i have a 1950 slabed ranch that i will be residing and installing new windows and door, I”m going to remove the 50 year old poorly installed craft faced R11 fiberglass and install dense pack cellulose. I was thinking of using 2″blue board on the out side verses polystyrene. due to the foil and price, my question is does it seem sensible to put the foam on the outside and does it really matter if i use 1 or 2 ” beside the r5? i was trying to achieve airsealing with the foam not r value, or maybe put some textured house wrap and put the 2″ on to achieve mass. insu. code?? any suggestion would be greatly app.
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
Fine Homebuilding is excited to be the official media partner of the 2024 Building Science Symposium series! This event offers builders, tradesmen, architects, designers and suppliers to discuss topics ranging…
Featured Video
Video: Build a Fireplace, Brick by BrickHighlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
If you're not concerned much about the R-value of the foam, less is better when it comes to siding the whole thing. Trying to hang siding over thick foam is a pain and not very secure.
If air sealing is the main goal, use housewrap over OSB. Them you'll have something substantial to attach the siding to in the places where, inevitably, trim or other siding elements will not fall right on studs.
it really matter if i use 1 or 2 " beside the r5?
What?
polystyrene. due to the foil and price,
what?
FYI - blueboard IS polystyrene and it doesn't have a foil face.
Air sealing can be achieved w/ plywood, too, so installing something like polystyrene is an expensive way to air seal. You have as many joints as plywood.
I'm confused ... maybe you could clarify a bit more. Maybe it's also too early and I can't read?! :)
Also ... there is a big benefit to the insulation ... it eliminates (reduces) the thermal bridging at all framing. This may be substantial in older construction. But you do have to deal w/ the details (e.g. around windows and doors, but usually that's not a big deal).
sorry about the confusion I know about the blue board being perm. and i know that the foil face icynen. is not to change gears alittle bit i have to correct some info. the building official is cringing to me about pulling the craft face fiberglass out to install dense pack cellulose, would you think this would eliminate the vapor barrier or is the info i have found incorrect? I also heard about just putting the dense pack cellulose in with out removing the fiberglass? what would ur suggestions be? thanks again for the replys
would you think this would eliminate the vapor barrier or is the info i have found incorrect?
What info? I think the cellulose still requires a vapor retarder which can be achieved in a couple of ways: Poly or vapor barrier paint (interior). I'm not a cellulose expert, but I don't think it is like spray foam where it becomes the vapor barrier (retarder). Your work is exterior only, is that correct?
ya it was going to be, Im trying to get the most out of this house while i have it open. to agree with you the inspector actually shot all my ideas down and told me to just tape all seams of the plywood and use the 3/8 foam fot the vynl siding. so all that for nothing, i thank you for your time and rplys.
Why wouldn't the inspector let you put insulation on the outside?
Where are you located?
How were you going to remove the R-11 from the outside?
How were you going to remove the R-11 from the outside?
Open wall, remove insulation.
i was going to remove the lower sheet of sheathing to remove the r11 single story ranch so the longest piece is 8', he didnt want me to add insulation on the outside of the wall unless the r-factor exceeded the code of r20, thermal bridge. dont have the extra 3500 to do this. so i have to abandond that whole idea, i thought the info i got was right. but it seems i missed the part where they were and where i am. i live in western mass. so vaper retarder is a must. but do you think with the insulation so poorley done wood it realy matter?