Ducts: The Unseen Backbone of Heating and Cooling Efficiency

efficient HVAC systems

April 25, 2017


Ductwork is a fundamental aspect of heating and cooling systems. These conduits are necessary in homes with any type of forced-air heating or central air conditioning.

Often unseen, ducts are easily forgotten about, so it is common to underestimate their importance. According to Energy Star, up to 30 percent of the heated or cooled air that moves through ducts could be lost to leaks, improperly sealed joints, or a lack of insulation.

These problems can lead to higher energy bills and even negate the savings that would otherwise result from upgrading to a more efficient furnace or central air conditioner. Different remedies can be applied to correct inefficient ductwork.

A homeowner could potentially see benefits from resealing, adding insulation, or replacing joints themselves. However, it is usually more beneficial (in terms of cost versus value) to hire a contractor to replace the entire duct system. These improvements may prove difficult if the ducts are hidden behind drywall or above ceilings. Yet, the chance to save 30 percent or more on heating and cooling costs means that this project will likely pay for itself over time.

Leaks Are Not The Only Problem

Leaks and seams are responsible for inefficient heating and cooling, but something called heat conduction also shoulders some of the blame. According to the Department of Energy, this phenomenon, in combination with air leaks and gaps, can reduce the efficiency of the heating and cooling system by as much as 40 percent.

Heat conduction means that the heat or the cool air created by the furnace or air conditioner passes through the metal walls of the duct. When this happens, the duct itself and the spaces directly surrounding it are heated or cooled. As a result, some conditioned air does not make it to the living spaces, where it is actually needed.

A Potential Do-It-Yourself Project

Some do-it-yourself improvements can increase the efficiency of the duct system. Homeowners can seal leaks and gaps with mastic sealant and metal tape, and they can also add insulation around the ducts. This can be an especially useful step in areas of the home that are usually cooler or warmer than the commonly used living areas (such as the attic or basement). These upgrades are possible in places where it is easy to access the ductwork: open attics and crawl spaces, basements that are not finished or that have easily removable false ceilings, and garages.

For a larger project, such as sealing hidden ductwork or undertaking a complete retrofit, it is best to hire a contractor. Luckily, most HVAC installers and maintenance professionals also have the equipment and expertise to install ducts.

Why Get Completely New Ductwork?

One reason to get new ductwork has to do with something called thermal regain, which actually takes advantage of heat conduction to decrease energy loss. When heat is conducted through the duct walls, it warms the surrounding space, which is typically an example of inefficiency. However, it can also prove beneficial – if the heat seeps into the living area, or if it warms the surrounding spaces so that it takes longer for the heat in the living area to escape.

Obviously, the best option to take advantage of thermal regain is to install the ducts directly in an insulated, climate-controlled space. This way, any heat or cool air that seeps through the ducts is still used to condition the air in the living space. Examples of this kind of placement include the space above false ceilings or in between interior walls. Since the conducted heat is making its way into the living space anyway, the thermal regain is 100 percent.

In attics, uninsulated basements, or crawl spaces, the thermal regain does not provide as much benefit. However, it may still increase efficiency because it will warm the area next to the living space. This will create a type of temperature barrier that will increase the amount of time it takes for the conditioned air inside the home to escape.

Duct Safety Issues

Ducts often have efficiency issues, but they can also affect the air quality and safety inside a home. While major life-threatening gases like carbon monoxide may be pulled into a living space from a gas-powered appliance like a furnace or water heater, it is far more common for particles and gases that are unhealthy, but not immediately fatal, to be drawn into the living spaces. Some examples of these potentially harmful substances include radon gas and trace amounts of exhaust from natural-gas-powered appliances.

The most common cause of this problem is when contaminants are drawn into the ducts by changes in pressure caused by the air-handling fan. Leaky ducts, especially leaky return ducts – which are meant to keep the air flowing through the living spaces evenly – can compound pressure problems. Improperly functioning ducts can also cause humidity to build up during the summertime and throughout the year in tropical climates. This dampness creates ideal conditions for mold growth.

These examples show that under-performing ductwork can lead to health and safety issues as well as lower the efficiency of a home’s heating and cooling systems.

Do you Need to Upgrade Your Ducts?

Homeowners can conduct a quick inspection of visible ductwork to check for leaks and gaps. They can look to see if ducts are placed in uninsulated areas of the home and even decide if additional insulation is necessary. However, more in-depth efficiency tests will require the services of a specialized contractor.

An HVAC specialist with a special calibrated fan and a pressure gauge will be able to test the whole duct network for leakage. More specialized equipment can also help locate the leaks to see if they are occurring inside (not as much of a problem) or outside (a bigger problem for efficiency). It is also important to measure air flow rates, which take the performance of the system’s fan(s) into account as well. Contractors perform this test with a device that measures air speed inside the ducts. Together, these tests can give a clear picture of the state of your ductwork.

Solutions to Underperforming Ducts

Replacing ducts is always an option, especially when you want to improve thermal regain percentages or replace a hopelessly leaking and outdated system. Another option is to add insulation to the exterior of accessible ducts.

Manufacturers produce special “wraps” that are specifically designed for ductwork. Patching leaks with sealant and metal tape may also prove helpful, as could having a contractor replace sections of ductwork (especially joints). Another option, as an independent project or in partnership with other improvements, is to create optimal airflow with additional exhaust fans placed strategically throughout the house. This will help ease problems related to uneven air pressure in the home.

Funding Your Duct Improvements

Duct replacement can lead to significant savings on energy bills. Because of this, projects may qualify for property assessed clean energy (PACE) financing.

PACE financing programs allow homeowners to pay for their project over time, as a line item on their annual property tax bill. Since poor ductwork can reduce efficiency by as much as 40 percent, a new system could bring about significant energy savings, quickly. This extra money, saved month-to-month, could then be used to pay for the project over time.


Interested in PACE financing to improve your property and enjoy the benefits of energy conservation? Contact Ygrene at (855) 901-3999; info@ygreneworks.com.