Panelcrafters,  (I'd not meant that you were arguing, I just didn't want you to think that my question was a torch.)

I think I understand:  If I have a complex ceiling pattern, then I need framing to support it; and, if I'm paying for some of the framing anyway, then I cannot obtain the full cost benefit of the SIPs' eliminating that framing.  (Thank you!  That's really obvious now that you've pointed it out.) 

But that raises another question:  Is there available data on comparable construction cost elements?

Has anyone built two similar homes with simple gable roofs, one framed or with trusses (and with enough detailing to achieve good leakage and thermal properties) and the other with a SIPs roof?  If so, would they share a detailed breakout of the roofs' cost elements? 

Very respectfully,
Larry

Well, kinda, sorta. A SIP roof will usually span from support to support(wall/beam/purlin). So, no framing is needed to support the SIPS.

Let's look at my 30' x 50' example. Suppose that 1/2 of that space was to have a true vaulted ceiling, and the other 1/2 was bedrooms with 8' ceilings. If I was to design it, I would have a ridge beam spanning 1/2 the distance, and the SIPS would run from it to the outside walls. Now the other 1/2? They would just be trusses.

Aren't you also forgetting the structure? I didn't see a price for trusses in your breakdown.

"Popping and crackling SIPS" - I guess you're not talking about steel SIPS.

PanelCrafters,

I'm still rolling the boulder up this learning curve.

If I consider your example, and if I assume that the house has a straight ridge line, then the costs and complexity would seem to favor using SIPs everywhere.  If the supporting ridge beam is already in place for half, then adding trusses under the beam would seem to add complexity and cost when just slapping down SIPs across the whole roof would seem to be quicker and easier. 
Why change in mid roof? 
Would you stop the beam at the mid poirt?

VERY respectfully,
Larry

Mid point? Bingo! Since, in my example, there would be trusses beginning at that point, my design included support for that beam at the mid point. The beam would no longer serve a purpose after the mid point, and would not serve as an obstacle to installing the trusses after the mid point.

Changing at mid point? Simple, the ceiling would not be vaulted, so why use SIPS and additional framing for a lower ceiling(unless you wanted a conditioned attic)?

PanelCrafters,

Yes, that makes sense.  But, to me, the mixed approach focuses the attention onto the total cost and risk that the builder achieves a tight and well insulated shell. 

Do you know of any real world cost data on SIP vs. framed roofing? 
I've not used them for 20 years, but would the Means books have valid data on construction costs involving SIPs?

Very respectfully,
Larry

No, I sure don't. I've got to think that just the materials(SIP Panel vs. Trusses, sheathing and insulation), the SIPS would be quite a bit more. Figure in the installaion labor, and it gets closer. If you insulate with spray foam, SIPS might be equal or less in cost.


Wow, that takes me back a bit(to school) and I won't divulge how long that's been! But, I did see something about Means covering SIPS. And, I'd be interested in reading that!

You guys are missing some of the value in SIP construction as they relate to smaller HVAC units (and less for future HVAC replacement cost), quicker construction time (means less construction interest) healthier indoor air quality (allowing less exterior polutants) Depending on where you build they are 3 times stronger than frame. Peace of mind for health and safety have no $$ value

Truss: Manufactured vs. Stick built

We're designing a complex multi dormer home in the moderate climate of Southern California.

We decided to go with truss.

Question: how complex can a truss manufacture go and is it a savings in time dollars and accuracy?