Thermal Insulation Above L.A.T. Ceilings

[north star]

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I have a metal building with rooms / spaces being partioned out in it. The

contractor has submitted plans showing the L.A.T. [ a typical suspended

ceiling ] grid installed throughout the building. Also, there is R-30 roll

insulation shown as "proposed to be installed".

Question #1: Is the thermal insulation permitted to be installed directly

on the top of the ceiling grid tiles? Seems like we have discussed this

issue before...

Question # 2: There is a 1 hr. fire rated Exit passgeway designed in

to the rooms / spaces [ w/ office spaces, 1 Restroom & 1 Breakroom ]

on either side of the Exit passageway. Thermal insulation is also

shown to be installed directly above the fire rated "drop ceiling".

I'm preety sure that I have never seen an approved, fire rated ceiling

assembly design that allows thermal insulation to be installed directly

onto the non-fire side. Does anyone know of a such a design,

or possibly an ES report, or other?

Thanks for your input!

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[georgia plans exam]

See Section 502.2.1 of the 2006 I.E.C.C. "Insulation installed on a suspended ceiling with removable ceiling tiles shall not be considered part of the minimum thermal resistance of the roof insulation."

I'm not sure about question #2 or about the 2009 I.E.C.C.

GPE

 

[north star]

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GPES,



Thanks for your input!

Question # 2 has to do the ' proposed ' fire rated ceiling assembly

above the exit passageway. I'm trying to find out if there is

a fire rated ceiling assembly that incorporates thermal insulation in

to its design, ...either by U.L., Factory Mutual, or some other

approved [ American ] testing agency.



The 2006 IECC doesn't really have any bearing in this particular

question.

Are you still doing the Plans Examining supervisory gig [ referring to

your sig. ]?

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[georgia plans exam]

north star,

Oh yes, I'm still the Supervisor. I opted to go back to just GPE so as not to toot my own horn. Thanks for asking.

GPE

 

[georgia plans exam]

Here's one. Item #2 of figure #2 would seem to indicate that the insulation should not be installed directly on top of the suspended ceiling. Still looking for one that does.

http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-1289.pdf

GPE

 

[north star]

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GPE,

Thanks for the ES Report and the reference. On this project, of course

Kornbread's Konstrukshun & Bilding Kompany doesn't know what an ES

Report is. D`OH !

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[Paul Sweet]

Insulation on a lay-in tile ceiling is a bad idea for 2 reasons.

1. It has to be moved to get access above the ceiling, and seldom gets replaced properly.

2. It has to be omitted above lay-in lighting fixtures.

Both instances leave large gaps in the thermal envelope.

 

[Plans Approver]

Would 06IBC 708.4, exception 3 be applicable? If the rated corridor wall has insulation allowed in its assembly certification/listing/approval, then so could the ceiling. No? Of course this drywall not LAT, my apologies.

 

[Uncle Bob]

The problem I see with not allowing insulation on the removable suspended tiles; is that in a strip mall, for example, the individual stores are losing energy into the unconditioned space above (which can be quite large). If the individual stores cannot insulate the suspended ceilings above them; they are wasting energy through the tiles.

The energy loss is also increased where adjoining stores are empty; and, especially in new strip malls where the tiles are not installed until the store is leased. Not sharing in conditioning the space above; and actually contributing to loss of energy from the operating store; because the adjoining store spaces are not conditioned spaces.

As for the light fixtures; require them to be listed for coverage by insulation.

If there is no insulation above the tiles the energy loss is much greater than if someone moves a single tile and doesn't replace the insulation batt.

Uncle Bob