Hi All,

My wife and I purchased an older home in Colorado a year and a half ago.  The house was built in 1948.  We plan to push out on all four sides, partly to increase usable square footage, and partly to improve an awesome heating penalty (most people discuss R-factor, we discuss wind chill index). We had been considering 6x construction, with a couple of inches of insulated sheathing on top of it.  However, if possible and practical, it seems SIPs would lead to a much tighter and better insulated home.  Some questions:
1) How difficult is it to mate SIP walls to a core shell of 2x construction?
2) Same question, but mating SIP roof panes to a 2x roof? 
3) We would like to provide the SIP manufacturer detailed drawings, and have the SIP panels precut prior to delivery.  My guess is that, in any roofline, there will be some variability in the roof angle, etc.  In an old house such as ours, I would expect an inch or two variation from peak to eave.  How does one deal with that with SIPS?
4) We are considering 8" walls, for looks, strength, and energy conservation. (The temperature here hasn't seen the warm side of 30 F since early Nov, there is a foot and a half of snow on the ground, and it is snowing now.) It looks to me that a weak spot is in the thermal bridging associated with the headers and framing around the windows. How do people normally handle that?

Thanks for the help, and happy New Year.

PMH

I cannot speak for the steel guys and their connectivity systems, those guys seem relatively bright so I am sure they have figured out a way, but with OSB SIPs it's as simple as screwing dimensional lumber into the existing structure to mate the OSB SIPs panels. I would have a structural guy give you his blessing as you spread out, but the addition of the panels is really simple.

If you have any concerns, give me a call...

Steel is as simple as srewing a metal channel to existing structure,


http://www.greenbuildingtalk.com/Forums/tabid/53/forumid/5/postid/71832/view/topic/Default.aspx

Also living in Colorado, I can understand the issues of weather. This morning it was 18 below when I got up. For what it’s worth, here’s my opinion. I think moving the walls out would be a very expensive and difficult proposition. You would need to have a new foundation and footer to support the new walls. This would entail digging dangerously close to your old walls and water lines and sewer lines entering your basement. Also, you would need to devise a method to support the roof while you moved the walls out, and then the roof structure wouldn’t match the walls. My suggestion is to leave the walls alone and purchase nail base SIP panels. Nail base SIP panels are like normal SIP panels, but have OSB on only one side. Remove your siding, doors and windows, glue and screw the nail base panels to your existing wall studs, OSB out, to the exterior of your house, cut out for the doors and windows from the inside, install the doors and windows, or replace them with energy efficient ones, Tyvec and re-side the house. You could also use insulated siding. You could use a 4” nail base panel that has an R value of about 14, and if you have a 2 X 4 wall with an R value of 11, that would give you a total R value of 25, and if you tape and caulk all the seams well, a very tight house and very little thermal bridging. Now the roof. As the home was built in 1948, I’m concerned that there may be issues with the combination of the weight of the SIP panels plus the snow load. If you have a flat ceiling, you can have another foot of blown in cellulose blown into the attic. If you have a cathedral ceiling, you could remove the ceiling material, add 2 inches of foam sheets, and reinstall the ceiling material to the underside of the ceiling. Now, take the money you saved, and add a solar water or electric system to defray your heating expenses.

Steve
GrandCountySIPs.com
[email protected]

Philip and Steve,
I installed 6"OSB SIPs on an existing house in upstate NY in the early 1980's. We used a steel angle plate bolted to the perimeter band joists of the first floor. Two stories high. Built out all the window and door jambs and installed new siding. It all worked like a charm. And we had only 10 ft between houses! The house was much more comfortable and it lowered the heating cost with a ROI of about 5 years. Added additional insulation to the attic, too.

Greg and Chris are correct. If you look at Chris' link you can see that his entire system could work on the existing structure with installing a new beam at the ridge, carried by the end walls and then install new roofing. Depending on the span, it may be able to be accomplished with OSB SIPs and a new ridge beam.

Best of luck to you.
Richm

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