Second floor with below floor insulat...

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Author Message Dale Hurttgam, NCARB, AIA,LEED AP, CSI Senior Member Username: dwhurttgam Post Number: 49 Registered: 10-2005 Posted on Wednesday, November 25, 2009 - 01:31 pm:    We are designing a low rise multi-story office building with an open parking area below the second floor. We have not done this type of construction frequently. The second floor slab needs to be two hour fire rated - architect is thinking that he may go with concrete frame construction at this level rather than steel. We are in schematic design and the concern is how to most economically insulate the slab. One approach is to use a sandwich floor slab with high density insulation on the structural slab and then an additional floor slab on top of that. However, the architect would like to avoid this and ideally insulate from the underside. Are any of you aware of spray foams that would work well on the underside of a concrete floor slab or that could be incorporated if the floor slab is incorporated into a steel framing system that would require 2 hour spray-on fire proofing. The intent is to not provide a ceiling in the parking area, but to leave everything exposed. There are a couple of product reps investigating options for me - but the primary suggestion so far is the sandwich slab concept that we already had under consideration. Colin Gilboy Senior Member Username: colin Post Number: 210 Registered: 09-2005 Posted on Wednesday, November 25, 2009 - 01:59 pm:    Dale, Check out the exposed spray insulation systems listed on 4specs. Most can provide an R=19. http://www.4specs.com/s/07/07-2300.html Colin Gilboy Publisher, 4specs.com 435.654.5775 - Utah 800.369.8008 Mark Gilligan SE, CSI Senior Member Username: mark_gilligan Post Number: 239 Registered: 10-2007 Posted on Wednesday, November 25, 2009 - 02:11 pm:    If you go with a concrete system you should be able to get your fire rating by ensuring that the concrete cover is adequate. Similarly 2 hour fire rated metal deck with concrete fill is very frasiblealthough you may still need to protect the steel bems. Talk to your structural engineer. On the west coast additional thermal insulation is not common in these situations if you have a concrete floor system. Lynn Javoroski CSI CCS LEEDŽ AP SCIP Affiliate Senior Member Username: lynn_javoroski Post Number: 970 Registered: 07-2002 Posted on Wednesday, November 25, 2009 - 03:01 pm:    What about precast insulated sandwich slabs (good spans), underfloor heat, and a topping slab? John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1138 Registered: 03-2002 Posted on Wednesday, November 25, 2009 - 04:33 pm:    I like Colin's suggestion, though we've also used suspended ceiling with blanket above--I wasn't so hot on that approach. If approved by the AHJ, you may be able to use spray-foam with a sprayed thermal barrier over that. (Must be a thermal barrier, though, not an ignition barrier.) Randy Cox Senior Member Username: randy_cox Post Number: 67 Registered: 04-2004 Posted on Wednesday, November 25, 2009 - 08:59 pm:    We used post tensioned concrete slabs in some residential construction with proper cover over the rebar and tendons to maintain a 2 hour rating. Below the slab we had an interstitial space for all the waste and drain lines required for residential work (a pain to get them all in the exact location). we had some small heaters in the intersitial space and R19 insulation below. This was separated from the garage with a ceiling grid using gypsum based panels. the concrete slab is the fire separation, but it gets tempered heat from below. It ends up as a hefty assembly, but the contractor was set up for it, and we didn't have to align bearing walls for the lowrise woodframe constuction with anything in the garage. Latest project is moving into dd with concrete covered metal deck, with Icynene sprayed below. My big question is whether or not I can spray icynene over the spray on fireproofing. Will it hold over time? I am especially wondering if the multiple layers will hold in a fire situation. Anyone seen any reports? Ron Beard CCS Senior Member Username: rm_beard_ccs Post Number: 317 Registered: 10-2002 Posted on Thursday, November 26, 2009 - 03:11 pm:    Dale: I strongly suggest you checkout Monoglass Spray-On Insulation. It is made from glass beads/fibers which can be applied to just about any surface and left exposed to the exterior. I have successfully used Monoglass on many different occassions in both interior/protected and in exterior applications including garage ceilings, underside of pedestrian bridges over truck driveways, and uses similar to the one you are considering. It has good thermal and acoustical qualities as well as completely fireproof. From the mfrs lterature: it is described as non-toxic, inorganic (does not support mold or bacterial growth), contains post-consumer re-cycled glass and can be sprayed to a depth of 5-inches (R-20) without need for mechanical support. And, for what's worth, it is "green." Dale Hurttgam, NCARB, AIA,LEED AP, CSI Senior Member Username: dwhurttgam Post Number: 50 Registered: 10-2005 Posted on Tuesday, December 01, 2009 - 01:09 pm:    Thank you for your suggestions. In the process of investigating them.