• Welcome to The Building Code Forum

    Your premier resource for building code knowledge.

    This forum remains free to the public thanks to the generous support of our Sawhorse Members and Corporate Sponsors. Their contributions help keep this community thriving and accessible.

    Want enhanced access to expert discussions and exclusive features? Learn more about the benefits here.

    Ready to upgrade? Log in and upgrade now.

Insulation above suspended ceiling

BrendanLead

BrendanLead

REGISTERED
Joined
Jun 20, 2019
Messages
17
Location
New Jersey
I am working on an office fit-out (B accessory use) in an S1 Use, Semi-heated warehouse. The perimeter office partitions only extend 12 feet up and do not go to the underside of the metal deck, which is about 40 feet up. My original drawings propose insulated walls with a suspended ceiling 10' AFF hung from the bottom of the warehouse roof deck with R19 batt on top of the ceiling t-grid to create a "sealed" environment for the conditioned space, but the more research I do, the more I come to realize this is not a recommended solution due to air leakage.

I can't find much in the codes discussing the proper handling of this situation. The only information I see is in the 2015 IECC, under C402.2.2 ROOF ASSEMBLY, which states, "INSULATION INSTALLED ON A SUSPENDED CEILING WITH REMOVABLE CEILING TILES SHALL NOT BE CONSIDERED PART OF THE MINIMUM THERMAL RESISTANCE OF THE ROOF INSULATION."

What is the best way to handle this situation? Is the only solution to place a "cap" on the office space with metal structural studs and gyp board to create an air seal?

Thank you in advance!
 
The building is actually semi-heated and constructed of tilt-up concrete panels with r21 rigid insulation on the roof deck. Essentially there is a conditioned office space inside of a semi-condiitioned warehouse space.
 
A cap is probably your best bet. I have never seen insulation on a suspended ceiling put back in place when a tile is popped out and put back again. The insulation is like swiss cheese after a few years.
 
Insulated ceiling tiles is the answer. Sounds like the roof already meets the building thermal resistance requirements

iscsupply.com

All-in-One Insulating Ceiling Tiles - ISC Supply

Insulating Fiberglass Ceiling Tiles are the perfect solution for jobs that require a lay-in ceiling panel with access above and high R-Value. They are made from a rigid 3″ thick fiberglass with a thin vinyl laminated to the face providing a stellar NRC value for noise absorption in the room and...
iscsupply.com iscsupply.com

1647883770280.png
 
Paul Sweet said:
A cap is probably your best bet. I have never seen insulation on a suspended ceiling put back in place when a tile is popped out and put back again. The insulation is like swiss cheese after a few years.
Click to expand...
Thanks Paul. Is there anywhere in the building or energy code I can find information regarding this matter? Given that I've already instructed the contractor to lay batt insulation on the suspended t-grid, I'd like to have something to reference.
 
mtlogcabin said:
Insulated ceiling tiles is the answer. Sounds like the roof already meets the building thermal resistance requirements

iscsupply.com

All-in-One Insulating Ceiling Tiles - ISC Supply

Insulating Fiberglass Ceiling Tiles are the perfect solution for jobs that require a lay-in ceiling panel with access above and high R-Value. They are made from a rigid 3″ thick fiberglass with a thin vinyl laminated to the face providing a stellar NRC value for noise absorption in the room and...
iscsupply.com iscsupply.com

View attachment 8723
Click to expand...
The roof meetings the rqrts based on a semi-heated building. Given that office space will be fully conditioned, I'm not sure this will work.
 
Unless it is a NJ thing I have never heard of nor can I find what a semi-heated building is in the energy code.
The reason for not allowing batt insulation on the ceiling grid is as Paul explained it never gets put back correctly. The ceiling tiles would eliminate that concern.
 
mtlogcabin said:
Unless it is a NJ thing I have never heard of nor can I find what a semi-heated building is in the energy code.
The reason for not allowing batt insulation on the ceiling grid is as Paul explained it never gets put back correctly. The ceiling tiles would eliminate that concern.
Click to expand...
I don't believe IECC covers semi-heated spaces. ASHRAE 90.1-2013 does. Semi-heated spaces are generally spaces that are heated to prevent freezing and to take the "edge" off. This is also a category type when performing COMChecks. Think large industrial/warehouse buildings.
 
