All forced air heating and cooling systems have return ducts, that is, the ducts that return "stale" air back to the HVAC system so that it can be filtered and then re-heated or re-cooled. What many homeowners don't realize is that nearly all return ducts leak, often substantially so. The leaks are caused from the seams that are naturally in the sheet metal, but also from "panned" returns whereby floor joists, vertical wall bays, and other "interstitial" areas of the home are used to transport air back to the system. Panned returns in particular tend to be extremely leaky due to their often being riddled with wiring and plumbing penetrations.
Taken together, these leaks cause air to be sucked into the HVAC (heating, ventilation, and cooling) system from areas where it should NEVER be drawing from. These areas consist of unused basements, garages, crawl spaces, attics, etc. For starters these are typically the dirtiest places in the home where chemicals are stored, cars are parked, high levels of dust and other pollutants are present, or even mold is present, and you simply DO NOT want to be pulling air into your home's ventilation system from them! As you'll see in this video, it is also possible to cause combustion appliances like hot water heaters to backdraft, which can literally cause the people living in the home to be poisoned as a result of leaks in their cold air returns.
Another factor with leaky cold air return ducts is that they will often cause air to be drawn in from outside the home's air barrier ---- meaning outside. This can significantly impact your home's energy efficiency if you are pulling in humid 95 degree outside in the summer and then using electricity to cool it back down to 50 degrees. And then in the winter if your leaky return ducts are sucking in 20 degree air from the outside and you are then burning gas or using electricity again to heat it back up.
Yet another factor where leaky return ducts cause a problem for homeowners is comfort. Many homes are two, three, or four stories in height. On hot summer days the upper floors tend to get much warmer than the lower floors do, so you NEED the return ducts in those upper floors to be pulling as much of that hot air back down to the air conditioner to be re-cooled as is possible.
The last area where leaky return ducts can negatively impact customers is with airborne dust in the home. The more leaks that exist in your return ducts, the more that the return grilles throughout the home are getting bypassed while the HVAC system is operating. That means the less stale, dusty air that is getting returned to the system to be re-filtered! So leaky return ducts can lead to higher levels of dust and airborne pollutants in your home because the air inside the home is not getting filtered to the degree that it could or should be.
What's the solution? The solution is use silicone, metallic HVAC tape, or duct mastic to methodically find and then seal every seam on your return duct system that you can locate. In many cases homeowners will find absolutely massive leaks in the form of wide open holes or missing sections of sheet metal (at Insulwise we find things like this in homes ALL the time...and it is often shocking). The leaks that are most important to seal are the ones that are nearest to combustion appliances like hot water heaters. The next most important leaks to seal are the ones that are outside the home's air barrier, such as the garage, crawl spaces, and attic areas, but the more of the leaks that you can find and seal, the more efficiently your HVAC system will operate (saving you money!) and the cleaner the air in your home will be!
17 июл 2024
