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What is best treatment for the top of elevator shafts?

BobRVt | Posted in Building Code Questions on

We do mostly home weatherization, but also get into frame and brick public buildings that have elevators.

Elevator shafts seem to be poorly insulated and air sealed at the top. Often they are just cement block or brick with a corrugated metal roof 6-8′ above the flat roof. There might be 1″ or 2″ of foam board above the corrugated roof, but no where near R-39 or R-49 (Mass or Vermont). No air sealing whatsoever, so these shafts look & behave like chimneys, sucking heat out of the buildings.

What is the best treatment for these? I am thinking 2-3″ Fire-rated foam board (such as Thermax) around the side walls and 6-8″ on the top? Has anyone done this?

What are the code issues? I assume we have to use fire-rated foam to seal the foam board. Is there a code for clearance around the elevator itself that prevents any improvement.


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  1. aaronhirshberg | | #1

    Did you ever find an answer to this?

  2. BobRVt | | #2

    Nope! And the customer did not hire us to spec their project, so I did not pursue it. Bob

  3. GBA Editor
    Martin Holladay | | #3

    Bob and Aaron,
    I am not an expert in commercial construction codes. Obviously, any plan would need to meet the requirements of the local building inspector.

    I'm visualizing a flat-roofed shed (with concrete-block walls) that sticks out of the middle of a flat commercial roof.

    If the metal roofing could be removed, one could take a PERSIST approach. Cover the walls and the flat roof with peel-and-stick membrane, followed by a couple of layers of rigid foam with staggered seams on both the walls and the roof. On the exterior side of the foam, you could install 2x4 furring strips. Then the building could be roofed and siding could be installed.

  4. BobRVt | | #4

    That about describes the top of this elevator shaft, and sounds like a good solution - do it from the exterior. What do you mean by PERSIST?


  5. GBA Editor
    Martin Holladay | | #5

    Here is a link to an article that describes the PERSIST approach: Getting Insulation Out of Your Walls and Ceilings.

  6. user-659915 | | #6

    An interesting aspect of this would be the pump effect, the additional positive and negative air pressure created by the piston-like elevator car moving in a fairly confined vertical chase. I'm pretty sure air pressure effects are routinely taken into account in the engineering of high speed high rise commercial elevators but not so much in more humble installations and probably with little concern for the enhanced stress on enclosure air barriers. Anyone know if this really is an issue with today's tighter enclosures? If so, should we be making the elevator chase wider than the minimal clearances required by the manufacturer, or adding transfer grills with clear return paths at top and bottom of the shaft?

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