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Community and Q&A

Insulating an Elevator Shaft

John Cuddy | Posted in General Questions on

I have a project in coastal Delaware, zone 4A.  The property is in a flood zone.  The house is designed with an elevator attached to the side of the main structure—think of a silo attached to the side of a barn.  The elevator shaft cross-section is approximately 6ft x 6ft and the walls are framed with 2×6’s on a short CMU stem wall.  The bottom portion of the shaft is framed with pressure treated lumber as it is below the base flood elevation.  The elevator shaft interior is within the air and thermal control layers for the overall structure.  We need to make some final decisions on how the wall cavities and the roof will be insulated.

Let me also add that my general contractor is good, but the inclusion of a rain screen and some of the air sealing measures I’m having him do are already outside of his standard building practices.  I’m looking for something effective and reasonably straightforward for a competent crew.

I had originally thought that the flood prone portion of the shaft would get closed cell spray foam in the wall cavities.  However, my GC tells me that when that section of wall does flood I’ll have to remove the insulation in order to insure the walls dry out properly.  If that’s the case, I think I’m inclined to use mineral wool in those wall cavities.  Above the flood-prone areas, I assume we will use the dense pack blown fiberglass the rest of the structure will get in wall cavities.

A hip roof has been designed for the top of the shaft.  My general contractor plans to frame that conventionally.  My thought was to ask him to use 2×10 rafters and pad out the bottom of those rafters with some strips of the extra 2-inch foam insulation panels he already has on site.  That would give me an 11.5 inch depth to flash and batt with about six inches of closed cell foam and the balance with the mineral wool batts (similar to option 5 in Martin Holladay’s article 5 Catherdral Ceilings That Work).

Does this sound sensible? Would it be easier to use fiberglass batts instead in the roof due to the uneven surface of the cured foam?    Do I need to add any strapping to ensure the roof batts stay in place?  Better alternatives?

Comments/thoughts welcome.  Thanks in advance.

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Replies

  1. Charlie Sullivan | | #1

    How high up are you expecting to be subjected to flooding? Is there equipment that lives in that lower part, and how will it survive the flooding? How do you access that space to remove insulation to enable drying? How is the rest of the house designed to survive the flooding?

    Sorry for so many questions.

    1. John Cuddy | | #2

      Charlie - My nominal lot grade is elevation 4. Base flood elevation is being changed to elevation 6. I'm assuming a near direct hit of a monster storm could flood us to elevation 9 (BFE + 3 ft).

      The elevator will open at grade level. I know they have to dig a pit at the bottom of the shaft, but I don't know how much equipment goes in the bottom. Our plan will have much of the hydraulic pumps and tanks remoted to another storage area where we can locate it significantly higher.

      I'm assuming I can stow the elevator cab on a higher level when I need to access the bottom of the shaft and then just open the exterior door to the shaft if we need to perform maintenance (or remove insulation after a flood).

      The first level of the house is elevated to elevation 8 (base flood elevation plus two feet of freeboard) with a CMU stem wall that has been backfilled and a slab poured over the top. We're assuming that could still flood but we only have entry space, some storage, laundry, and utilities at that level. The remainder of the house is elevated on piles 12 feet up.

  2. Expert Member
    Zephyr7 | | #3

    I would run whatever you're planning on doing past your elevator contractor -- there are a lot of special elevator codes and a lot of them are life safety related, so a big deal at inspection time.

    If you keep everything on the OUTSIDE of the shaft, that's probably a better way to go in terms of any issues with the elevator and related codes.

    Bill

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