EES Energy Saving Tips #2

In our previous Energy Saving Tips we discussed air sealing those pesky thermal bypasses – cracks and holes about the home that occur over time from settling or were never sealed up in initial construction from plumbing, ductwork, pipes, etc. allowing air to come and go easily, thus requiring your heating and cooling systems to work harder to bring you your desired comfort level on your thermostat - costing you more money!

We’re going to keep on that same theme, but take a look particularly at the ductwork of your heating, ventilation and air conditioning (HVAC).  Your ductwork is an integral part of your building systems that brings a supply of conditioned air, either heated or cooled, into your home and returns the air that the conditioned air is replacing outside.

Your ductwork starts from your heating and cooling system’s air handler – the big metal rectangular piece of equipment usually in a basement, crawlspace or attic.  Sometimes it can be located in a utility closet on a living floor.  When the air handlers are installed in an attic or crawlspace, the ductwork has to travel far distances in unconditioned spaces until they reach the inside of the home it is trying to bring a supply of air to. 

During the summer in our area, attics are very hot and crawlspaces have higher than usual moisture levels.  While in the winter, both attics and crawlspaces are very cold.  That means your heating and cooling system is producing cool air in the summer, which has to travel through either hot air in the attic, or moist air in the crawlspace; and it produces warm air in the winter, which has to travel through cold air both in the attic or crawlspace.
This means we need to make sure our ductwork is sealed air tight so we don’t lose the warm air in the winter or gain the hot air in the summer through infiltration.  We also want to make sure we insulate the ductwork so we can reduce the impact of heat transfer. All this causes your heating and cooling system to have to work harder to achieve the desired temperature setting in your home!

Common findings in a residential energy audit on a home that has its ductwork in the attic or crawlspace are that there is high potential for ductwork to not be fully sealed, particularly at the joists and the ever dreadful, “panned return” where the HVAC contractor used the wood floor joists and floor board for three sides of the ductwork, this is extremely inefficient as conditioned air leaks through a multitude of areas.  And duct tape is not the solution!  It expands and contracts and falls off quickly!

So, what we recommend is air sealing the ductwork around the joists, panned returns and other nuances that you see allowing infiltration of your ductwork system.   Duct Mastic is a wonderful product that is water soluble and you can apply the putty like material with a paint brush – USE GLOVES! – it can be messy.   You can find a half gallon of duct mastic at your local building supply store for around $10 and it will go a long way.  Identify the areas that need to be addressed and apply!  Wait for it to set for about a day and then you can move onto installing duct insulation!

There are many forms of duct insulation out there to accommodate the many different shapes ductwork can be.  The main thing we want to focus on is achieving a good R-Value.  The R-Value is the “Resistance” of heat transfer the insulation provides.  For ductwork, we would like to achieve at least an R-Value of R-7.  It’s easy to ask your local building supply where you can locate in their store and they can suggest what are the best options for your particular duck system!


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