Mark Meshulam is a construction consultant located in Northbrook, IL. He is an expert in mockup testing.

Video: A Visit with Sak 2009

This article, originally written in 2006 is being reprinted here in very fond memory of my friend A.A. Sakhnovsky, a pioneer in the field of building performance mockup testing. Sak passed away on Fathers Day, 2011. He was 85 years old.

A.A. "Sak" Sahknovsky, a pioneer of building envelope testing
A.A. “Sak” Sahknovsky, a pioneer of building envelope testing

The Construction Research Laboratory is an amazing, one-of-a-kind place located in a gritty, industrial area of Miami. Since 1975, companies like mine (Builders Architectural) have built and tested mockups of entire portions of buildings (usually windows and large walls of glass called curtainwalls”) at this world-renowned facility. Nowadays we call these assemblies PMUs – Project Specific Mockups.

Left: test chamber awaiting its next victim. Right: curtainwall <yoastmark class=

After testing is complete, the actual building will be built “for real” almost anywhere in the world, utilizing knowledge learned here. The process is called building and testing a “mockup” or “PMU”, and sometimes these mockups can be 40 feet wide and 60 feet tall!

World-famous proprietor A.A. Sakhnovsky – Sak to most everybody – though clearly no spring chicken, unstoppably shuttles between numerous mockups.

Sak tinkering in his spotless, state of the art laboratory
Sak tinkering in his spotless, state of the art laboratory

Sak directs his able crews in the construction, deconstruction and configuration of all manners of custom-made testing chambers, the large reinforced steel and concrete boxes upon which PMUs are built. In addition, he schedules a staggering array of testing procedures, as each project uniquely requires.

Structural steel is used again and again to make each custom-configured chamber
Structural steel is used again and again to make each custom-configured chamber

From the Palmetto Expressway just North of the 74th Avenue exit, you can see the lab off to the West. From the random outcroppings of structural steel, you immediately assumes the site to be unrepaired devastation from the most recent hurricane.

Looking closer, however, you notice that the steel has an odd appearance. Some pieces are old, some new. It is more of a patchwork quilt made of conglomerated hunks of steel, wood and concrete. The vintage steel has been used, reused, and used again. It has been cut, moved, welded, cut, drilled, sealed, cut apart, craned and bolted. It has seen searing Florida sun, torrential rainfalls, and uncountable PMU tests.
Now about the tests…

A typical test sequence for a prominent building in Chicago would list as follows:

  1. Air Infiltration Test
  2. Static Water Penetration Test
  3. Dynamic Water Penetration
  4. Uniform Load Deflection Test
  5. Retesting of Air and Water
  6. Structural Overload Test

A brief explanation of each will be worth your while. Remember that each mockup is sealed to a reinforced steel box – the chamber. This allows the lab to use big blowers to force air into or out of the chamber and apply powerful forces to the test specimen.

Air Infiltration

Air infiltration test
The first step in an air infiltration test is to mask off the “specimen” – that’s the assembly you intend to test – and measure the airflow through the chamber. This allows you to isolate the air infiltration attributable to the specimen.

In this test, lab personnel pump air from the chamber with a blower while measuring the amount of air being removed while maintaining test pressure, often 6.24 psf (pounds per square foot), the equivalent of a 50 mph wind. Using plastic film sequentially removed, the lab determines how much air is passing through each element of the mockup. Air tests can be harbingers of results to come, so we participants tend to hold our breaths awaiting the outcome.

This test procedure is ASTM E283 Standard Test Method for Determining Rate of Air Leakage Through Exterior Windows, Curtain Walls, and Doors Under Specified Pressure Differences Across the Specimen

 Static Water Penetration

Water penetration test
A spray rack is used to apply hurricane-volumes of water to the test specimen while blowers are used to create a negative pressure on the inside. If the specimen sucks in uncontrolled water, the test is a fail, and that sucks because the testing cannot proceed until the leak is diagnosed and fixed.

The lab removes air from the PMU chamber to achieve test pressure while dousing the mockup with hundreds of gallons of water delivered by large spray racks. Witnesses (such as myself) are inside the chamber with flashlights and scuba tanks (kidding) looking for leaks.

The test runs for 15 very long minutes. Drowning during this test is infrequent, however heat exhaustion is a distinct possibility because the chamber air conditioner often fights a losing battle against a baking Miami sun.

This procedure is ASTM E331 Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform Static Air Pressure Difference

Dynamic Water Penetration

dynamic water test
In the dynamic water test, an airplane engine is used to propel a barrage of water spray against the specimen. The violent buffeting action of the air blast has been known to shake the dentures out of witnesses inside the chamber

Same spray rack, also 15 minutes. This time the pressure comes from a very large airplane engine which roars to life with an explosion of smoke and oil, and rattles the bejeesus out of the specimen and the witnesses inside. When this mockup test takes place, about a third of the lab must run for cover and those of us inside the chamber have plenty of time to mentally review our estate planning.

