SacBuildingPerformance

Based on field testing conducted statewide over a number of years, the California Energy Commission estimates the average duct leakage in California homes regardless of size and vintage to be 30%.  This means of course some homes have more efficient ductwork and some have leakier systems and all points in between.  This translates into an increase in heating and cooling costs of approximately 25% for the average home.  

Contributing Factors

One of the major contributors to this is poor system design and installation.  Equipment is oversized and the ductwork undersized.  Often homeowners complain of their energy bills being too high yet their homes are still colder or hotter than they’d like.  Or certain areas of the house are comfortable while other areas are not.  The HVAC contractor may just take the “bigger is always better” approach to system design and install an oversized piece of equipment.  This often leads to short cycling of the AC equipment and increased static pressure in the ducts which causes greater leakage, all the while not addressing the fundamental customer concerns of high energy bills and reduced comfort.  Replacing the heating and air conditioning equipment without testing and upgrading the ductwork is like pouring water into a leaky bucket.  Not a very efficient decision.  The current energy code in California requires duct sealing when equipment is replaced and the existing ducts are reused.  The maximum allowable leakage rate is 15% in this situation.  Many existing duct systems are under insulated and were originally sealed with duct tape.  Standard duct tape is great for miscellaneous home repair but terrible at sealing ducts.  A duct system pressure test should be an integral part of any comprehensive energy audit or upgrade project.

Duct Blaster®

The Duct Blaster® is a diagnostic device comprised of a calibrated fan/flex duct assembly that accurately measures air leakage in ductwork and air handling equipment such as furnaces.  All registers in the system with the exception of one return air grille are sealed off with masking.  The duct blaster fan is attached to the open return grille and pressurizes the ducts to 25 Pascals (a unit of pressure measurement).  Linked to a digital manometer (a device that measures pressureand airflow) an accurate assessment of a home’s duct system performance can be reached.  Along with a visual inspection of the ductwork and other diagnostic testing of the HVAC equipment, an informed recommendation for repair or replacement can be provided based on empirical evidence, not rules of thumb.  Upon completion of the work a post-remediation test is conducted to verify the performance of the system.

Call Sustainable Building Performance at 916-416-0676 or email info@sacsustainable.com  to schedule a free consultation to discuss solutions to improve your homes comfort and energy performance.

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