Those SIP walls should make them about as energy efficient and air tite as possible. Seal any 'holes' (electrical wires, pipes, etc) with a good foam insulation. Would not worry too much about air leaks into attic from outside but do worry about leaks from the floor below. In fact, you will want good ventilation thru attic spaces. Be sure to use a good vapor barrier and seal all possible 'holes' from the floor below. If using cannister lighting, be sure to use the IC & air tite ones that will go into attic spaces. Your using an ERV is an excellent idea since modern sealed homes have ventilation problems.

Hi,

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[This message has been edited by Chicago Stoam (edited January 09, 2003).]

www.buildingscience.com is a good source of information. They are consultants for the Department of Energy and have books available.
I bought the book for my area "mixed hummid climate" which is my area of the US (in Virginia). There is good free info on there website.
I am trying to build a house similar to you. My house has a complex truss roof.
Having a crawl space, I decided to include that in the envelope.
I started with 1/2 rigid foam on the ground inside the foundation.
6mil poly and then a 2" slab of concrete to hold the poly in place.
I will have spray foam put on the inside of the foundation for insulation and none between the floor joist since that area will have a supply and return duct.
This does several things:
1.Reduces termite infiltration.
2.Dryer air will infiltrate my walls (past mud sill) instead of moist unconditioned air which usually reduces the R value.
3. Hardwood floors do not sweel and shrink as much.
4. tile floors will be warmer in the winter.
5. air handling unit is in a conditioned area which reduces heating & cooling costs.
6. when duce work starts to leak, it will leak into the envelope.

You need to use something like Sill Sealer between the block foundation and the mud sill. Available at Lowe's in blue close cell foam rolls.
Seal 1st plate with a soft spray foam like DAP Tex.

I am planning on using Icynene spray foam on the foundation walls, all walls and under the roof sheathing. I will not be venting my attic either. The roof sheathing I am using is made by LP and has a aluminum foil that reduces radiant heat from the roof. By insulating the underside of the roof sheathing, I will once again, be including the air handling unit and duct work in the envelope. Tests have shown this makes the unit perform 25% better. No worries about loosing conditioned air past lights and the attic access door. I will have a return and duct for the attic to condition the attic area and remove moist air.
The foam is more expensive but I can use a smaller tonage HVAC system since the typical 25 to 30% "fudge factor" can be taken out. Batt insulation reqiures a fudge factor because of all the air infiltration it allows. Damp insulation also reduces the R value which should not occur with the foam.

Also make sure to use gutters to move water away from the house foundation on rainy days.

People will tell you that insulating the roof sheathing in the attic will void your shingle warranty but testing has shown that it only increases the temp of your shingling 10 degrees which is not a big deal.
Elk and Certainteed have seen the light so to speak and GAF told my roofer that they will give me the full 40 warranty on my shingle. Hope this helps.

Oh yeah, I to plan on an ERV. A must for a truly tight house.
Drak

[This message has been edited by Drak (edited March 18, 2003).]