What are the problems with recessed lighting?
While they are an elegant alternative to a chunk of metal fastened to your home’s ceiling, cutting a hole into your drywall and sticking a hot light into it HAS to cause some issues, right?
The Architect And The Auditor
One of my closest friends is an architect, meaning he is in the business of building aesthetics. I’m an energy auditor meaning I’m in the business of building efficiency (at least heating and cooling); we often don’t quite see eye to eye. He wants beautiful buildings and while I certainly don’t want ugly ones, an airtight, well insulated box does appeal to my little energy auditor heart.
Now, I don’t ever recall Greg and I arguing about recessed lighting (we’re more apt to just drink a pitcher of beer and let the issues lie) or ever discussing them. But it’s the type of conversation we would have. It’s also indicative of how the larger move toward modern aesthetic look challenges making those buildings energy efficient. Adding complicated framing, green elements like green roofs or full wall windows make improving the thermal, vapor and air control layers a challenge.
The Problems With Recessed Lighting
Recessed lighting is a version of this found everywhere in modern homes. 50 years ago ceiling lighting was limited to a squat assortment of lamps bolted into the ceiling. They were not an attractive bunch so it was inevitable a more asethetic choice would crop up.
Recess lighting is a light fixture installed into a hole in the ceiling (aka the air barrier). Anyone else see where this will be a problem? Recessed lighting come in two flavors: insulation contact (IC) and non-insulation contact (Non-IC). The name is right there on the tin…Non-IC recessed lights put out too much heat to safely have them in contact with insulation. IC recessed lights are a lower wattage (and less hot) and can safely remain in contact with insulation.
You can see where this is going. You’ve avoided something as gauche as an overhead lamp or *gasp* track lighting, but you’ve punched a 6-inch hole through your ceiling. Non-IC recessed lights require a 3-inch clearance around the lighting can, the junction box and insulation meaning a 12-inch hole through your thermal envelope. Insulation contact recessed lights are better; at least you can insulate right up to the can light.
The same heating issues stymie efforts to airseal the giant hole punched in your ceiling. Even IC recessed lights generate a fair amount of heat. One approach (that is not recommended at all) involves building a box over the recessed light and air sealing it to the ceiling drywall. Try putting an incandescent bulb inside a small box; what happens? It gets really, really hot. Hotter than you’d want anywhere near any paper or wood. So that’s no fun.
Fortunately, because of the heating issues inherent to recessed lighting, UL approved recessed lighting have thermal protection switches built in. If the heat reaches a set point, it automatically turns off the fixture.
Your Best Options With Recessed Lighting
What is your best option for a recessed light to be airtight and insulated? Well, can I interest you in some nice track lighting? Yes, the best way to insulate and airseal recessed lights is by not having them.
However, like an enormous bay window overlooking the mountains, not many folks would want to board it up, insulate and sacrifice the view in the name of heating efficiency. Not likely. Given the options most home owners like their recessed lights.
Many lighting manufacturers now make models where the lighting housing is sealed. The next best option then becomes installing sealed IC recessed lights and caulking it tight against the ceiling drywall. Once caulked you can absolutely bury it under a mountain of loose rockwool which has a melting point north of 2500 F.
From an energy standpoint, recessed lights can be a real pain in the butt. A ceiling built with many recessed lights are nearly fatally flawed (check out this article where we discuss vented attics). With so much airflow, it practically defeats the purpose of a roof (at least it keeps off the rain). However, mixing recessing lighting with other lighting fixtures can minimize their number while creating more nuanced lighting effects. Those recessed that are installed should be sealed IC fixtures, allowing an air seal and complete insulation. Using the best building practices and materials can help create a beautiful home and avoid the worst problems with recessed lighting.