Duct Testing in the San Francisco Bay Area

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.