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Concrete balconies and thermal breaks

jackofalltrades777 | Posted in Green Building Techniques on

On a residential application with a 2-story home using ICF walls and an InsulDeck 2nd floor. When it comes to thermally breaking the exterior concrete balcony, there is not much out there in details that can properly thermally break such a setup.

I have found this German made product called “Schock”
http://www.schock-us.com/en_us/solutions/concrete-slabs-190

It is designed to carry the load and thermally break the concrete balcony. It runs for around $80 per linear foot. So on a 22′ wide balcony, one is looking at around $1,760.

In a Zone 4 climate, would it make sense to go to the effort to thermally break a 2nd floor balcony?

Are there less expensive alternatives out there?

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Peter,
    A cantilevered concrete balcony is a thermal disaster. The Schock product is one solution -- the only one I know. It isn't cheap, as you have discovered, but at least it solves a problem that should never have occurred in the first place.

    This idea (a cantilevered concrete balcony) should have been ridiculed by professors in architecture school, so that no architect had to embarrass himself or herself by proposing it once they left school.

    More information on the topic:

    Second-Story Balconies

    Thermal Bridges Redux

    The best solution is to support the balcony on columns and an independent foundation.

  2. jackofalltrades777 | | #2

    Martin,

    Besides the thermal issue which can be solved if a cantilevered concrete balcony is thermally broken by a product like Schock. Are there any other thermal issues in regards to a concrete balcony? Once it's thermally broken with the R3 Isokorb break, the problem is solved, right?

    The "Thermal Bridges Redux" Building Science article discussed the Schock solution for the balconies. Like the author, I do like the architecture of that high-rise building in Chicago and like the author stated, they should have used the Schock system to thermally break those concrete balconies. Sadly, they did not, and it will be an energy penalty for the life of that building. The renters/owners will be stuck with the endless energy costs to deal with that poorly designed balcony. Theoretically, that concrete building should be standing for the next 500+ years.

    Price wise, it's not as bad as I thought it would be. Personally, I would rather spend $1,800 on thermally breaking a 22' wide concrete balcony than spend it on some overpriced piece of counter top or TV. The energy efficiency of the home is something that is long term. With a concrete home like this, it should be standing for the next 300+ years from now. With a thermally broken balcony of course :)

  3. TwoFlatRemade | | #3

    This idea (a cantilevered concrete balcony) should have been ridiculed by professors in architecture school, so that no architect had to embarrass himself or herself by proposing it once they left school

    While there's no doubt that thermal issues are important, consider that some of the most widely lauded and recognized architectural designs by Frank Lloyd Wright used them extensively (e.g. Fallingwater). I imagine the thermal performance of that house leaves much to be desired, but I think the idea of a concrete cantilever is far from deserving ridicule.

  4. GBA Editor
    Martin Holladay | | #4

    Matthew,
    You wrote, "Consider that some of the most widely lauded and recognized architectural designs by Frank Lloyd Wright used them extensively."

    I stand by my statement: "This idea (a cantilevered concrete balcony) should have been ridiculed by professors in architecture school, so that no architect had to embarrass himself or herself by proposing it once they left school."

    Oh -- and Wright's roofs leaked. Almost all of them.

  5. jinmtvt | | #5

    Peter : why use concrete ?? weight and cantilever doesn't usually make a great mix...

  6. jackofalltrades777 | | #6

    Jin,

    The entire home is ICF/concrete with the 2nd floor also being ICF/InsulDeck/concrete.

  7. jinmtvt | | #7

    Peter: my house is ICF also ..all floors are concrete on steel deck .
    that doesn't mean you have to do everything in concrete
    ( i swear i was thinking the same when is started )
    building is not a "theme "
    every situation has its own best design and material

    Can you show a detail of the building and the balcony ?

    Anything underneath it ?

  8. jackofalltrades777 | | #8

    Jin,

    The entire 2nd floor is InsulDeck and it spans from the interior to the exterior, including the balcony. The ICF 2nd floor is stacked on top of the InsulDeck flooring. Underneath the area is the 1st floor covered porch. There is living space above the 2nd floor InsulDeck projections.

    I don't mind the solution of using Schock Isokorb to thermally break the slab. It's actually pretty simple and the engineers work to create the detail, plus its an easy application out in the field. It's no harder to insulate or break a slab than it is to use this product.

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