To elaborate on thermal bridging since it was brought up again... there are several ways to calculate it, but to keep it as simple as possible, here is how it affects your total wall's insulation. First thing, if you put in r20 rated insulation product, you are certainly not getting an r20 wall for cavity walls. Other products such as ICF and SIPs (some SIPs even have thermal bridges) are nearly thermal bridge free and have what is called continuous insulation. My home is an ICF house from the footings to the roof, and there are no thermal bridges anywhere until the roof line. This gives me an r28 continuous insulation. However with wood frame structures, you have a framing reduction to take into account. Most new homes, studs, heads and plates take up anywhere from 18-25% of the wall area. (lets keep the numbers whole and rounded for easy math) Say you select blown fiberglass in a 2x6 wall, gives you roughly r20. You have 1000sqft of wall surface. That r20 is only for the stud bays, and every 16" roughly you only have an r1 due to the stud (framing factor) So you have 800 sqft of wall at r20 and 200 sqft of wall at r1. . Your "r20" wall is performing at an r16 on average with the studs acting like heat sinks. Add just 1" of XPS foam to the exterior (r5). Your r20 turns into r25, and your r1 turns into r6. Now 200 sqft of your wall is an r6 vs an r1 and reduces the heat sink effect.The materials to add that 1" XPS would be roughly 500-600 for that 1000 sqft wall. The upgrade from blown fiberglass to open cell foam is typically more than that. For adding exterior foam, details are pretty simply up to about 1.5" thick. After that, the details change and become more costly. Luckily for you, in zone 4. 1.5 is about as thick as you need to go. 1" would be a good start, and your details really do not change. I have detailed 1" foam and windows 1 of 2 ways. Either install the sheathing and foam and then the window. Or with 1" foam, most window flanges are 1 1/8"+ wide, so you can install the window and then install the foam. This gives them about 1/8"+ lap for a caulk joint for trim to hide the foam. The trim stands proud of the window with this detail obviously. 1.5" adds another step. I like to detail a frame out around the windows and butt the foam into it. So frame the wall as normal, install sheathing, then rip a 2x4 in half to give them 1.5x1.75 furring to frame out around the window RO. Install the foam, butt into the furring around the window, and then set the window, nailing into the furring. Everything planes out, and quite simple. Obviously this can also be done with 1" foam too, its just not necessary. There are lots of details floating around out there. Check out green building advisor as well. You can also checkout my blog for more details and nerdy building information. Again, a very untechincal explaination, but you get the idea hopefully. Here is a link that might be useful: home building blog

Regarding the building code, any homeowner is responsible to the city for meeting all codes and ordinances and even if the homeowner assigns that responsibility to a licensed contractor, it does not relieve the homeowner from their obligation to the city. If you are going to make important design decisions about your house you should buy a copy of the code and read it carefully before asking the building inspector any questions. It is always better to make an informed proposal rather than ask an inspector how he thinks you should build something. Many inspectors will understandably want to give you a simple answer rather than a full explanation of your options.

Option 1 we've covered. Option 2 is ok IF main roof and new roof are continous and pitch doesn't change. Except change of style in front,option 4 is very similar to the way I did mine several years ago and there hasn't been a problem. Peak (aka ridge) in option 4 must start at least a few feet up from edge of main roof. Change of style at front will be fine only if the dormer pitch doesn't meet wall on main house. You can't use enough flashing and tar to prevent leaks if it does. Dormer should be positioned away from main wall so that new roof run's continuesly along wall from peak to drip. Close attention must be given to flashing high side of chimney. I won't try and give you step by step but instead tell you to make certain roofer know's what he's doing. If the person framing and decking isn't one and same as applying shingles,have roofer give instructions on how frameing, decking and flashing should meet wall and chimney. Framer/decker is in best position to install most flashing at wall and chimney. I'm a huge fan of crickets on high side of chimney,esp if there is a large expanse of run off above. Option 5 might be having new ridge hit old wall a foot or more below drip of old roof if measurments work. As stated earlier for best appearance pitch is best maintained throughout if it can be done without interfering with pratical considerations. Shingle mfgr reps are a good source to bounce drawings off of before construction if you have doupts.

I agree and so does DH, the shed looks best. Thanks to robo for the mock up! Eld6161, my boys' room has one small porthole-style octogon window. I think it's because my second floor probably originally had only two very large bedrooms upstairs. At some point, a previous owner added a wall between one if the rooms to make a third bedroom upstairs. As a result my DD's room on the back dormer has two big windows and no windows in the front room which is the boys.