progress. To use ductless heat pumps in most homes, you need some combination of superinsulation, separate heads for isolated areas, open doors, hi/low baffled ducts, ducts connected to an alternate system (heat pump or fossil fuels), non-ducted zoned heat source (eg. electric baseboard, radiant - but these don't help for cooling).

Posted By Dana1 on 04 Apr 2013 02:14 PM 
Call me crazy, but I trend toward the "Do the math"  approach on both carbon and cash.

Sure math is great, but dont forget about COMFORT with better heat distrubution, filtration, humidification as well as appearance.  Splits fall behind, in varying degrees, in those catagories for typical north east homes in most all cases.  No? 

Sure, comfort comes at a cost and splits have their place, but you usually downplay those downsides as "nothings", which they are not.  Its not just about providing BTU's at the lowest cost.  I always learn tremendous things reading your very informative posts Dana, but I think there is a limit to promoting splits (endlessly) on a GEO forum.  You know splits work well, but most code homes of typical design will not be as comfortable as with a distributed sytem by some measure.  Some may not care, but it will be there. 

Sure the application is very tempting when upfront cost and simplicity(some cases) to put it, and other factors fit the bill.  I promoted my friend to go with a split for his new addition and three car garage space.  2 heads, works awesome, but the floor plan is open.  Quite dry in the winter though. 

He has GEO in the main house and is very happy.

Posted By chrisbiker on 04 Apr 2013 03:09 PM

Posted By Dana1 on 04 Apr 2013 02:14 PM 
Call me crazy, but I trend toward the "Do the math"  approach on both carbon and cash.

Sure math is great, but dont forget about COMFORT with better heat distrubution, filtration, humidification as well as appearance.  Splits fall behind, in varying degrees, in those catagories for typical north east homes in most all cases.  No? 

Sure, comfort comes at a cost and splits have their place, but you usually downplay those downsides as "nothings", which they are not.  Its not just about providing BTU's at the lowest cost.  I always learn tremendous things reading your very informative posts Dana, but I think there is a limit to promoting splits (endlessly) on a GEO forum.  You know splits work well, but most code homes of typical design will not be as comfortable as with a distributed sytem by some measure.  Some may not care, but it will be there. 

Sure the application is very tempting when upfront cost and simplicity(some cases) to put it, and other factors fit the bill.  I promoted my friend to go with a split for his new addition and three car garage space.  2 heads, works awesome, but the floor plan is open.  Quite dry in the winter though. 

He has GEO in the main house and is very happy.

Emphatically NO! 

Mini-splits are signficantly more comfortable (and quieter) than most fossil-fired ducted-air systems, and they neither dry nor add moisture the air,  which are separate functions from heating, and should be controlled & dealt with separately.

If you need to add humidity to the air, it's a building envelope infiltration or overventilation problem not a heating system problem. (Unless of course you only sleep there, always eat out rather than cook, and never bathe...) Seriously- it doesn't take a super-tight house to keep the interior RH in the healthy zone, but it usually takes active ventilation to keep a super-tight house from hitting interior moisture levels too high for the health of your house, since higher interior dew points leads to higher moisture accumulation in the cold side of the building assemblies (notably wall sheathing and roof decks.)

"Typical" rural New England homes don't come with 3 car garages with a huge barely-used bonus room rec area over it. If your friend's addition is dry, I'm sure he can afford a standalone humidifier, but I wouldn't use that example to say much of anything about mini-splits, or any other heating systme Seriuosly- do most GSHP systems come with humidifiers? (It would be news to me.)  Active humidification is a mold-disaster in the making, as a general rule, particularly for not very tight timber frames in colder climates, since the moisture will accumulate along the exfiltration paths, creating mold and rot issues. Tight houses usually need DE-humdification, even in winter (achievable via ventilation rate control in winter) to get it into the 30-35% RH @ 68-72F range. If you let it climb to 40-50% in winter even vapor-diffusion (rather than air leaks) can cause mold-issues, even in a zone 5 climate

