Air sealing guidelines

Air sealing installment also requires that manufacturer’s instructions, Massachusetts Building Code (780 CMR), and all other appropriate codes are followed. Tests must be performed and properly documented in ICC ES reports or Unordered list form (where code is used for showing the requirement of specific testing for specific use), such as: 

  1. low-density foam left exposed in an unoccupied attic space 
  2. Cellulose fiber installed as an air retarder and fire-stop in a rated wall between units.

For any use that might go beyond the specific listing, a special jurisdiction by a local authority must be obtained, before installing.

  1.  Performance Criteria: 

It is the Mass Save Contractors’ responsibility to tightly seal all the access hatches, framing voids, and chimney, but plumbing and wiring, also chase between the conditioned space and unconditioned attics, knee walls, and other buffer zones. It is also the Mass Save Contractor’s responsibility to define where the pressure and thermal boundaries of the home are to be. The air sealing measures taken should be: 

  • Continuous and durable. 
  • Able to support all expected loads. 
  • Impermeable to airflow (as indicated by chemical smoke at a pressure difference of 50 Pascals).
  1.  Conditions for Materials Use: 

Before installing the material, The Mass Save contractor must make sure that the following conditions are met: 

  1. Follow not only the manufacturer’s instructions but also all the applicable codes when installing Air impermeable barrier materials and sealant. 
  2. The Sealant used (on exposed joints), should conform to not only the performance requirements but also be able to blend in perfectly with the material. All this needs approval from the owner before installation. 
  3. The sealant should be installed with: 
  • Backing, if the gap (exposed or covered) is wider than 3/8”. 
  • all joints are supposed to be tooled. 
  1. In the case of Rigid barriers, they should be cut to friction fit openings with gaps no more than 1″ for foam sealant and extra material on edges for fasteners: 
  • To achieve a smooth finish and avoid sagging, support shall be provided.  
  • Larger enclosures of rigid foam or fiberglass board barrier material for pipes, whole-house fans, or folding stairs shall be fastened and sealed at all edges with weatherstrip provided at operable joints and edges sealed to the substrate where fixed. 
  1. The combustible material is not to be used as rigid barriers to bridge the clearance space to heat sources (such as chimneys and metal combustion vents). The non-combustible rigid barrier might include sheet metal or cement board etc. 
  2. Similarly, combustible sealants should not be used for fuel chimneys or oil vents instead use a non-combustible sealant like furnace cement or E 136 rated caulk to seal gaps in hot temperature (500 F, 600F) gas vents between the rigid barrier and heat source, material like RTV-approved silicone should be used.  
  3. Besides a non-combustible barrier a clearance dam to maintain a 3” or greater leeway around the chimney or vent for the full height of the insulation with the following material is also required: 
  • Unfaced mineral fiber meets the criteria. 
  • a folded metal collar, with the following requirements, is recommended: 
  1. 2-4” taller than the final height of insulation. 
  2. folded into the vent to close the top space. 
  3. fastened at the bottom and the vertical seam. 
  1. As per the BPI standards and code requirements, about 6” of clearance in single-walled metal fuel pipes should be maintained (like kitchen exhaust ducts). 
  2. Different conditions may call for different sealants, for example: 
  • For sealing gaps 1 part sealant foam may be used. 
  • For spaces around penetrations of up to 1-5/16” in width and 1.5”, full depth of wood plate for firestop (combustible, so should be used with heat sources). 
  1. For openings from 2” to 4” wide the 2-part sealant foam may require backing and infill of rigid barrier material for openings wider than 4”. 
  2. Insulation must be kept 3” or more away from the sides of a non-IC rated recessed light fixture (including any wiring box or ballast) and no insulation is allowed above the fixture. Unless the Mass Save Contractor provides the PA vendor with signed documentation by a licensed electrician, all recessed fixtures shall be treated as non-IC rated. (PA vendors that allow different treatment for IC-rated fixtures will provide additional requirements for treatment and documentation.) 
  3. If an air-tight box is installed to limit air leakage, it shall be sized for clearance from the fixture, taller than the adjacent insulation, and with a non-insulating moisture-permeable top of gypsum board or equivalent material. 
  4. If access does not allow installation of the box, 3” clearance from insulation is still required with no insulation allowed above.  
  5. The gap between the fixture and ceiling may be sealed with fire-rated caulking. 
  6.  For airtightness and insulation continuity, replacement with an airtight IC-rated fixture or infill of the opening and replacement with a flush mount fixture are preferred recommendations. 
  7. Dimensional limits: 
  8. Siliconized acrylic shall not be used in openings or cracks over 3/16″ without a backer, and generally should not be used in openings or cracks more than3/8″. 
  9. Pure silicone shall not be used in openings or cracks over 3/8″ without a backer, and generally should not be used in openings or cracks more than ½”. 
  10. Foam shall not be used to span gaps or openings more than 1 ½” without a backer material. 
  1.  Flexible air barrier or other sheeting materials approved for air sealing use shall not span gaps larger than 24” without the use of framing for support. 
  2.  Foam sealant will not be used where exposed to sunlight or other heat-producing sources. It will not be used near any heat-producing device unless a clearance of 3” can be maintained for double-walled flue pipes and masonry chimneys, and 6” for single-walled flue pipes.
  3.  Typical Air Sealing Locations:  

