Q: We live in a two-story house that has recessed floodlights in the first-floor ceiling and have been told that we cannot add insulation to the second-story floors because of the floodlights.

We plan to build a two-story house with lots of recessed lighting. How do you use recessed lights and still soundproof the floors?

A: We love recessed lighting and have put a lot of it in over the years. When installed properly, it does its job, it looks good and, at $10 or so a fixture, it’s inexpensive.

When you say “soundproof,” we hope that you are asking how to limit the sound transmitted between floors, not totally stop it.

Eliminating sound on the ground floor created by foot traffic on the second floor is virtually impossible and definitely impractical in a residential application.

Although recessed lighting (we call them cans) is an obstacle because of the heat it generates, the problem is not insurmountable. We suggest you approach sound attenuation in the following manner.

First, and most important, you must check the manufacturer’s specifications for the fixtures to determine the distance recommended between the fixture and combustible material.

Such material includes the framing and any insulation you may install in the plenum (the open area between the framing members).

We think your best bet is to buy IC-rated cans. These recessed housings cost a little more than the nonrated ones, but because they allow direct contact with insulation they eventually will pay for themselves in energy savings.

The trade-off is that most likely you won’t be able to use as high a wattage light bulb as you could with a non-IC fixture.

If you go with non-IC cans, decide where you will put each housing and install blocking between the floor joists to create a space for each fixture. Drill holes in the blocking or joists through which to run the electrical cable.

You can then install insulation in the cavities that don’t contain the cans.

This will help with sound reduction. But this is not the whole story.

There are two types of sound affecting the noise level in a structure:

  • Airborne sounds are created by sound waves traveling through the air. An example might be the sound of a jet plane.

  • Impact sound is the noise transmitted by impact within a building. Examples are leather-soled shoes walking on a hardwood floor, or a piece of furniture being dragged across tile.

Sound reduction in buildings is affected by choices you make in the floor system (carpet, wood or tile), the substrate (plywood, lightweight concrete), the ceiling below (gypsum board) and any insulation in the plenum.

Sound transmission, whether it is impact sound or airborne sound, can be limited to a greater or lesser extent depending on which materials you select for these components and how they are installed.

For more information on this subject, check out these two Web sites: www.thetiledoctor.com, a publication of Ceramic Tile Institute of America; and www.regupol.com, a company that makes a buffer to be installed under a ceramic tile floor.


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