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Fire-resistant energy efficiency

ranson | Posted in Energy Efficiency and Durability on

Eventually, for my work, I may want to build a very small fire-resistant electronics lab/office building in zone 5. Now, I know that stud construction with gypsum is remarkably resilient, and an extra layer of gypsum may be the ticket. What options are there to build a structure that would be fire resistance from internal sources, but also energy efficient and low environmental impact?


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  1. Expert Member
    Michael Maines | | #1

    John, Comfort Block might be the perfect product for you: It's surprisingly energy efficient, considering the fact that it's a slightly modified CMU--approaching R-30. I've had quite a bit of correspondence with the product developer, and have tried to sell several clients on using it. It's a little low on the R-value scale for what I try to design, but it might be perfect for your situation.

  2. ranson | | #2

    While that satisfies the fireproof side of the equation, I'm not sold on the overall energy efficiency. They claim an effective r-value of R-30, but there's a clear serpentine thermal bridge through the concrete bypassing the EPS. Until they get lab testing done, I'm very skeptical about that number.

  3. walta100 | | #3

    Nothing is more fire proof than a CMU (Concrete Masonry Unit) to make it energy efficient wrap it in house wrap as air will blow thru the pores block and cover that with R21 of rigid Rocksol insulation in 3 layers with staggered joints. Top it with a raised heal truss cover the ceiling with 2 layers of drywall without any penetration covered with R60 cellulose insulation. Access the attic from a small exterior door in the gable wall. All electrical is surface mounted in conduit.


  4. Expert Member

    John, The first thing I'd do is make a list of what combustion sources and flammable materials you intend to have in the building. There is no point going wild on the structure if there is not much to burn.

  5. ranson | | #5

    It's a good point, and my work has both. A fire resistant structure is a risk mitigation which hopefully never pays off, but it's sensible in my line of work.

  6. Expert Member


    Yes for sure. Most houses have a lot of combustable furnishings and surfaces. Many workshops have tools, machinery or electronics that can take fire too, but if the floor is non-combustible, and the wall and ceiling surfaces are rated, then they aren't really at risk.

    You may find using 1 hour fire-rated assemblies that rely on drywall sufficient, which makes the construction a lot easier. Commercial kitchens and many industrial occupancies take this approach. It's a rare building that goes to concrete or CMU construction to mitigate the fear of fire originating from inside. They are usually used to stop the spread of fire from one occupancy to another.

  7. ranson | | #7

    Makes perfect sense. I think combined with a flammables cabinet and keeping boxes and loose paper out of the work area, fire rated gypsum is probably the way to go.

    This brings up a question: Are there standard fire rated wall assemblies that go beyond code minimum energy efficiency? While official fire rating probably isn't my goal here, it might make an inspector happy.

  8. user-6184358 | | #8

    A Fire Sprinkler system will save the structure and limit the damage.

  9. Expert Member

    John, Tim has a good point. I'm not sold on them for single family residences, but for a workshop that may be the way to go.

    It's a bit of a simplification, but basically building assemblies rely on their surfaces for their fire rating. If you have a wall with rated drywall, the wall can be a deep and as energy efficient as you would like.

  10. ranson | | #10

    I've thought about sprinklers, and I don't think they're the right solution in this case. I work with electrical equipment. Sprinklers will save the structure, but will damage my lab almost as surely as fire. Something like a water-free fire suppression system might be a better fit, but would cost a pretty penny. Essentially, I would want a small fire to go out without spreading, and a bigger fire to be extinguished without destroying other equipment. I want to do the best I can to achieve that without sprinklers, and before considering expensive fire suppression.

  11. ranson | | #11

    To be clear, the extinguished part would take some sort of fire suppression. But I want to do the best I can before adding in something like that.

  12. user-6184358 | | #12

    Fire sprinklers are heat activated. They will only spray water in the area where there is excessive heat. They are not like yard sprinklers,like they show in the movies, where the all go off at once.
    As for use in single family residences I think it is in Arizona where they mandated sprinklers here is the NFPA analysis on the impact of fire sprinklers.

  13. SwitchgrassFarmer | | #13

    In my past corporate "life" I was involved with the design, construction, and maintenance of technical facilities that were protected by wet and dry pipe sprinkler, as well as gaseous suppression (FM-200 and before that Halon) systems. They are a pain-in-the-behind. I understand trying to avoid these systems if you can.

    Some thoughts:

    1. FM Global is your friend here. They are the source for discussion about what construction methods to use for best fire rating. Look for "FIRESAFE BUILDING CONSTRUCTION AND MATERIALS" at (I often accompanied the folks from FMGlobal and IRI as they did site inspections.)

    2. I don't know what exact type of electronic work you do, but here is a scenario:

    A new piece of electronic gear is on the bench "burning in" over night. A component fails and for some reason the circuit breakers or fuses don't open quickly enough; it starts to smoulder.

    This is where a VESDA (Very Early Warning Aspirating Smoke Detection) system can save your behind. The VESDA system can call you, text you etc so that you can run over to the lab and investigate. It's peace of mind. (One downside, they can false trip on occasion.)

    3. If you think there is any chance you might go to a gaseous fire suppression system, be sure to air-seal your construction very thoroughly. In fact my first exposure to a blower door test wasn't for energy reasons, it was for fire protection. That gaseous suppression agent needs to stay resident in the space long enough to extinguish the fire. So you will be looking at gasketed doors, high quality HVAC dampers for fresh air, etc. And also provision for a future "purge" system, to remove that suppression agent so that the fire fighters can enter your space.

    (I had a bonehead fire protection contractor inadvertently discharge multiple tanks of FM-200 during a yearly readiness test. It's unbelievable what the pressure of those tanks can blow around, noisy as hell also. Witnessed it first hand, before I ran for the door. Only good thing, we got to test the purge fans!)

  14. ranson | | #14


    That info is great. You've captured one of my biggest worry scenarios perfectly (unattended burn-in). I don't leave tests unattended right now, just for that reason.



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