6.6102.1 Outside Air Ventilation Supply Ducts

Topic: 
Supply
Subtopic: 
Components
Desired Outcome: 
Ventilation supply ducts effectively move the required amount of air and prevent condensation
For supporting material, see Referenced Standards and Building America Solution Center.
TitleSpecification(s)Objective(s)
6.6102.1a
Duct design and configuration

Ventilation ducts will be as short, straight, and smooth as possible

Ventilation ducts will not be smaller than the connections to which they are attached

Effectively move the required volume of air

6.6102.1b
Duct insulation

Ventilation supply ducts installed outside of the thermal envelope Envelope The separation between the interior and exterior environments of a building that includes a combination of air and thermal barrier will be insulated to a minimum of R-8 or equivalent to local codes

Prevent moisture condensation

6.6102.1c
Duct support

Flexible and duct board ducts and plenums will be supported every 4' using a minimum of 1 ½" wide material

Support materials will be applied in a way that does not crimp ductwork or cause the interior dimensions of the ductwork to be less than specified (e.g., ceiling, framing, strapping); duct support must be installed in accordance with authority having jurisdiction

Metal ducts will be supported by 1/2" or wider 18-gauge strapping or 12 gauge or thicker galvanized wire no less than 10' apart

Effectively move the required volume of air

Preserve integrity of the ventilation supply duct system

Eliminate falling and sagging

6.6102.1d
Duct connections

All connections will have a contact overlap of at least 1"

Ducts will be connected and sealed as follows:

  • Round metal-to-metal or metal-to-PVC will be fastened with a minimum of three equally spaced screws
  • Other metal-to-metal or metal-to-PVC connections will be securely fastened and sealed with welds, gaskets, mastics (adhesives), mastic-plus-embedded- fabric systems, or tapes
  • Flexible duct-to-metal or flexible duct-to-PVC will be fastened with tie bands using a tie band Tie band A strap, often made of nylon, that mechanically squeezes a flexible duct to a fitting. Must have a minimum performance temperature rating of 165° (per UL 181A-type test) and a minimum tensile strength rating of 50 pounds tensioning tool
  • Flexible duct between the cable tie and end of metal or PVC duct will be screwed
  • PVC-to-PVC materials will be fastened with approved PVC cement
  • Other specialized duct fittings will be fastened in accordance with manufacturer specifications

Outdoor air ventilation supply ducts attached to the return side of forced air systems will be:

  • Attached as close to the heating, ventilation, and air conditioning ( HVAC HVAC Heating, ventilation, and air conditioning ) systems fan as possible while remaining in compliance with manufacturer specifications
  • Set up to provide filtration of outdoor ventilation air before reaching the HVAC HVAC Heating, ventilation, and air conditioning system (for minimum MERV MERV Minimum efficiency reporting value 6 filter)
  • Attached via a mechanically fastened takeoff collar

All joints and connections in ductwork will be fastened and sealed with UL181B or 181B-M welds, gaskets, adhesive mastics, or mastic-plus-embedded-fabric systems

Effectively move the required volume of air

Preserve integrity of the ventilation supply duct system and building envelope Envelope The separation between the interior and exterior environments of a building that includes a combination of air and thermal barrier

6.6102.1e
Duct materials

Flexible air duct material will meet UL UL Underwriters Laboratories 181, NFPA NFPA National Fire Protection Association, www.nfpa.org 90A/90B, International Mechanical Code, or the Uniform Mechanical Code

Effectively move the required volume of air

Preserve integrity of the duct system and building envelope Envelope The separation between the interior and exterior environments of a building that includes a combination of air and thermal barrier

6.6102.1f
Outdoor air intake location

Outdoor air intake will be installed in accordance with the following:

  • A minimum of 6" from grade
  • A minimum of 10' from contaminant sources or exhaust outlets
  • Above local snow or flood line
  • A minimum of 18" above an asphalt based roof
  • Never on a flat roof
  • As required by authority having jurisdiction

Prevent contaminants from entering house

Ensure unrestricted air flow