Air Duct Installation Tips to Improve Indoor Air Quality

Getting air duct installation right improves comfort, energy efficiency, and indoor air quality (IAQ). Ventilation is one of the core components of any HVAC system. Your ductwork provides passages for conditioned air to flow to each room and return to the system to be heated or cooled again. It’s often the source of IAQ issues. Therefore, achieving improved indoor air quality in your home starts with proper air duct installation. 

The following tips for installing ductwork can help improve IAQ and make your indoor air healthier to breathe:

Place Ducts Within Conditioned Spaces

Contamination from the attic, basement, or crawlspace can compromise indoor air quality. It’s often caused by duct leakage in these unconditioned areas. Installing ductwork in conditioned spaces instead limits access to pollution, even if there is a leak. It also minimizes heat loss. To achieve these benefits:

• Install air ducts in a dropped ceiling or chase.
• Place under-floor ducts in open-web floor joists (in a multi-story home).
• Put the air handler in an interior utility closet.
• If installing an air handler in the garage, place it in an air-sealed closet.
• Ensure the attic or crawlspace is unvented, air-sealed, or insulated at the perimeter.

Enclose Attic Ducts In Insulation Wherever Possible

If you can’t install ducts within the building envelope, bury them as deep as possible in attic insulation. Using R-8 or higher insulation can prevent heat loss and condensation, especially when it’s hot and humid (or at least R-13 in climate zone 3a, which includes the Greater San Francisco Bay Area). 

This method is just as effective as installing ducts in a conditioned space. The International Residential Code (IRC) was updated in 2018 to reflect the benefits of buried ducts. It also requires ceiling insulation above and below them to be at least R-19.

Choose High-Quality Ductwork Materials

Subpar ductwork materials can affect IAQ, especially improper insulation. Poor insulation inside air ducts can cause temperature imbalances that lead to condensation and mold growth. Mold spores can then be released from the ductwork and spread throughout your home. Dust, pollen, and other external pollutants can also get into ducts that aren’t properly insulated.

The material a duct is made of matters as well. While easy to install and corrosion-resistant, aluminum ducts aren’t very strong. They’re also vulnerable to thermal expansion and prone to damage that can affect indoor air quality. Flexible ducts can also cause issues. They must be installed properly or else tearing, crimping, and sagging can cause airflow and IAQ issues. The more sustainable materials to consider for air duct installation include:

• Galvanized Steel: Sheet metal ducts are non-porous, reducing the risk of mold. They’re also strong, durable, and non-combustible. They are available as rectangular ducts that more easily fit in limited spaces and round ducts that maximize airflow capacity.
• Fiberglass: Fiberglass insulation is often used in sheet metal ducts to prevent condensation. Fiberglass ducts are highly insulative, corrosion-resistant, and block sound from HVAC components and other sources.
• Fiberboard: Fiberboard ducts consist of resin-bonded fiberglass strands. A foil covers the exterior and provides an air and moisture barrier. While the interior isn’t smooth like metal, fiberboard is airtight so long as joints and seams are properly sealed.

Install a Filter at the Return Intake

Return air should be filtered at the last possible point before it reaches the fan. The ideal location is where the return duct connects to an HVAC unit’s intake. A filter here can capture particles from any source, ensuring clean air and protecting mechanical components.

Return grille filters are different. They cover vents that suck air from a room that’s pulled back into your HVAC system. However, they don’t protect against contamination from leaky ducts. Leaks in return ducts beyond the filtration point can pull air and pollutants from the basement, garage, attic, crawlspace, or outside. Properly installed ducts and a well-placed return filter prevent dirt, mold, asbestos, rodent feces, lead dust, and fumes from paints and solvents from getting pulled into the system.

Make Sure All Filters Are Properly Sized

People often think high-efficiency filters block airflow and cause pressure drops in their ductwork. However, a high-quality filter shouldn’t have much of an impact. The Minimum Efficiency Reporting Value (MERV) measures how well a filter captures airborne particles and common pollutants. A MERV 13 filter is considered highly efficient. Despite a thicker filtration media, such a filter works best if it’s well-constructed and fits the filter area (so no air can get around it).

Use Mastic to Prevent Leaks

Mastic can be used during air duct installation to seal all joints and seams. It’s also easier to put on ducts during installation when you have full access to your ductwork. When properly applied, mastic can minimize air leakage over the long term, as it’s resistant to deterioration and doesn’t lose adhesion.

Install an In-Duct Air Purifier

In-duct air purifiers serve as whole-home air filtration systems. They include ultraviolet (UV) air purifiers that neutralize germs and odors in your home. Ionization air purifiers are also available. They electrically charge air molecules, causing dust, smoke, and other particles to bond with them and fall to surfaces where they can be wiped or vacuumed away. 

Installing an air purifier during air duct installation ensures you benefit from clean air right away. It can also prevent dirt from building up in ducts in the first place.

In addition to improving indoor air quality, an in-duct, whole-home purifier can have the following benefits:

• Increased Energy Efficiency: Fewer particles and buildup in your ductwork means air can flow more smoothly, allowing your HVAC system to work more efficiently.
• Fewer Repairs: Dust and debris in ducts can make their way into blowers, compressors, and other components; efficient removal can avoid damage and increase the system’s lifespan.
• Reduced Maintenance: Clean, properly installed ducts help reduce repair costs and the need for professional air duct cleaning, which averages a few hundred dollars.
• Smoke-Free Home: If your house has a chimney, smoke can get through air vents. An in-duct air purifier neutralizes smoke before it pollutes indoor air.
• Cleaner Air: High-quality air duct installation, along with a whole-home purifier, can mean bacteria, viruses, fungi, pollen, animal dander, and other contaminants are removed before they can cause allergy symptoms, respiratory problems, or illnesses.

Contact Trio Heating & Air

Properly installed ductwork can improve indoor air quality. At Trio Heating & Air, we provide air sealing, insulation, and duct cleaning services in the Greater San Francisco Bay Area. Our experienced professionals also replace air duct filters and install whole-house purification systems. They also install air scrubbers in the ductwork. For more information about our HVAC, insulation, and air quality services and to request help, call (415) 234-4728 today.