Having a tight building envelope can dramatically reduce the energy used by a building’s HVAC system.

Using a high efficiency HVAC unit can reduce energy use, but it is entirely dependent on how tight or leak-free the conditioned space is. Imagine using an ice chest cooler with many holes in it to keep your picnic food cold… it wouldn’t stay at the desired temperature long enough without the continual addition of ice because the conditioned air would be leaving through the holes and, undesired, non-conditioned air would be infiltrating the cooler. A building’s envelope works in much the same way: leaks expel conditioned air from the building, and unwanted air from the outside enters the conditioned space. This causes the HVAC system to work harder because the actual capacity needed to properly meet a desired setpoint is much higher than what it should be if the building was properly sealed.


Another factor for air tightness in buildings is the ductwork that moves conditioned air to a desired space. Leaky ducts cannot maintain adequate grille pressures and designed flow rates without increasing leakage and fan flow dramatically, thereby wasting energy. Leaks increase heating and cooling loads by improperly distributing conditioned air and by increasing infiltration through the building envelope.


WCEC acknowledges the importance of air tightness in buildings and its impact on energy efficiency. To that end, WCEC works to answer these questions:

  • What is the actual energy-use impact of building leaks?
  • Can we create a non-invasive building retrofit that will seal building shells? What impact would this technology have in building codes and standards?



WCEC Literature



External Resources