Following the PA vendor’s instruction, all air leakage pathways must be located, uncovered, and sealed, no matter if the areas are conditioned or not. 

The areas include (but not limited to):   

  • accessible attics 
  •  side attics 
  •  crawlspaces 
  •  unconditioned basements 
  •  attached garages,  
  • leakage from the basement to the outside.  
  • Gaps, penetrations, and fixture openings allow interior air into inaccessible roofs, slants, and outside wall cavities. 
  • Major direct openings between conditioned space and outside. 

Due to the basements being usually used as semi-conditioned spaces, so usually if a basement is deemed outside the conditioned space, then it is not included in the scope of work.

  1.  Air leakage may occur in many forms, and there are many ways to find out from which some are as given below: 
  • If the Mass Save Contractor finds dropped soffits or lowered ceilings or if there is a change in the ceiling height. 
  • Plumbing wet walls, duct chases, duct seams, joints, and boot leaks. 
  • Check for any leakage in Chimney and combustion vent chases. 
  • Any excess openings in the bathroom (opening behind/under tubs, showers, tub/shower enclosures, etc.). 
  • Wall tops opening into the attic, gaps between gypsum ceiling and wall plates. 
  • Annular (Ring-shaped) space at wiring, pipe penetrations through plates, and at ceiling fixtures. 
  •  Wall tops/Wall topped with gable having openings at level changes/ends, or if knee walls have any floors open.  
  • 2nd story floors open to attached roofs over porches and additions or garages. 
  • Indoor vertical farms with openings into attic stairs or landings. 
  • Pocket door framing open into the floor above and exterior walls. 
  • Seams and openings in walls and ceilings between attached garages and house. 
  • Non-IC rated light fixtures are Non-insulating, so any holes for air leakage must be addressed. 
  • Usually, Bathrooms and Kitchens have exhaust/venting fans.  
  • Mass Save Contractor should inspect all the joint seams and holes for any kind of gaps/air leakage. 
  • There could be gaps in the tongue in groove paneling, wherever there are angle changes at hips/valleys or if there are any slants and ceilings. 
  • Suspended Ceilings and acoustical tiles with no gypsum might cause air leakage. 
  • Missing gypsum behind decorative ceiling light trays; built-in cabinets in knee walls. 
  • Missing gypsum or open joints above decorative ceiling beams 
  • Gaps below baseboard and behind carpet nailing strip at subfloor joint to exterior wall. 
  • Common wall openings between dwelling units. 
  • Attic access openings, operable doors, and hatches without tight weatherstrip. 
  • If the attic access stair covers are pulled down.  
  • Rim joist junctions and gaps between sill and foundation. 
  • Utility penetrations and direct openings through foundation walls 
  • Openings in gypsum board above the suspended ceiling and behind cabinets 
  • Openings between window and door assemblies and their respective jambs and framing.
  1.  Confirmation of Air Sealing Effectiveness: 

After sealing all air leakage, it is necessary to perform an air leakage test through not only visual also with one of the options below: 

  1. Chemical Smoke Test: During the blower door test a chemical smoke can be chucked in, and visual inspection can then be made for any air leakage. 
  2. Building test: A whole building leakage test is conducted: 
  • The equipment used in the test must be used by following the manufacturer’s instructions and should be in conformance to the Standard CAN/CGSB 149.10-1986, ASTM E-1827-07, or ASTM E-779-03.   
  1. Infrared test: Or instead of chemical smoke, an infrared inspection can be done with the blower door test, the infrared operation should meet the following conditions: 
  • An 18° inside to outside temperature difference following ASTM C1060 (1997). 
  • Any air leakage pathways were discovered using ASTM E1186 (2009).

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