Air filtration, similar issue- a heating system should never be considered an air purification deal (though some Daikin's have that function.)  How do (the majority of older New England) hydronic-heated homes EVER survive without ducted air?  Ducted air filtration is a solution-problem- it cleans up the dust that it brings into the home via air-handler induced infiltration, and keeps suspended by the high-cfm air flows.  Yes, mini-splits move air too, but at lower CFM, with no duct leakage to suck crud in from non-conditioned spaces or off the floor near the return registers, and they DO have filters (albeit not HEPA grade filters.  If you have so much indoor sources of pet dander or dust that you need air filtration, buy a $99 HEPA filter at Best Buy and be done with it, or learn how to use a vacuum cleaner.  :-) 

What's perceived as promotion by me of mini-splits on this forum has primarily been defending against mis-characterizations of how they actually behave & perform. They're far from ideal for every app, but they're WAY better than some of the less-informed critics here make them out to be (and there is ample third party empirical-test & user-satisfaction-survey data to support that assertion, not merely second & third hand anecdotal stuff.)

This thread was about getting the northeast off the economy-draining heating oil habit using heat pump technology, not specifically a mini-split promotion, though the economics & local subsidies make it a more compelling near-term partial solution for those homes, even if GSHP systems might be a nicer solution, when upfront money is less of an issue.  I've yet to see compellingly positive efficiency data on cold climate ducted ASHP systems- most of what I've read from third party testing indicates they fall short in this climate. (But when that changes I'll be happy to report it here! :-) ) But both geo & ductless really DO work well enough here to be net carbon-emissions reducers when displacing oil heat, even with the current northeastern grid sources. Pissing & moaning about the mere mention of ductless options in that context seems a wee bit sensitive to this observer, especially when you throw up all of the usual whining about what ductless systems don't do compared with GSHP. What they don't do is burn oil or emit copious carbon via the regional grid, which was the point of the RMI analysis. So what if it's only a partial, if substantial solution for most retrofits?

ductless ASHP into a ducted design."
Sure you can, simultaneously tanking the efficiency.

Looking at Daikin's web site, their ducted, cold climate inverter heat pump has a HSPF of 12 and their ductless units vary from 8.5 to 12.5. Are we sure that a bigger fan/ducted design tanks efficiency?

Dana- So a typical north east home, say 1500 to 2500 sq ft, of typcial code construction, Rancher or Colonial, will have a more even heat distribution in all the rooms, healthier RH in mid winter, better filtration, and look better on the interior with say 2 to 4 mini split heads than with a properly set up central GSHP or ASHP with good pleated filter and Aprilair style humifier? I don't think I am alone with disagreeing with you on this.

Sure, tightened up smaller homes, 1000 - 1500 sq ft, with more open floor plans are great candidates for splits. Or homes with boiler/rads without existing ducting. Splits should be considered in lieu of retrofitting ducts/centralized. For homes with existing ducts, I would think splits would be down the rung in choices.

All homes I have seen up here, boiler/rads, central ASHP/GSHP, underslab/hydronic, whatever, run shockingly(lol) too dry in mid winter without humidifiaction being added by some means. Outdoor dew point air in the teens/single digits gets in and just drys the place out. This is on typical homes and that is what I am referring. Not homes of energy experts who do all the proper stuff to get the shell tight.

I am all for removing oil, and that is the purpose of this thread, but the reality is that splits should be considered, but there are limits and some downsides to them. You have had great success with them, but there are some limits by application that need to be considered.

"When I look at Daikin's web site, their ducted inverter heat pump has a HSPF of 12 and their ductless units vary from 8.5 to 12.5. Are we sure that a bigger fan tanks efficiency?"

I don't believe I mentioned a bigger fan. I said ducting a ductless throws the numbers out the window. To counter you are showing a system that was designed to be ducted. That is my point. If you want ducts, don't use a ductless system and expect the best results. Use a system designed for ducts.

"Lots of folks chime in on the radiant forum with hydronic heating system issues that have nothing to do with radiant heating, but I don't recall anybody trying to shoo them away for being off-topic. It's not as if there's another "hydronic heating" forum that would be more appropriate. If we try to slice & dice it too narrowly, something is lost. "Green building" requires treating the whole house as a system rather than isolating the mechanicals separately from the building envelope. GSHP doesn't deserve an automatic "Green-Pass" in isolation any more than radiant floors do, even though both can be among the lowest carb and long-term cost-effect solutions in the right context. Call me crazy, but I trend toward the "Do the math" approach on both carbon and cash."

