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The Engineer: Simulation Q&A

When I started I didn’t know how some very small changes can substantially impact the performance of a window or curtain wall system.

March 16, 2022  By David Heska

It was June 1989 at an ASHRAE conference in Vancouver when the idea of a National Fenestration Rating Council was born. Thirty-three years later, much has changed. Something that has not changed is the value that window simulations continue to provide to manufacturers, designers and clients.  For a fraction of the cost of physical apparatus, computer modelling can be completed leading to very accurate results when compared to physical hot-box testing. In this article, I’ve chosen to interview my colleague Zeljka Lazarevic asking her a few questions about her career working in the industry.

DH: Zeljka, how many years have you been doing this?

ZL: I’ve been working in the window industry for the past 25 years.  I started with Enermodal Engineering here in Kitchener, Ont., and over time have grown along with the company to be a part of WSP today.

DH: What are some of the recent changes you’ve seen in the window industry over the past five years and how have these changes impacted your computer simulation work?


ZL: Our industry is continuing to innovate and improve.  I have seen many manufacturers pushing new technologies. Because of the drive towards net zero buildings, many have realized that smaller changes are not good enough anymore. It’s not enough just to take your existing frames and add a low-E coating or new spacer. Entirely new frames are needed, comprised of various materials and a range of new technologies.

DH: What is the hardest part of simulations your team completes using the THERM simulation software developed at the Lawrence Berkeley National Laboratory?

ZL: Becoming familiar with the software is an adjustment at first. But once you are familiar with it, it’s not that hard. Sometimes what takes time is compiling all of the information that is required together.  Sometimes window manufacturers do not have the required drawings or all of the information they need to pass along to us. As an accredited NFRC simulation laboratory, every two years we are required to pass an audit so that also takes some time.  All of this is required so manufacturers can get U-factor, SHGC, VT and CR ratings necessary for building energy code compliance.

DH: Why would someone want to get into the window simulation industry?

ZL:  My simple answer would be to help clients improve their fenestration products. We all want to build better buildings and for me that includes providing technical advice to manufacturers related to their research and development. A career in the window simulation industry also allows for career progression.  A few steps one can take include becoming an NFRC certified simulator and even becoming a simulator in responsible charge.

DH: What are the shortest and longest projects you’re currently working on?

ZL:  Some trials projects can take only a couple of hours. A repeat client may call us and ask for some assistance with a new component they are developing. But we also have $50,000 projects that can take our team two to four months to complete. It all depends.

DH: What do you know now that you wish you knew 25 years ago?

ZL: I wish I had all this experience. When I started I didn’t know how some very small changes can substantially impact the performance of a window or curtainwall system. A small piece of advice can have a huge impact.

DH: Thanks, Zeljka, for sharing this with me today and for serving our industry over the past 25 years.

David Heska, P.Eng. is a director with WSP’s building sciences team in southwestern Ontario. 

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