EXISTING HOMES
AT 1.0—Introduction
This section lists work and details that shall be performed before insulation is installed in attics, and specifications for how to install insulation and attic-related ventilation. To qualify for an Existing Homes insulation incentive, existing condition must be R-18 or less, and the attic must be insulated to R-38, or greater, unless otherwise specified herein. Insulation shall be installed to reduce heat loss between conditioned space and unconditioned spaces or to the outside of the house.
All accessible attic areas, regardless of eligibility for incentives, must meet the applicable requirements in order to be considered a complete measure, unless a requirement is waived by Existing Homes or physical barriers exist (see section IN 1.5). Areas where existing insulation is greater than R-18 are not eligible for incentives. However, areas where existing insulation is greater than R-18 must meet all applicable specifications so that areas where existing insulation is less than R-18 may qualify for an incentive.
AT 1.1—Attic Air Sealing
To prevent transmission of water vapor and to support the effective R-value of the attic insulation, it is recommended that all accessible attic penetrations are sealed, including plumbing, wiring and duct penetrations, and similar openings in the air barrier of the attic. Caulk, foam or other compatible sealants shall be used. Target areas are listed below in Table AT 1.1. See the Air Sealing section in this manual for specifications.
Table AT 1.1—Recommended target areas to be air sealed before installing insulation
| Chimney chases |
Fire rated materials shall be used |
| Duct chases |
If opening larger than 1/2 inch, covered with rigid material to attic floor level and sealed |
| Plumbing, electrical and HVAC penetrations |
Seal with foam or caulk. If opening is larger than 1/2 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 |
| Top plates |
Recommended: seal with foam or caulk |
| Knee wall transition |
Plug cavities that connect conditioned space to unconditioned space (See AT 2.7) |
| Knee walls |
Seal penetrations with foam or caulk |
| Exhaust fans |
Seal fan housing to ceiling with foam or caulk |
| IC-rated recessed lights |
Seal housing to ceiling with foam or caulk |
| Accesses |
Weatherstrip access hatch perimeter |
Metal flue pipes and heat producing fixtures shall comply with the baffling requirements in AT 1.6.
eat producing fixtures may include:
- Metal flue vents
- Non-IC rated lights
- Non-IC rated bath fans
- Fans with heaters
- Transformers
AT 1.2—Knob and Tube Wiring
Before installing insulation in contact with active knob and tube wiring, the electrical system shall be inspected and receive written approval 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
Existing Homes 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, the upper vent area shall not exceed 80% of the total installed vent area. Gable vents may be considered lower ventilation, provided the installation allows cross-ventilation of the attic spaces.
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. See Existing Homes Quick Reference Guide on page 56 for net free area (NFA) calculations.
Any ventilation opening within six inches of the final insulation level shall be baffled with a rigid material, such as moisture-treated cardboard.
AT 1.4—Baffles for Eave and Soffit Vents
Eave and soffit vents shall be baffled to prevent wind washing through the insulation and blockage of the vent; all insulation types shall comply. 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 NFA 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. It is acceptable for compression to occur due to a narrowing roofline.
AT 1.5—Dams
Dams shall be installed between insulated and uninsulated areas, such as attics and garages. Areas where final levels of insulation differ, such as ceilings with different heights, also require a dam. Dams shall be installed to maintain a consistent R-value by one of the following methods:
- A durable, rigid material such as plywood, oriented strand board, moisture-treated cardboard, or foamboard, installed along the full length of required area.
- A 14 ½” wide (or wider) insulation batt, with an R-value equal to that specified for the attic, laid flat along the full length of the required area.
See AT 1.11 for specifications for damming attic accesses.
Sloughing is not permitted.
Illustration AT 1.5
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. When using noncombustible-rated insulation, contractor shall provide documentation to Existing Homes.
|
Item |
For insulation rated as noncombustible (ASTM E-136) |
For insulation not rated as noncombustible |
|
Metal flue |
Approved baffle |
Approved baffle |
|
Masonry Chimney |
No baffle required |
Approved baffle |
|
Transformers |
Approved baffle |
Approved baffle |
|
Non-IC rated Vented fan/light combo |
Approved baffle |
Approved baffle |
|
Miscellaneous electrical |
Approved baffle |
Approved baffle |
|
Non IC rated light |
Approved baffle |
Approved baffle |
|
IC rated recessed light |
No baffle required |
No baffle required |
|
Low-voltage electrical |
No baffle required< |
No baffle required |
|
Vented exhaust fans |
No baffle required |
No baffle required |
Baffles shall be made of rigid noncombustible material. Use Table AT 1.6 to determine baffle requirements. Batt-type insulation is not an approved baffle for any heat-producing fixture.