It's not just "off-topic" it is a somewhat competative technology. I don't happen to be a one solution dealer so I am all for do the math (particularly on cash) for my customers.
I mentioned before you are even handed and I recall many occasions where you suggested geo as the best fit. You might recall more than once that I have suggested geo is not the best fit.
But.....
Why the geo forum? It's not an "HVAC" forum. I didn't pick the catagories. There is a general "green-building forum" that discusses the whole house. If something is lost by subdivision, then why are we already subdivided. (if you wanna see lost by subdivision check out the geo exchange forums good lord it's divided by everything but brand)

Again my stated purpose for an air source forum is to attract contractors with vast air source experience. Many of the onlookers around here seem to think splits are ideal for every situation (hey just duct them a little if you need ducts).........

How nice would it be to find the Doc Jenser of airsource with actual measured performance. There are air source products claiming 6 COP. So many of the studies we look at are flawed in one way or another. Maybe that could be you. Do you have Welservers on mom's mini splits?

Anyway, I'd like the whole world off oil and I don't really care what technology they use to do it. I think you generally offer great advice to that end. I also never thanked you for that PM or link.

I don't believe I mentioned a bigger fan. I said ducting a ductless throws the numbers out the window.

What you said was (incorrectly, at least in the case of good ducts):

Larger or second fans... The greater efficiency of ductless is due in large part to being "ductless"....

At least Dana has a point in that some ductless "cold climate" heat pumps aren't (yet?) available in ducted versions. And of course ducts cost money (even if you only have to do a few rooms).

Posted By chrisbiker on 05 Apr 2013 08:47 AM
Dana- So a typical north east home, say 1500 to 2500 sq ft, of typcial code construction, Rancher or Colonial, will have a more even heat distribution in all the rooms, healthier RH in mid winter, better filtration, and look better on the interior with say 2 to 4 mini split heads than with a properly set up central GSHP or ASHP with good pleated filter and Aprilair style humifier? I don't think I am alone with disagreeing with you on this.

Sure, tightened up smaller homes, 1000 - 1500 sq ft, with more open floor plans are great candidates for splits. Or homes with boiler/rads without existing ducting. Splits should be considered in lieu of retrofitting ducts/centralized. For homes with existing ducts, I would think splits would be down the rung in choices.

All homes I have seen up here, boiler/rads, central ASHP/GSHP, underslab/hydronic, whatever, run shockingly(lol) too dry in mid winter without humidifiaction being added by some means. Outdoor dew point air in the teens/single digits gets in and just drys the place out. This is on typical homes and that is what I am referring. Not homes of energy experts who do all the proper stuff to get the shell tight.

I am all for removing oil, and that is the purpose of this thread, but the reality is that splits should be considered, but there are limits and some downsides to them. You have had great success with them, but there are some limits by application that need to be considered.

I'm a data type guy- show me the data, if you and everybody who shares that opinion can find it, if you think it actually exists.  (A good dataset trumps all opinions, including mine.)

Fix the envelope tightness, and you the wintertime dryness problems become wintertime humidity management problems- manageable by ventilation.  Retrofit tightening to that isn't always super-cheap or easy (though it often is) but most houses can be made tight enough. If it works in Edmonton & Saskatoon, it'll work on any lower-48 US home. (And it does, at tightness levels nowhere near as tight as an R2000 program house.)  Blower door & IR imaging guided air sealing is your friend...

Yes splits should be considered for displacing oil use, and yes, there are some downsides- but those downsides aren't about air quality or comfort (at least for the spaces the splits serve.)  At the daunting cost of oil, even imperfect solutions can be worth it, if it can be financed in net-positive cash flow manne rather than a total-lifecycle decades-long approach.  At $4 oil mini-split are there even for crummy sub-code housing (like mine :-) ). Those who can afford it should be looking at both GSHP and serious envelope upgrades, without a doubt, but my gut tells me that those folks represent the frost on the tip of the iceberg for housing stock in New England currently heated with oil.  It's a great solution if you can afford it, but until/unless better financing options are on the table, GSHP won't be more than a bit-player for getting the region off oil, however worthwhile that goal might be from a public policy point of view.

