Recessed lighting, also known as “can lighting”, refers to lighting that is installed directly into a ceiling or wall. Since its introduction over 60 years ago, recessed lighting has presented a difficult challenge in cold climate construction. Inadequately installed recessed lighting can cause significant problems like ice dams, high energy bills, and moisture damage in the roof due to heat loss and air leaks. This does not mean that it is impossible to air seal and insulate a modern insulation contact (IC) rated, airtight, recessed light in new construction – it simply means that the extra knowledge, workmanship, and expense required to avoid problems often fall short. And in some situations, including those common to cathedral ceilings, the light fixture may inevitably displace enough available insulation space that significant heat losses to the roof surface are unavoidable.
Cold Climate Challenges
In winter time, cold outdoor temperatures create significant air pressure differences between the outside environment and the heated space in a home. As outdoor temperatures get colder, the outdoor air becomes denser. In contrast, as indoor air becomes warmer, it becomes more buoyant relative to the outdoor air. These air pressure differences between indoors and outdoors in winter make the upper regions of a home similar to a balloon that is trying to seal in warm indoor air. The upper region of a home, where indoor air wants to aggressively escape outwards in winter time, is often referred to as the positive pressure zone. The ceilings under the roof of a house generally represent the highest points in the positive pressure zone. Due to the positive air pressures, recessed lighting installed in the ceiling of a home is prone to excessive winter time air leakage and heat losses. To compound matters, light bulbs produce heat and raise the air temperatures around the bulb. Older style incandescent bulbs, for example, may get hot enough to triple the air leakage rate through any holes through, or around the light fixture.
Solutions for New Construction
Fortunately, in new construction, builders and homeowners now have better choices in lighting with fixtures such as surface mount LEDs that can give the appearance of a can light while minimizing the level of detailing needed to insulate and seal around the smaller fixture.
- A junction box compatible surface mount LED fixture only requires an electrical box for mounting. Fortunately, air tight and/or air sealing products for junction boxes are readily available. Since often all that is required is an electrical box to house the lighting, much less insulation is displaced by the fixture.
- A second option is to install 1-½” furring (sometimes called a service cavity) across the ceiling vapor retarder so that all junction boxes can be conventional and do not require air sealing.
Figure 1. Typical non-airtight, recessed “can light fixtures” waste energy in several ways (Source: Improving Recessed Lighting 2011).
Solutions for Retrofits
Due to the widespread problems with recessed lighting in ceilings in cold climates, an entire industry has evolved around products and methods to properly insulate and air seal recessed light fixtures in both new and existing construction.
One overreaching challenge with air sealing and/or insulating existing can lights is the variety of situations an inexperienced DIY’er might encounter. For example, depending on the year and brand of manufacture, different cables will have drastically different temperature ratings. This temperature rating becomes very significant when an existing recessed light gets retrofitted with air sealing and insulation measures since the temperature inside the light enclosure may increase beyond the rating of the cable. Newer lights will have thermal safety switches to turn off the light if the fixture overheats, older lights may not. Additionally, some lights are IC-rated, while some are not. Even lights that are IC-rated may overheat when the wrong bulbs are installed.
Looking forward, one solution to the issue with existing can lights is to replace them entirely by removing them and installing a low profile, surface mounted LED fixture mounted to a junction box. An upgrade of this type may also lend itself well to cathedral ceilings as the junction box can be more readily air sealed and displaces far less insulation volume than the existing can light. Because of the safety considerations involving recessed light retrofit work, CCHRC recommends anyone attempting to replace or retrofit existing can lights consult a licensed electrician to evaluate the various system components for safety.
Source:
Related videos: