Another attic insulation project...

So with all the insulation projects goin on around here, I thought I'd pile on too since that's what I'm working on right now...ugg...this might get wordy.
I have a classic cape cod style with the typical one long room upstairs. Anybody familiar will know that the upstairs room is basically completely surrounded by cold (winter) or hot (summer) attic air and they tend to present some extra challenges to properly insulate/air seal this area.
My place was insulated years ago, but only with R11 fiberglass in the attic. I have blown in cellulose over it, but not enough really. Right now I am more concerned with how exactly to deal with insulating the 2cnd floor room/space specifically.
Starting from the bottom and working up.
I originally started filling the floor joist between the 1st and 2cnd floor (under the upstairs room floor) with "shake and rake" insulation, since we were not heating/cooling upstairs I wanted to completely fill it. But now we need to use the room regularly and will heat and cool it now, so I am ok with "loosing" some heat from the 'ground floor to this area.
So my plan is to cut some 2" foam insulation board to plug each floor joist cavity off from the larger vented attic area on both the North and South sides (the room runs E/W) That deals with insulating/air sealing the floor.
For the knee walls I will run another layer of R11 from floor to roof joists (to fully fill the stud bay, overkill?) and then I'm covering the whole wall with 3/4" polyiso foam panels to air seal things.
Now for the ceiling...specifically the part that runs parallel with the roof (on a 45* angle) It is about 3' long on each side of the room and has R11 fiberglass in there now...not enough! My idea there is to once again go to 2" polyiso board. Cut panels 3' long to slide up between each 2x6 (on top of the existing R11) just to where the ceiling takes the turn to flatten out. Then rig up some sort of long hose/straw setup to get up in there to seal the foam to the 2x6s with spray foam (if they don't seem to fit tight enough) Keep in mind I cannot fill this space completely to the roof due to the attic venting running from the lower N/S dormer gable vents, up to the higher E/W ridge gable vents which are above this room...oh, and the roofing nails sticking through about 3/4" too...that will add an extra degree of fun too I'm sure!
Now for the flat part of the ceiling. First of all, there is no access to get up there...well, the gable vents could be removed, but nope, not doin that. Gonna cut an access in the ceiling then install an attic ladder. Once up there, I'm assuming there will be R11 up there too...I could fill up with cellulose...or more foam board...more fiberglass...dunno, might just figure it out once I get up there and look around a lil bit.
So, anybody have any better ideas, tips, suggestions...case of Tylenol?

 

Really...26 hrs and nothing...from anybody?!
All my ideas must be so good nobody can improve on them, eh?

 

Yeah, I saw that one too...but thanks Eric!

 

It seems strange to me that, the way I read it, the foam board for the roof would be place on the side farthest from the cold and air infiltration. I understand the fiberglass insulation is already there, but since the foam board will also (for arguments sake) be a moisture seal, I would think that it would basically trap moisture in the R11, which would be bad. Maybe I'm reading it wrong, or maybe my theory is wrong?

 

I despise my cape for this same reason!
Terrible design! We use the second floor for storage only. Ugh!
I'm thinking it will remain the same till it gets a complete demo and can be spray foamed.
Subscribed...

 

I think I get what you are saying...if you research it, that seems to be a huge debate...as far as how to properly seal up a cape cod attic

 

I'm sure, just as there are debates on how to seal up a below-ground foundation (some say vapor barrier some say not). I would not even think twice if you said you were removing the old batting, putting up the foam board to the cold side (and sealing) then installing the batting below the foam board. But I'm not even close to an expert and you seem to have researched so I hope it works well for you

 

Not sure how I missed this last night........................
the only concern I have is, you need to maintain an air gap against the roof sheathing otherwise you "cook" the shingles shorting their life. You should have soffit and ridge vents but it sounds like the house is of the age that it does not. When you slide the foam board in you will compress the FG lessing its efficiency, something to think about.

The last big cape I built, 4500 sq ft, being a new build all the roof rafters were 2x12 so there was more room for insulation still not optimal.
I also have one right now I am rehabbing, kind of it is what it is and there is not much you can do about it.

So to conclude, you only have a 5 1/2 inch cavity, that is all the insulation you are getting in there unless you reframe the area. R11 in the walls works and the small flat ceiling do what you can but keep in mind it is not going to change much because of the rest of the area.
The optimum would be spray foam for R value.\ and air seal to minimize drafts again spray foam does this too.

 

I read a couple articles that talk about putting foam board on top of the roof sheathing to avoid thermal bridging of the rafters... As ironpony mentioned, I’d be concerned about the life of the shingles if just traditional asphalt.. if you need a new roof, this might be something to consider...

Rigid Foam on the Roof and Walls - Fine Homebuilding

I considered insulating between my rafters with 2” foam board... plan was to affix spacers that would maintain a 3/4” gap from the soffit to the ridge to allow air flow... I’m now considering the method above, but that will delay my ability to do the project... I would think If you went with a metal roof, the hotter roof temperatures wouldn’t affect it quite so much.

 

That was interesting reading - thanks

 

you know they make foam baffles for that purpose to leave an airspace.

 

NotbSure how I missed this one, brenndatomu how old is your roof on the house now? We have a lot of capes here, and what I think is the best case scenario, if your roof has to be replaced. Spray foam from the roof deck down leaving air flow. Most money, most effective.

If that's a no, do you have vapor barrier on your R 11? The one problem I've seen is people using multiple vapor barriers and that causing mold issues. Have you done a blower door test yet?

 

30 year shingle in 2010. This is only the 3rd roof the place has ever had...built in 1940...it has 6/12 and 8/12 roof pitch, so I know that helps shingle life too...

Yes, its facing up...away from the drywall.

No. The place actually isn't too bad to heat as it is now, so once the these obvious issues are addressed (picking the low hanging fruit so to speak) I'm sure it will be plenty good enough. The only reason I'm doing this now is that we need to use the upstairs room now, it was used as a guest room/storage before and 99.9% of the time was left unheated or cooled...I'm sure it would add quite a bit of load to the heat or A/C if left as is.

 

I didn’t see the point in paying for foam baffles for the entire length of the rafters if I was going to be using a rigid insulation. Looks like they are about $0.25 a linear foot. Seems pointless to use a foam baffle when you could just make a spacer for practically free that would serve the same purpose..

 

Yes venting is so important. My house does not have an attic or ridge. So soffet vents have no where to go to be vented to. I hot decked a 1.5 square shed roof spayfoamed it shut as it vented to inside home. After hip replacement I will add newer vents to top. But when I replaced roof 5 years ago, it was leaking and on a budget, you do what you got to. Roof rafters are 2 by 12. I checked on special vents was 2000 more.

Contemporary homes are not always better

 

well just finished up with a realtor, the house in the above picture which I was working on, is on a commercial lot. His buyer made me an offer and I could not pass it up. The house will be torn down and a gas station is going in. I am sad because when I bought this house I was originally going to keep it, that has since changed. The house sits on 1/2 acre and is 5 bedroom 2.5 bath with the garage you see and another 28x32 in the back. All real oak hardwood floors. Ah. progress.

these are oaks in the back yard, about 32 in dia. probably 60 ft tall