HOME ENERGY SOLUTIONS

Weatherization Specification Manual

ATTIC INSULATION

AT 1.0—Attic Preparation Work

This section lists work and details that shall be performed before insulation is installed in attics as well as specifications for how to install insulation and attic related ventilation. These specifications will not cover every situation. If you have questions, call the Trade Ally Coordinator at 1-866-365-3526, and a program field technician will get back to you ASAP.

AT 1.1—Attic Air Sealing

At this time, there is no program requirement to air seal attics before adding insulation, but HES recognizes that there are significant energy savings and lost opportunities associated with attic air sealing. Recommended target areas are listed below in Table AT 1.1. The program will offer air sealing training to interested program contractors. (See section on air sealing).

The program has an air sealing measure and incentive. The air sealing measure requires a blower door “test in” and “test out” in order to receive air sealing incentives, and the customer must to be charged for the air sealing measure in order to be eligible for an incentive. Incentive details for air sealing can be found on forms 320E and 320P for single family and two- to four-unit residences. The forms can be found at www.energytrust .org.

Table AT 1.1—Recommended areas to be air sealed before insulation installed

Chimney chases	Fire rated materials shall be used
Duct chases	If opening larger than ½ inch, covered with rigid material to attic floor level and sealed
Plumbing chases	If opening larger than ½ inch, covered with rigid material to attic floor level and sealed
Drop soffits	Covered with rigid material to attic floor level and sealed
Open wall cavities	Covered with rigid material to attic floor level and sealed

 

AT 1.2—Knob and Tube Wiring

Before installing insulation in contact with active knob and tube wiring, wiring shall be inspected and approved in writing by a licensed electrician. Insulating attics with knob and tube wiring shall be at the discretion of the contractor and homeowner and shall adhere to state and local code jurisdictions.

AT 1.3—Passive Attic Ventilation: Sizing and Distribution

Home Energy Solutions requires 1 sq. ft. of net free area (NFA) of ventilation for each 150 square feet of attic area, if all the vents are on one level. The area may be reduced to a ratio of 1 sq. ft. to 300 square feet, if the vent area is divided between upper and lower ventilation. When vent area is divided, at least half of the required area shall be lower ventilation and at least half of the required area shall be higher ventilation. The upper vent area shall not exceed 80% of the total installed vent area.

The vent area shall be the NFA, defined as the actual open area of the vent after subtracting any area blocked by screens or louvers. All vents shall be screened.

If used for lower ventilation within 6 inches of the final insulation level, roof jacks shall be baffled with a rigid material such as moisture-treated cardboard, which shall be attached to the rafters underneath the vent.

AT 1.4—Baffles for Eave and Soffit Vents

Soffit and eave vents shall be baffled to prevent wind washing through the insulation and blockage of the vents. Baffles shall be installed before adding more insulation. Baffles shall maintain an opening equal to or greater than the size of the vent. Baffles shall be fastened to roof rafters with at least 9/16-inch staples or roofing nails. Anchor points shall be spaced no more than 4 inches apart down each side, in the upper one-half portion of the baffles. Baffles shall be rigid, impervious to wind, and resistant to moisture. All baffles shall extend 4 inches above the final level of insulation.

Illustration AT1.4

A continuous dam shall be installed along continuous soffit or eave vents. Where a continuous soffit vent is existing, baffles shall be installed somewhat equally spaced along the length of the soffit and allow enough net free area to satisfy the lower ventilation needs based on the standard set in section AT 1.3. Unbaffled bays that open to a soffit shall be blocked and sealed with a rigid moisture resistant material so blown product is not able to enter soffit. Baffle shall be installed far enough into the bay to reach the exterior side of the top plate. If compression occurs because of a narrowing roofline, that is acceptable.

AT 1.5—Dams

Dams shall be installed between insulated and uninsulated areas, such as garages, covered porches and along the upper edge where ceilings differ in height to keep loose-fill insulation from falling over the edge. To build dams, use batt insulation laid flat, with an R-value equal to that in the attic. The batt shall be at least 14-1/2 inches wide. Other acceptable dam materials would be plywood or moisture-treated cardboard.

Sloughing is not permitted.

Illustration AT 1.5

Dams shall be installed around storage areas and covered 2 feet into the insulated area to comply with Human Contact requirements (See Human Contact Areas).

