Tying exterior insulation into an existing roof
Hi Guys, thank you all for your input and time.
I currently have to reroof and don’t have the space to over roof with rigid foam so i have to go conventional roof and spray foam. The windows and siding are also a disaster and need to be replaced sometime in the near future. currently i have wood siding covered in vinyl with a mixture of rotten wood windows and cheapo vinyl replacements. it is a cape in zone 4a, It seems to be a lot less fuss to use something like Zip R when that time comes and kill 2 birds with 1 stone as there is no wall insulation to speak of and the house is super drafty. How do i tie the walls into the existing roof? i unfortunately can’t afford to rip off the old soffits, trim and coil stock right now to extend them and wrap in a peel and stick. what are my options? Am i doing this completely backward? thank you very much!
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Replies
Hi Jack.
You have lots of options for doing this work well and doing the re-roof first shouldn't be a problem.
First of all, I recommend that you read these two articles to make sure that you are taking a sensible approach to insulating the roofline, specific to typical Cape details:
Insulating Behind Kneewalls
How to Build an Insulated Cathedral Ceiling
It sounds like your walls don't have any sheathing. If I have that right, when it comes time to redo the siding and windows, you'll have open stud bays, which will make retrofitting insulation from the outside pretty straightforward. Again, you'll have lots of options to consider.
You could then install plywood or OSB sheathing followed by exterior continuous insulation or as you suggested, you could use ZIP R. The key decisions you'll have to make about the walls are outlined in this article: The Four Control Layers of a Wall.
Thank you brian.
The plan is to follow the advice in the how to build an insulated cathedral ceiling. I looked at your article as well thank you for that. I was wondering more in terms of terminating whatever wrb i use and where to end it, which i think will be zip r. Most/all roofers and siding people i spoke to over here are no help, they are still telling me the house needs to breath. im trying to avoid doing thing twice i don't think i will be insulating from the outside in as i will do that when we upgrade all the electrical, kill the old steam radiator system and deal with all the rest of the ancient problematic issues with a poorly maintained 100 year old house and not a great repair budget.
Jack, it might help to be a bit more specific in your question and what you are trying to accomplish. The heart of your questions appears to be:
"How do i tie the walls into the existing roof...in terms of terminating whatever wrb i use?"
And the caveat being: "I unfortunately can’t afford to rip off the old soffits, trim and coil stock right now to extend them and wrap in a peel and stick."
Are you planning on doing the residing / adding zip-R also without pulling the soffits? The obvious answer would appear to be to terminate the wrb as high as possible so it is protected by the roof control layers and ideally integrated with them as well. Taking off the soffit might be the simplest way to do this. Taping and/or caulking the wrb to some form of roof/ceiling air control layer will help to make the envelope continuous.
The key—and something to keep in mind before you begin any work, including re-roofing— is to find a way to make the connection between the air control layers. This may mean the roof connects to the top-plate via spray foam, and your to-be-installed WRB then connects to the top plate via tape or caulk from the exterior.
Tyler, thank you very much.
Yes exactly that is my plan to redo the soffits then. I guess ill bring the Zip R as high as i can and use either tape or a fluid applied to complete the connection. That was my question, i'm sorry if i wasn't clear, i was trying to understand the roof to WRB transition. My assumption would be that the new roof will be where the old one was, if i pull off the old coil stock when the time comes ill work my way down from the drip edge to complete the connection.