The LESSCO Air Vapor Barrier box is an extension of the vapor barrier or the air-vapor barrier system (depending upon construction techniques).  It is NOT an extension of the electrical system and therefore, does not need to be UL listed. It would be like trying to UL list 6 mil poly!

The electrical box is the item that needs to be UL listed. I believe part of the discrepancy arose when the “airtight electrical box” appeared. That product does need a UL listing as it is designed to take the place of a standard electrical box. By using the LESSCO Air Vapor Barrier box, you are not substituting a UL listed item for one that is not UL listed. You simply use a UL listed “standard” electrical box and mount it inside the LESSCO.

To put it in even simpler terms, if you wrapped the UL listed electrical box with 6 mil poly and attempted to attach it to the vapor barrier to help seal the electrical box, that does not mean that the 12″ square of 6 mil poly needs to be UL rated. The LESSCO is made from Low Density Polyethylene. That is the same plastic resin that is used to manufacture 3, 4, 6 mil and the cross laminated poly’s.

Let’s go even one step farther. When the Canadian double wall or the Alaskanavian strapped wall is used, all electrical boxes on the exterior walls are “inside” the air-vapor barrier envelope. In those techniques, it would seem that those wall systems or at least the poly air-vapor barrier system would need to  be UL listed but are not and do not need to be rated. By using the LESSCO, you are mounting the UL listed electrical box inside the vapor barrier system.

I have found in the past that when the architect or engineer considers the LESSCO as part of the electrical system, they are in error. To repeat, the LESSCO is an extension of the air-vapor barrier system.

When I attempted to have the LESSCO rated by UL, they did not place it in the same category as electrical boxes. If a category existed for UL listing Poly, the LESSCO would be in that category.  But the listing for Poly doesn’t exist, to my knowledge.

~ Stephen Lentz – President
The Low Energy Systems Supply Company, Inc.