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 and Exhaust Fans
All exhaust fans shall be vented to the exterior of the structure and secured to the exterior sheathing with no gaps to prevent any exhaust air from entering back into the attic (see Illustration 1.7). At least one back-draft damper shall be functioning in each system, either at the fan or where vented to the outside. It is highly recommended that exhaust ducts traveling through unconditioned space be insulated to prevent condensation.
Fan shall be vented to nearest feasible location. Exhaust ducts shall not sag, and shall be as straight as possible to maximize effective air flow, and have no more than two 90-degree turns, or equivalent. Sags, turns, bends and elbows restrict air movement and the effective flow of air from the exhaust device. 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 at each joint and to the fan housing using mechanical fasteners, such as screws or metal clamp-type straps mechanically tightened. A securely tightened metal clamp will be acceptable in locations where space prohibits installation of sheet metal screws. Sealing materials such as tape, caulk and foam are not acceptable mechanical fasteners. To seal gaps in exhaust ducts, UL-listed metal HVAC tape or mastic tape may be used.
Existing flexible plastic or metal vent ducts may remain if they are free of holes and kinks, and are in otherwise good condition. Existing plastic or metal ducts shall be vented to the exterior, free of gaps and sealed to prevent exhaust air from entering back into the attic. Exhaust ducting shall be insulated to a minimum R-4 when required for code compliance.
Illustration 1.7—Exhaust boot connected to sheathing
AT 1.8—Kitchen Fans
Kitchen exhaust fans shall be vented to the exterior of the structure and secured to the exterior sheathing with no gaps to prevent any exhaust air from entering back into the attic. Existing rigid metal or flexible metal ducts may remain; however, existing plastic ducts must be replaced. Sealing materials such as tape, caulk and foam are not acceptable mechanical fasteners. To seal gaps in exhaust ducts, UL-listed metal HVAC tape or mastic tape may be used.
Ducts shall be fastened to vent with mechanical fastener, such as sheet metal screws. If a new exhaust duct is required for a kitchen stove, it shall be at least 28-gauge galvanized steel, stainless steel, copper or aluminum, and have a smooth interior surface. The exhaust duct shall be airtight and extend directly into a code-approved, metal vent cap. Vent ducts shall be securely attached at each joint and to the fan housing using mechanical fasteners. The exhaust duct shall meet manufacturer’s requirements and all local building codes. At least one back-draft damper shall be functioning in each system, either at the fan or where it vents to the outside. Exhaust ducting shall be insulated to a minimum R-4 when required for code compliance.
See UN 2.7 for downdraft exhaust fan venting requirements.
AT 1.9—Dryer
Exhaust Fans
Dryer exhaust venting that travels through the attic shall comply with AT 1.7. See UN 2.6 for dryer exhaust ventilation specifications.
At 1.10—Water
Pipes in Attics
If water pipes exist in the attic, they shall be insulated to meet specification UN 2.3.
AT 1.11—Interior
Attic Access Doors
Illustration AT 1.11—Interior attic and kneewall accesses shall be insulated and weatherstripped.
All operable attic accesses opening to interior spaces shall be insulated, weatherstripped and protected from having loose-fill insulation fall through the opening. Weatherstripping shall be permanently attached to create an effective air seal between the attic access frame and the door. Accesses with air leaks which cannot be weatherstripped shall be repaired or replaced prior to insulating. Ceiling accesses shall be insulated to R-30 with batt-type or rigid insulation. Knee wall accesses shall be insulated to a minimum of R-15.
Batt-type insulation shall be attached to the door with twine which 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-type insulation.
Alternatively, R-5 or greater rigid insulation installed between the access cover and a rigid protective material (OSB, plywood or other durable rigid material) attached over the entire insulation area is allowed. Insulation must be sealed around the perimeter to the access cover using caulk, adhesive or spray foam. Access-cover assembly must be tightly sealed using weatherstripping around the entire perimeter.
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:
- 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 or foamboard are not acceptable materials for attic access damming.
- B. A 14 ½” 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 ½” 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 weatherstripped and insulated to a minimum of R-10. Insulation and weatherstripping 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. New pull-down stair assemblies with a minimum R-5 insulation rating will be permitted provided the insulation is between conditioned space and the attic stair assembly and gaskets or weatherstripping prevent air infiltration. For questions about this specification, email the trade ally coordinator at existinghomesta@energytrust.org or call 1.866.365.3526 option 9.
AT 1.13—Exterior Attic Access Doors
Any outside access shall have a door that is easily opened to permit inspection, and shall be weather- and vermin-proof.