I learned a new word today. Wythe. Definition is “masonry layer”. In an insulated tiltup sandwhich the inside layer is the “facia wythe” and the external layer is the “structural wythe”.
One of my “must haves” is a non-thermally conductive connector to fasten the facia and structural wythes together through the insulating foam. It looks like Owens Corning has just the ticket. The pins made by Owens Corning are designed to have an exterior surface layer of 3″ for proper strength, but with ferrocement I don’t see that being an issue. The pins designed to be pressed through the rigid foam insulation into the initial layer of concrete. Very cool. (Installation instructions recommend vibrating or walking on the insulation at the point of the connector installation to establish good cement coverage around the point of the connector pin before the top layer of ferrocement is added).
Here’s the technical pdf link. PinkCoreXPS.pdf
I talked to Frank at our local Home Depot. Before we realized we were talking about two different things, he gave me the following prices. 3″ (R-15) sheets of Foamular (note this is not PinkCore) run $35.90, shipped in bundles of 32, 4″ (R-20) sheets are $48.11, shipped in bundles of 24. According to the PDf file the connectors are shipped separately but (I think) included in the price.
The first two pods will use 3¼ 4’x8’x3″ sheets per wall and there are 14 walls for a total of 45½ sheets. I will have 18 sheets left over at a surplus cost of $646.20 for the walls.
The amount needed for the roof equals what is needed for the walls, but in 4″ thickness. This bundling comes out about right, with two bundles equaling 48 sheets, 46 of which are required for the roof. Surplus cost on the roof is $96.22. Actually, because the pods nest the actual count for the roof will be a little more than 2 sheets less than what is required for the walls, boosting the surplus cost to $192.44.
Total cost for the Foamular, including surplus cost, is $4606.88. Update: Pinkcore (designed to be used with the connectors) isn’t Foamular and can’t be ordered from Home Depot. It’s a professional product and I’ll have to get it from a local distributor. Availability/pricing for pod insulation is now totally up in the air.
The edges of the Foamular are tongue and grooved and fit together snuggly. I don’t know if that’s the case with the Pinkcore.
I can get scrap EPS for the cost to get it here. So, say, for <$200 I can get it here and use my time and labor to cut and piece it. (I'll need to factor in the cost of the connectors which I haven't confirmed I can get.) Can I thoroughly seal the EPS seams to eliminate any thermal break? Inquiring minds . . . Truly, this entire process needs tested. It's possible I may not like how piecing the EPS goes. Or, I may find it a breeze and see no reason to go to the expense of purchasing Pinkcore XPS. I may piece the walls but not the roof. I may build the roof in place ala mxSteve instead of tilt-walling it and use 6″ surplus EPS as my insulation. Testing is a must. No firm decisions can be made until testing has been done.