Electricity: conductors and insulators – Boxes and housings
Reexamination Certificate
1999-05-20
2001-05-29
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Boxes and housings
C174S058000, C220S004020, C029S854000
Reexamination Certificate
active
06239365
ABSTRACT:
BACKGROUND OF THE INVENTION
Residential and commercial building codes have been changing in recent years to require higher levels of efficiency in the heating and cooling of buildings. The most effective way to lower heating and cooling costs is to raise the level of insulation in walls and ceilings and to suppress the movement of air known as infiltration. In typical residential construction, insulation, generally batts of fiberglass insulation, is used to fill the space between the studs, thereby creating small pockets of immobilized air, which decrease the thermal conductivity of the walls. A vapor barrier, often a sheet of polyethylene, is then secured to the inside of each wall. In order to be completely effective, the vapor barrier must suppress the movement of air and water vapor through all of the walls, ceilings and floors of the building structure or residence so that a separate environment or envelope is created within the building structure. However, any penetrations or openings in the vapor barrier provide passage ways for water vapor or conditioned air. Because of the number of electrical outlet boxes that are used in modern homes, and the need to penetrate the vapor barrier to provide electricity using state of the art electrical outlet and electrical junction boxes, there is great potential for the creation of a significant number of passage ways in the vapor barrier for infiltration or escape of water vapor or conditioned air, resulting in an inability to adequately provide such a separate environment and an inability to adequately provide for efficient control of the environment within the building structure.
In building energy efficient housing, one faces many obstacles. The main obstacle is being able to find affordable and readily available components with which to complete the assembly of the structure. As noted above, one area requiring attention to detail is electrical outlets in exterior walls. The average new home has probably at a minimum 25 such exterior wall outlets and maybe as many as 50. Using conventional outlet boxes
5
, shown in
FIGS. 10 and 11
, with air leaking in or out at all wiring perforations
8
and all around the front edge of the outlet box the inevitable heat loss is considerable.
Air flow, or the passage of air from one environment to another, occurs whenever there is a pressure gradient across a wall and a path for air to follow. Air is generally lost outwardly through the walls during heating seasons because, as the air inside the building is heated, the air pressure increases, creating a pressure differential which forces the heated air through any perforations in the vapor barrier. Just the reverse happens when it is warm outside and air conditioning is used on the inside to lower the temperature and, perhaps, the humidity. In this case, the inside of the building will actually have a negative pressure differential in relation to the outside environment, such that warm outside air may pass inside or infiltrate through any openings in the vapor barrier to balance the pressure differential. Whenever the inside air is heated or cooled, a pressure differential will be created between the inside environment and the outside environment causing a movement of air either inwardly or outwardly through any openings or penetration in the vapor barrier. This movement is further exacerbated by wind creating a positive pressure on the windward side and a negative pressure on a leeward side of a building.
Moisture, generally conveyed by the air, passes through walls in the same manner. Whenever there is a difference between the outside humidity and the level of humidity inside, a vapor pressure is established. This vapor pressure can be significant, especially during winter months in colder climates when the outside air is extremely dry. Under such conditions, the moisture inside the building is generally driven outside through any existing penetrations in the walls in response to a differential in the humidity level, regardless of the actual air pressure inside and outside of the building. In northern climates, where the outside temperature is below freezing, the effects of moisture passing through the walls can be very detrimental. As water vapor passes through a wall, the temperature in the wall will drop to the temperature outside of the building, from a temperature equal to that of inside the building, over the distance from the inside to the outside of the wall. Following the downward sloping temperature gradient, the moisture in the air first condenses into water droplets. At some point in the wall, the temperature drops below freezing and an ice barrier forms. This wall of ice not only results in destructive forces due to the expansion of the water as it freezes, but it also contributes moisture to rotting processes through moisture retention which continues to destroy wooden structures in the warmer periods of the year.
During warmer months, air movement through the walls can also result in the retention of moisture in some building materials due to their hygroscopic nature. Moisture passes through the walls and the backside of the siding material and often stops when it gets to painted surfaces. The moisture can then build up between the paint and the backside of the siding, causing the paint to blister and peel. Damage of this kind, along with the increased heating and cooling costs associated with air and water vapor infiltrations and escapes of the kind seen in typical residential housing, have led to many of the changes in building codes which have occurred in recent years.
It will be understood therefore, that in order to efficiently control the temperature and moisture levels in both residential and commercial building structures, and in order to prevent damage to structural aspects of the respective buildings, there is a need for a way to stop the passage of air and moisture through the walls of building structures . More specifically, in order to do this, there is a need to prevent the loss of vapor barrier integrity through and around electrical outlet and electrical junction boxes. Many attempts have been made to effectively and efficiently stop air movement at electrical outlet boxes.
Some builders use conventional electrical outlet boxes in conjunction with a separate poly box with a flange to provide a means to fasten the vapor barrier to the outlet box. This system requires two separate components, however. Another method is an outlet box with a ring that makes a seal between the vapor barrier and the electrical box, and the wiring penetrations are sealed with a neoprene strip. The problem with this system is that drywall applicators typically use a router to cut outlet openings and the vapor barrier will be cut and destroyed around the entire perimeter of the outlet box. Still another method is a one piece electrical box with a flange for making the connections between the vapor barrier and outlet box. This system does not adequately address the electrical penetrations at the rear of the box where a significant amount of air leakage can occur. These attempts have been largely unsuccessful at either stopping the air flow near the wiring or around the box, or at providing a cost-effective solutions which can be installed quickly and easily, so as to be more likely to be effectively used.
A number of patents disclose similar solutions to these problems. Balkwill et al. (U.S. Pat. No. 4,158,420) disclose the use of conventional electrical outlet boxes in conjunction with a thin flexible cover. After the outlet box is installed, the thin plastic cover is placed over the box and nailed to a stud. Holes are then punched through the thin plastic to receive the wires. A true vapor seal is not achieved either around the box or around the wires.
Lentz U.S. Pat. No. 4,757,158) teaches the use of rigid boxes with flanges that cover a conventional electrical outlet box. The flanges provide a surface on which the vapor barrier can be glued, providing an effective seal around the boxes. However, like the Balkwill solution, air can
Moore & Hansen
Patel Dhiru R
Reichard Dean A.
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