The User’s Guide to Glazing, Part 1: Understanding U-Factors & Solar Heat Gain

By NanaWall Systems, May 7, 2018

NanaWall Solid Wood Folding Glass Wall

We may have mentioned this before, but when it comes to glazing, there’s a lot to know. Even a single pane of glass is more than simply a pane of glass – depending on where it was made it is likely to have a different mineral makeup, and potentially color, than if it had been made elsewhere.

SL60 Aluminum Framed Folding Glass Walls

Once we start talking about actual fenestration (a category that from a technical standpoint, includes opening glass walls), we have entered an entirely new ballpark in terms of complexity.

NanaWall Folding Glass Walls

One of the many factors to consider when talking about fenestration is efficiency, which is due in large part to the fenestration’s U-factor and Solar Heat Gain Coefficient.

NanaWall HSW60 Single Track Sliding system

Understanding U-Factors

U-factors measure the rate of heat transfer, and the level of insulation that the product can provide. The numbers that make up the U-factor usually range from 0.20 to 1.20 – the lower the number, the better the performance. For instance, a rating of <.30 is considered a very good U-factor.

NanaWall aluminum folding glass wall

Understanding Solar Heat Gain

Conversely, the Solar Heat Gain Coefficient (SHGC) measures a product’s ability to keep unwanted heat (heat coming primarily from outside) out. SHGCs are scored between 0 and 1, with the lower numbers indicating better performance.

Click here for a list of our most efficient products (this will be especially pertinent to those looking to satisfy Title 24 requirements).

Have additional questions about glazing and efficiency? Send us an email at