RE: vastly exceeding the ROI point of diminishing returns: Prices are rising, but if your ROI is based only on current costs (low for fossil fuels right now) unless you factor in the historical price increases of these fuels, the ROI calculation is meaningless. Minispilts, however, can run off PV panels, so that (with net metering) when the array is paid off (usually 7-10 years worth of typical annual costs) you heat is free. We know PV panels have a life exceeding 30 years, so a true ROI comparison over 30 years must compare the cost of 20 years of free fuel with the future cost of gas or oil.

We definitely have a big decision to make on the heating source. I found a similar sized house nearby that has a Mini split visible in back of the house and took my wife to show her. She isn't a big fan of the unit outside, the piping running on the back walls or the units inside (I showed her pictures of those on my phone). Maybe there is a way to minimize the eyesore factor? It's looking like a mini split may be a hard sell if not.

Right now I am working on the framing details and I have a couple questions there. My wall stack up from inside to outside is looking like this;

Drywall
Vapor barrier on walls and ceiling
2x6 studs with Rockwool R23
OSB sheeting caulked to the studs (possibly taped as well)
House wrap (2 new rolls of this was also given to me by a friend)
2-3" of foil backed Poly Iso
Furring strips
Siding (probably vinyl for cost)

First question is how do I connect the outer vapor barrier to the inner? Is this even necessary to do?

My thought was to lay a strip of vapor barrier down on the outside walls before we set the trusses. Then I could seal to that inside and outside after the Poly Iso goes up on the outside.

Second, what is the preferred method for window attachment? I plan to use new construction style windows with the nailing strip. Is it Ok to just picture frame all the windows with furring strips, seal over those and attached the window to the strips?

Can Anyone recommend a readily available new Construction style window that is budget friendly?

Vapor barrier on walls and ceiling
...
2-3" of foil backed Poly Iso

Tape or gasket your air barrier(s) and don't build a partition that can't dry to the exterior or the interior.

Jonr has it right.

If you have a vapor barrier, not to be confused with air-sealing, you must pick one. Inside or outside--climate matters--not both.

I'm used to poly vapor barrier on the interior and house wrap on the exterior. This is all new to me.

Which is preferable? Or should I say which is easier to accomplish given my plans? If you choose to seal the exterior sheeting, how do you tie that to the seal for the ceiling?

House wrap is not a vapor barrier - it is an air barrier that allows water vapor to pass through. But the foil facers on that polyiso are vapor barriers; therefore, you do not want an interior vapor barrier with that stuff installed on the outside.  Interior + exterior vapor barriers are bad news.

Using Membrain instead of poly would be a close match to your plans and can serve as an interior side air barrier. Foil faced polyiso is easy to tape as an exterior side air barrier. Air barriers on both sides is a good thing. Best is to have vapor barriers on neither side.

Posted By Bob I on 21 Oct 2016 12:12 PM
RE: vastly exceeding the ROI point of diminishing returns: Prices are rising, but if your ROI is based only on current costs (low for fossil fuels right now) unless you factor in the historical price increases of these fuels, the ROI calculation is meaningless. Minispilts, however, can run off PV panels, so that (with net metering) when the array is paid off (usually 7-10 years worth of typical annual costs) you heat is free. We know PV panels have a life exceeding 30 years, so a true ROI comparison over 30 years must compare the cost of 20 years of free fuel with the future cost of gas or oil.

What's rising? (other than sea level, that is. :-) ) The notion that future price inflation for any commodity fuel isn't well founded. The best you can predict is that prices are volatile. The price of #2 oil isn't particularly low now relative to the 25 year average, which bottomed in 1998 1999, and peaked about 7-8 years ago. Gas pricing is volatile too.

But in inflation-adjusted terms electricity has had a long term deflationary trend over the past 50 years, and with the ever dropping levelized cost of both solar and wind power there is plenty of reason to believe that will continue. Unlike fossil-burners, the marginal cost per kwh is near zero (no fuel), and the levelized cost is all built into the financing costs. The technology keeps getting both better and cheaper. With or without net metering, these already-competive technologies will continue to put downward pressure on electricity pricing, no matter what fossil fuel prices are doing.

