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Community and Q&A

Insulating attic trusses for storage only

tgdunham | Posted in General Questions on

I just read your blog on roofing rules. I need the storage space so I am going with room in attic trusses. I am just going to use the space for storage.

I plan on using cellulose blown-in insulation but to do that in the floor and still have a floor for storage what is the best way to build up the floor to allow enough depth for the insulation? I have to do R38, but the bottom chords are just 2×6, so I would need at least 10″ and would prefer to go with 12″. Should I run an extra layer of 2X8 perpendicular to the trusses to put the plywood on or run them on top of the bottom chord of the trusses?

Or do I only have to do R19 on the vertical walls. From what I can see they are only 2x4s so can I just staple insulation onto the 2×4 even though the insulation is 6″ deep, and if I do that do I have to cover it or can I leave the insulation exposed?

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  1. GBA Editor
    Martin Holladay | | #1

    Your post raises several questions.

    First, anyone who plans to use attic trusses for storage needs to be sure that the trusses were engineered for that purpose. Most roof trusses are not engineered for storage. Adding any weight to the attic floor (beyond insulation) is not allowed.

    I can't tell from your post whether your trusses were engineered for storage.

    If they were, you can go ahead and install an attic floor. If the bottom chords aren't deep enough to hold the insulation you plan to install, you can install new floor joists perpendicular to the existing bottom chords.

    You don't need to insulate the vertical walls on either side of the storage area if you are insulating the attic floor. The storage will be outside of the home's thermal envelope. Objects stored in this area will be hot in the summer and cold in the winter.

  2. user-901114 | | #2

    How will you be accessing this attic? Permanent stairs?

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