Construction Materials-Recessed Lighting

Recessed lighting, sometimes called a recessed can or recessed luminaire has been a very popular lighting choice for many years.  When I worked as an electrician, I installed thousands of this type of light fixture.  Advantages of this type of lighting are several different fixture sizes, trim options and trim colors, and a low profile, clean look.  There is one big disadvantage though, which I will get to in a bit.

Typical recessed light fixture.

The typical recessed light fixture consists of a metal housing which includes a junction box for the electrical wiring and a light bulb socket.  Some models also have a safety device to prevent overheating.  More on that in a minute. The metal housing is typically attached to the framing of the building with the fixture extending into the floor above or attic space.  Only the decorative trim and bulb are visible from below.  The bulb is usually a flood type, but some trim options have a non-replaceable bulb manufactured into the trim.

The building and electrical codes have a couple requirements regarding recessed light fixtures.  First the building code. The 2012 International Residential Code states:

N1102.4.4 (R402.4.4) Recessed lighting. Recessed luminaires installed in the building thermal envelope shall be sealed to limit air leakage between conditioned and unconditioned spaces. All recessed luminaires shall be IC-rated and labeled as having an air leakage rate not more than 2.0 cfm (0.944 L/s) when tested in accordance with ASTM E 283 at 1.57 psf (75 Pa) pressure differential. All recessed luminaires shall be sealed with a gasket or caulk between the housing and the interior wall or ceiling covering.

The key points of this code reference are all recessed light fixtures installed where they penetrate the building’s thermal envelope must be air sealed and listed as an IC-rated fixture.  An IC-rated fixture, IC meaning insulation contact, will have a thermal overload cut-out device that will automatically turn off the bulb if too much heat is created within the fixture.  This type of fixture is allowed to be covered with insulation.  Non-IC-rated fixtures are only permitted to be installed when not in direct contact with insulation, such as between two floors within the building envelope or when installed in soffits.  This code also requires the manufacturers of the fixtures to achieve an air leakage rate of no more than 2 cfm @ 75 Pa, this test is conducted by the manufacturer or independent testing laboratory.

Recessed light fixture after installation. Tag states bulb sizing and IC or non-IC rating of fixture.

The electrical code requirements are listed in the National Electric Code in articles 410.110 through 410.122.  These codes cover installation temperatures, clearances, wiring conductors and manufacturer requirements for this style fixture.  There is also a code requiring accessibility of the electrical conductors after installation.  The National Electric Code states:

314.29 Boxes, Conduit Bodies, and Handhole Enclosures to Be Accessible. Boxes, conduit bodies and handhole enclosures shall be installed so that the wiring contained in them can be rendered accessible without removing any part of the building or structure…

A recessed light fixture contains a junction box where the electrical connections are made.  This junction box must be accessible after installation from within the conditioned space (some attics are inaccessible after construction, access to the wiring connections can only be achieved from the room or space they service).  For this reason, recessed light fixtures cannot be spray foamed or otherwise sealed in place without some protection to access the junction box.  I have had conversations with building inspectors that were not aware of this electrical code.  Spray foaming a recessed light fixture may also run the risk of over-temperature within the fixture causing the over-temp safety device to turn off the bulb.

Air sealing recessed light fixtures can be challenging, which is the biggest disadvantage of this style of lighting.  Un-sealed recessed cans can leak conditioned air into the attic space, which can cause moisture to accumulate on the underside of the roof.  When used in vaulted ceilings, the displacement of the insulation can lead to melting snow in areas on the roof.  Ice damming and roof damage may result.  Then there is the heat loss, causing the energy penalty.  Back when I worked as an electrician, it wasn’t uncommon to install 30 or more recessed cans in a new home.

Air sealing recessed cans requires the use of mastics, gaskets, or tape to seal the can’s housing to the air barrier is required by the building code.  This air sealing technique will reduce the air leakage around the housing of the fixture, but not eliminate the leakage through the interior of the fixture.  The fixture is permitted to have a maximum leakage rate of 2 cfm @ 75 Pa or roughly 1.5 cfm @ 50 Pa, which is the pressure achieved by the blower door test.  If 20 recessed cans were installed within the home, all with a 1.5 cfm leakage rate, a total leakage rate would be 30 cfm and could mean failing the blower door test.

Thermal imaging of recessed light fixtures during a blower door test.

Several options of recessed can covers are available.  These covers are installed over the top of the recessed can housings and sealed to the air barrier, reducing the air leakage through the housing.  Recessed can covers will work both in new construction and can be retrofit in existing installations. Insulation is then installed over the box.  This option works well if there is enough space in the attic to install the box and still achieve the required R-value insulation level.  Many times, this cannot be achieved in vaulted roof assemblies.

The best option is not to install any recessed light fixtures where they penetrate the air barrier.  There are several manufacturers producing light fixtures that resemble the look of the recessed fixture but install into a standard shallow electrical box.  All the fixtures of this style I have seen utilize an LED bulb.  Much easier to install, air seal, and are energy efficient.

One last piece of advice regarding recessed lighting, be sure to use the proper bulb.  I have been in many homes where a standard incandescent light bulb is used in this type of fixture and the homeowner questions why the bulb “blinks”.  The reason is the fixture heat sensor is overheating caused by the wrong bulb style or a bulb with too high of a wattage.  I always recommend using an LED style bulb in all recessed light fixtures.

I recently took training on fire protection and the presenter, a well known independent fire investigator from the upper Midwest, showed several photos from fires that started with recessed light fixtures in direct contact with cellulose insulation.  One fire had IC rated fixtures and the proper size bulb installed.  Changes when using cellulose insulation with IC rated recessed light fixtures may be coming.

E-mail me if there is a topic you would like to discuss, need further explanation, or disagree with something I’ve said. I’d like to hear your comments.

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