If you’re specifying chamber testing (ASTM E1105) to evaluate the water resistance of your building envelope, you’re not alone. It’s a widely accepted standard. But here’s the uncomfortable truth:
Chamber testing alone isn’t enough to guarantee performance.
On a recent project, we were conducting two ASTM E1105 chamber tests. The foreman for the window installer, a guy who clearly knew his craft, was watching the process closely. To run the test, we brought our dynamic testing rig, complete with a 1,500-gallon water tank, as the building didn’t have a water source. The size and setup of the equipment made an impression.
As he looked down at the rig and watched us work, he made a spontaneous comment that cut straight to the core of the issue:
“I completely understand how chamber testing works, but I like the dynamic testing a lot better. With chamber testing, it’s too easy to believe you don’t have a problem because it’s simulated. Dynamic testing is wind and water. It’s natural. There’s much less to believe. It leaks or it doesn’t.”
That offhand comment said everything, and it came from someone who installs the systems we’re testing. So why aren’t we listening?
Let’s dig into why dynamic testing deserves more attention and why chamber testing shouldn’t be where the conversation ends.
What Is Chamber Testing?
Chamber testing, formally known as ASTM E1105, is a standardized method used to evaluate water penetration through installed fenestration systems (windows, curtainwalls, etc.). It works by applying water spray to the exterior of the system while simultaneously creating static negative air pressure inside a sealed chamber.
It’s designed to simulate wind-driven rain—and it works to a point. But real buildings don’t exist in controlled lab conditions.
The biggest limitation? Chamber testing is static.
- It doesn’t easily replicate wind gusts or rapid pressure changes.
- It doesn’t account for building movement or installation defects under dynamic loads.
- It can give a false sense of security when nothing leaks — until it does, during the first big storm.
What Is Dynamic Water Testing?
Dynamic water testing combines water spray with real airflow, either per AAMA 501.1 or custom protocols, replicating actual wind-driven rain.
At Building Envelope Professionals Group (BEPG), we use a custom-built rig we call “The Beast.” It includes a 1,500-gallon water tank and a high-powered fan (think: airboat propeller) that creates wind conditions equivalent to code-level design wind speeds.
This test doesn’t simulate anything — it creates real-world pressure and water exposure. And the results are binary: It leaks, or it doesn’t.
There’s no guessing. No lab assumptions. Just clear, observable performance.
Why the Foreman’s Comment Matters
The field foreman wasn’t reading from a spec book. He was speaking from experience. Chamber testing makes it easy to believe everything is fine, even when it isn’t.
His preference for dynamic testing wasn’t theoretical. He saw the difference, and more importantly, he trusted the results. That instinct is what the industry needs more of: confidence based on reality, not simulation.
Why Dynamic Testing Is Still Rare
Given the clear benefits, you might wonder why dynamic water testing isn’t more common.
Here’s why:
- Cost and logistics – It requires more equipment, space, and planning.
- Perceived sufficiency – Specs often stop at ASTM E1105. If it’s not required, it’s not done.
- Industry inertia – Many still rely on legacy approaches, even as failures mount post-occupancy.
But when a $100 million building fails because of unseen envelope defects, the cost of skipping dynamic testing looks trivial.
Why Dynamic Testing Deserves a Place in Your Project
Here’s what dynamic testing offers that chamber testing does not:
- Realistic simulation of wind-driven rain
- Early detection of leaks before occupancy
- Increased confidence in construction quality
- Reduced liability and post-construction claims
It’s a simple equation: More realism = fewer surprises.
What We Do at BEPG
At BEPG, we don’t test for show — we test for truth. That’s why we built The Beast: to deliver dynamic testing that exposes hidden problems before they become costly failures.
Whether we’re working in the upper Midwest or on the road in Texas, we bring full-performance testing to every project. Our tests are designed to challenge the envelope, not check a box.
Final Thought: From Simulation to Certainty
Chamber testing still has its place, but it’s not the whole picture. If you’re relying solely on ASTM E1105, you may be leaving performance to chance.
The foreman said it best: “There’s much less to believe.”
And when it comes to the building envelope, belief isn’t enough.
It leaks, or it doesn’t. We test to find out. Want to discuss dynamic testing for your next project? Let’s talk: Contact BEPG to learn more about how real-world performance testing can protect your building and your reputation.