Things to know about Nashville blower door and duct leakage test

What do you need in order to test?

We have been getting a lot of calls from builders and mechanical contractors about the duct leakage test and blower door test requirements in Nashville. So I figured we would update our webpage to answer some of those questions.

The current requirements in Nashville are outlined in the 2009 IECC, which states the blower door test must be below 7 Air Changes per Hour (ACH) and the duct leakage test must be below 8% to the outside or 12% total at post construction, or final. This can also be written as 8cfm per 100 sq ft or 12 cfm per 100 sq ft. The duct leakage/duct blaster test can be performed at pre-drywall but the leakage allowance drops to 6%. You will also need your air handler set or the supply and return looped and connected by a collar. If your air handler is not set at testing during the pre-drywall stage then the energy Rater must add 2.5% leakage to account for the leakage the air handler will have. If you decide to perform the leakage test at pre-drywall you do have a better opportunity to repair any leaks before drywall covers up any duct systems. 

These requirements are not hard to meet and many contractors are not having to alter their installation procedures in order to pass.The average total duct leakage test in Nashville at this time is averaging around 10%, and the average blower door test is around 5.5 to 6 ACH. These numbers will decrease as the market gets accustom to testing.

TPI is also a consulting company for some of the largest builders in the nation and we do have partners testing below 3 ACH on the blower door test with standard fiberglass insulation. So if your building company is wanting to build tighter, more efficient homes we can advise you on how to accomplish this. We also have many HVAC contractors testing below 4% total leakage on their HVAC systems.

Please be aware that duct leakage test is performed and results are based on a PER SYSTEM basis. If you have hired a company other than TPI to test your systems and they are adding the systems together to get the results you are wasting your money, and putting your business at risk. We get calls constantly from homeowners about issues in their home, and many times we find their duct systems have "passed" testing without a test or the test was performed incorrectly. 

For all test

  • Your square footage per floor
  • Your building permit number
  • Your address

For Pre-drywall duct leakage test

  • Your system fully connected to the air handler
  • If no air handler will be set until final the supply and return need to be connected with a collar
  • After passing the test you will have to seal your supply boots to the drywall when the house is trimmed out.

For Final duct leakage test and blower door test

  • All attic hatches or pull downs installed
  • All exterior doors and windows installed
  • Drywall completed
  • All exterior door weather-stripping installed
  • HVAC supply boots sealed to the subfloor or drywall (Highly recommended)
  • HVAC supply grills installed (recommended)
  • HVAC return grills installed (recommended)
  • Power to the home is on

We highly recommend that the home is as close to move in ready as possible for your test results to be accurate. For us to be able to properly test we can not test with people constantly going in and out of the home. We will be pulling pressure on the home and monitoring meters through out the test, it makes our job impossible with some subcontractors such as cleaners and painters in the home.

We HIGHLY recommend all homes have some form of mechanical ventilation installed that satisfies ASHREA 62:2. TPI recommends a balanced system for this but we encourage ventilating the homes with any type of system instead of none. Whether builders are trying to or not, the homes of today are tighter in construction due to practices and materials compared to homes of the past, and for this reason ventilation is recommended.  Nashville is currently not requiring a ventilation system on homes but the code does state that if the home test below 5 ACH then ventilation is required. If you are building in Murfreesboro, they will require ventilation if the home test below 5 ACH.

If you or your company decides not to hire TPI to do your testing we highly recommend, that whom ever test your homes is a RESNET Rater. Rater's are required continued education, proctored exams, proctored QA test, and we must prove calibration of our equipment annually. TPI has been performing building diagnostics testing for the last 7 years and has proven that we perform quality inspections every time.

Please feel free to call 615-564-0074 or email if you have any questions about blower door or duct leakage testing in the Nashville, Murfreesboro, Brentwood, Mt. Juliet or surrounding areas.