· by Michael Blair, Nashville's Electrician
Most people asking about recessed lighting are picturing the room: how many, how far apart, what color of light. The part that decides whether the job is done right is above the ceiling. On a single-story house, or the top floor of any house, the can sits in the boundary between the conditioned rooms and a hot attic, with insulation on one side and a light source inside it. The housing’s rating decides whether that insulation is allowed to touch it and how much household air it lets through. This post covers what those ratings mean, what the code says about each, and what we do with older cans already in a ceiling, which is a regular part of the recessed lighting and outlet work our electricians take on.
What IC and ICAT mean on a housing
Every recessed housing carries a label inside it. The two letters to look for are IC, for insulation contact. A non-IC housing is built on the assumption that air can move around it and carry heat away. The Building America Solution Center’s recessed lighting code brief, published by Pacific Northwest National Laboratory for the Department of Energy, summarizes the electrical code this way: a non-IC fixture has to keep its recessed parts at least 1/2 inch from anything combustible, and insulation cannot be installed above it or within 3 inches of its housing, wiring compartment or other electrical parts. A Type IC fixture is allowed to touch combustibles and to sit fully buried in insulation.
The AT in ICAT stands for airtight. An IC housing that is not also airtight still has gaps and holes in it, and on a ceiling under an attic each one is a small chimney. In summer the attic over a Middle Tennessee house gets far hotter than the rooms below it, and the air-conditioned air in the rooms finds its way out through whatever openings the ceiling has. A row of leaky cans down a hallway adds up. An ICAT housing is tested and labeled for how little it leaks, and it is the one we put into any ceiling with an attic over it.
What the energy code adds to the electrical code
The electrical code is concerned with heat and fire. The energy code is concerned with air, and it goes further. As the same PNNL brief lays it out, using the 2015 IECC and IRC, a recessed light installed in the building’s thermal envelope has to be IC-rated, labeled as leaking no more than 2.0 cubic feet per minute when tested to ASTM E 283 at 75 pascals of pressure, and sealed to the ceiling with a gasket or caulk between the housing and the drywall. The brief notes those requirements have not changed across the last three editions of those codes. In practice that means an IC housing alone is not the finish line; it has to be the airtight kind, and it has to be sealed where it meets the ceiling.
Which editions apply depends on where the house is. The Tennessee State Fire Marshal’s list of currently adopted codes shows the 2017 National Electrical Code adopted statewide, with a few Tennessee exceptions. In Davidson County, Metro Codes announced that the Council adopted the 2024 International Code Council building, trades, accessibility and energy standards, effective July 16, 2025 for plans and applications submitted after that date. Williamson, Rutherford and the other counties around us run their own permit offices, and we check what the local office enforces before we pull a permit, rather than assuming one county matches the next.
- Non-IC: keep insulation 3 inches away and none on top
- IC: insulation may cover it, but it may still leak air
- ICAT: insulation may cover it and it is labeled for low air leakage
- Any of them under an attic: sealed to the drywall with a gasket or caulk
Older cans already in the ceiling
A lot of houses around Nashville and Davidson County have recessed lights that went in before airtight housings were common. Some are non-IC cans that were later buried when someone blew more insulation into the attic, which is the combination the code clearance exists to prevent. Others are non-IC cans with a gap of bare drywall around them, where the insulation was pulled back properly and the attic now leaks air through every one. You can usually tell from the attic side: look for a housing with insulation packed against it, or a ring of exposed ceiling around it.
The Building America guide on insulating and air sealing existing non-ICAT recessed lights says the best fix is replacing them with ICAT-rated housings, or with LED fixtures that mount at the ceiling and need no can at all. That is what we recommend in most cases, because it settles both the heat question and the air question in one step. Where replacing is not practical, the guide describes building a fire-rated enclosure over each can, such as a box of 5/8-inch fire-code gypsum, with at least 3 inches of clearance on every side, sealed flush to the ceiling drywall, tall enough to rise above the insulation and open enough at the top to let heat out. It specifically warns against rigid foam boxes, which do not carry a one-hour fire rating, and against air sealing a can from the room side, because that traps heat in it.
Two more cautions from the same guide matter to an electrician. A non-IC can that gets enclosed should not keep running incandescent or halogen bulbs; it should be switched to LED or CFL first. And the wiring feeding older cans needs a look before anything is closed up around it, because older NM cable without the B rating has a lower temperature limit than modern cable. Our post on what old wiring in Nashville homes means covers what that wiring looks like and when it becomes a larger job.
What we check on a recessed lighting job
When we quote recessed lights for a ceiling under an attic, we go into the attic first. We look at the joist depth and direction, how much insulation is up there and what kind, whether there are existing cans and how they are rated, and what wiring we would be tying into. That tells us whether new-construction housings, remodel housings or ceiling-mount LED fixtures make sense, and whether any old cans should come out while we are there.
On the install, the housings we set under an attic are IC and airtight, the trim is gasketed or the gap caulked to the ceiling, and the insulation is put back over them rather than left pulled away. Where we are adding fixtures to an existing circuit, we check what else is on it before adding load. If you already have cans with a light that cuts out after it has been on a while, that can be a non-IC housing’s thermal protector tripping from heat, and it is worth having looked at; our post on flickering lights and when they are dangerous covers the other reasons lights cut in and out.
If you are planning new recessed lighting, or want to know what is above the ones you already have, ask us for an estimate and we will start in the attic.
Sources
- Building America Solution Center (PNNL), Recessed Lighting Code Compliance Brief — NEC 410.116 clearances for IC and non-IC fixtures; IECC/IRC requirement for IC-rated, labeled airtight (2.0 cfm at 75 Pa, ASTM E 283) and sealed fixtures in the thermal envelope.
- Building America Solution Center (PNNL), Insulating and Air Sealing Existing Non-ICAT Recessed Lights — Replacing old cans with ICAT or ceiling-mount LED fixtures; fire-rated enclosure method; no rigid foam boxes; LED before enclosing; older NM cable temperature limit.
- Tennessee State Fire Marshal’s Office, Currently Adopted Codes — 2017 NEC adopted statewide with Tennessee exceptions.
- Metro Nashville Codes, Metro adopts 2024 International Building Codes — 2024 ICC building, trades, accessibility and energy standards effective July 16, 2025 in Davidson County.