roof insulation - minimum or average

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Author Message Robin E. Snyder Senior Member Username: robin Post Number: 114 Registered: 08-2004 Posted on Friday, June 15, 2007 - 12:00 pm:    Do you typically spec your roof insulation for a minimum R-value or an average R-value? John Bunzick, CCS, CCCA Senior Member Username: bunzick Post Number: 739 Registered: 03-2002 Posted on Friday, June 15, 2007 - 01:36 pm:    Average R-value (for thermal), but minimum thickness (for span and durability). Mark Gilligan SE, CSI Senior Member Username: markgilligan Post Number: 186 Registered: 05-2005 Posted on Saturday, June 16, 2007 - 03:07 am:    Where the insulation is used to control condensation I would want to control the minimum value. I would give the Mechanical Engineer a call. Phil Kabza Senior Member Username: phil_kabza Post Number: 262 Registered: 12-2002 Posted on Saturday, June 16, 2007 - 03:24 pm:    I give a minimum thickness and a minimum average thickness. I don't want to engage in disputes over the interpretation of R-values. Anne Whitacre, FCSI CCS Senior Member Username: awhitacre Post Number: 569 Registered: 07-2002 Posted on Monday, June 18, 2007 - 04:08 pm:    I would also suggest that some AHJs are very specific about what they want -- either "minimum" or "minimum average" value for the roof insulation and this has not been subject to our interpretation. in my experience, the values required by the local energy code are on the code sheet of the drawings; my specs require whoever supplies the insulation to meet the required R values -- in whatever form they are required. Phil Kabza Senior Member Username: phil_kabza Post Number: 263 Registered: 12-2002 Posted on Monday, June 18, 2007 - 06:29 pm:    To repeat a favorite smart remark: "Designing a building that meets the code merely means that if you required anything less, it would be illegal." Doug Frank FCSI CCS Senior Member Username: doug_frank_ccs Post Number: 191 Registered: 06-2002 Posted on Thursday, June 21, 2007 - 04:13 pm:    I specify the Materials,, and their appropriate LTTR, and the sequence in which they get installed,,, but leave actual thickness of intermdiate layer(s) to drawing notes and details.