I wanted to reach out and see how other departments have been addressing this issue, as we have had some confusion from contractors and architects. With families living in these new homes it is important that we get this stuff right, to avoid mold/moisture issues or unnecessary financial loss. So here goes...
It is a common trend in local new construction to stucco the soffits without vents and spray foam insulation in the attic below the roof sheathing and above the soffits. These unvented attics are allowed per R806. The problem arises when a knee wall is built and sprayed with insulation separating the garage or outdoor living attics from the rest of the attic space.
By spraying these knee walls we are moving the building thermal envelope to the knee wall and isolating the garage or lanai, which make them no longer conditioned spaces and ineligible for being unvented (See R806.5(1) below).
[RE] BUILDING THERMAL ENVELOPE. The basement walls, exterior walls, floor, roof and any other building element that enclose conditioned spaces. (Also see Section R202 of the Florida Building Code, Energy Conservation.)
[RE] CONDITIONED SPACE. An area, room or space that is enclosed within the building thermal envelope and that is directly heated or cooled or that is indirectly heated or cooled. Spaces are indirectly heated or cooled where they communicate thru openings with conditioned spaces, where they are separated from conditioned spaces by uninsulated walls, floors or ceilings or where they contain uninsulated ducts, piping or other sources of heating or cooling.
Thanks for your time and consideration. I look forward to seeing your thoughts on the matter, and seeing how others are crossing this bridge.
It is a common trend in local new construction to stucco the soffits without vents and spray foam insulation in the attic below the roof sheathing and above the soffits. These unvented attics are allowed per R806. The problem arises when a knee wall is built and sprayed with insulation separating the garage or outdoor living attics from the rest of the attic space.
By spraying these knee walls we are moving the building thermal envelope to the knee wall and isolating the garage or lanai, which make them no longer conditioned spaces and ineligible for being unvented (See R806.5(1) below).
Some contractors have sprayed the bottom chords of the garage/lanai and removed the knee wall, bringing them back into the thermal envelope.
This change may affect the energy calculations and require a rated attic access to maintain garage separation
Others have gone back after the fact and added soffit or ridge vents to these garage/lanai attic spaces and kept the sprayed knee wall.
I have been told by a few insulation contractors that open cell foam should not be used in vented, unconditioned attic space because it will collect moisture.
We have also had architects revise the plan and add a mini-split to the garage, conditioning the garage and in so doing, indirectly conditioning the attic above it as well.
It's not exactly cost effective to condition the garage in Florida, as it will all be gone the second the garage door opens, and there may be loss of efficiency if there are hydrostatic vents
[RE] BUILDING THERMAL ENVELOPE. The basement walls, exterior walls, floor, roof and any other building element that enclose conditioned spaces. (Also see Section R202 of the Florida Building Code, Energy Conservation.)
[RE] CONDITIONED SPACE. An area, room or space that is enclosed within the building thermal envelope and that is directly heated or cooled or that is indirectly heated or cooled. Spaces are indirectly heated or cooled where they communicate thru openings with conditioned spaces, where they are separated from conditioned spaces by uninsulated walls, floors or ceilings or where they contain uninsulated ducts, piping or other sources of heating or cooling.
Thanks for your time and consideration. I look forward to seeing your thoughts on the matter, and seeing how others are crossing this bridge.
