Duct sealing & duct insulation

The Mass Save Program also handles the Duct sealing and duct insulation. (See Appendix 16.5 for airflow testing guidelines).  

  1.  General:

Duct Sealing can improve the overall atmosphere of the house, into: 

  1. Better indoor air quality. 
  2. Better humidity control. 
  3. Improved comfort. 

For improved and long-lasting insulation, it is necessary to first seal the duct before insulating. Due to the lack of airtightness in the lower boundary of the duct system, it is recommended to start the sealing process from where the air pressure is greatest (i.e., close to the air handler) and then move on to the ends of the duct. Any uninsulated section of the duct system located in unconditioned space shall be insulated to current code requirements. 

  1.  Locations and Use: 

For energy saving via the Mass Save Program, it is recommended: 

  • Not all Ducts are evaluated for sealing and insulation, but only those with 30% or more unconditioned space (measured by linear feet of ducts) should be evaluated. 
  •  According to the Mass Save program, The ducts located in semi-conditioned spaces are observed to have marginal payback.  
  • Thus, ducts that are in ventilated spaces (like attics, open crawl spaces, etc.) should surely be sealed after approval from the Mass Save PA. 
  • Not just any material can be used for duct sealing, as it should first be approved by the Mass Save Program (as described in the sub-section below).
  1.  Duct Sealing Installation Requirements: 

Following are the approved installation requirements for duct sealing (but not limited to), as per the Mass Save program: 

  1. Non-insulated Ducts: or insulation replaced duct should be sealed with Duct Mastic or any other approved duct sealing tape when sealing duct joints, seams, and connections.  
  2. Insulated Duct: does not require the seams along the edges to be sealed due to existing insulation barriers. However, all connection points and joints should be sealed.  
  3. Holes or seams: on the duct system, crossing the ¼” limit, needs to be backed with mesh tape and then sealed with duct mastic. 
  4. Flex Connections: In the duct system require hard duct connectors which are fixed with vinyl tension straps. The inner liner and the hard duct connection should also be sealed with duct mastic. 
  5. Filter Slot: should have an operable door that can open and shut (tightly). But in case of now or loosely closing door: 
  6. A temporary blocker must be installed (like aluminum tape). 
  7. The Mass Save CUSTOMER should be notified and advised to install a more permanent solution. 
  8. Sealing work scope: According to the Mass Save program, the following also fall into the air sealing work scope: 
  9. Boot to the floor. 
  10. Wall connections for supplies and returns. 
  11. Ceiling connections for supplies and returns.
  12.  Duct Insulation Materials Requirements 

Following are the approved insulation material requirements, as per the Mass Save program:  

  • Unconditioned Spaces: should be insulated with a duct wrap (having an R-value of 8) 
  • Insulation Tape: should be used for duct insulation (e.g., FSK Facing Tape, Aluminum Foil/Fiberglass Scrim on Polyethylene Coated Kraft Paper). 
  • Tools: used for insulation may include Plier Staplers and staples.  
  • Cable Zip ties: with the size of 10-14” will be required.
  1.  Duct Insulation Installation Requirements 

The following are some insulation installation requirements, as per the Mass Save Program: 

  • Installation: The following insulation installation steps are required: 
  • Wrapping and attaching approved insulation around the ductwork with the help of a plier stapler. 
  • For a neat tight finish, without compressing the insulation, a wrapping of at least 2 inches is recommended. 
  • Insulation should not be pulled tight enough to compress and decrease its R-value.  
  • There should be a maximum of 2 inches of space between seam staples.  
  •  Seams and tears: Mass Save Program approved tape (FSK Facing Tape, Material Aluminum Foil/Fiberglass Scrim on Polyethylene Coated Kraft Paper), should be used to seal any seams/tears in the vinyl vapor retarder. No fiberglass will be left exposed.  
  • Insulation Connections: Hard duct connectors with a vinyl tension strap should be used to make flex duct insulation connections. 
  • Insulate everything: Everything in the duct system from the return boots to supply should be insulated.  
  • Floor joist bays: will have duct insulation wrapped around 3 sides and secured near the top of each joist or to the subfloor on each side. They will be used as return ducts and insulation must be in substantial contact with all sides of the duct area. 
  • Existing Insulation: Duct systems with existing insulation should: 
  • Have their insulation peeled back to expose joints and connections or have their insulation compressed to feel the joints (applicable in straight ducts). 
  • Have the insulation cut and peeled back neatly to expose the located joints and seal them enough for mastic application. 
  • Have the insulation that was cut be back in place with no voids in the coverage with an approved tape. 
  • Use additional materials like cable (zip) ties or staples for additional support in case the insulation was removed completely removed. This will prevent the insulation from coming off from the duct.

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