MAC’d Houses Are Green Houses

If you hear about a house getting MAC’d, it usually means that some high-quality “Green” improvements have been done to a house near the MSP airport.  The purpose is to minimize noise issues with houses, and that’s great, but I think some of the best benefits of the MAC program have to do with energy savings.


The Metropolitan Airport Council (MAC) implemented a Residential Sound Insulation Program in 1992, and since has gone through thousands of homes near the airport making improvements in sound insulation. This partial list of home improvements comes from the MacNoise web site:


  • Reconditioning or replacing existing doors and windows
    • Adding acoustical exterior storm windows and storm doors
    • Replacing weatherstripping
  • Adding wall and attic insulation
  • Adding baffles to mail slots and chimneys.
  • Adding central air conditioning if not existing


Every ‘MAC’ home I’ve inspected has had professional work performed – these aren’t just quick handyman home improvements.  They’re high quality improvements that make houses much more comfortable and save money in energy costs.  The average cost of the improvements done to homes has averaged a low of $17,300 in 1995, and a high of $45,000 in 2001.  In 2003, homeowners were asked asked if they were satisfied with the quality of the improvements, and 100% answered yes.


Window and door improvements are pretty easy to understand – a better insulated window means less noise, as well as less heat loss.  Insulation in the attic is also pretty obvious, but the one thing I’d like to point out is that MAC does an excellent job of adding insulation.  They seal up attic bypasses, they add ventilation when needed, and they get the vapor barriers right.  Seeing all this insulation done properly on an old one-and-a-half story home just gives me the warm-fuzzies J.


Central air often gets added if it isn’t already present, and while this alone doesn’t do much for energy efficiency, it often means that other stuff has to be done in order to get central air – like replacing gravity furnaces!  If you’ve read my blog on gravity furnaces, you know how inefficient they are.  In order to add central air, old gravity furnaces need to be replaced with forced air furnaces, and this is a HUGE improvement in energy.  Adding central air also requires room in the electric panel for a major appliance, and most of the older fused panels don’t have room for this.  This means an upgrade of the electric service too.

Chimney Fan

Because MAC houses end up getting much 'tighter', they also take air changes in to account, and additional steps are taken to ensure all of the fuel burning appliances in homes will still operate properly in tighter conditions.  Sometimes this means the installation of a direct vent furnace, a powervent water heater, or even a forced draft fan at the top of the chimney, as shown at right.  A combustion air duct is always installed.  MAC houses also usually get some sort of whole-house fan installed to make sure the air in the house gets changed out several times per hour – sometimes it's an HRV, other times it's a fan installed in a central location that constantly exhausts at a very low speed.  

If you’re shopping for a home near the MSP airport, don’t be afraid of houses that have been MAC’d – it’s a good program.  To learn more about the program, including future improvements, visit  

Reuben Saltzman, Structure Tech Home Inspections - Email - Richfield Home Inspector

Written By

Reuben is a second-generation home inspector with a passion for his work. He grew up remodeling homes and learning about carpentry since he was old enough to hold a hammer. Reuben grew up thinking he was going to be a school teacher because he enjoyed teaching others so much. In a sense, that’s a lot of what home inspections are about, so Reuben truly does what he loves. Sharlene has worked with Structure Tech since 2000 and Reuben has been contributing to her blog since 2008.

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