Duct Design, Sizing and Installation
A proper ductwork installation ensures comfort, a proper air distribution and a more economical operation of your cooling and heating equipment.To achieve it, pay attention to the layout issue, the materials, the size of the ducts, the sealing details and the insulation levels…
Where To Install The Duct Systems: The Layout
Ducts should be installed inside the conditioned living space or in semi-conditioned spaces of the house. Avoid exterior wall cavities whenever possible. The goal of this rule is obvious: possible duct leakage in ducts installed in the conditioned spaces will not be wasted. Besides, ducts will not need any insulation, or will only demand a minimal insulation.
If you can’t install the ducts in a conditioned space, if the attic is subject to the summer’s high temperatures prefer crawlspaces or basement to attics.
Avoid Non-Ducted Systems
Do not use wall, floor or ceiling cavities as ducts… Cavities are difficult to seal and insulate and will not ensure a good distribution due to turns, twists and improper size. Bet in a completely ducted system.
The Size Of The Ducts
Only a proper size of the ducts ensures an accurate distribution of the conditioned or heated air, and a proper functioning and a longer lifespan of the equipment.
That size depends on the type of equipment (heat pumps require larger ductwork than furnaces…), and also on insulation, climate or home layout. An informed professional will be able to audit and assess your situation and determine the right duct size. Avoid non-informed contractors. They tend to oversize the duct systems.
Installation Standards For Ducts
There are several international standards for duct installation. Underwriters Laboratories (UL) standards are applied worldwide. In North America you may also consider standards from the Sheet Metal and Air Conditioning Contractors’ National Association, Air Diffusion Council (ADC) or North American Insulation Manufacturers Association.