Assessment of the Exterior Walls and Enclosed Cavities

All exterior walls, overhangs, and enclosed cavities need to be fully insulated to make a proper thermal envelope. The energy specialist can use an IR camera to help validate the existence or lack of insulation in the wall cavities. The Energy Specialist would determine the area of each element and know the depth of framing cavities.

Refer to Section 2.9 for more information about calculating areas.

Wherever the enclosed cavities are inaccessible, know that the insulation types and depths are like the cavities that are accessible.

 All enclosed cavities having air leakage paths that cannot be air sealed must be with dense-pack cellulose. Minimum three inches of free space should be present for the cellulose hose to fit into the cavity correctly so that the enclosed cavity is properly insulated. The arrangement of the cavity must be able to bear the installation of dense-pack cellulose for the upgradation to be recommended. Use the following measures given for specific kinds of wall insulation measures available in the Mass Save program.

Exterior Wall Insulation: 

  • Exterior Blow – An exterior blow is recommended if there is removable siding. 
  • Interior Drill and Blow – An interior drill and blow are recommended if the home has stucco, brick, masonry, or asbestos siding, though the siding type is different. When stipulating wall insulation in homes with brick or other masonry exteriors, ensure there is sheathing under the masonry, as cellulose must not be installed directly with masonry. Interior Walls: Interior walls should be recommended for separating conditioned space from unconditioned space, like hallway garage wall, be insulated with dense-pack cellulose via interior drill and blow method.


Any overhangs that are not insulated or are insufficiently insulated can be recommended and should have a minimum of 3 inches of empty cavity space available, be insulated with dense-pack cellulose or through the floor of the living space. 

Garage Ceilings: 

Enclosed garage ceilings insulation should be recommended using dense-pack cellulose as long as concealed distribution pipes and plumbing are safe from cold temperatures and at least 3 inches of empty cavity space is available. Proper protection usually involves installing a bigger R-value between the pipes and the exterior than between the pipes and the interior of the home.

Other Cavities:

Dense pack cellulose insulation is recommended for uninsulated or inadequately insulated enclosed cavities as mentioned in the Material & Installation standards if there is a minimum of 3 inches of empty cavity space. These areas should be insulated either from the interior living space or from the exterior, based on accessibility.

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