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In reviewing various stone coated steel roofing manufacture specifications I find little if any information regarding ventilation requirements for metal roof systems on residential housing in CA. I have several questions:
1. Is attic ventilation required in warm climates such as Southern CA? The building inspectors are somewhat amblivient about this saying that if required by the manufacturer its required by them. Some say that on a reroof (with tearoff) over spaced sheathing the new ventilation only needs to be the same as the preexisting ventilation, even if it is below UBC requirements. Some say it must comply with the UBC. What is the answer to this delima?
2. Can the metal roof system be impacted by a lack of attic ventilation or from under ventilating the attic?
3. How much "breathing" does a metal roof do? Some contractors have indicated that vents may not be needed because the metal roof breaths. This appears to be contrary to my understanding of the design of metal roofs to resist air infiltration to assist in roofs resistence to wind-up life.
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The building codes in your area do, I believe, require ventilation.
Ventilation helps wto avoid the inefficient and potentially unhealthy accumulation of heat and moisture in your attic and living space.
Metal roofing neither increases nor decreases the need for ventilation.
The "breathing" of a metal roof, if any, is determined by the exact product chosen and its method of installation.
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John, ventilation is my pet pieve as the building officials and the old rash of codes in the US generally do not understand or require ventilation. The new IBC code about to be adopted in CA January next does require it in both attic and vaulted assemblies. I will tell you that it is the most energy efficient and long lasting thing one can do to any home for little money.
As long as the climate passes over the dew point condensation will form. The new codes finally recognize that one needs to look at the complete roof assembly which is; interior finish, air barrier, insulation, framing, ventilation, moisture barrier and roof covering.
We refer to our products at Dura-loc as granular coated and the systems are all designed with ventilation accessories included in our product manual.
Granular metal roofs are air permeable but not enough to ventilate the structure to code. I have seen our metal roofs installed over existing roofs with insulation in the void and because of lack of ventilation heated air is pressure exhausted out the seams bring dust and oils from the old roofing underneath.
As to wind uplift,, air permeable ,etal roofs means the suction is transferred to the sheating, If your roof is installed over skip sheathing with an (moisture barrier)underlayment then the underlayment is sucked to the back of the metal and will pull the system off in the right wind. Look for products that have a UL 580 and UL1897 wind up lift testing.
Our Premium products carry this aproval in our current ICBO-ER report and I would invite you to communicate with me directly if you would like more information on ventilation and the building codes.
8/13/2003
Or copy this URL: https://www.metalroofing.com/spirit/comment/2147/find/Isaiah Industries, Inc.
8/17/2003
Or copy this URL: https://www.metalroofing.com/spirit/comment/2148/find/Dura-Loc Roofing Systems, Inc.
8/19/2003
Or copy this URL: https://www.metalroofing.com/spirit/comment/2149/find/