For new construction, several key areas need to be addressed. First of all, if individual vents are used in the soffit, the rafter space immediately in front of and on either side of the vent should be provided with an air chute (Figs. 7.5 and 7.6). Other spaces should be totally blocked. Where a continuous strip vent is used in a soffit, an air chute should be provided every third rafter space, with the other spaces completely blocked. The small cavities around door and window frames should be insulated prior to installation of the interior covering. The material should not be forced into the cavity so tightly that frames or finishes are distorted. Finally, insulating the corners of attics in buildings with hip roofs may require special nozzles or placement tools. Alternately, corners can be insulated with suitable insulation before the gypsum wallboard or plasterboard is installed. Any other areas that will be inaccessible after the interior finish is installed must be handled in like manner.8
For existing structures, preparation should be performed in critical areas where the insulation may not be contained. For example, in joist areas, where soffit vents are installed, the opening from the attic into the soffit area may be blocked by use of pieces of batt-type insulation between and at the ends of the joists. Insulation should not totally fill the space between ceiling and roof. There should be a 1-in opening next to the roof for ventilation from the soffit area (or a chute or baffle may be installed).
For new and existing structures, a number of areas typically will be addressed in a similar manner for each project type. These include
1. Blocking should be placed around access to the attic to prevent insulation from falling out.
2. Blocking should be placed around recessed light or heating fixtures, chimneys, and flues. Clearance between heat-producing elements and combustible construction should follow applicable codes. Blocking should be placed permanently so as to keep insulation a minimum of 3 in away from all sides of recessed lighting fixtures and other heat-producing devices. The open area above recessed lighting fixtures and other heat-producing devices should not be insulated, per the National Electrical Code.
3. Cabinet bulkheads, stairway wells, and wall cavities that open into an attic should be covered by backer board to support the insulation.
4. The open side of any wall between a heated and unheated area should be covered by backer board to form a cavity for retaining the loose-fill material.