Recessed Lights Require Extra Attention

For dramatic downlighting that really shows off a new home, recessed lights can’t be beat. For some home buyers, these inexpensive fixtures are a hallmark of elegance. Being hidden is one of their advantages, but recessed lights also have three hidden drawbacks.

First, standard recessed fixtures cannot come into contact with insulation, so extra time and expense must be expended to install a baffle that holds insulation at least three inches away from the fixture. This gap in the insulation can allow a lot of heat to escape. Special fixtures– designated as “IC”– overcome this problem, because they are designed to be covered with insulation.

Even when covered with insulation, IC fixtures can leak indoor air—carrying away heat and transporting moisture into attics.

But even IC models often lose heat another way– through air leakage. This is the second drawback of recessed lights. Heat generated by the light creates a “stack effect” that pulls heated air out of the living space. In some IC fixtures, the housing has a variety of holes and seams. Covering the assembly with insulation does little to stop air movement through holes and seams or around the housing.

The third drawback is related: air leaking out of the house carries water vapor. As this air moves into the attic, it cools and the vapor condenses onto roof framing and sheathing. In well-ventilated attics, including cathedral ceilings made with scissors trusses, this moisture shouldn’t cause major problems.

However, in true vaulted ceilings—where the insulation and ventilation are enclosed completely in the space between rafters—cool surfaces are only inches from the fixture. To make matters worse, vaulted ceilings often have only the bare minimum of ventilation to carry away the moisture.

Specs for recessed lights
In an effort to minimize these problems, Super Good Cents specifications restrict the type and number of recessed lights. These restrictions apply only to insulated ceilings where heat loss and moisture accumulation will occur. No restrictions apply to uninsulated ceilings, such as the first floor of a two-story house.

• One IC-rated fixture is allowed for every 400 square feet of insulated ceiling area.
• Recessed fixtures may be installed only in ceilings below ventilated attics, including areas with scissors trusses.
• Recessed lights are not allowed at all in true vaulted ceilings.

To get more lights
However, due to their popularity, many utilities have interpreted the standards to accommodate recessed lights. They have developed techniques that allow builders to exceed the one fixture to 400 square feet restriction.

These techniques fulfill two requirements. First, heated air and water vapor must be prevented from escaping through the fixtures. Second, the R-value of the insulation above the recessed fixture must be the same as the rest of the ceiling.

Using one of the four installation methods below should allow the local utility to approve recessed lights in any type of ceiling. Before you try any of these, be sure to contact your Super Good Cents representative for local requirements.

This article appeared in Energy Source Builder Vol. I No. 3, June 1989,
©Copyright 2008 Iris Communications, Inc.