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TOPIC: Roofing over existing roof

Metal Roof over Shingles (unheated) venting?

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I'm installing a Fabral Grandrib 3 roof over my existing shingle roof over an unheated garage. I will install horizontal furring strips. I am confused about underlayment and venting. Do I need to use felt paper? Under or over the furring strips? While the furring strips will create an air space, the ridge and eaves will be sealed with the foam closure strips, so there won't be any airflow. Will this create any problems? Should I add vents?
Guest User

9/7/2004
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Please contact the manufacturer. I can tell you that the code calls for an underlayment unless tested without one. It also calls for ventilation and while not required generally in unheated areas I would strongly recommend it. The cde does allow you to instal ametal roof over one layer of existings hinles and sometimes two but no more. Subject too the manufacturers recommendations, if the product is allowed on strapping, I would install fely underlayment over the existing shingles and the the strapping. I would use vented eave and ridge closure to ventilate the air space and depending on your climate consider venting the garage.
Allan Reid
Dura-Loc Roofing Systems, Inc.

9/8/2004
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Does a darker color metal roof ( charcoal gray or ash gray ) cause your electrical cost to go up significantly in the summer by attracting heat from the sun. Is there a chart anywhere on the web that would show the different possible electrical percentage increase by your choice of color. Thank you, Ben in SC
Guest User

9/14/2004
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Lighter colors are more reflective. This is regardless of whether the roof is metal, tile, composition, whatever. Therefore, it should not be looked at as there being a "penalty" for choosing a darker color. Lighter colors, though, are more reflective and will reduce attic heat gain. Additionally, though, some metal roofing manufacturers are using new reflective pigment technology in their paint systems. With this technology, even dark colors get reasonable ratings for reflectivity. Additionally, energy efficiency is more than just color. Attic ventilation is critical. And, with many metal roof systems, there is or can be an airspace between the metal itself and the roof deck. That is also very effective becaus eit blocks heat transfer by conductance. Visit www.coolmetalroofing.com for more details.
Guest User

9/14/2004
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I will be installing a metal roof over shingles. My plan is to lay 30 lb felt, fur the roof with 1x4 yellow pine. Are you saying to secure the 1x4's and then lay the felt over the shingles and 1x4's ?
Guest User

9/20/2004
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