Commercial Blower Door - Air Door
Fan - Residential Blower Doors
Codes adoption is against fundamental human nature. We don’t like rules and
All great cities suffered through losing a major part of their populations due
to Black Death, Typhus, and many more diseases before they agreed to sanitation.
The cost had to become unbearable to force change. All major cities burnt to the
ground: Rome, Paris, London, and San Francisco, before fire regulations were
developed and enforced. On the health and safety front, the concerns have been
addressed only after the cost of ignoring them became too high—look at how many
decades we believed smoking was harmless, and many still refute the regulations.
If we have pioneers among us, they can show us new ways of doing old things
better. Look at Apple’s success over the past ten years: from nothing to the
world’s richest corporation. Not by embracing change but jumping on top of
change and daring to be great, then doing everything it did better than everyone
By Colin Genge
IS IT BETTER TO TEST WITH A POSITIVE OR NEGATIVE PRESSURE?
A very common complaint about duct testing is that the covers get blown off the
registers. Most code language leaves the choice of pressurizing or depressurizing up to the
tester, but experience has shown that the positive pressure made sealing
registers much more difficult, and could triple the time to perform a test.
This has influenced most new codes, such as North Carolina, which makes a point
to state that a single point depressurization test is sufficient. It also means
that inexpensive Saran Wrap could be used to seal registers, making it much
easier to remove, and less likely to cause damage to paint or ceiling surfaces.
All states allow results under Depressurization, with the exceptions of
Washington, Delaware, Idaho, and California. If you’re testing there, we suggest
doing a depressurization test until you know it will pass, and then quickly turn
around your fan to pressurize. This way, if you get significantly different
readings you may be able to attribute it to blow register seals, for easier
If your state’s regulations have the option of duct leakage to outdoors, and you
go the pressurization route, an easy way to avoid blowing register covers off is
by pressurizing the house first then reducing the duct to house pressure to
zero. How do you avoid blowing register seals?
POWER FLOOD HOODS – SHOULD WE BITE THE BULLET?
In November 2011, the California Energy Commission conducted a public workshop
to present proposed revisions to the building code—namely eliminating the option
of non-powered flow hood devices.
The commission must have been on the receiving end of a lot of criticism from
HVAC contractors and energy raters as they have now released some information
about a delay in such a requirement.
According to Docket 12-BSTD-01 from March 9 2012, staff is considering
recommending that non-powered flow hood devices continue to be allowed in an
upcoming proposal, which states “an industry standard e.g ASTM or ASHRAE should
be developed to provide the basis for flow hood accuracy ratings to measure
residential system airflow pursuant to Appendix RA3.3.” (source)
It looks like PIER (California’s Public Interest Energy Research program) has
allocated funding for flow hood research to develop measurement standards for
reference in the next revision of the standards.
So what is a tester to do, should we bite the bullet and just move over to
powered flow hoods?
By Silvie Votrubova