We are right at the beginning of a huge transition in our country's housing stock related to performance and health. Build your house the old way (probably local code minimum) and you will get a home with average energy costs and perhaps more importantly, un-healthy Indoor Air Quality IAQ. Build your house the new way (IECC 2012) and you will get a cost-effective energy efficient home with dramatically better IAQ. Insulation is important along with the other things discussed in this thread. The two topics that deserve more light are 1. Airtightness (as measured by blower door test). 2. Fresh Outdoor Air Introduction with mechanical ventilation. Meeting the minimum requirements of the International Energy Code IECC 2012 is a cost-effective path to low- energy bills and healthy indoor air. Individual opinions and anecdotal evidence can be helpful but meeting these minimum guidelines is ones best bet for those results. Building with deep floor trusses is an easy way to get ducts into conditioned space. Even better, hang the trusses from the wall to reduce air leaks and thermal bridging. jowens751, Murphy is beautiful. Its in building climate zone 4 but personally, I would build to Zone 5 minimums due to your exposure. I would also go for less than 1.5 ACH50 on the blower door test. International code is currently at 3 ACH50 for zones 4 and above but Iam pretty sure the 2015 version will be much closer to 1.5 so try to stay ahead of history if possible. Airtightness is much easier to measure than real world R value and it has a much bigger impact on energy costs. Insulative sheathing (foam being most affordable and popular option) is practically required in the new energy code for Zones 3 and up. Open cell foam for cavity insulation has become cost competitive with densepack cellulose in many areas and blocks air movement better. Find out your local climate zone and see what the minimum energy codes (future laws) require in Table 402.1.1 of the IECC 2012. lexmomof3, I would probably upgrade but might want to cross post to HVAC forum. SEER ratings are rarely accurate as they depend on different Compressors, Air Handlers and duct install. In other words, a 12 could be outperforming a 16 but thats usually an exception. Probably more important is to get a variable speed or two stage unit to better handle de-humidification.

I've got the answer for you... If you're planning on finishing the interior walls and you want the house to be real tight, you should consider using icynene foam. Icynene does have to be installed by a contractor, but I recently insulated a 3000 sf 1850s post and beam farm house with it and the entire intstallation took about 2 hours and was less expensive than estimates with traditional fiberglass bats. The materials are more expensive, but the labor was cheap! Icynene will give you a complete seal - NO drafts and no need for roof venting. It does not have as high an r-value as other poly based foams, but it is water based and does not off-gas so it is very GREEN. It still has a much higher r-value than rigid foam, or fiberglass, and by virtue of creating a complete seal, will HUGELY increase the efficiency of your home. You are lucky in that your interior walls are not yet finished. Sprayed on foam options aren't great if you have to strip the interior walls first. Icynene is the ONLY option I'd consider in your situation. Good luck.

Hiring a competent licensed contractor to do the earthquake retrofit and other items that will be demanded of you during this permitted renovation would be the first order of business. He can guide you as to what would be the most cost effective approach. It won't be what you've indicated. Almost no return on the large amount of expense and labor to do what you're suggesting.

Here's a bit more info to give you a better idea. Zone 5B, Cold winters, hot summers (rarely humid but like this year...humid and hot summer!) My walls will be 2x6 with either dense fiberglass or mineral wool insulation (products readily available locally). My current debate among my thoughts is trying to decide about the WRB (MY HOUSEWRAP) and at what tier/level/plane to install it (Or even two). Windows are not permanent, and in a forever home (God willing), windows will need to be replaced in the same lifetime I live. Therefor, I don't want to choose some method that would hinder future upgrades/replacement. (Such as installing foam over a flange so it must be cut out, or installing a type of flashing that requires more of the foam wall or window box to be torn out to replace the next time around. I am debating between a quality house wrap to prevent moisture and also act as an *air* barrier not a *vapor* barrier. Basically, on a cool winter day with 50 MPH Wind, I don't want that wind (air) easily permeating through the house because I will a.) not be sealing the joints of foam b.) possibly not even taping the foam joints c.)not going to use any internal poly as a air or vapor barrier. I am not sealing the foam joints because foam shrinks and expands and those joints will not stay tight forever. If I have the luxury, I will install (2) layers of 1" thick versus (1) layer of 2" thick to provide staggered joints and prevent air from moving inwards that much more. There is a wealth of information on greenbuildingadvisor, but it seems to boil down to personal preference on two things. One being that I can opt for innie (windows set towards the OSB wall sheathing layer) or outie (windows that are at the most exterior plane as possible). And we all know that flashing a window opening is important for multiple reasons, and that the standard way includes integrating your house wrap (WRB) into the rough opening with multiple methods. I would like to use a flexible peel & stick flashing that will seal to/against the house wrap. My concerns for those who have rigid foam on the exterior are a.)where did you locate a house wrap (Or WRB)? and b.)in what fashion did you set your windows? It varies by foam thickness, but generally 1.5"+ of foam requires framing out a window frame/buck for window support whereas under 1.5" doesn't seem to need the additional support. And of course the other option is the fasten the window like standard construction, on the sheathing level right against the sheathing (osb in my situation) and into the studs. This would then mean I would either use the WRB at the same time to detail the window opening, or perhaps not. But also means I would have to design a custom flashing to cover the exposed foam around the window, since the window is set inside from the foam and siding. I am surprised house wrap (a WRB) seems to not be the norm. It is here...and it is something I do not want to overlook. My understanding is that in new construction with rigid on the outside, builders extend the window opening (like you said Mushcreek) to the same thickness as the foam, therefore that foam will not have an exposed edge. I read on GBA that instead people build plywood boxes for the windows the thickness of the foam + 3/4" and then use a 1x3 or 1x4 flat around the window opening fastened thru the foam into the window opening studs. Then the window flange is fastened to this flat 1x3 or 1x4 frame, and it also brings the window out the extra 3/4" so that 3/4" firing strips can be used to install siding. I do not think house wrap *over* the extended window frame would be as effective as if I just installed the windows flush with the foam level, allowing my flexible sticky flashing tape to easily fold over the opening and adhere to the foam. ---starting to think I should just not be so concerned about this detail. Turning my hair grey.