# Are glass curtain walls "openings" or "walls"?



## lee1079 (Dec 23, 2015)

2012 IBC 705.8 regulates allowable area of openings in exterior walls. My question is whether glass curtain walls should be considered walls or openings?


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## Builder Bob (Dec 23, 2015)

Building Envelope Design Guide - Curtain Walls

by Nik Vigener, PE and Mark A. Brown - Simpson Gumpertz & Heger Inc.

Revised by the Chairs of the Building Enclosure Councils with assistance from Richard Keleher, AIA, CSI, LEED AP and Rob Kistler, The Facade Group, LLC.

AAMA logo

Development and review supported through a grant from the American Architectural Manufacturers Association

Last updated: 06-25-2012

Within This Page

Introduction

Description

Fundamentals

Applications

Details

Emerging Issues

Relevant Codes and Standards

Additional Resources

INTRODUCTION

A curtain wall is defined as thin, usually aluminum-framed wall, containing in-fills of glass, metal panels, or thin stone. The framing is attached to the building structure and does not carry the floor or roof loads of the building. The wind and gravity loads of the curtain wall are transferred to the building structure, typically at the floor line. Aluminum framed wall systems date back to the 1930's, and developed rapidly after World War II when the supply of aluminum became available for non-military use.

Curtain wall systems range from manufacturer's standard catalog systems to specialized custom walls. Custom walls become cost competitive with standard systems as the wall area increases. This section incorporates comments about standard and custom systems. It is recommended that consultants be hired with an expertise in custom curtain wall design for projects that incorporate these systems.

It appears that a curtain wall is a system which requires it to meet the requirements for walls as per code.


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## north star (Dec 23, 2015)

*@ ~ ~ @*

Also, ...see Section 2404.3.3 in the `12 IBC.

*@ ~ ~ @*


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## Pcinspector1 (Dec 23, 2015)

Is the curtain wall inspections being done by a third party inspector?


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## PhiladelphiaGlass (Jun 24, 2016)

Curtain Wall = Wall
Curtain Wall System - Depends


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## cda (Jun 24, 2016)

PhiladelphiaGlass said:


> Curtain Wall = Wall
> Curtain Wall System - Depends




Well Welcome

We always need someone that is transparent


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## mark handler (Jun 28, 2016)

In my opinion some of the glass portions of curtain walls are openings in exterior walls.
Not all curtain walls are glass.
Not all curtain walls that use glass as a component are openings. Many curtain walls that use glass as a component have infill portions of metal and gypbd.

Many times opening limitations can be mitigated with dedicated *sprinkler* systems to _*protect the glazing.*_
*
Glazing can be a component in a wall but is not a wall.*


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## Paul Sweet (Jun 29, 2016)

Except for the rare instance where the curtain wall system is fire rated (I don't know of any that are) I would consider the opening area as the opening in the rated back-up wall assembly.


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## mark handler (Jun 29, 2016)

Paul Sweet said:


> Except for the rare instance where the curtain wall system is fire rated (I don't know of any that are) I would consider the opening area as the opening in the rated back-up wall assembly.


*No one has ever shown me anything in the code that allows Curtain Walls, glazed or otherwise, from not meeting the fire rating and maximum opening requirements of the code. There are "Alternative methods" of mitigating the requirement, including but not limited to, water curtains.*

Paul:
*fire-rated curtain walls*
http://www.aluflam-usa.com/curtain-walls/
http://www.fireglass.com/framing/curtainwall/


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## ADAguy (Jul 5, 2016)

Curtain walls may be of "fixed:" or openable glazing. If openable, that which is is an opening that which is fixed, isn't.

Openable/opening relates to air circulation, no?


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## mark handler (Jul 5, 2016)

ADAguy said:


> Curtain walls may be of "fixed:" or openable glazing. If openable, that which is is an opening that which is fixed, isn't. Openable/opening relates to air circulation, no?



So are fixed windows openings?


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## Builder Bob (Jul 6, 2016)

Depends... is the exterior wall required to be fire resistant rated or not?


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## mark handler (Jul 6, 2016)

Builder Bob said:


> Depends... is the exterior wall required to be fire resistant rated or not?


Still an opening in wall regardless of fire resistivity.


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## ADAguy (Jul 6, 2016)

If "fixed" then how is it an "opening" for other than light?


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## mark handler (Jul 6, 2016)

ADAguy said:


> If "fixed" then how is it an "opening" for other than light?


You are going down the rabbit hole


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## Builder Bob (Jul 7, 2016)

It is still an opening due to radiate heat exposure ---- you still get the warmth of the sun light rays thru a window - and worse if the fire is in the building next door....... in the old days of firefighting we used water curtains to protect exposures ---- ended up being a waste of time as the radiate heat still penetrated the water curtains - the only thing protecting the exposures was the water hitting the exposed materials --- it did not protect the curtains hanging inside the windows and we had a few rooms catch on fire from the radiant heat from the neighbor's house


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## ADAguy (Jul 7, 2016)

In summary:

A curtain wall is a "wall" system (that may or may not be fire rated subject to code requirements) that may or may not contain openings (translucent panels) that may or may not be "openable", allowing for radiant heat to pass through the panels.


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## mark handler (Jul 7, 2016)

ADAguy said:


> In summary:
> 
> A curtain wall is a "wall" system (that may or may not be fire rated subject to code requirements) that may or may not contain openings (translucent panels) that may or may not be "openable", allowing for radiant heat to pass through the panels.


radiant heat passes through walls as well... poor definition


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## ADAguy (Jul 7, 2016)

Radiant heat comes in two (2) forms, invisible (heat) and visible (light). Light can be transmitted with some control of radiant heat when transmitted through translucent openings.
The resistance to radiant heat in a wall with insulation differs from a translucent (glass) panel that may or maynot be multiglazed and with or without low E glass.
Walls (vs certain types of curtain walls (unlike KalWall type)) do not typically allow for transmission of light, translucent (glass) openings typically do, dependent on material selected.


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## JBI (Jul 7, 2016)

"*Glazing can be a component in a wall but is not a wall."*
Fire resistance rated glazing would constitute a wall (or portion of a wall) if properly tested, listed, and labeled.


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## Builder Bob (Jul 7, 2016)

Although you are wise and true about heat transmittal in walls, it boils down to how quickly heat transfer takes place....if the rate of heat exchange is quick enough, the curtains on the inside of the window will catch on fire causing fire extension into adjoining structures even when separated by twenty or thirty feet.

The shielding of the wall surfaces (exterior, air space, insulation, and interior finishes) will slow down the rate of heat transfer therefore are less likely to allow a fire to spread from one structure to another.


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## ADAguy (Jul 7, 2016)

JBI, interesting quote, what is its source? That would be "fixed" glazing, no?
I believe the Germans now have a one hour rated glass wall but it is very heavy.


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## JBI (Jul 7, 2016)

ADAguy, Yes that would be a fixed panel. For operable windows (or doors) there is also fire protection rated glazing. 
For fire resistance rated glazing see Section 703.6 (2015 IBC) and 716.3 (2015 IBC) for fire protection rated glazing.


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## mark handler (Jul 8, 2016)

ADAguy said:


> JBI, interesting quote, what is its source? That would be "fixed" glazing, no?
> I believe the Germans now have a one hour rated glass wall but it is very heavy.


There are products MADE in the USA. and they are not that heavy
http://www.fireglass.com/specifire/


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## JBI (Jul 8, 2016)

Excellent link mark handler. Curtain walls with up to 120 minute ratings...


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## ADAguy (Jul 8, 2016)

no limits to technology, eh?


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