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Is my metal roof ventilated properly?

jimmy04 | Posted in GBA Pro Help on

Is my metal roof ventilated properly? If not, will this correction be expensive?

The home we purchased in North Florida was originally constructed with a shingle roof (4/12 pitch) and vents(ridge vent with eave/soffit vents). The original owner replaced the roof with a standing seam metal roof and closed off the ridge vent but kept the soffit vents. The home is currently under renovation and has a cathedral/vaulted ceiling(4/12 pitch) with no attic space. The general contractor had all the original insulation (R-19) from 1959 removed and the electrician installed IC recessed cans in the living area as well as the bedrooms.The ceiling is still exposed, as of now and we have about 7 1/2 inches of space available between the joists. The general contractor told us that everything is fine and not to worry about the ventilation and to proceed with the renovation.

We believe the general contractor has misguided us and that we have “at-least” two major problems:

#1- We have soffits with no ridge vents for air to escape.

#2- We have recessed cans and electrical wires in between our joists with not much insulation space.

My wife has totally panicked because she believes these problems will destroy the existing metal roof and the plasterboard ceiling that was going to be installed after the R-19 was replaced.

What is the best way to provide ventilation to this roof?

Is it possible that the metal roof is being vented between the plywood (underlayment) and metal roof itself?

Should we install new R-19 insulation and proceed to blue board application?

Is anyone aware of some solutions to help us recover from this potential disaster or can someone provide a referral?

Your assistance is greatly appreciated!

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Jimmy,
    You are located in Climate Zone 2. The 2009 International Residential Code calls for a minimum of R-30 insulation in your climate zone. This can be accomplished with about 5 inches of closed-cell spray polyurethane foam (or a little less).

    If you choose to insulate your rafter bays by spraying closed-cell foam against the underside of your roof sheathing, ventilation channels are not necessary. For more information on this topic, see How to Build an Insulated Cathedral Ceiling.

    So, the short answer to your question is: your contractor hasn't messed things up. Yet.

    For this approach to work, you'll need at least 6 inches of clear space above the top of your can lights. If you don't have that much room on top of your can lights, you'll have to remove the can lights, spray the foam insulation, install your drywall ceiling, and then install surface-mounted fixtures (for example, track lighting).

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