SPRAYFOAM Professional - Spring 2016 - (Page 57)
AIR LEAKAGE PATHS IN A
TYPICAL WOOD FRAMED
BY LAVERNE DALGLEISH, PRINCIPAL,
he Air Barrier Association of
America (ABAA) worked with Oak
Ridge National Laboratories (ORNL) to
conduct assembly testing on a wood
framed wall to determine what part of
a wall would leak the most. The testing
was conducted at Tremco's facility in
Cleveland Ohio, where they have a fully
automated ASTM E2357 test apparatus.
The funding to ORNL was supplied by
DOE's Building America Program.
This research was an extension to the
ABAA Research Project on Air Barriers,
which was to determine whether there
were energy savings when making a
building very air tight.
The baseline specimen was a more
detailed ASTM E2357 test specimen,
where the wall was purposely made
very leaky. The specimen was framed in
a wooden buck for ease of mounting into
the test apparatus. A foundation was
simulated with CMU and a wood mud sill
was installed with spacers between the
mud sill and the CMU to represent normal site conditions. Simulated floor joists
with a header were then installed and
then a strip of sub floor was installed.
The sub-floor was shimmed to replicate
the drying and movement of wood framing members on the construction site.
A wall was then framed using 2 x 4s
with a single bottom plate and a double
top plate. The wall was sheeted with
OSB. A 1/8 inch gap was maintained
between the sheets of OSB which is a
standard practice on job sites to allow
for the expansion and contraction of
the material due to temperature and
Details on the construction of this
wall specimen were documented so that
the base specimen could be replicated
for additional testing with various types
of air barrier materials being installed.
To identify how much air would leak
through a specific air leakage path, it
was decided to test the complete wall
specimen to start with and then to seal
one crack at a time and test after each
air leakage path was sealed.
The baseline wall was inserted into
the test apparatus and the wall proved
to be so leaky, that it was impossible
to create a 25 Pa pressure difference
across the specimen. This proved the
goal of making the baseline specimen
very leaky was achieved. Now we talk
about a certain air leakage rate at 75
Pa but this is the reported leakage rate.
In ASTM E 2357 we actually test up to
600 Pa, then 800 Pa and finally 1200
Pa. You will find that all the testing is
conducted at multiple pressure differences and normally much higher than
the reported test pressure.
The next issue that the crew faced
was to find a sealant that would set up
in a short period of time so that the testing could be done almost continuously.
Normal sealants and caulks require a
curing time which would drag out the
testing process. Finally an answer was
found, which was to use a glue gun.
This material set up as soon as it was
cooled and provided a structural seal
that withstood the loads imposed upon
them by the test procedure which created a pressure difference across the
wall assembly. To give you an idea of
the loads placed on the wall assembly,
The other interesting observation
was that 92% of the air leakage at
the wall/roof intersection was at the joint
between the OSB and the top plate."
| SPRAYFOAM PROFESSIONAL 57
Table of Contents for the Digital Edition of SPRAYFOAM Professional - Spring 2016
EXECUTIVE DIRECTOR’S CORNER
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SPF RESEARCH ON AIR QUALITY – PART 2
NEW CONSTRUCTION NEEDS OPEN DOORS FOR SPF INDUSTRY
TOP TRUCKS FOR SPF CONTRACTORS
BEHIND THE FOAM
2015 SPFA CONTRACTOR AWARDS
ASK THE EXPERT – How to Write Clear Contracts
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SPRAYFOAM Professional - Spring 2016