resistance
Senior Member
- Location
- WA
Has anyone read, or heard of this?
Insulation of attics in older homes through utility programs is effectively on hold right now in California. Utilities there have placed a moratorium on insulating attics where knob-and-tube wiring is present, prompted by changes in the national and state electrical codes. This is having serious effects on many of the utility insulation programs, and will likely have a significant impact on insulation contractors in the state.
Knob-and-tube wiring was the most common form of home wiring before about the mid-1940s. With this type of wiring, the two conductors are completely separated as they run through the house, and join only when they reach the electrical device. Each wire is insulated with cloth and held in place with porcelain "knobs." When the wires run through a joist, porcelain "tubes" are used to keep them away from the wood. Although knob-and-tube wiring is seldom used today, most older homes are still likely to have it.
The concern over insulation of attics with this type of wiring arose with a recent change in the National Electrical Code (NEC). Prior to 1987, the NEC did not mention thermal insulation with knob-and- tube wiring at all. With the 1987 edition, however, NEC Section 324-4 was revised to say "Concealed knob-and-tube wiring shall not be used in... the hollow spaces of walls, ceilings and attics when such spaces are insulated by loose or rolled insulating material." In the 1990 edition, the Code was further changed to exclude foamed insulation, and to specifically exclude only insulation that "envelops the conductors." The stated reason for this prohibition is that the thermal insulation prevents the wires from dissipating heat, which could cause insulation to ignite. However, James O'Bannon, Chair of the Statewide Loosefill Insulation Task Force, performed an extensive survey of all the fires that took place in California over a ten-year period, and found none that were attributed to knob-and- tube wiring.
Since NEC only restricts insulation that envelops the conductors, one way to comply with the code is to avoid placing insulation directly over the wires. This involves either avoiding the cavities that contain the wires, constructing baffles around the wiring, similar to the way baffling of light fixtures is currently done, or laying batts up to, but not touching, the wires. The California Department of Economic Opportunity issued procedures for this type of baffling in the state's low-income weatherization programs. State utilities also adopted these standards for their programs.
Although the procedures allow contractors to insulate knob-and-tube homes safely, this solution is not without problems. Gaps in the insulation, of course, reduce its thermal effectiveness. Detailed baffling and blocking of the wires in an attic is also much more labor intensive, and therefore more expensive, than simply blowing insulation into the whole attic. One weatherization crew estimated that it takes several extra hours to do a knob-and-tube attic in this way. Of course, it should be easy to simply avoid the stud cavities containing wires, which reduces effectiveness but actually saves time. This solution may not be viable for walls where it is much more difficult to baffle the wiring.
Since no fires related to insulation around knob-and-tube wiring had occurred in California, the Insulation Contractors Association (ICA) challenged this section of NEC. The California Department of Housing and Community Development (HCD), which is the state agency with authority to adapt the NEC in order to create the State Electrical Code, met with the ICA, Underwriter's Laboratory, the Electric and Gas Industries Association, the State Building Standards Committee, and the State Fire Marshall to review the Code. As a result of these meetings, on February 15, 1991, they amended the State Electrical Code. The amended code allows insulation that envelops knob-and- tube conductors as long as (among other things) a licensed electrical contractor certifies that the wiring is in good condition, and an appropriately sized fuse that cannot be altered is installed.
Although these requirements will allow weatherization crews to more easily insulate attics, they also will drive up the costs of insulating these older homes. First, they would require firms to hire an electrical contractor. They may also place liability on the firm, and increase insurance costs to the contractor. It has been suggested that in many cases it may be less expensive to install new wiring in the attic or walls than to inspect the knob-and-tube wiring and assume the liability. Another problem is that often the wiring was overloaded to begin with, and the fuse replaced with a smaller one. This makes the wiring safer, of course, but it is almost guaranteed to result in immediate complaints from the occupants; they can no longer use the toaster when the air conditioner is on, etc.
Since the State Electrical Code was being reconsidered, in November 1990 the California utilities placed a moratorium on the insulation of attics that have knob-and-tube wiring. Under this moratorium, no knob-and-tube attics can be insulated in the utilities' low-income direct weatherization programs. The moratorium also rules out rebates for insulation in knob-and-tube attics and walls, and for services such as free inspections for compliance with local residential energy conservation ordinances.
The moratorium is having a large impact on some contractors in the state. While some larger firms are able to shift their work from one region to another, smaller firms and community action programs that are limited to individual areas consisting of mostly older homes are seriously affected by the moratorium. At press time, it was not known when the utilities will lift the moratorium, or what their post- moratorium insulation policy will be.
The cost of insulating knob-and-tube homes will increase regardless of whether contractors choose to use baffling techniques, or to hire electrical contractors to do inspections or rewiring. These changes may disproportionately affect small insulation contracting firms, since larger firms would more easily be able to absorb these costs or to concentrate their work in different locations. In most areas, attic insulation will remain cost effective, however. Since one out of three homes in the U.S. was built before 1950, knob-and-tube homes are still an important sector of the building stock.
