If you’re installing a replacement HVAC system in your home, you may also discover that duct replacement is necessary to ensure the best and most efficient operation of your new heating or cooling equipment. Here’s a brief introduction to duct replacement and design that can help you understand the factors that apply in this vital area of HVAC installation.
The Critical Value of Ductwork
Ductwork is the network of large pipes that extends from your furnace, heat pump or air conditioner to vents in the floor, wall or ceiling of your home. All of the heated or cooled air that produces indoor comfort will travel through ductwork. Usually each room will have at least one vent where heated or cooled air from your HVAC system exits. The system will also have several return air ducts to bring expended air back to the HVAC unit to be reconditioned, filtered and redistributed.
Duct Design Matters
Since all of the air that heats or cools your home travels through the ductwork, any problems in this air distribution network can have a significant effect on indoor comfort, energy efficiency and the amount of money you pay each month for heating and cooling.
- Efficiency – Poorly designed ductwork can reduce the efficiency of your HVAC system by restricting airflow or producing more airflow than is needed. In this case, your heating or cooling equipment won’t be able to operate at its most efficient level.
- Effectiveness – If too much or too little air is flowing through the ducts, your indoor environment may become warmer or cooler than expected. You may waste energy and money trying to adjust temperatures at the thermostat. In addition, HVAC equipment may experience unnecessary wear trying to compensate.
- Air leaks – Any gaps, holes and openings in the ductwork can lead to air leaks, which will allow heated and cooled air you’ve already paid for to escape unused. This wastes significant amounts of money and energy. Not only have you wasted conditioned air that you’ve already paid for, but you must also pay for more conditioned air to make up for the loss.
Factors for Effective Duct Design
- Run ducts through conditioned areas – Make sure the ductwork is routed through areas of your home that already receive heating and cooling. Don’t use uninsulated or unconditioned areas such as crawl spaces, unfinished basements, uninsulated attics or garages. Ductwork in these area, for example, can cause cooled air to heat up before it gets to your home’s indoor spaces.
- Insulate and seal ductwork – All ductwork should be well insulated to prevent energy loss through the material of the ducts. Rigid fiber board if a common insulator. In some cases, ducts can be insulated by wrapping them with fiberglass blanket insulation. Make sure all sections of ductwork fit snugly together and that all connections are sealed with mastic or metal tape. Have your HVAC professional inspect and test the ducts to ensure all potential air leaks have been located and repaired.
- Keep balanced airflow – Install manual dampers where each branch of the duct system connects with the central trunk. This will give you a way to balance the positive-pressure air leaving the supply ducts and the negative-pressure air being brought back in through the return ducts.
- Create clear airflow paths – When possible, make sure each room with a supply duct also has a return duct. If this isn’t possible, install a central return duct in a main hallway, under a major stairway, or in another large common area.
- Use actual ductwork – In the past, some duct systems were designed to use crawl spaces or cavities in the home’s wall as part of the air distribution pathway. This will lead to excessive air and energy loss. Make sure you use only real metal or fiberglass ducts throughout your home.