Existing ducts come in many states of design/repair/function, and many should simply be ripped out and replaced.  The presumption that you can just hook up a pretty-good ASHP/GSHP to some random set of ducts and get good performance is not well founded.  I'm still looking for ANY ducted ASHP solution that measures better than a COP of 2 in-situ a New England type climate, let alone one that uses the crusty left-over duct system from an oversized soot-belching oil fired furnace (like the one I kept patching & tweaking in a slum-lord rental in Cambridge MA back in the mid 1980s.) 

The ducts in my current house were installed in 1923, and while I've improved them substantially during my tenure here I'd be loathe to hook up any heat pump to them- they would still bring the heat pump efficiency to it's knees, and the registers are not well placed for higher efficiency/tepid-air output comfort. They're mostly in dis-use but not completely abandoned. The air handler has an oversized 6 ton AC coil for the 3-10 days/year I actually need sensible cooling (whoever did that one was an f'n' IDIOT, but at the low low duty cycle there's no incentive to change it), as well as a low temp hydro-air coil as the "Hail Mary" back up second stage for the gas-boiler should the floor radiation + wood stove somehow be unable to meet the load during the 25 year cold snap.  With 125F water I get ~100-108F exit temps at the registers, which is OK sitting in the draft, but 90F air would be far less pleasant, and there's no way to reconfigure the rooms to avoid the draft when it's running.  If I ever go with GSHP it will be an all-hydronic show, but at my current loads (and the fact that I'm on the gas grid) it's not even on the "maybe, someday" chart for this particular house. (There's a remote chance of a mini-split future in the ~350' of attic rooms if it's still overheating after I finish the roof insulation upgrades, but it heats just fine in winter with the hydronic rads even pre-improvement.  A tiny window-shaker can keep up with the cooling loads even as-is, so it's a "probably never" on the mini-split too.)

The real drag on better market penetration of GSHP systems in New England is the daunting upfront cost- better financing packages might help, but if even a 30% subsidy can't seem to make it move, something even slicker has to be devised.  The industry as a whole has a fairly spotty record in terms of poor system design & implementation (take the current/recent thread here about the oversized system in MN they're considering scrapping as prima facie), as well as inflated efficiency claims that omit air handler & pump power, but there's no reason competent designers/installers can't get excellent performance out of them at a reasonable cost/investment value to their clients, and at a reasonable profit for themselves. This current blog piece sums up the downsides of the regional GSHP market pretty well, even if I don't fully share the authors conclusions (on either  GSHP or solar thermal), though like him, I'm a "Put the real money into the building envelope and let the mechanicals take care of themselves" kind of guy, particularly on new construction and bigger rehabs, like my friend's DER I'll be seeing again tomorrow.

[edited to add]

Joe: You're welcome on that link- the guy is quite the character, eh?  I hope he actually instruments that chimera-system, to be able to tease some real numbers out of it. I'm not super hopeful since he's using a pretty messed up looking duct system, but since his loads are so drastically reduced the true efficiency numbers many not really matter the way the would in the pre-DER condition. (I'm sorry that the link isn't really public yet too.)

I'm a data type guy- show me the data ... but those downsides aren't about ... comfort

I agree with the former, so let's see some hard numbers on how comfortably a ductless heat pump serves closed door rooms. With super insulation and just "decent insulation". IMO, the burden of proof is on the newer, less implemented design (ductless ASHPs for heating in the NE).

you need some combination of superinsulation...

What are we calling "super insulation"? I think I barely meet code for this area. My sense is that the air sealing is as important as the insulation level and maybe more.

I go in an increasing number of homes here in the PNW that have thrown out their old heating system in favor of ductless. Almost all of them do some envelope improvements at the same time, but I am continuously surprised by how few heads they use. Typically, it is two and they claim to be better off than they were with the last heating system.

Nice re write Jonr- What I said was
"The greater efficiency of ductless is due in large part to being "ductless". Larger or second fans, friction loss etc.".....
talking about a variety of systems. A PSC larger fan on an air handler for instance (in a conventional ducted system) or a small fan on one of these ducts for ductless wall pass throughs I've seen. All cost more to run.

The thrust of your original question was why don't we duct a ductless- my point was the ductless performance numbers would necessarily change when you added ducts. If you want ducts by a ducted system.

