Q: My HVAC system is a mystery to me. What can I do to maintain it and keep my home comfortable year-round?
A: For most people, the inner workings of the HVAC system are out of sight, out of mind. The system is ignored until something goes wrong.
Understanding the basics of how a heating and cooling system works will help you create a more efficient, comfortable living space. To get started, let’s go over how it works.
If you have a forced-air system, you have ducts. A forced-air system consists of the equipment that heats or cools the air and the ductwork that moves it around the home. Your furnace, or air handler, has a fan inside that pushes the heated or cooled air through the supply ducts into the rooms. The return ducts bring air back to the furnace to be heated or cooled again and sent back through the home.
This continuous loop of supply and return is susceptible to inefficient practices and leakage.
Here are some steps you can take to keep your system running efficiently and maintain a comfortable living space.
Check your vent dampers.
Make sure the air you paid to heat or cool is freely moving through the home.
I wish vents were made without dampers because the feature creates the misconception they should be closed. Closing registers does not save energy. It can cause your system to work harder, shortening its lifespan and increasing duct leakage.
If you don’t do anything else after you read this, do check that your supply register dampers are open and not blocked by furniture or rugs throughout your home. This is easy to do and costs nothing.
Seal your ducts.
If your ductwork travels through an attic, crawl space, or other unconditioned (not heated or cooled) space, it could have holes, cracks, or gaps that cause duct leakage. This wastes energy and money by heating or cooling spaces you don’t use.
The U.S. Department of Energy estimates 20% to 30% of the air moved through duct systems is lost due to duct leakage. You could have the most efficient heating or cooling unit available, but if your ducts leak, you are wasting energy.
In addition to wasted energy, leaky ducts can cause air-quality issues. Leaks in the return ducts can pull air into the ducts from surrounding spaces, through the furnace and then deliver it into the home. This can introduce dust, dirt, insulation particles, and other gross stuff that is in your attic, crawl space, or walls.
Left: A forced air system consists of the equipment that heats or cools the air and the ductwork that moves it around the home. Your furnace fan pushes the heated or cooled air through the supply ducts into the rooms. The return ducts bring air back to the furnace to be heated or cooled again and sent back through the home. Graphic courtesy of Duy Mai, Pioneer Utility Resources
Right: Holes, cracks, or gaps in your ductwork cause leakage. This wastes energy and money by heating or cooling spaces you don’t use. You can hire a professional to test your ducts for leakage with specialized equipment and seal your ducts. Graphic courtesy of Duy Mai, Pioneer Utility Resources
Sealing ducts can be difficult because they are hidden behind the walls, floor, and/or ceiling. Attics and crawl spaces can be hard places to work. You can hire a professional to test your duct system for leakage with specialized equipment and seal your ducts.
If you seal ducts yourself, do not use duct tape. I know it is hard to believe, but duct tape dries out quickly and loses its adhesion. Seal with metal tape or duct mastic specifically designed for the job.
One relatively easy place to seal is where the duct meets the floor, wall, or ceiling. Remove the registers and look for cracks or gaps around the edges. Remember to wear gloves to protect your hands.
Change your filter.
The filter is on the return side of the duct system. It could be in the return registers or in the furnace. Checking your system’s filter regularly and replacing it when dirty can help you improve your heating and cooling efficiency.
When it comes to filters, my philosophy is buy cheap and replace often. I don’t know about you, but I have a much more difficult time throwing away a $20 filter than a $5 filter. Save by buying filters in bulk or set up auto-ship for every three months.
In most cases, filters are designed to protect the furnace, not improve air quality. If you are worried about your home’s air quality, getting the ducts cleaned and sealed can help. Add an air purifier if you need additional air filtration. Look for Energy Star-rated models.
Now that you know the inner workings of your HVAC system and what it needs to run efficiently, you can improve and maintain the comfort in your home year-round.
Miranda Boutelle writes on energy efficiency topics for the National Rural Electric Cooperative Association, the national trade association representing more than 900 local electric cooperatives.