Is changing the pressure in the whole room with a blower door sufficient when performing the ASTM E1105 or the AAMA 502.08 or 511.08 spray test?
No. You must have a specific pressure difference at the surface of the test specimen.
ASTM E1105-00, paragraph 6.2.1 Test Chamber—
A test chamber or box made of plywood, plastic, or other suitable material and sealed against the test specimen. Test chambers mounted on the interior must be made so that interior surfaces and joints of the specimen can be easily observed for water penetration during the test…

Scott Wood Says: 
October 7th, 2008 at 3:35 pm   editIn your comment on using a blower door to depressurize a room you state it cannot. You go on to suggest a specific pressure difference at the surface of the test specimen is required. “Is changing the pressure in the whole room with a blower door sufficient when performing the ASTM E1105 or the AAMA 502.08 or 511.08 spray test?
No. You must have a specific pressure difference at the surface of the test specimen.”
I’m still trying to understand the physics. Would not measuring the pressure difference at the surface of the window, both exterior and interior, and adjusting it to the specified pressure difference provide proper surface test pressure? A pressure difference between the room (test chamber or box) would be the same unless makeup air was providing a pressure variation on the surface. However, since you can monitor the pressure difference at the window surface verse the exterior, a uniform pressure over the window surface would be provided using either the room or a test chamber. Please help me understand the requirements for the test chamber verse room pressure difference. Thanks

Todd Mikkelson, RM Group

todd@sprayrack.com

I understand that you’re thinking the room itself could be a huge air chamber. It’s not so much that that is a wrong assessment, because theoretically it’s not wrong. But by performing a test in this manner you’re modifying the standard. Whenever you modify the standard you’re making yourself vulnerable to an invalid test ruling during litigation.

The ASTM E1105 specifies in paragraph 6.2.1:
Test Chamber–A test chamber or box made of plywood, plastic, or other suitable material and sealed against the test specimen…
…At least one static air pressure tap shall be provided to measure the chamber air pressure versus the ambient air pressure and shall be so located that the reading is unaffected by exterior impinging wind , or by the velocity of air supply to or from the chamber.
6.2.2 Air System–A controllable blower, compressed air supply exhaust system, or reversible blower designed to supply the required maximum air pressure difference across the specimen. The system must provide essentially constant air flow at a fixed pressure for the required test period.
6.2.3 Pressure measuring apparatus–A device to measure the test pressure difference within a tolerance of plus or minus 2% or 2.5Pa (0.01 in. of water column), whichever is greater.

Then there’s a diagram of a chamber built within a room and around the inside of the test specimen with an air system with a control valve and a pressure measuring device.

I used to be hired by a window company to video spray tests and record the application by the test engineers among other things. The slightest deviation from the test standard on my video was the first thing looked at by their lawyers. They would go to court and motion that the test application was not performed according to the ASTM or AAMA standard, therefore the test was invalid, and that was about it. They were off the hook of having to take any responsibility to replace windows. Of course it was usually not the window that turned out being the problem, but any one of the possibly responsible parties could contend the performance of the test procedures.

It would be pretty easy for a lawyer or an expert witness or consultant to have the court look at these paragraphs and the diagram from the E1105 I’ve quoted here and then point out that none of these things were done in this fashion and it would be ruled an invalid test.

I realize there are people who do the test with a blower door because it saves them from doing the task of building an air chamber. But the test also says that you must remove the trim and whatever else surrounds the window so that you can see all parts of the window frame that’s inside the wall in order to observe water penetration. That’s actually the hardest part of building the chamber anyway.

The method of measuring the air pressure at the window surface is also an issue here. The only way of doing this that I can think of in a case where a blower door is being used would be to hold a barometer close to the window. That’s not going to give you the plus or minus 2% accuracy also required by the standard and it’s barometric pressure instead of static air pressure.

So basically the point is that whenever you’re modifying the procedure, you’re not performing the test according to the standard. This is why the standard is so specific. There’s got to be some set of rules in order to have performance tests on the materials being used in the architecture.

Thank you.

Scott Wood Says: 
December 22nd, 2008 at 3:35 pm   edit

Todd,

Thanks so much for confirming my suspicions. Yes, a standard is not one unless it is followed the way it is written. Hope you have a happy holiday. Thanks again for the information.