Most houses built in the last 30 years have HVAC (heating, ventilation, and air conditioning) systems that include a central furnace and AC unit which suck air in from “returns” in your house, and blow it out through “supplies” in different rooms. When installed properly to code, these are healthy systems.  Unfortunately most are not built properly and create dirty air in your house… even with a filter installed!


Extra Cost: <$500 

There should be no extra cost to have your ducting installed correctly and to code.  Unfortunately, the many HVAC installers DO NOT install it properly.  They cut corners to save cost and lower their bid to you.  Hence, the extra cost you may pay is the cost to hire someone who doesn’t cut corners and installs correctly.

What: Make sure that all joints in your ducting are fully sealed with high quality, non-toxic ducting tape.

Why: Most ducting is not properly sealed at the joints, creating openings.  Because of the physics of air flow and pressure, dust, dirt, mold, specks of insulation, and other contaminants inside your wall cavities end up getting sucked into your ducting through improper seals, and then and blown into the air in your house.  Because the contaminants can enter the ducting AFTER your HVAC’s filter, they do not get filtered out, and hence having an air filter doesn’t help much.1

How: Hire an HVAC contractor who won’t cut corners.  Tell them you will inspect the duct work seals before the walls are closed up, and if they aren’t sealed properly, you will make them redo it.  Tell them you can settle any differences of opinion by doing a pressure test on the system and if it shows air leakage, they will have to redo the ducting.  They will certainly respond to that!

Extra Credit 1:

Once the ducting is installed properly, the next best thing to keep air quality good, is to get a HEPA+ activated carbon filter.  The HEPA filtration material will filter out dust and small contaminants, and the carbon will filter our gases and other chemicals in the air.  

Extra Credit 2:

Add a Fresh Air Intake into your HVAC system.  This is simply a duct that pulls fresh air from the outside into your return ducting, so it gets filtered and then blown into your house.  This is a very easy way of ensuring that you always have fresh air in your house.  The other thing it does is creates “positive pressure” in your house.  Positive pressure helps ensure that chemicals and other contaminants don’t leak through your walls into your house.


1. Combat Hidden HVAC Contaminants - Buildings.com

Properly sealing HVAC ducting
Pure Air HEPA and Carbon Filter