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TOPIC: General Discussion

Double Bubble Foil

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We have ordered our metal roof and are now deciding whether or not to put the bubble foil over the felt paper under the metal. Does anyone have any strong feeling either way on this. Our builder has never put it on before. I know one thing it does is reduce noise which is not important to me but does it make a huge difference in reflecting heat? We have tongue and groove pine on the rafters then 4 inches of styrofoam insulation and then 3/4" plywood then feltpaper so I guess is the foil really necessary? Any advice is greatly appreciated.
Guest User

6/28/2005
I have never heard it referred to double bubble before. The first thing to do is talk to the metal roofing manufacturer and get their blessing and then check to see if it is in their product approval. Their are certain areas of the country that have fire requirements as well however the most important aspect of your roof assembly is going to be the ventilation. The building code calls for a minimum of 1" of free air between the roof covering and the insulation on vaulted assemblies. Additionally it requires an interior air barrier and the exterior moisture barrier (underlayment) under the covering. Your assembly as described does not have the interior air barrier or the air space. Additionally reflective barriers effectiveness is reduced unless it is 1" away from the roof covering. I do not believe that it would return on investment here and I would suggest getting an Energy Star reflective roof which will be mor effective in keeping the heat out and lastly with no interior air barrier, I would cover the plywood with self adhesive ice and water shield which will do double duty.
Allan Reid
Dura-Loc Roofing Systems, Inc.

6/29/2005
Allan thanks for the reply. One thing I did not mention is that this in in a log cabin with a vaulted open ceiling so there is no attic. The ceiling of the second floor is the roof so does that change things? We will be able to control the temperature in the house but not above the garage where we have living space but is not going to be finished right away. thanks again for your response and suggestions.
Guest User

6/29/2005
The building code ventilation requirements I talked about are for a vaulted ceiling. For an attic they require 1 sf of vetilation for every 150 sf of ceiling area. If as example you had a 2100sf home then you would need to provide 7 sf of free air and it must be provided 50% at the eaves and 50% at the ridge. The vaulted air space of minimum 1" must also be vented at the eaves to allow intake and at the ridge for exhaust. Providing proper ventilation is a very importnat aspect of a healthy, energy efficient and comfortable home.
Allan Reid
Dura-Loc Roofing Systems, Inc.

6/30/2005