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Community and Q&A

5-inch EPS foam

Jeramia | Posted in Green Building Techniques on

Hello, I am looking to build a 24x30x10 pole barn to use as a shop/ extra garage. I am not planning to use concrete on the flooring just yet because of the cost. Eventually I would like to pour a slab though. I am researching insulation and think I will use a radiant barrier for the roof to under the metal sheets to reflect the roof heat. Actually the siding is metal as well. I was also given (84) used but in great condition 4×8 sheets of 5″ eps foam. I am trying to figure the best way to go about it all. Any would be grateful for any suggestions.


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  1. GBA Editor
    Martin Holladay | | #1

    A pole barn is inexpensive, and (as long as you don't try to heat it or cool it) will work well to keep rain off of equipment, animals, or hay.

    A pole barn doesn't work well if you intend to try to insulate the walls and roof. Here are links to previous Q&A threads on the topic:

    Here are some quotes from some of the answers I posted to these previous questions. (Forgive the repetition):

    "The main problem with insulating a pole barn is creating a good air barrier. There are many opportunities for air leakage: between the insulated sections of the wall and the vertical posts; at the base of the wall (which either meets dirt, gravel, or a concrete slab); and at the intersection of the wall and the insulated ceiling. You should strive for airtightness when you create this assembly. It won't be easy -- but do your best."

    "It's tough to insulate a pole barn. First, there is the question about the floor. Do you have a slab or gravel? If it's a gravel floor, it's hard to air-seal the bottom of the walls. If you have a slab, we'll need to know your climate zone or location, so we can recommend whether you need a horizontal layer of rigid foam under the slab. Next, you still have issues of how to support the insulation. In most pole barns, you don't have studs. You have posts and horizontal nailers between the posts. This makes air sealing difficult, and using conventional insulation difficult. The best way to proceed is to work on the exterior side of your structural frame. Again, either SIPs or nailbase is one approach -- and if you use SIPs, you could skip the pole barn structure, and just build a SIP building. Another approach is to install a stud wall on the outside of your pole barn to hold the insulation -- but again, this raises the question, why not just build an ordinary building with stud-framed walls if you need it for insulation?"

    "I'm afraid that 'energy efficient pole building' is an oxymoron. If you want to make a pole building energy-efficient, you pretty much have to build an entirely new building -- either inside the pole building or outside the pole building -- to create an air barrier and provide somewhere to install the insulation. That's why people who are interested in energy efficiency don't choose dirt floors or pole construction. However, if you decide to let go of the idea of energy efficiency, you can certainly build a dirt-floored tiny house with a pole frame."

  2. Jeramia | | #2

    Thank you for such a quick response. I am not trying for an super energy-efficient building. I figure that the radiant barrier in the roof will help to reflect most of the summer heat so it's not extra hot in the summer. And the 5" eps will help in the winter to hold some heat in while I out there working. I just don't want to create issues with mold.

    I was reading on your site something about if you had thick enough foam that it should work as a vapor barrier...or something like that......again I am new to this and need more guidance.

    You I am planning on gravel, then maybe in a few years I could pour a slab. Could I put the insulation under the gravel? Would that be beneficial? Also run the insulation down the wall and stick it in the ground so many intches. I don't know I am just throwing stuff out there.

    Again thanks.


  3. Dana1 | | #3

    Without a rigid slab to protect it the EPS would be damaged by gravel with any animal or equipment traffic running over it. Unless your subsoil is permafrost, insulating the slab before insulating the walls & roof would make the place less comfortable, with higher temperature swings than it would otherwise.

    Depending on location insulating above/around the foundation footings would decrease the odds of frost heaving (but that is not usually a problem to be concerned about below US climate zone 5/6.)

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