AT 1.6—Baffles for Light Fixtures, Fan/Lights, Chimneys and Miscellaneous

Most unfaced fiberglass batt insulation brands meet the ASTM E-136 noncombustible rating, but some do not. When using noncombustible rated insulation, contractor shall provide documentation to Home Energy Solutions.

Baffles shall be made of rigid non-combustible material. Use Table AT 1.6 to determine baffle requirements.

To prevent heat build-up, insulation shall not be in contact with fixtures as described above. When needed, baffles shall keep the insulation at least 3 inches, but not more than 4 inches, from the sides of the electrical fixtures, flues, and chimneys. Baffles shall extend at least 4 inches above the final level of insulation. (See Illustration AT 1.6.)

Illustration AT 1.6

AT 1.7—Bath Fans

Existing flexible plastic or metal vent ducts may remain if they are free of holes and kinks and are in otherwise good condition, provided they are vented to the exterior of the structure.

Exhaust fans that terminate in attics shall be extended through to the outside and sealed to prevent any exhaust air from entering back into the attic. At least one backdraft damper shall be functioning in each system either at the fan or where vented to the outside. To avoid sags, approximately 5 feet of flexible metal duct shall be allowed per fan run. The remainder of the duct shall be rigid metal.

Fan shall be vented to nearest feasible location. Exhaust ducts shall not sag or have more than two turns. If attic vent is used for fan exhaust, it shall not be included in attic vent area calculations (see section AT 1.3).

Vent ducts shall be securely attached to the fan housing using mechanical fasteners, such as screws or compression straps mechanically tightened.

AT 1.8—Kitchen Fans

Kitchen exhaust fans shall be vented to the exterior of the structure. Kitchen exhaust shall be extended through to the outside and sealed to prevent any exhaust air from entering back into the attic. Duct shall be fastened to vent with mechanical fastener, such as sheet metal screws or compression strap mechanically tightened. Existing plastic ducts are unacceptable.

If a new exhaust duct is required for a kitchen stove, it shall be at least 28-gauge galvanized steel. The exhaust duct shall be airtight and extend directly into a code-approved, metal vent cap. Use screws to attach sections of the duct to each other. The exhaust duct shall not have horizontal runs or 90-degree bends and shall meet all local building codes. At least one backdraft damper shall be functioning in each system either at the fan or where vented to the outside.

Downdraft exhaust ducts may have a 90-degree turn, shall exit through the foundation or exterior wall, and shall end in a metal vent cap.

AT 1.9—Dryer Exhaust Fans

Dryer exhaust fans shall be vented to the exterior of the structure and shall have a backdraft damper. New dryer vents shall be rigid metal and shall be permanently supported. Exhaust systems shall be as straight as practical and shall not exceed 25 feet.

To prevent blockage with lint, dryer vent ducts shall not be connected with screws.

Existing flexible plastic or metal vent ducts may remain if they are in good condition, provided they are vented to the exterior of the structure.

At 1.10—Water Pipes in Attics

If water pipes exist in the attic, they shall be insulated to meet the specifications in the Water Pipes section in the UNDERFLOOR INSULATION specifications.

AT 1.11—Inside Attic Access Doors

Illustration AT 1.11—Inside attic and kneewall accesses shall be insulated and weather-stripped.

Weather-stripping shall be permanently attached. Accesses with air leaks that cannot be weather-stripped shall be repaired. Ceiling accesses shall be insulated to R-30 with batts or rigid insulation. Kneewall accesses shall be insulated to a minimum of R-15.

Batt insulation shall be attached to the door with twine. The twine shall be stapled to the edges of the door. Stapling the insulation directly to the door is unacceptable. Rigid insulation may be fastened to the door in lieu of batt insulation.

Attic accesses shall be protected from having loose-fill insulation fall through the opening. The full level of ceiling insulation shall be maintained to the edge of the attic access opening by one of the following methods:

1. The opening may be framed with wood or plywood boards. The framing shall be permanently attached and extend at least 4 inches above the final level of insulation. Cardboard is not acceptable.
2. A 14-1/2-inch wide (or wider) insulation batt laid flat, with an R-value equal to that specified for the attic, may be placed tightly around the perimeter of the access opening. This 14-1/2 inches shall be maintained in all outward directions from the access opening, including corners. Scoop out all loose-fill insulation from the edges before laying batts.

