Page 471 - Construction Waterproofing Handbook

ENVELOPE TESTING 12.11
Mock-up testing of the envelope involves three types of tests, including

● Air infiltration and exfiltration
● Static water pressure
● Dynamic water pressure

Additional envelope testing can include

● Thermal cycling
● Seismic movement

Air infiltration and exfiltration testing
The air infiltration and exfiltration test determines envelope areas that will allow air to pass
into or out of a structure. Although this test is typically for control of environmental con-
ditions, if air can pass through an envelope, water can also pass through.
Wind loading can force water into a structure, or unequal air pressures between exteri-
or and interior areas can actually suck water into a building. Therefore a building must be
completely weatherproof to be completely waterproof. A completely waterproof building
is therefore completely weatherproof.
Air infiltration or exfiltration tests are typically conducted according to ASTM-283.
This test is used for measuring and determining any airflow through exterior curtain
walls. This is a positive pressure test, meaning that positive pressures are applied to an
envelope face.
To conduct this test, a sealed chamber is constructed to enclose the back of a compos-
ite envelope portion being tested completely. Air pressures can be lowered in the chamber
by removing air and creating a vacuum in the chamber. Figure 12.10 shows a tare bag in
place for an air infiltration test in accordance with ASTM-283.
The lower air pressure then draws air through the envelope from higher-pressure exte-
rior areas. Air is drawn through any envelope deficiencies. This air penetration can be
determined by measuring pressure differentials within the chamber. However, if air pene-
tration is occurring, it is difficult to locate specific failure areas during testing.
This testing can be reversed by forcing additional air into the chamber to create higher
chamber air pressures. This type of test creates negative pressure on an envelope face. (The
explanation of negative and positive air pressure testing is similar to the explanation of
negative and positive waterproofing systems.)
With this testing, air that is forced into a chamber can be mixed with fabricated smoke
or colored dyes. This allows leakage areas to be easily identified when the colored air begins
escaping through envelope components to the exterior. Areas of leakage can then be marked
and later inspected for causes. Proper repairs can be completed and areas retested until
weathertight.
When testing masonry mock-up panels or curtain walls that contain masonry por-
tions with weeps, it is expected that a certain amount of air will penetrate the envelope
through these weeps. The amount of air infiltration that is within satisfactory limits
must be determined, and testing must be done to check that infiltration does not exceed
these limits.