Roof Insulation Retrofit
We have a 2 story tall-and-skinny with rooftop access in Seattle that needs to be redone for drainage purposes anyways, it’s currently a cold roof (entire thing is 2% tapered trusses starting at 16” H to 12” H filled with batt insulation, vents on both sides are just 2” holes drilled through siding with bug screens) that does okay during hot days but the house is cold during the winter (high electric bills), would it be worth converting to a warm roof? I will be resloping with Type II eps before having a company install PVC and I want to build parapets (which already bring their own problems) for privacy, with that I considered running continuous exterior insulation on the roof but I don’t know if it’s worth it to plug the existing vents. In addition the second floor is full of windows (great for natural light) but none are energy efficient so the house effectively gets too cold with a cold roof but would get too hot in the summer with a warm roof (plus the kitchen and master bath are on the second floor). We are planning on staying in this house for a very long time.
Edit: On parapets, the consensus seems to be to wrap them in a continuous layer of insulation so they are part of the envelope. That makes sense when the structure as a whole is wrapped but does it make sense when the structure is not? I think individually it might make sense to wrap the parapet as added insulation on what is a thin exposed wall by itself, but it also seems like overkill when you can just vent the parapet instead. The issue of building a parapet above a cold roof is an added issue, as insulating seems like a wasted effort at that point. In an ideal world I would seal the cold roof and wrap the whole building, but that might have to wait.
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