Point-Supported Glass Systems

Specification & Product Discussions MasterFormat 2004 Discussions
1

Several years ago, I developed a section for a point-supported glass canopy at a hotel entrance and have used it as a starting point for several other projects. I used Section 08 68 00 “Point Supported Glazing Systems” (not a standard MasterFormat designation). I now have a point-supported curtain wall system, and MasterFormat uses Section 08 44 26.19 “Point Supported Structural Glass.” A manufacturer has supplied a section with a Division 13 section number (which actually seems to make a lot of sense given how these things are designed).

I would like to make a distinction between systems than enclose space (curtain walls) and systems that cover exterior areas (canopies, not really skylights). The first section would use an insulated glazing unit and is going to have a bunch of stuff on thermal performance and air and water infiltration; the second would use laminated glass and concentrate on structural performance.

Does anyone have any thoughts?

2

10 73 00 “Protective Covers” which includes 10 73 16 “Canopies.”

3

How are you going to get better thermal performance? Will you be using films on the glass or do you intend to insert an air gap between the panes. The second approach might be incompatible with the point support systems.

4

Good question, Peter.

The Division section, 133413 Glazed Structures, is more intended for fabricated, pre-engineered structures such as greenhouses, swimming pool enclosures, sunrooms, and solariums.

I think Division 08 is most appropriate location. In the past I’ve specified structural glass canopies under an 088000 section. At first glance, 086000 Roof Windows and Skylights is really not appropriate since canopies aren’t over interior space, but I think it is the most logical place, especially if 086000 was expanded to include glazed canopies.

I suggest you submit this as a request to the MasterFormat Maintenance Task Team. I can’t submit it since I am on the MFMTT.

5

As a counterpoint to Dave’s position, Division 08 is called “Openings” and a glazed canopy is not an opening.

Although glazing is located in Division 08, it doesn’t mean that all things glass-related should be located there (if that were the case, wood doors would be in Division 06). I suggest looking at the overall “work result,” since that is what MasterFormat is classifying (according to the very first paragraph in the introduction).

That is why I believe the Division 10 numbers and titles I offered in my earlier post are more appropriate for this situation. If you want to get more specific, then a Level 4 number could be added with the title “Glazed Canopies,” or something along that line.

6

Although I have developed a section for protective covers that includes the AVADeck extruded alumnum systems so popular here in Houston, it really did not occur to me to look at that for the point-supported glass systems.

Mark: The curtain wall systems can include insulated glazing units which may or may not include laminated units. The monolithic glass may be more than 6 mm thick and is usually tempered. The design depends on the wind loads, the size of the glazing unit to be supported, and the number of supports.

Dave: These beasts are really like “pre-engineered” structures, but I like them better described as “curtain walls.” In fact, they seem to be very closely related to structural sealant glazed curtain walls since that is the material used between glazing units.

Ron: I am surprised that you didn’t pick up on the distinction that the IBC makes between a “canopy” (partially supported by a building) and an “awning” (totally supported by a building). “Walkway covers” would be individual shelters over pedestrian walkways. As you probably do, we generally lump these altogether under the description “canopy,” but I rely on you to keep us straight on such matters.

7

Curtain wall systems with mullions can be one layer thick but I do not believe that it is advisable when you have point supported systems. Talk to an glass expert with experience with point supported systems.

I have done some design of a point supported system and I would always require at least two layers with and interlayer.

8

I spoke with one last week. The reality is that unless these are insulated glazing units, they cannot achieve the thermal performance mandated by the energy codes (both U-value and SHGC).

It sounds a little hinky to me, but I think if you would check on systems installed in the last 3 years, the glazing would be insulated glazing units.

9

Well, MasterFormat does indeed carry section number and title for this.

Division 8

08 44 26, Structural Glass Curtain Walls, Includes: structural glass walls and tensile curtain walls.
and
08 44 26.19 for Point Supported Structural Glass

MasterFormat puts canopies squarely in 10 73 16. Though if the canopy was integrated with or the same type construction as the entrance or curtain wall it covers, I would put it into division 8.

The majority of these kinds of systems for a full wall are insulated glazing units, it can’t be otherwise. The same for the skylight versions . If you are seriously thinking of doing something that is more than just an incidental application (meaning its more than just a small canopy, entrance system, or an interior wall), then you need to be able to engineer the performance requirements, or work with a fabricator that can engineer them.

One of my projects, US Coast Guard HQ in DC (completed in 2013) has 3 of the very cutting edge type systems, all 3 systems using insulated units … a point supported curtain wall that spans the very large entrance lobby, a cable net curtain wall system that runs down one side of the major lobby area, and over the entire huge lobby area, a point supported skylight system (which is actually a blend of point support system and cable net).

If you go to http://www.wdgarch.com/portfolio/projects/us-coast-guard-headquarters you will see the main entrance eventually scroll around. There are 2 images view of the entrance area, one far away, one closer. That’s the point supported wall. In the closer image you can see through the glass and note that there is light coming from glass over the lobby area further inside, thats the skylight. There is no view of the cable net wall which is the one wall you can’t see at all outside or through the inside of the close view.

My preferred working partner is Sentech Architectural Systems http://www.sentechas.com/ as they have given me the quickest responses and have good answers for my project architect’s numerous questions. Novum is also very good, but the working relationship is more difficult since they want to be guaranteed that they get the project - unless they have changed their strategy in the past year. Another is Pilkington, though I have never worked with them.

The Sentech site has general information about their systems. For instance, we are talking about limitations on size of insulated glass units ranging from 12 to 15 feet on a side…and that limitations relates to the kind of coating used, pyrolytic or sputter. And they have good images of their projects.

I would not hesitate to work with any of those.

I have done numerous small scale canopies and store front entrances that are point supported and handled that easily working with manufacturers like CR Laurence to make recommendations about specific anchorages, sizes, etc. But when you get to a true structural glass wall, you need someone with major engineering capabilities, even alloy selection for the connectors is critical.

10

Peter: You mentioned canopies, so I stuck with canopies. The IBC does define them separately. However, the definitions are more than what you describe. A canopy can be freestanding or can be attached to and supported by a building on one or more sides. An awning is either wholly supported or partially supported by the building. Thus, a partially supported awning can also be considered a canopy. However, a partially supported canopy can only be considered an awning if it’s constructed of lightweight framing.

BTW, MasterFormat does have a separate number and title for awnings: 10 73 13 “Awnings.”

As for “walkway coverings” (10 73 26), the IBC does not define those, but it does have requirements for pedestrian walkways, which applies to walkways with covers. However, the IBC section also addresses connecting underground tunnels and elevated bridges.

11

Ron: I knew you knew more about this than I did.

When I originally developed my section for a glass-supported glass canopy section, I focused on the overhead glass aspect of the application which led me into thinking “skylights.” I am giving thought to changing the name and number of my master. Dave, I will be making a suggestion to the committee. I think the current Division 08 designation is intended to be for applications where the primary supports to resist wind loads are glass. Most I have seen have recently are steel.