Well your "roof assembly" meets the IECC so I do not see where C402.2.2 is applicable to your project. You may even argue that your project is in a lower climate zone since it is inside a semi-heated space

Run the insulated ceiling tiles by the AHJ and get their input
 
mtlogcabin said:
Well your "roof assembly" meets the IECC so I do not see where C402.2.2 is applicable to your project. You may even argue that your project is in a lower climate zone since it is inside a semi-heated space

Run the insulated ceiling tiles by the AHJ and get their input
Click to expand...
Yes, AHJ may be the way to go at this point. I am just thrown off because it's a conditioned space inside of a semi-conditioned space so I wasn't sure if the insulation requirements would be more stringent.
 
We have discussed this in the past, click on the link

Insulation Over Ceiling Tiles

> ? > ? > ? I see a lot of construction plans with thermal and \ or acoustical insulation installed \ laid on top of the ceiling tiles. I seem to recall that this was not an approved type of installation. Q1) Is installing thermal or even acoustical insulation on top of ceiling tiles...
www.thebuildingcodeforum.com
 
C402.2.2 Roof assembly. The minimum thermal resistance
(R-value) of the insulating material installed either
between the roof framing or continuously on the roof
assembly shall be as specified in Table C402.1.3, based on
construction materials used in the roof assembly. Skylight
curbs shall be insulated to the level of roofs with insulation
entirely above deck or R-5, whichever is less.
Exceptions:
1. Continuously insulated roof assemblies where the
thickness of insulation varies 1 inch (25 mm) or
less and where the area-weighted U-factor is
equivalent to the same assembly with the R-value
specified in Table C402.1.3.
2. Where tapered insulation is used with insulation
entirely above deck, the R-value where the insulation
thickness varies 1 inch (25 mm) or less
from the minimum thickness of tapered insulation
shall comply with the R-value specified in
Table C402.1.3.
3. Unit skylight curbs included as a component of a
skylight listed and labeled in accordance with
NFRC 100 shall not be required to be insulated.
Insulation installed on a suspended ceiling with removable
ceiling tiles shall not be considered part of the minimum
thermal resistance of the roof insulation.
 
On warehouse/manufacturing projects with accessory office spaces, or restrooms or any other similar small space inside the large building, we typically show it as a self-contained "box" inside the large volume. It has surrounding walls that go up so high, and then a cap or "dust cover" on top. That cover could be metal deck on cold-formed joists, or even 1 or 2 layers of sheetrock on top of joists, if there are enough walls inside the space to support those type of joists. Otherwise steel bar joists might be needed. Then the finished suspended ceiling inside gets suspended from that lower structure, instead of having to go all the way up to the roof deck. The cap can also contain insulation similar to the walls, to separate the fully conditioned space from the semi-conditioned space.
 
PatrickGSR94 said:
On warehouse/manufacturing projects with accessory office spaces, or restrooms or any other similar small space inside the large building, we typically show it as a self-contained "box" inside the large volume. It has surrounding walls that go up so high, and then a cap or "dust cover" on top. That cover could be metal deck on cold-formed joists, or even 1 or 2 layers of sheetrock on top of joists, if there are enough walls inside the space to support those type of joists. Otherwise steel bar joists might be needed. Then the finished suspended ceiling inside gets suspended from that lower structure, instead of having to go all the way up to the roof deck. The cap can also contain insulation similar to the walls, to separate the fully conditioned space from the semi-conditioned space.
Click to expand...
I usually see plywood for the cap. The space is used for light storage.
 
If it is a change in space conditioning, full compliance with todays code for the envelope is required...

CHANGE OF OCCUPANCY OR USE
C505.1 General. Spaces undergoing a change in occupancy
that would result in an increase in demand for either fossil
fuel or electrical energy shall comply with this code. Where
the use in a space changes from one use in Table C405.4.2(1)
or C405.4.2(2) to another use in Table C405.4.2(1) or
C405.4.2(2), the installed lighting wattage shall comply with
Section C405.4.


