This post is contributed by Joe Truini, guest blogger at The Home Depot.

Part 3 of our DIY Home Energy Audit Series

Now that you’ve inspected your home for drafts and improved the insulation, it’s time to make sure your heating and cooling equipment is in good shape. Those units are the heart of your home’s energy efficiency and should be inspected for tell-tale signs of failure or potential wear and tear. Here’s how to do it.

  1. Check for rust on the ductwork of your heating and cooling units (inside the house and in the attic, wherever they may be). Shine a flashlight inside the ducts and if you notice any signs of rust, have the ducts cleaned.
  2. Examine the ducts for dirt and grime buildup to ensure the unit isn’t trying to strain or push out dirty air. If there are dirt streaks on the exterior of the duct work, that may be an indication of an air leak.
  3. Make sure the air filter return in the home is snug and fits. When replacing air filters, go for a pleated filter, which catches more dust and allergens and allows the unit to function properly.

Michael Chotiner, a former general contractor and contributor to numerous home improvement publications, stresses the importance of changing the air filter. “Most manufacturers of forced-air HVAC equipment recommend checking or changing air filters every 30 days,” he says. “In my experience, almost nobody does it that often, despite the fact that it’s the most effective practice a do-it-yourselfer can follow to maintain the efficiency of their heating and cooling systems.”

If your unit is more than 15 years old, it should probably be replaced, regardless of the condition. Always have a professional install new HVAC equipment. And don’t attempt to replace any HVAC units on your own.

How to repair ventilation issues in the ductwork

Difficulty level: Moderate

Heating and cooling units

It’s crucial to ensure the ducts are functioning properly so that your heating and cooling units aren’t working overtime. Fran Donegan, a home improvement expert and author of Pools and Spas and Paint Your Home, recommends 2 tips to keep your system in top shape.

1. Pro tip: Seal leaks! Inspect the ductwork (where air is being pushed out) in forced-air systems. Ducts that run through an unconditioned space, like a basement or attic, should be insulated.

Remember that leaks in ductwork equal wasted energy. Dirt streaks where duct sections join together indicate a leak. Seal leaks with professional-grade duct tape or mastic duct sealant.

2. Pro tip: Evaluate your HVAC equipment. First, try to determine the efficiency of your heating and cooling units. If the equipment is maintained on a regular basis, you may already have the AFUE (the annual fuel utilization efficiency for heating equipment) and the SEER (the seasonal energy-efficiency ratio for cooling equipment). If not, have an HVAC contractor maintain the system and run efficiency tests. In general, older systems — those over 10 to 15 years old — aren’t as efficient as the newer products on the market.

You should also see whether openings for items such as pipes, ductwork, and chimneys are sealed. If they aren’t, close any gaps with an expanding foam caulk or some other permanent sealant. And when sealing gaps around chimneys or other heat-producing devices, be sure to use a noncombustible sealant.

Check out the rest of our home ownership series, where we go over leaks and draftsinsulation, lighting, and electric appliances.


Joe Truini writes extensively about DIY home remodeling and repair, including performing energy audits to evaluate efficiency. He has worked as a remodeling contractor, cabinetmaker, and union carpenter. Joe is the author of 8 home improvement books, including Building Sheds and Stanley Homeowner’s Guide to Tiling, both published in 2016. He also writes for The Home Depot on home improvement topics like installing storm windows.

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