AT 1.12—Pull-Down Stairs

Pull-down stairs in heated areas shall be weather-stripped and insulated to a minimum of R-10. Insulation and weather-stripping shall not prevent easy operation of the stairs. Factory or site built pull down stair covers are recommended and shall have a minimum R 10. For more information, call 503-523-4828.

AT 1.13—Outside Attic Access Doors

Any outside access shall have a door that is easily opened to permit inspection, and shall be weatherproof and vermin-proof.

AT 1.14—Kneewalls in Attic Areas

Kneewall accesses shall be insulated to R15 and weatherstripped. If kneewall is used for storage, fibrous kneewall door insulation shall be covered to prevent human contact (see section IN 7). All penetrations through the wall shall be sealed with caulk or foam.

Kneewall insulation shall be installed prior to installing ceiling insulation. Kneewalls that are uninsulated shall be insulated to a minimum of R-15 in a 2x4 cavity, and R21 in a 2x6 cavity. When adding new insulation over existing kneewall insulation, the cavity shall be completely filled. Do not install new insulation with a vapor retarder on top of pre-existing insulation. Horizontal installations shall be insulated to R21.

Illustration AT 1.14

Kneewall insulation, whether new or pre-existing, shall be covered with a durable, vapor permeable air barrier material to prevent air penetration of the insulation, and to ensure that the insulation is held in full contact with the wall cavity. Air barrier material shall be tested and labeled to meet Oregon fire protection standards. The air barrier material shall be permanently fastened so that it supports the kneewall insulation.

GENERAL ATTIC INSULATION REQUIREMENTS

AT 2.0—Introduction

In attics with no pre-existing insulation, vapor retarders shall face the heated area of the building. Do not install new insulation with a vapor retarder on top of pre-existing insulation. There should only be one vapor retarder in the assembly and it should be in contact with the heated ceiling. If existing attic insulation has a vapor retarder on top surface, slash with razor knife every six inches before adding more insulation.

If the added attic insulation compresses the existing insulation, the final R-value shall be R-38, or greater. After installing the insulation, eave and soffit vents shall remain unblocked.

Decked storage areas above conditioned space shall be insulated to the highest practical level. When decked storage areas exceed 5% of the attic area or 64 sq. ft., whichever is greater, they shall not be included in the calculation of the insulated areas for purposes of incentives, but shall be insulated. When decked storage areas are less than that limit, they shall be included in the incentive area calculation. When unusual circumstances allow only for the cavity to be filled, contact the Home Energy Solutions program for incentive information.

AT 2.1—Installing Loose-Fill Insulation

Loose-fill insulation shall be level and smooth, with a uniform R-value. The number of bags used to attain the added R value shall reasonably match manufacturers estimated bag count.

AT 2.2—Installing Batt Insulation

If batt insulation is installed, prepare the attic in the same way as for loose-fill insulation. As stated in section AT 2.0 above, do not install vapor retarders over existing insulation. In attic areas where no insulation exists, batts with vapor retarders may be used. The vapor retarder shall be in contact with the ceiling.

Batts shall be cut to fit and placed tightly together with no gaps except those required for clearance around heat-producing fixtures. Where practical, place one row of batts between the joists and another row of batts on top of the first row and at right angles to the joists.

AT 2.3—Floored Attics

Insulation shall be installed under the boards of floored attics. To fill the cavities, the boards can be lifted or holes can be drilled into them no more than 4 feet apart. Joist cavities shall be tightly packed with insulation.

Areas with loose-fill insulation next to a floored attic shall be dammed to prevent insulation from falling onto the floored attic.

AT 2.4—Sloped Ceilings with Side Attics and Upper Attics

Uninsulated sloped ceilings between attics shall be insulated with either batt or loose-fill insulation. When using loose-fill insulation, the lower opening of each cavity must be dammed to prevent insulation from falling out of the cavity.

AT 2.5—Vented Vaulted Ceilings

If insulation is added to a vented vaulted ceiling, a 1-inch air space shall be maintained above the insulation. Each cavity shall have an upper and lower vent.

AT 2.6—Unvented Vaulted Ceilings

If insulation is added to an unvented vaulted ceiling, it shall be filled with tightly packed insulation.

AT 2.7—Insulating Side Attics

When insulating side attics, floor cavities from adjacent heated spaces shall be sealed with air-impervious materials.

Illustration AT 2.7