The LG Files

Buildings with large glass curtain walls offer vibrant interiors full of natural light that can help boost occupant morale. So it’s no wonder the use of glass in building enclosures has grown significantly over the years.

But there’s a dark side to too much natural light: direct sunlight, especially in hotter climates, can wreak havoc on utility bills because of the stress it puts on air conditioning systems. Fortunately, there are strategies you can employ to get the benefits of natural light while controlling energy costs. This article explores one way to do just that.

You have a project that requires delegated design, which means you need to have an engineer provide an analysis of your framing systems and provide stamped calculations. We were curious about exactly what was included in the calculation package, and possibly what was not included.

We reached out to one of our trusted engineering resources to ask exactly what they include, and don’t include, in an analysis. For the items not typically included, make sure to ask for that additional help if it’s needed on your project. Please do not assume that everything is reviewed 100%. Lastly, it is important to review the specifications in their entirety to make sure the engineering services you have requested match your requirements.

Below is the engineer’s response to items that are typically included, items that are included but may not be obvious, and items that are typically omitted from the engineering review.

Engineers try to provide as complete a package as possible without taking on additional liability for components that they should not be responsible for, which fall under someone else’s scope of work.

Typically included items in the calculation packages:

• Analysis of wind load and seismic values to use on the project
• Review of codes and specifications to determine project requirements
• Vertical mullion deflection
• Horizontal mullion deflection
• Corner zone analysis to identify frames affected by alternate wind loads
• Anchor designs and locations, i.e., wind load anchors, dead load anchors, clips, etc.
• Fasteners review for all attachments to the surrounding structure
• Attachment of secondary systems, such as sunshades, to the glazing systems
• Thermal movement (vertical and horizontal) for effects on the curtain wall system

Some items that are included in the review that may not be apparent include the following (these items may not actually be in the calculation package, either):

• Screw spline/shear block attachments for horizontal members
• Caulk joint thickness at jamb/head to account for deflection/thermal movement
• Expansion splice thickness (caulk width) for thermal movement and live load deflection
• Vertical slot sizing for wind load anchors
• Relationship between WL/DL anchors and splice locations/type and any needs for change. This is one of the biggest problems engineers see in drawings.
• Silicone bite width for SSG systems

Specific items within the calculations that are omitted unless specifically needed or requested:

• Glass design unless specifically requested by the customer and/or specifications
• Doors – glass, framing, hardware, etc. These are components typically tested within the system, and engineers default to that testing.
• Thermal performance of the CW/SF system
• Structural adequacy of the surrounding conditions to which engineers are attaching. EOR’s responsibility is to provide us with adequate structure.
• Pressure plate attachments. These are tested and typically overkill per installation instructions.

In conclusion, it is important to understand which elements are not reviewed by, or the responsibility of, the engineer, and if your project is requesting these items. This way you can avoid hidden charges and liability that you and your company should not be taking on.

Also keep in mind that most engineering services are happy to review the project up front, along with the specifications and requirements to help identify these hidden issues. If a non-typical request exists on your project, you can address it at the beginning to save time and money.