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All conditioned airflow in your Chicago area home is channeled through the duct system. So, the potential impact of ductwork on your pocketbook and comfort is quite tangible and constant. If your energy bills are getting out of hand and you just can’t seem to find a comfortable thermostat setting, duct sealing can provide instant relief.

Duct System Basics

The air ducts in a typical home are square or round tubes fabricated from sheet metal. The basic components of a ductwork system consist of duct runs, boots, grilles, outlets, diffusers and various connecting and sealing tools. Following is the structure and setup of a typical duct system:

  • Plenum – The plenum connects the duct trunk to the heating and cooling system on the air return and air supply sides.
  • Supply side – Duct trunk, runouts and branches channel airflow from the heating and cooling system to the air supply outlets.
  • Return side – Airflow is received from the living spaces through the return grilles. Airflow is then channeled to the heating and cooling system through return ducts, which should be equal to supply ducts for handling air volume.
  • Sealing components – Connections at duct seams, joints, grilles and outlets are sealed with metal tape, mastic sealant and/or an aerosol-based sealant.

Duct Sealing: Good for Your Pocketbook and more

Ductwork is to the HVAC system what pipes are to the plumbing system. Ductwork and piping systems channel vital elements to household appliances and occupants, and both need to be clean, tight and corrosion free to deliver healthful air and water, respectively, for use and consumption.

Efficient transportation of air depends on good sealing tools, design and techniques. When there’s a water leak in the home, there may be obvious signs, such as water damage or mold and mildew appearing through walls. But a leak in your air ducts is much harder to detect because air is an invisible gas. Duct systems are typically located out of sight in attics, basements and wall cavities. Good home efficiency and low energy bills can only be achieved with good ductwork. The same goes for indoor air quality and home comfort.

  • Home efficiency – Good duct sealing and design deliver balanced air pressure, airflow and temperatures through the entire home. Uneven temperatures typically mean unbalanced air pressure and airflow. This promotes air leakage through the home shell, which basically translates into a leak in your pocketbook since it results in higher energy bills.
  • HVAC efficiency – The typical ductwork system loses about 20 percent of airflow before the conditioned air reaches the living spaces, according to Energy.gov. That’s a substantial hike in energy bills, and extra work for your gas furnace and A/C. More work means more wear and tear, and a shortened service life.
  • Air quality – Leaky ducts not only result in higher energy bills, but also lead to contaminated air circulating through your home. Contaminants could include VOCs (volatile organic compounds) released from building materials, insulation fibers, pesticides, garage fumes, dirt and dust.
  • Comfort – It is next to impossible to enjoy maximum comfort in every room with a leaky duct system, because the air pressure decreases past the leak. That means less warm or cool air will be delivered.
  • Safety – A duct leak problem near a combustion appliance could result in back-drafting, with dangerous carbon monoxide entering the air ducts and circulating through your home.

How to Detect a Leak in Your Air Ducts

Your ductwork system has no gears, bearings or any moving parts, but that does not mean it won’t make any noise when there is a problem. Other symptoms of air duct issues are temperature and air pressure variances in certain rooms. Following are telltale signs of leaky ducts:

  • Rattling – Loose connections at duct seams, joints, grilles and outlets make noise. All these metal materials and components will rattle and clamor until they are sealed up tight.
  • Hot and cold spots – Not all duct leaks make noise. Holes, dented ducts and fallen ducts result in hot and cold spots in affected rooms Needless to say, this causes energy waste and higher electric bills.
  • Unbalanced air pressure – Uneven air pressure from the supply outlets signals substantial duct leakage and/or poor duct sizing.

Duct Evaluation

Over the years, air ducts endure a substantial amount of static pressure. Any and all flaws in duct sealing and design will eventually be revealed, as mediocre and poor sealing methods result in leaks. A thorough duct evaluation can reduce energy waste, eliminate discomforts and resolve other issues that are caused by leaky ducts.

  • Professional evaluation – Your HVAC professional has the experience and training to correctly evaluate ductwork for leaks, damage, and obstructions. He will inspect the entire ductwork system with special equipment, such as an infiltrometer, ito locate leaks.
  • Evaluation by Homeowner – If you are handy around the home you may decide to inspect the air ducts yourself. You must take extra precautions when venturing into the attic, crawl space and unfinished basements. Wear long sleeves and pants, a hard hat, goggles, gloves and a respirator. The tools you will need include a flashlight, smoke pencil (or incense stick), grease pencil to mark the leaks, and patience.

Turn on the furnace, A/C or ventilation system so that airflow is circulating through the ductwork. Hold the smoke pencil to each duct joint and connection. If the smoke wavers, you have identified an air leak. Mark it with the grease pencil, and that’s it.

If any portions of ductwork is insulated, look for dirt streaks on the insulation to help pinpoint air leaks. If you come across any damaged, wet or moldy insulation, it will need to be discarded and replaced. Air ducts are often located in inaccessible areas, such as inside wall cavities, requiring the expertise and equipment of your HVAC pro.

Duct Sealing

Once the duct evaluation is complete, you are ready for duct sealing. Whether your HVAC professional performs duct sealing or you do it, the tools are basically the same. You will need the same safety gear for your protection, and a combination of metal tape, mastic sealant, aerosol-based sealant, fiberglass mesh and compression collars. Following are the basic steps of duct sealing:

  • All duct connections and joints eventually will be wrapped with metal tape (no cloth-backed “duct” tape). So, the real challenge to duct sealing (and your patience) is sealing larger holes, gaps and seams with mastic, aerosol and/or fiberglass mesh.
  • Mastic is a gooey paste that is malleable upon drying. Duct connections and joints endure substantial stress, so mastic is an excellent sealant.
  • Mastic may be applied by hand or wooden stir sticks (wear latex gloves with either method). Allow the mastic to dry overnight before wrapping the repair with metal tape.
  • For larger holes and gaps, coat the area with mastic first. Apply fiberglass mesh to the hole or gap, and cover with mastic.
  • Aerosol-based sealant may be sprayed on top of metal duct tape. It offers an easier application than mastic, but it does not offer the flexibility mastic delivers.
  • If you have portions of disjointed flex ducts, use a compression collar and metal tape to secure the joint.

Ducts and Home Efficiency

If you are upgrading your HVAC systems, have an HVAC professional evaluate the ductwork system for compatibility. Your furnace and A/C equipment will perform as efficiently as the air ducts that channel the heated and cooled airflow to the home.

Moreover, your HVAC pro can evaluate airflow through the living spaces. The goal of good duct design and home efficiency is to promote free and sealed airflow through the air ducts and living spaces, with minimal air leakage and heat energy losses at the ducts or through the home shell (e.g. leaks around doors, windows and attic hatch). Workmanship and parts should be guaranteed with a reputable company

For more expert tips and information about duct sealing, duct design and evaluation, please contact us at Comfort24-7 today to speak with an HVAC professional near your home. Our professionals serve homeowners in Chicagoland & the surrounding areas.