C503.1 General. Alterations to any building or structure
shall comply with the requirements of the code for new construction.
Alterations shall be such that the existing building
or structure is no less conforming to the provisions of this
code than the existing building or structure was prior to the
alteration. Alterations to an existing building, building system
or portion thereof shall conform to the provisions of this
code as those provisions relate to new construction without
requiring the unaltered portions of the existing building or
building system to comply with this code. Alterations shall
not create an unsafe or hazardous condition or overload existing
building systems.
Alterations complying with ANSI/ASHRAE/IESNA 90.1.
need not comply with Sections C402, C403, C404 and C405.
Exception: The following alterations need not comply
with the requirements for new construction, provided the
energy use of the building is not increased:
 
PatrickGSR94 said:
On warehouse/manufacturing projects with accessory office spaces, or restrooms or any other similar small space inside the large building, we typically show it as a self-contained "box" inside the large volume. It has surrounding walls that go up so high, and then a cap or "dust cover" on top. That cover could be metal deck on cold-formed joists, or even 1 or 2 layers of sheetrock on top of joists, if there are enough walls inside the space to support those type of joists. Otherwise steel bar joists might be needed. Then the finished suspended ceiling inside gets suspended from that lower structure, instead of having to go all the way up to the roof deck. The cap can also contain insulation similar to the walls, to separate the fully conditioned space from the semi-conditioned space.
Click to expand...
I like the way you think!
Why even bother with the suspended ceiling if you are going to use ceiling joist to hand the suspended ceiling? Park the airhandler and even the outdoor unit (heat pump?) on the ceiling joist. Do you really care if you are absorbing or reject heat into this minimum temp storage space?
Just rock it with the walls and you have your air barrier and a logical place for your batt insulation.
As far as insulation R values, this accessory office Is NOT the Structure, so you are just using a reasonable amount of insulation to reduce the size and operating cost of providing some Heating and Cooling to this occupied space. I don't even see the need for Outside Air ( ventilation) given the small office's relation to the large space

As the Bldg Code Official, you can determine that these reasonable efforts meet the INTENT of the Code
 
mtlogcabin said:
Insulated ceiling tiles is the answer. Sounds like the roof already meets the building thermal resistance requirements

iscsupply.com

All-in-One Insulating Ceiling Tiles - ISC Supply

Insulating Fiberglass Ceiling Tiles are the perfect solution for jobs that require a lay-in ceiling panel with access above and high R-Value. They are made from a rigid 3″ thick fiberglass with a thin vinyl laminated to the face providing a stellar NRC value for noise absorption in the room and...
iscsupply.com iscsupply.com

View attachment 8723
Click to expand...
Yeah, these are good. I purchased these to replace conventional ceiling tiles that had expanded with humidity and were a problem removing and reinstalling resulting in crumbling.
 
In my state, warehouses are exempt from the energy conservation code per C101.2, and it applies to the whole building where the primary occupancy is F, S, or U. Is that not typical elsewhere?
 
We don't have this exception in PA but all warehouses I have inspected use this in the IECC:

C402.1.1 Low-energy buildings. The following low energy
buildings, or portions thereof separated from the
remainder of the building by building thermal envelope
assemblies complying with this section, shall be exempt
from the building thermal envelope provisions of Section
C402.
1. Those with a peak design rate of energy usage less
than 3.4 Btu/h • ft2 (10.7 W/m2) or 1.0 watt per square
foot (10.7 W/m2) of floor area for space conditioning
purposes.
2. Those that do not contain conditioned space.
3. Greenhouses.
 
Rick18071 said:
We don't have this exception in PA but all warehouses I have inspected use this in the IECC:

C402.1.1 Low-energy buildings. The following low energy
buildings, or portions thereof separated from the
remainder of the building by building thermal envelope
assemblies complying with this section, shall be exempt
from the building thermal envelope provisions of Section
C402.
1. Those with a peak design rate of energy usage less
than 3.4 Btu/h • ft2 (10.7 W/m2) or 1.0 watt per square
foot (10.7 W/m2) of floor area for space conditioning
purposes.
2. Those that do not contain conditioned space.
3. Greenhouses.
Click to expand...
Interesting....I wonder if they actually hit it or if they just claim they do.....
 
You must log in or register to reply here.
Back
Top