EXISTING HOMES
DS 1.0—Introduction
Performance-based duct testing shall be performed only by technicians certified by Performance Tested Comfort Systems™ (PTCS). All duct sealing shall be verified to meet Energy Trust requirements for material and workmanship by a PTCS existing homes duct sealing-certified technician. All accessible ductwork in unconditioned spaces must meet the applicable requirements to be considered a complete measure, unless a requirement is waived by Existing Homes or physical barriers exist (see section IN 1.5).
Basements containing HVAC ducts or which have a direct access to the interior conditioned space of a home shall be considered conditioned space. If a portion of the basement is treated as conditioned space, it shall be included in testing procedures and volume calculations. Duct sealing performed on systems contained completely within the conditioned thermal envelope shall not qualify for the duct sealing incentive.
Duct sealing on Existing Mobile Homes is only permitted if the trade ally is a participating contractor in the Existing Mobile Homes program. Contact Existing Mobile Homes for more information.
DS 1.1—Measurement
Measurements of duct leakage to outside and duct leakage reductions shall be performed in accordance to PTCS requirements. To receive a duct sealing incentive, the PTCS Duct Sealing Certificate & NW Duct Sealing Form (with a complete Section E) shall be submitted with an Existing Homes incentive application form and contractors invoice marked “paid in full.” All leakage tests shall be duct leakage to outside—tested at 50 Pascals of pressurization—with reference to outside.
Duct leakage to outside shall be measured before sealing (pre-test) and after sealing (post-test). Reductions in duct leakage shall be measured as follows:
Pre-test CFM50 - Post-test CFM50 = Total Leakage Reduction CFM50
If a duct system is unable to reach 50pa of pressure, the highest possible pressure shall be used when performing a pre-test or post-test.
In extreme cases, duct system leakage may be tested as a split system (testing supply leaks only). Pre-and post-tests shall be conducted as a split system. When a split system test is performed, all accessible components of the supply and return ducting must be sealed according to DS 1.5. All accessible ducting in garages shall be sealed to prevent carbon monoxide and other pollutants from entering the duct system.
DS 1.2—Duct Testing Replication Standard
When a QC inspection is performed on a duct sealing job, the Quality Control post-test CFM50 shall be within 20 percent or 40CFM50, which ever is greater, of the contractor’s post-test CFM50, as recorded on the contractor’s invoice.
Diagnostic equipment should be maintained and calibrated according to the manufacturer’s requirements (see section IN 1.9).
DS 1.3—Duct Repair
Inferior sections of duct—such as rusted, crushed, disconnected or sections otherwise ineffective—shall be repaired or replaced before duct sealing is performed. When there are large gaps in sheet metal or duct connections, repairs shall be made using sheet metal, sheet metal screws, and/or mastic and mesh reinforcing tape. Gaps greater than 1/8” shall be reinforced using mesh-reinforcing tape before applying mastic. Disconnected, loose-fitting or new metal ducts shall be secured using at least three sheet metal screws at each connection.
DS 1.4—Supporting Repaired Ductwork
To minimize sagging, ducts shall be supported with durable supports. Flexible ducting supports shall be listed as UL-181 approved, be at least 1.5” wide and not restrict airflow. If possible, ducts shall be supported above the ground. When contact with the ground is unavoidable, closed-cell rigid insulation shall be placed under the ducts.
DS 1.5—Materials and Application
Ducts shall be sealed using pliable water-based mastic labeled as meeting UL 181 standards. Boot-to-floor connections shall be sealed with silicone caulking, pliable mastic or expanding foam. Foil or mastic HVAC tape labeled as meeting UL 181 standards may be used only on the air handler.
All accessible connections of the supply and return plenum and trunkline, and all accessible take-offs, runs, and boots—including the gores on adjustable elbows—shall be sealed with approved materials. The following areas are examples of duct sealing opportunities:
- Plenum
- Air-handler cabinet to plenum
- Plenum-to-take-off connections
- Branch T’s, Y’s and L’s
- Boots
- Boot-to-floor connections
- Duct-to-duct connections
- Gores on adjustable elbows
The presence of insulation alone shall not be considered a barrier to accessibility. If continuous R-4 or higher insulation exists and is in good condition, it shall be in the same or better condition upon completion of duct sealing. Refer to DU 1.2 for duct insulation requirements, when replacing insulation.
Loose tape shall be removed from rigid ducts prior to sealing. Secured tape must be completely covered with mastic which shall extend at least ½” beyond the tape edge on either side and be at least 1/8” thick.
DS 1.6—Flex Duct Connections
All flexible ducts shall be joined to a section of rigid duct of matching diameter, including locations where two separate sections of flex duct meet. Both the inner and outer lining shall be tightly fastened using a compression strap tightened with a tool designed for that purpose. Tape may remain as long as a compression strap is installed to maintain a permanent connection. Flexible ducting shall be supported (See DS 1.4) and comply with UL-181 requirements.
DS 1.7—Combustion Appliance Zones
An Air Handler Effect test shall be performed in accordance with PTCS testing procedures after duct sealing in all Combustion Appliance Zones, or CAZ. A CAZ is any zone in the house or attached space which contains a combustion appliance. Appliances with a properly installed combustion chamber sealed to the exterior of the structure are not considered combustion appliances for the purposes of the CAZ test. Forced-air system operation shall not depressurize a CAZ by more than 3 Pascals with reference to outside.
DS 1.8—Carbon Monoxide Detector
A functioning UL-listed carbon monoxide detector shall be installed according to manufacturer’s specifications whenever combustion appliances are present in the home, garage or other attached space.