Wall section questions
I am a (future) homeowner designing a 1400 sf custom home in Northern California. Climate zone 3C. Pretty mild climate, but with an average of almost 60 in of rain. I am trying to put together a set of plans for an architect to start from. I would like to avoid re-inventing the wheel pertaining to wall sections. I don’t plan to get too detailed for the architect, but would like to show what I had in mind from roof to footing. I started with Lstiburek’s “Builder’s Guide to Mixed-Humid Climates” I got at a conference a while back. While it had some great sections (and information), they weren’t quite what I wanted. I’ve found the attached sections for roof, roof-to-wall, and wall from this great website and I have some questions.
– I would like to suggest an ICF conditioned crawlspace foundation. Can someone point me to a wall section illustrating this?
– We are planning for GSHP radiant floor heating. I’ve read that recently most installers have moved away from suspended slabs to staple up. Is this true? Either way, I am assuming that even with an insulated crawlspace (ICF or not) I would need underfloor insulation as well. Is this correct? If so, can I reduce that insulation with an insulated crawl space?
Of course I have dozens of other questions, but let’s start from there for now.
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Replies
Hi Jim,
I looked through the library and couldn't find an ICF crawlspace detail. However, as far as gathering information, it wouldn't look a whole lot different than many of our insulated crawlspace details except that instead of a poured concrete or concrete block wall with either interior or exterior insulation, you'd have an ICF wall. The footing, slab, and wall-to-floor details would be similar.
As far as your second question is concerned, I hope you'll get some more helpful responses soon. There are many GBA users with much more knowledge and experience with radiant floor systems than me. I believe however, that you are correct that builders have moved towards staple up systems for a few reasons including quicker response times to temperature changes and that both heat transfer plates and insulation improve performance of these systems, even if the space below is insulated.
Jim, a conditioned crawlspace is just a short basement. Check out the details we used for the 2016 Fine Homebuilding House in Rhode Island: https://www.finehomebuilding.com/2016/06/28/solid-well-insulated-foundation. Most manufacturers have details available as well. At the time of our build, Amvic had the highest R-value blocks, but now Nudura has an R-35 product.
>"– We are planning for GSHP radiant floor heating. I’ve read that recently most installers have moved away from suspended slabs to staple up."
For the amount of money it takes to do GSHP and the higher temps required for a staple-up it might be cheaper/better/ more efficient to go with a reversible air source chiller and an above-the-subfloor system such as Roth Panels or WarmBoard, either of which are more responsive than staple up, and MUCH more responsive than slab radiant. The radiant would be slightly more expensive than with a staple up but an air source chiller is far cheaper than any GSHP solution, and in a 3C location can be as-efficient at any given water temp, and would be more efficient if the heat can be delivered at very modest temperatures.
Don't get hung up on concepts such as "ground sourced heat pumps are always more efficient". or "radiant heating is always more comfortable and more efficient." Getting to the optimal heating solution starts with a careful heating/cooling load analysis- leading with a preferred notion of "the solution" then hammering it into working often leads to spending more money for less comfort with no meaningful difference in efficiency.
>"I am assuming that even with an insulated crawlspace (ICF or not) I would need underfloor insulation as well. Is this correct? If so, can I reduce that insulation with an insulated crawl space?"
What is your local deep subsoil temperature?
Is the crawlspace slab going to be insulated?
What do you thing the water temp requirements are on this as-yet-undesigned radiant floor heating for the as-yet-undetermined heat load?
As a general rule staple-ups would need R10+ under the floor for zone isolation, but at very low water temps and an above the floor system, and subsoil temps in the "Goldilocks zone" it's conceivable that sub-floor insulation wouldn't really be needed at all. (I'm aware of a house in Idaho where the "radiant floor" was achieved by heating the air in a very well insulated crawlspace to something like 80-85F with a mini-split .)
There are too many unknowns to solve this with a "design by web forum" approach.