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Roofing/insulating a roof with soffits

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Question
House built 1959, steel shingles, no insulation on rafters. Do I use the Styrofoam vents to run from roof ridge to soffit vents and then insulate. Will I have to vent each space between rafters or only to the soffit vents?

Answer
Dean,
I'm trying to make sure that I have the construction correct - is there no insulation in the attic space at all? You indicated "no insulation on rafters" I'm not sure if you are referring to the rafter portion that the substrate is attached to, or if there is no insulation in the entire space.
If the intent is to install insulation between the rafters near the sheathing, a minimum of 1" must be allotted for between the sheathing and the insulation. All of the ventilation must be 1 square foot/150 square feet of attic space - attic spaces may be defined as any closed space. The ventilation is essential. It must ventilate all spaces and achieve a 50/50 ratio of intake (eave or soffit) and exhaust (ridge).
The Styrofoam vents are a retro-fit product in the event that proper space is not allotted for with the insulation, provided that you allow for the proper spacing of the insulation, the Styrofoam would not be necessary.
Ventilation is the key element in this installation. Insure that each space is properly ventilated (1:150) and space above the insulation (1" minimum) and you should be fine.
Good luck,
Aaron

Roofing

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Aaron Nelson

Expertise

All types of questions with regard to roofing, waterproofing and sheet metal. This includes commercial and residential buildings, along with the various aspects of the construction means and methods, ventilation, steep-slope or low-slope, code requirements, installation errors and other such problems

Experience

I started in roofing fabricating and installing sheet metal flashings out of high school for a large commercial contractor. I worked for the same contractor in the office estimating and project managing commercial project for 10 years. I left the construction side of roofing and now work as a roof consultant, which I have been doing for 8-years.

Organizations
RCI, Inc.

Education/Credentials
I am a Registered Roof Consultant (RRC) and a Registered Roof Observer (RRO) through RCI, Inc. RCI is a international group of building envelope professionals. I am an approved instructor for RCI educational programs.

Past/Present Clients
We have worked with many local school districts, insurance companies, HOA's, building management companies, and we have a national client with buildings located throughout the US.

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