Posted By jonr on 06 Jan 2016 11:57 AM

And as mentioned, you might use one ASHP to over-heat an insulated crawl space. Little equipment, no visual impact and radiant comfort.

Very cool idea, and it would put the register down low where my brain intuitively thinks it should go. We'd have to encapsulate the space, for which the lowest bid so far is $30k. And that doesn't include the foundation work needed to close off four large access "wells" (the floor is just above grade, so to access the space, you have to climb down the well and then across under an opening in the foundation). Guessing that's $15k more. Call it $45k to condition the crawl space. Because of that, I had originally been thinking we should do radiant under there (stapled up PEX).

ASHPs sound great, way better than propane FAU, BUT with electricity at .43/kwh, it's probably no savings, and consequently we'd likely still stay cold.

With a good mini-split ASHP, I estimate a savings of more than 30% (from $4/gal propane) - even at $.43/kwh. A little less if over-heating the crawl space. Not sure what your ROI would be.

Hmm, at $3.39/gal for gasoline, you could burn that in a generator and get heat and electricity for much less than propane (not accounting for generator costs).

I'll report back with the ASHP costs when I receive the proposal (another one is bidding tomorrow as well). At 30%, I could consider skipping the solar to run it, and instead put that money toward the insulation/sealing.

OK, for a 4000' house with minimal solar gain you're probably looking at 2.5 tons of modulating ASHP to cover the loads, not 2. Tightened up a bit and with an unvented crawlspace you're probably looking at something between 30-35,000 BTU/hr. If you want to go with something as expensive as the Carrier Greenspeed instead of ductless you'd probably be looking a the 3 tonner. When you get the load numbers at the 99% & 1% outside design temps, plug them in to this tool, and see which air handler & compressor combination covers you at the 99% design temp:

vhttp://www.tools.carrier.com/greenspeed/

If somebody comes back with a 4-5 ton ASHP proposal make them prove that it's needed.

$30K to encapsulate HOW big of a crawlspace, (and with WHAT)?

Cool. Thanks, will do.

The $30k is for ~4000 sq ft of crawlspace, with about 2' of clearance under there. 20mil gets laid down and run up the foundation, sealed. Includes a drain (to tie into an existing drain), dehumidifier, and access sealing (but not the foundation work needed to keep those access wells from becoming pools). I'm a good negotiator, have been dealing with subs forever, and can say these guys wouldn't budge much below that. Crazy.

AztecSD, just checking here but are you using the letter "K" to represent a thousand?

there is always the option of putting in furnaces (probably much smaller), in an ECM variable speed fan, 2 stage setup
This really should not cost a lot  (relatively), although I see that everything in california is $$$$. by definition should improve efficiency by 16-18%

Are you part of a propane buying group or coop? propane is all over the place and i'm sure again california is near the top.

does it make any sense to consider venting the crawl space and insulating the house from the crawl space?

I they can actually GET $7.5 per square foot just for a 20 mil vapor barrier, drain, dehumidifer and some air sealing, no insulation makes me believe I'm in the wrong business. If you sprayed 2" of closed cell foam on everything (including the ground) and shot it with intumescent paint it wouldn't add up to more than $10K, maybe $12K for having to work in such a tight space. In your climate insulating just the foundation walls & band joists would be enough as long as there were a ground vapor barrier in place.

With only the vapor barrier (no insulation) it's sealed, but it's not conditioned.

Yes, it's a definitely a PITA to work in a 2' tall crawlspace laying out the vapor barrier, but really... There must be a lot of much easier work to choose from, not very hungry at all.

Hey Jelly, around here "K" just might mean millions!

Patonbike, no, not part of a coop. This area is... challenging, because so few of us are on propane. Natural gas surrounds my town on all sides, and it's just because of our unique low density that we remain on LPG. And the people in our town, well, let's just say no one cares what the price is. Other than me, apparently.

Dana1, yeah, I know. Few contractors do encapsulation in my area, and they apparently are very well fed. There's a price/level of PITA intersection, below which I do work myself. This one is really attractive for DIY because of the upper part of that ratio. But the lower part, man, I swore a decade ago, after shear-walling cripple walls and fixing ducts under 18" of muddy spaces with rat droppings falling onto my face, that I was done under houses.

Posted By Dana1 on 07 Jan 2016 05:33 PM
...just the foundation walls & band joists would be enough as long as there were a ground vapor barrier in place.

BTW, we might not even need to insulate the walls because the house is pretty much at grade. The stem walls are below grade save for maybe the top 6" or so. The proposal doesn't include any insulation at all. Just encapsulation, drainage, and dehumidifying.

Posted By AztecSD on 07 Jan 2016 06:13 PM
...Few contractors do encapsulation in my area, and they apparently are very well fed...

I think they must see your Rancho Santa Fe address and they reckon they'll get whatever they quote you. I used to live in Mission Hills, so I know how high the cost of living can be there in southern California. But holy cow! I'm thinking I should look at plane tickets and come out there and I would still undercut your contractor!

Posted By AztecSD on 07 Jan 2016 06:16 PM

Posted By Dana1 on 07 Jan 2016 05:33 PM
...just the foundation walls & band joists would be enough as long as there were a ground vapor barrier in place.