Insulation of attics in older homes through utility programs is effectively on hold right now in California. Utilities there have placed a moratorium on insulating attics where knob-and-tube wiring is present, prompted by changes in the national and state electrical codes. This is having serious effects on many of the utility insulation programs, and will likely have a significant impact on insulation contractors in the state.
Knob-and-tube wiring was the most common form of home wiring before about the mid-1940s. With this type of wiring, the two conductors are completely separated as they run through the house, and join only when they reach the electrical device. Each wire is insulated with cloth and held in place with porcelain "knobs." When the wires run through a joist, porcelain "tubes" are used to keep them away from the wood. Although knob-and-tube wiring is seldom used today, most older homes are still likely to have it.
The concern over insulation of attics with this type of wiring arose with a recent change in the National Electrical Code (NEC). Prior to 1987, the NEC did not mention thermal insulation with knob-and- tube wiring at all. With the 1987 edition, however, NEC Section 324-4 was revised to say "Concealed knob-and-tube wiring shall not be used in... the hollow spaces of walls, ceilings and attics when such spaces are insulated by loose or rolled insulating material." In the 1990 edition, the Code was further changed to exclude foamed insulation, and to specifically exclude only insulation that "envelops the conductors." The stated reason for this prohibition is that the thermal insulation prevents the wires from dissipating heat, which could cause insulation to ignite. However, James O'Bannon, Chair of the Statewide Loosefill Insulation Task Force, performed an extensive survey of all the fires that took place in California over a ten-year period, and found none that were attributed to knob-and- tube wiring.
Since NEC only restricts insulation that envelops the conductors, one way to comply with the code is to avoid placing insulation directly over the wires. This involves either avoiding the cavities that contain the wires, constructing baffles around the wiring, similar to the way baffling of light fixtures is currently done, or laying batts up to, but not touching, the wires. The California Department of Economic Opportunity issued procedures for this type of baffling in the state's low-income weatherization programs. State utilities also adopted these standards for their programs.
Although the procedures allow contractors to insulate knob-and-tube homes safely, this solution is not without problems. Gaps in the insulation, of course, reduce its thermal effectiveness. Detailed baffling and blocking of the wires in an attic is also much more labor intensive, and therefore more expensive, than simply blowing insulation into the whole attic. One weatherization crew estimated that it takes several extra hours to do a knob-and-tube attic in this way. Of course, it should be easy to simply avoid the stud cavities containing wires, which reduces effectiveness but actually saves time. This solution may not be viable for walls where it is much more difficult to baffle the wiring.
Since no fires related to insulation around knob-and-tube wiring had occurred in California, the Insulation Contractors Association (ICA) challenged this section of NEC. The California Department of Housing and Community Development (HCD), which is the state agency with authority to adapt the NEC in order to create the State Electrical Code, met with the ICA, Underwriter's Laboratory, the Electric and Gas Industries Association, the State Building Standards Committee, and the State Fire Marshall to review the Code. As a result of these meetings, on February 15, 1991, they amended the State Electrical Code. The amended code allows insulation that envelops knob-and- tube conductors as long as (among other things) a licensed electrical contractor certifies that the wiring is in good condition, and an appropriately sized fuse that cannot be altered is installed.
Although these requirements will allow weatherization crews to more easily insulate attics, they also will drive up the costs of insulating these older homes. First, they would require firms to hire an electrical contractor. They may also place liability on the firm, and increase insurance costs to the contractor. It has been suggested that in many cases it may be less expensive to install new wiring in the attic or walls than to inspect the knob-and-tube wiring and assume the liability. Another problem is that often the wiring was overloaded to begin with, and the fuse replaced with a smaller one. This makes the wiring safer, of course, but it is almost guaranteed to result in immediate complaints from the occupants; they can no longer use the toaster when the air conditioner is on, etc.
Since the State Electrical Code was being reconsidered, in November 1990 the California utilities placed a moratorium on the insulation of attics that have knob-and-tube wiring. Under this moratorium, no knob-and-tube attics can be insulated in the utilities' low-income direct weatherization programs. The moratorium also rules out rebates for insulation in knob-and-tube attics and walls, and for services such as free inspections for compliance with local residential energy conservation ordinances.
The moratorium is having a large impact on some contractors in the state. While some larger firms are able to shift their work from one region to another, smaller firms and community action programs that are limited to individual areas consisting of mostly older homes are seriously affected by the moratorium. At press time, it was not known when the utilities will lift the moratorium, or what their post- moratorium insulation policy will be.
The cost of insulating knob-and-tube homes will increase regardless of whether contractors choose to use baffling techniques, or to hire electrical contractors to do inspections or rewiring. These changes may disproportionately affect small insulation contracting firms, since larger firms would more easily be able to absorb these costs or to concentrate their work in different locations. In most areas, attic insulation will remain cost effective, however. Since one out of three homes in the U.S. was built before 1950, knob-and-tube homes are still an important sector of the building stock.