This procedure is AAMA 501.1, Standard Test Method for Water Penetration of Windows, Curtain Walls and Doors Using Dynamic Pressure

Uniform Load Deflection

deflection test
These are just a few of the many gauges used to measure deflection of every part of the specimen while it is being subjected to wind loads far greater than anything the building will see in its future service life.

Lab personnel attach an impressive array of dial indicators on various parts of the specimen, then chamber pressure is cranked up. The indicators record the amount of deflection(bending) which occurs. Yes, glass does indeed bend, Virginia, but it also breaks. Therefore standing near the mockup during this test without a suit of armor is discouraged.

This procedure is ASTM E330 Standard Test Method for Structural Performance of Exterior Windows, Doors, Skylights and Curtain Walls by Uniform Static Air Pressure Difference

 Retesting Air and Water

According to Sak, 95% of test specimens fail their first water test. According to me, diagnosing and fixing the leaks can take many frustrating days.

You might imagine the foreboding we feel when re-entering the chamber for a water test after our windows have been bent like a banana during the deflection test. We might as well cancel any return flights for the immediate future.

 Structural Overload

This test is similar to the Uniform Load Deflection test, except that the pressures on the mockup are increased by an additional 50%. Any permanent bending or breakage would constitute a failure. Usually somewhere around this point in the sequence, participants have the suicide hotline on speed dial.

 Test Anxiety

Surviving the testing program is only one source of mockup test anxiety. Usually the manufacturer forgets to send something, and invariably it is the very first thing you need to install. Then you forget to bring an important tool and bravely tangle with insane, lawless Miami traffic (the original inspiration for “bump-em cars”) to procure a hot crescent wrench from a local kid in a very white tee shirt.

Then a storm blows through and drenches everything you were just about to caulk. Then you get a nasty sunburn on the top of your head which creates dandruff the size of corn flakes. Then you get the runs from an unfamiliar delicacy served from the “roach coach” which followed cramps from drinking a mug of colata (you learn later the locals drink the concentrated coffee delight in thimbles). Then a huge Palmetto bug, a mutant cockroach the size of a small poodle saunters confidently by, knowing full well it could whup you and your buddies. Then you look down and notice you are standing in a puddle of water crawling with questionable electrical cords while welding sparks fly at your head from out of nowhere, which you couldn’t hear because the noise is deafening.

An Awesome Experience

caliper used to measure material thickness
But with all the adversity, Sak’s place is truly loved by almost all who enter its creaking chain-link gates. It is a last rugged outpost of American individualism and in-the-trenches know-how. The vibe is one of fun, laughter, and comeradery forged in a nihilistic caulderon of absurdity.

When we arrive, we feel a great sense of freedom and excitement. When things get tough, we wonder if we will ever escape. But for most, myself included, a stint at Sak’s place will become one of the most cherished experiences of our professional careers.

Construction Research Lab Announcement

Construction Research Lab Announcement

Need a window test or curtainwall test?

Mark Meshulam at lab
Mark Meshulam, Chicago Window Expert testing, and being tested, at Sak’s Construction Research Laboratory.
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contact me, Mark Meshulam,
the Chicago Window Expert
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23 thoughts on “Test Your Mettle at Construction Research Lab”

  1. Dear Mark,
    So sorry to hear about your good friend, Sak. I imagine, with all his expertise, he’s probably “testing” our heavenly mansions for us, now.

    Thanks for the article. You have a delightful light-hearted way of conveying information, transforming what might be potentially dull and boring, and energizing it into something very interesting and amusing.
    Having grown up in Miami, I can relate to your ‘non-exaggerated’ descriptions. Thanks for the laughs and the info.

  2. Dear Mark:

    After Reading your article is obvious that you cherished Sak and reflected the personality of a good guy through his business.

    I just can say I am sorry because I know that when a good friend leaves, only stays an empty space in the heart that can´t be filled even with the arrival of another good friend. Receive my condolences and empathy


    Arq. Rafael Pérez Molina.

    Vetrotec de México, S.A. de C.V.

  3. This is a sad sad day in the fenestration industry. My heartfelt condolences. I am quite sad right now

    Jim De Koch


  4. Thanks
    I am sorry to hear
    I believe I had met him in 1982 at a curtain wall test down in Florida
    Demetrios Criezis
    Criezis Architects Inc

  5. I remember SAK from all of the curtainwall tests and window tests on the high rises I built in Chicago many years ago. He was a truly unique individual and a credit to our industry.