BTW, we might not even need to insulate the walls because the house is pretty much at grade. The stem walls are below grade save for maybe the top 6" or so. The proposal doesn't include any insulation at all. Just encapsulation, drainage, and dehumidifying.

In US zone 3 crawlspace code-min is R5 continuous or R13 in studwalls to a foot below grade, so it won't be a whole lot of insulation, which is why the decimal point on the quote seems to be in the wrong place. An inch of closed cell polyurethane costs a about a buck a square foot, installed. You're probably looking at less than 500 square feet of foam to insulate & air seal the place and a 20 mil tarp is ridiculously cheap stuff per square foot. With the drains & dehumidification stuff I might see $5-6K, maybe even $10K if they're out to gouge you. $30K feels like a triple-gouge.

And that's exactly why I am not doing it. I'd love to encapsulate, but the 3x gouge is totally off the table. If you guys could see the bids for building very simple cabinets or staining, well, you'd be as annoyed as I am.

Posted By Jelly on 07 Jan 2016 09:07 PM

Posted By AztecSD on 07 Jan 2016 06:13 PM
...Few contractors do encapsulation in my area, and they apparently are very well fed...

I think they must see your Rancho Santa Fe address and they reckon they'll get whatever they quote you. I used to live in Mission Hills, so I know how high the cost of living can be there in southern California. But holy cow! I'm thinking I should look at plane tickets and come out there and I would still undercut your contractor!

Brother Jelly, you are spot on. I'm to the point that I will never give my city or zip code for anything over the phone until I hear the price first. Whenever a sub tells me "yeah, I know people charge more for your town, but I charge the same whether you are Vista or Rancho" I know I'm in for an even bigger markup!

You might get a quote on a Chiltrix HP. Very flexible in terms of radiators/fan coils. Output range can be addressed with a buffer tank.

Posted By AztecSD on 07 Jan 2016 11:54 AM
I'll report back with the ASHP costs when I receive the proposal (another one is bidding tomorrow as well). At 30%, I could consider skipping the solar to run it, and instead put that money toward the insulation/sealing.

OK, I got proposals for replacing the two propane FAUs. Using a pair of ASHPs and traditional ducting, lowest was $23k, highest $25k. One contractor preferred using a 3 zone and 2 zone duct-type minisplit (Fuji or Mitsu), $25k.

With the Chiltrix pricing as above, I would think that 1/2 of that would be enough. But sounds like CA is crazy expensive.

Is that a 3 zone ducted mini-split for one floor and a 2 zone for the other? That's $10K more than I'd expect to pay in my neighborhood, but I live in a much slummier place that that! :-)

A friend recently installed a pair of 3- zone ductless Fujitsus on Martha's Vineyard MA (a really slummy area, summer playground for the rich & semi-famous non-glitterati such as the POTUS :-) ) for about $15K, and had been quoted a 1.5 ton ducted + 1.5 ton ductless for comparable money. She had to use an off-island contractor for that. The on-island local contractors were quoting $25-40K solutions, some ridiculously oversized for the loads.

The modulating efficiency, and cassette zoning rather than damper zoning and comfort of the mini-split solution tips in favor of fossil-fired hot air or bang-bang 1 or 2 speed heat pumps. You'll barely hear the mini-splits (should be quieter than your refrigerator if sized correctly), but you'd definitely hear an old-school heat pump or fossil burner. Zoning central heat pumps with dampers increases air infiltration when the air handler is operating, lowering the as-used efficiency. If it's nominally equal money as the propane central heat pumps, it's definitely a better solution. The minimum modulated output of the multi-zone compressors are high enough that it won't modulate nearly as much as if it were sized ideally for your loads, but it'll still be more efficient than a 1 or 2 speed with dampered zoning.

It's a 3 zone for 2/3 of the house (or more) and a 2 zone for the remainder (2 bedrooms and 3 baths).

I'm not sure what you meant in the bottom paragraph, other than that the central heat increases infiltration because of the quantity/force of moved air.

It's not the total air volumes, it's the pressure changes. Duct systems are designed with balanced and proportional supply & return paths, which keeps the room-to-room pressure differences small. When you close a zone damper it unbalances the duct system, which increases the pressure differences between rooms, which in turn increases the pressure differences between the rooms and the great outdoors. Rooms with the supply duct dampers closed become pressure negative relative to the great outdoors, pulling air in, and the rooms where the supply ducts are still flowing become pressurized relative to the outdoors, pushing air out.

If you lived in the tightest house in California the effects on efficiency would be pretty small, but that's not your house.

There are other potential gotchas with damper zoning that involve minimum air flows through the coils to avoid ice-up in cooling mode, but it sounds like you wouldn't be air conditioning very often.

If you zone it by mini-duct cassette with balanced ducts, the pressure differences are small don't change, since the ducts are always balanced. Zones can ramp up or down without the more active zone affecting the pressurization of the less active zone or conversely. The lower overall air volumes that work with modulating systems also helps, but it's primarily the fact that the supply/return duct balancing never changes.