As a HERS rater I travel all over the San Francisco Bay Area
and test HVAC systems for code compliance.
What I so often see is systems that just barely scrape past
the code requirements or are over and need more work to get them to pass the
duct test. Recently I learned about a club of HVAC contractors who actually
pass the test so well that the test equipment can’t even read how much air is
leaking from their systems. That is because there is almost no air leaking from
their ducts, fittings and air handler units. How do they get these contractors
get their systems to be so air-tight?
To begin, there are only eight HVAC contractors in California who are building
HVAC duct systems so tight as to earn their way to the “4 Ring Club”. Ring 4 refers to the Energy Conservatory
duct leakage test system’s #4 ring which is the smallest. It is the one used on
the smallest and most leak-free systems. These installers build ducts that even
Ring 4 can’t register. These elite contractors can be found at http://ring4club.com/. They are all Home
Performance contractors, a title that discerns them from standard HVAC
contractors. They install high performance comfort systems. They are the hot
rodders of the HVAC world.
What do they do differently? One, they see the house as a
system and create larger work scopes than standard HVAC contractors. They start
at the shell of the building and do a home energy retrofit rather than
just “changing out the box” or replacing
an old furnace or air conditioner with a new, usually same sized unit. These
techs do it by the book. They do a manual J heat load calculation, manual D
duct design and a Manual T register design to dial in performance to every part
of their HVAC system.
When it comes to installations, what they do differently is to
actually commission their work. This means that after the work is done, and
even during installation, they test every performance aspect of their work.
Regarding ducts, they paint every piece of metal duct connections
and any part of metal to metal with a thick application of air duct mastic. Secondly,
they properly clamp the flex ducts onto the sheet metal. Here, properly means
that instead of hand tightening the zip-ties over the connection, they use a
tensioning tool such as http://www.homedepot.com/p/Malco-Manual-Cut-Off-Tensioning-Tool-with-Grips-TY4GTS/100161814. A recent Home Energy Magazine article notes
that the difference between hand tensioning and using a tensioning tool is
significant air loss. Lessen: use a tensioner for tight ducts.
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