Styrofoam is usually 1.0 pounds per cubic foot. It has a flame spread
rating that is considered too high to be left uncovered. It will not burn
unless the flame is supported by other material, but it will burn under
The moldings you see are made from recycled styrene material and are a much
higher density, thus a lower flame spread. They are usually used in lesser
amounts also. Please, they are different materials.
You asked for advice. I've been working with foam plastics for 37 years
(packaging, building products, aircraft products, pharmaceutical products)
so I have some idea what I'm talking about. I'd not do what you propose in
my house and I advise against doing it in yours. No recessed lighting in
Thanks for your post.
I've got two types of styrofoam (polystyrene). A bag white decoration sheets
clearly and sold as intented to be glued to the ceiling. They won't support any
And then I've got blue much better quality looking (denser) larger sheets. At the
depot they said it can be painted. My son uses them for miniature carvings. He
carves it with chisel and hot wire.
What part of the word "RECESSED" do you not understand?
How in the f__k are you going to install recessed lights in a concrete
ceiling when you only install 1 1/2 inches of foam? Thats barely deep
enough for an electrical box. Unless you bust a hole in the concrete,
this simply is not going to work. Either start over your plans from
scratch, or get rid of the recessed lights and use surface mounted
lights which will work well since the box will be close to level with
the foam surface. Of course, you are probably violating building
codes and in a fire you'd die in seconds from the burning foam.
Why not just glue on furring strips and add ceiling tiles? Either
way, forget the RECESSED lights. WAKE UP..... this is NOT going to
Unless the styrofoam was made with a chemical additive, and most
likely it wasn't, it isn't considered flame retardant. UL once
classified it as "self extinguishing", meaning the material will quit
burning if the source of flame is removed , but UL was heavily
criticized for giving that classification to styrofoam, and apparently
the "self extinguishing" label was based on a test where the material
sat horizontally in a wind tunnel and set on fire.
BTW, the term "fire resistant" can apply to materials that burn fairly
easily, including fire wood. :(
The self extinguishing term was used until some time in the mid 1970's when
the lawyer changed it to "modified" material. They add bromides for the
fire retardant. The reason for the change was a lawsuit where some idiot
burned his house down and claimed he thought hte foam would put it out or
some such nonsense.
In practice, the modified material will go out if you remove the source of
ignition. When surrounded by other flammable materials, the flames from
those materials supports the burning of the foam, thus the need for
covering. An exception to this is drop out or melt away ceiling tiles used
below sprinkler systems. They are usually 1/2" thick.
Another clarification here. Styrofoam is the registered trade name of Dow
Chemical's extruded polystyrene board, colored blue. There are other brands
of extruded board in different colors. Then there is the expanded
polystyrene board that is wire cut from billets. Often called "bead board"
since it is made of molded beads of the material. Any material used in
construction must be made of the modified material. When used in packaging
or cooler, regular material is usually used and is more likely to burn and
keep burning once started.
That's the missing link here. It **seems** he's using something he found
laying around, without having any idea if it's safe to use indoors. Read ALL
the messages in the discussion. The guy has a deluxe reading comprehension
No offense, but are you nuts??? Exposed styrofoam is a major fire
Styrofoam burns so badly that almost every locality forbids it to be
left exposed, but even if there isn't any law against that, you still
want it covered with something highly fire resistant, like plaster or
sheet rock. Recessed lighting is bad enough for causing fires even
when it's housed properly and surrounded by fireproof insulation with
adequate clearance from the light.
Styrofoam (brand name of polystyrene) is often used as a residential
Any reasonable amount of space should be sufficient (say, 1") or the
lighting cans designed for the purpose.
But, as you said, Halogen bulbs are hot. Plus expensive to buy and run. I'd
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