Structural Thermal Breaks: Not Just For Balconiesfrom Chris Ford
Let’s play a word association game – what’s the first thing that comes to mind when you see or hear “structural thermal break?”
There are two common responses to this question: either “what?” or “balconies.” If your response was neither, then congratulations, you are in the minority (for better or worse).
Traditionally within the North American construction market, there has not been much awareness created around what thermal bridging is, and solutions to their applications. Due to this, most entities are uninformed about the negative effects of thermal bridging on structures – ranging from something immeasurable like occupant discomfort to more tangible issues like energy loss and mold.
But let’s put the negative effects of thermal bridges and benefits of incorporating thermal breaks aside for now and simply identify the location of the major thermal bridges on a structure. Without first knowing where they are, what good is it knowing there are thermal break solutions for these applications?
As we talk to more project shareholders, we are discovering the majority of personnel have either never heard of thermal breaks or, for those with some understanding of the way thermal breaks work, are of the mindset that thermal bridging “most commonly” occurs at balcony connections. While balconies do account for a major percentage of the potential applications for structural thermal breaks within building construction, there are other potential applications for which we need to increase awareness.
There are two specific applications for which the need for structural thermal breaks is growing exponentially. They are:
- roof mechanical system connections
First, let’s address parapets, which are the most commonly overlooked applications when discussing structural thermal breaks. They are essentially the same “balcony-style” type of concrete connection, with a modified orientation to our structure. Rather than running horizontally out of our building (like a balcony), they run vertically. However they are nearly identical in terms of their thermal bridging characteristics.
While a substantially smaller portion of buildings may have balconies, nearly all new construction buildings contain a parapet wall in their design. Unless treated with some form of insulation, the entire parapet will act as a thermal bridge out of the structure. In fact, because of heat’s natural tendency to rise, buildings frequently lose more energy on a percentage basis of total area when contrasted against balcony applications.
Many designers who are aware of this plan to wrap the same extruded polystyrene insulation from their roof, up and over the parapet wall. This does help limit the effect of thermal bridging, however, without having a complete thermal break incorporated into the design or wrapping the parapet entirely, a thermal bridge will continue to exist.
Below is a picture and diagram of a Schöck ISOKORB Type-A, which is used to effectively stop thermal bridging at parapet applications:
Now, let’s look at roof mechanical system connections, which are typically steel plate connections bolted directly to the roof slab, again acting as a thermal bridge. A solution to alleviate this dilemma involves using a Schöck S22 steel connection module, most-typically used at steel balconies and beam connections, and changing the orientation by 90 degrees. By doing this, the bolts from the S22 module will be embedded into the roof pour on one side, maintain the continuous insulation of the roof, and provide the thermally-broken bolt connections for our roof mechanical systems. The S22 module is shown below:
Once you know where the issues will occur, only then can you start designing the right solutions to address the problem of thermal bridging.
Visit the Schöck North America website for more information about structural thermal breaks for concrete and steel connections. Explore the full range of Isokorb® products for balcony, canopy, steel beam, exposed slab edge, parapet and rooftop connections.
Considering structural thermal breaks for an upcoming project? Have a Schöck Engineer call you to answer your specific design questions.