    Jeffrey D. Kaplan


    Phoenix Construction Consultants

  6. Very sad to hear – we worked with Sak going back to the 1970s. A true giant in this field.

    Choyce, Charles

  7. Mark:

    Great tribute and article, and wonderful account of what happens in the testing world.


    Sara Dyben

    Executive Assistant

    HTL, LLC Corporate Headquarters

    6655 Garden Road | Riviera Beach, FL 33404

  8. My sincere condolences to his family and yourself Mark. Not knowing AA, he certainly sounded like a heck of a human


  9. Sak is a cutie and your article is great…

  10. Hi Mr. Meshulam —

    I just wanted to thank you for running your article on my dad (Sak) and CRL. My brother Tim and I have many, many memories of growing up with dad & CRL. It is really heartwarming to see his impact shared. The comments from professionals and other items being posted at
    are very nice as well.

    I believe there will be a celebration of his life at some point in the summer, and will be happy to let you know; I am sure Pat and Richard at CRL will keep you posted as well


    Nick Sakhnovsky

  11. Mark, that is such a wonderful tribute to Sak.

    I forwarded it to Odelia (Sak’s wife) so she could see it as well.

    The picture you took which is the one on the web page
    is the one that Odelia is using for the obituary.

    They have a large picture that is the same hanging in their
    living room which I believe you gave them. She still talks
    about the collage you did on CRL.

    MM note: Patricia Caswick has been the core of the Construction Research Lab’s office for 30 years. She is a wonderful lady!

  12. Mark:

    We saw your e-mail about Sak; USGNN is posting a story on him today and I wondered if you could email me a comment about working with him that I could use. Also, would you be willing to email the image from your newsletter as we’d like to include in our article.

    Thank you so much!

    Best regards,
    Ellen Rogers

    Architects’ Guide to Glass & Metal:
    Follow us on Twitter:

    Decorative Glass (DG) magazine:
    Follow us on Twitter:

  13. Hi Ellen,
    Attached please find some images you can use.

    Here’s a quote:
    “A few years ago I tested five mockups at CRL in one year and had the honor of being around Sak quite a bit. If you didn’t know him, he could be intimidating because he is so focused, knowledgeable and to the point. But I soon found out that he would spend a half hour rummaging through his loft to help you find an odd-sized bolt. Once I showed him a proposed attachment of a window-washer tieback that we were going to build and test. I asked his opinion of the detail. He gave me that toothy grin of his and said, “It’s NFG, you know what that means?”


  14. Great article. What do you think will happen to the company with Sak gone?


  15. I was very saddened to hear the news that “Sak” Sahknovsky had passed away. “Sak” was a long, long, long time member of E06 and E06.51 and an early contributor to the development of several of our standards in .51. He will be missed.

  16. Hi Mark,

    Sorry about your friend, Sak.

    I will be out of the office for months to spend more time in asia and home but I would still love to hear from you when you post another article. Your articles are a good read. I’ve even passed them around to senior colleagues, not just the article but your contact info as well.

    Anyway, until your next expose J. Hope all is well on your end. Talk to you soon!

    Yours sincerely

    Abbie Legara

    Facade Designer

  17. Hello, Mark. Monday was indeed a sad day for our industry. Your article was a perfect testimony to honor our old friend and yes, it did make me smile. My first mockup at CRL was in 1979 and I will never forget lessons learned and Sak’s infinite wisdom. Thank you again.

    Neal Treu

    Wausau Window & Wall Systems

  18. Hi Mark,

    Like you I have some very fond and special memories of SAK and his many contributions to the industry. I met him over 40 years ago when he had his test set up at the old hanger. He was truly a pioneer in the testing of walls, glass systems, building envelopes, etc and will remain a legend in our field. You have done a nice job in paying tribute to him as well. Thanks.

    Best Regards,

    A. William Lingnell, P. E.

    Lingnell Consulting Services

    Engineering Consultant

  19. Mark,

    It was with a feeling of great loss that I read about your longtime friend and colleague “Sak” having left our terrestrial world. It was also through this wonderful article about him, his team and his surviving family that I have a far-greater understanding of your talents, and where you honed such skills. Thanks for sharing a small “window” into the life and accomplishments of someone who was not just a giant in his field of expertise, but perhaps the actual founder of an industry!

    It has been enlightening to work with you over the past several months on our current case, and I also look forward to both Kathleen and I continuing to work with you in the future, as it has been a wonderful learning experience to do so.

    Best Regards,

    Best Regards,


  20. I just discovered this webpage, the photographs and the story, and the tributes posted below. Kudos! Beautiful photo of Sak! Sak and his lab inspired me through the years. The curtain wall scene will not be the same without him. Chapter of history closed with his passing.
    Best Regards,
    Karol Kazmierczak

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