The current price of natural gas in inflation adjusted terms is below the 2008 peak, but it's well above the 50 year average. The current price of heating oil is nearly 2x what it was during the 1998 low point, and well above the 50 year average. Residential electricity is about 30% cheaper in real terms than it was 50 years ago, but primed to go lower. see:

http://www.eia.gov/forecasts/steo/realprices/

OK, so the real question, when you finish fact checking analysis (I admit I was shooting from the hip): does the "inflation-adjusted" long term price of fossil fuels in economic terms as well as ecological terms makes solar panels illogical?

Ok, So my stack up should look like this;

Drywall
Membrain on walls and ceiling
2x6 studs with Rockwool R23
OSB sheeting caulked to the studs
House wrap
2" of foil backed Poly Iso taped at all seams
Furring strips
Siding

I had an interesting conversation yesterday that has me thinking. One of the insulation guys called me back about ordering. I told him it would be a while and what I was going to be doing with it. He suggested I go to see a guy that lived way out in the middle of nowhere and ask him about his house. So I did. Turns out the guy is nice and chatty but a little eccentric. I asked about taking pictures and he said no way. Anyway he has one of the very few well insulated houses in the area. He had some funny ideas on some things. He was not a fan of mini splits at all. He said they were marketed by electric companies and their performance was exaggerated. He scoffed when I told him my plans and said it was a waste of wood. He said I should stick to 2x4 walls and go with 3" Poly Iso. Or better yet he said would be two alternating layers of 1.5" sheets. His opinion was it would be cheaper to build and preform better than the 2x6 walls. That's basically how he built his house and it was extremely comfortable inside. We had a little bit of a cold snap and it was really windy yesterday. The house was dead quiet inside and warm. He heated his house with a heat pump.

Is he right? would a 2x4 wall with thicker rigid insulation be cheaper to build and preform better than a 2x6 wall?

Cost depends on the cost of labor and screws. His methods (at R4 for Roxul & R6.5 for polyiso) would yield R33.5, yours R35. Not enough difference there to matter, but more exterior foam is better than more insulation inside stud bays, simply because the foam is spanning the entire wood structure, and you are minimizing thermal bridging. The warmer you keep the wood structure, the better the house will perform. OTOH, it would probably be hard to tell the difference. Joe Lstiberek (BuidingScience.Com) says that the ideal insulation is 100% on the exterior of the structure. We build double stud wall houses since the labor cost for exterior foam is high - especially without specially trained crews.

I don't see any need to install house wrap on the outside of the sheathing and under the foam. I assume you are taping the seams of the OSB - if not you need to. If you want to use a layer of house wrap, use it over the foam and under the strapping, and use a drainage wrap.

Labor is free for me. I'm building this myself with help from some friends and family. Possibly a crew to dry it in if needed.

2x6 framing is more expensive than 2x4 but it's not a huge difference. Maybe a few hundred $'s in material. Screws would be a few hundred more so it's almost a wash there.

One thing the visit did do is give me confidence I'm moving in the right direction. I'm getting more and more excited every day to get started. I'd love to make house something people want to copy as the new standard around here.

the most important issue by far is to make your home airtight, but these iterations are good to understand. It was good for you to experience your eccentric neighbor's house - that's what you are aiming for - and something that is hard to describe to disbelievers. Also - many people who do thing differently than the "standard" - (or We've always done it this way") is that they are labeled "eccentric". Someday, we'll just call them "smart".

I like your eccentric neighbor. The stick hold up the roof. The insulation makes you comfortable at the lowest possible recurring fuel cost. It is a conservative investment and a hedge against rising fuel costs, however unlikely they may be.

the " lowest possible recurring fuel cost" - solar, right? (what's lower than nothing?)

Send the panels and the crew. I have the room and a well insulated building :-).

I don't install solar, but I'm sure there are plenty of local folks that do!

He was definitely smart about some things, other things he seemed a little paranoid-ish. He went off about solar energy. He wasn't a fan of that. He was pushing me towards building a windmill. He welcomed me right into his house, showed me around and then when I left I mentioned bringing my wife over to see it and he told me nicely not to come back or tell anyone where he lived. Super nice guy and I'm glad I went but he was just a little bit "off".

reminds me of reading an "underground" student newspaper back in college - lots of paranoid articles about the methods we were using in the pursuit of the war of the decade. Or they seemed pretty paranoid and bizarre until a few years later when it came out in the mainstream press that those paranoid reports were the truth, and we had been fed lies for years by the government.