" IMO, the burden of proof is on the newer, less implemented design (ductless ASHPs for heating in the NE)"

If you wanna be a data guy start by installing things to the factory spec.

For what it's worth I don't believe any performance numbers offered by a maufacturer. Whether it's geo or air source and they talk about 6 plus COP while it's achievable I'm interested in average COP cause that's where dollars are saved or spent. We know geos are 3.5 to 4 ish depending on a variety of factors I have no idea what ASHPs are but I'm taking a swag at 2-2.5.

BTW priced Altherma for a customer interested in it and "katie bar the door" sucker must be made of gold. Cost difference between that and a water to water 5 ton could pay for 1/2 the ground loops.

....definite character Dana and a little self defeating if I recall

If one looks at the manufactured published efficiency claims for ducted minisplits one sees the SEER numbers drop by 1/3 or more over the ductless. Not sure about HSPF - we don't pay too much attention to that in my AO.

If one looks at the manufactured published efficiency claims for ducted minisplits one sees the SEER numbers drop by 1/3 or more over the ductless

Without data...

Data from Daikin's web site:

Ducted inverter: SEER = 20, ductless multi-head models: SEER = 18.8 and 15.1. Single head systems (not really an affordable option if there are many isolated rooms): SEER = 15.5 to 26.1.

BTW: The guy with the ducted Daikin/Goodman hybrid showed up the Deep Energy Retrofit (DER) open house on Saturday and I got to chat with him a bit.  He's still editing/adding to his blog documentation of his own DER, which includes quite a bit on issues with the heat pump, but is fine with posting the link.

There is quite a bit of info on the NEEA's online documentation of their ductless program about 90% satisfied customers, with 96% of those heat pumps being used as the primary heat source, the  measured in-situ efficiency in regions covering US climate zones 4-6, and the effects of partial solutions total energy use, but unfortunately there was not extensive datalogging of room-to-room temperature balance issues. IRRC Ecotope had measured that in a handful of houses in the Willamette Valley, but in a quick search I haven't been able to re-find it online.

The room to room balance issue doesn't matter a whole lot for offsetting oil use. People who are setting the T-stats to 60F to survive the economics oil aren't going to be put out too much if the corner bedroom hit's 60F over night on the coldest night of the year while the main zone closer to the mini-split is a balmy 72F, while saving half or more on their heating costs.  Those with the means to add ductless heads or ducted/hydronic GSHP surely can (and will), but most houses heated with oil could still take a huge cut in operating expense with a boost in overall comfort by adding a mini-split to cover a large zone.

The theoretical room-to-room temperature differences in heating mode at my friend's DER by design worked out to about a ~5F delta steady-state at the +5F 99% outdoor design temp, assuming no curtains and no occupants (but WITH exhaust-only ventilation on those rooms drawing ventilation air from the fully conditioned common space via door cuts).  In speaking to some of the third floor tenants none had wintertime comfort complaints, but those with east-facing bedrooms mentioned that during last September/October the AM solar gain would sometimes roast them out if the don't leave the door open. The folks on the second floor (which is better shaded by the adjacent house) claimed they didn't have that issue.  Whole-wall R is ~R40, the windows are all U0.18-0.20, insulated at the roof deck to ~R55-60 (varies a bit by roof section, being a gable with 2 dis-similar  dormers.)

I'm not sure exactly where the heating/cooling out door temp balance points are on these units are in their as-used plug loads & occupancy, but it's clearly under 50F.  There was no perceptible room-to-room temperature differences on Saturday, but it was in the 40s F with intermittent sun and a fairly steady breeze outdoors. None of the splits were kicking on, despite the doors to both the front and back stairwells being open for 4 hours straight, as well as the front and back doors to the units being open to the stairwells.  (I kept checking on them, since I wanted to show one of my friends who showed up how loud they were, but it would have been a bit cheeky to mess with the setpoint without permission of the tenants.)

Without separate metering on the mini-splits it's hard to say for sure what the heating bills were- it's way under $50/month in mid winter on any of them and may be under $25/month, and that's at 15 cents/kwh.  The hot water is heated with condensing gas, but none of the power bills for any of the units has ever come anywhere near the $100 mark, thought they edged up from the baseline in Jan/Feb.