Floor Design Can Cut Down Overhead Noise
QUESTION: We plan to build a two-story room addition and we want the floors as soundproof as possible. Will adding fiberglass insulation under the second floor help and will it reduce our heating and cooling bills?
ANSWER: There are several designs of floor/ceiling construction that can greatly reduce noise transmission through the floors. There are also some simple improvements and products that you can add to existing floors to reduce the noise transmission between them.
Most of the designs use some type of insulation sandwiched between the floor and ceiling. The actual energy saving from the addition of the second-story-floor insulation is minimal.
When you compare the level of noise transmission through a floor, there are two index ratings--sound transmission class (STC) and impact isolation class (IIC). The higher the index ratings, the quieter the floor.
The STC rating ranges from 37 for standard wood floor construction to 59 for the quietest floor construction. The IIC rating ranges from 34 to 72. For example, at an STC of 35, loud speech is heard, but not intelligible through the floor. At an STC of 50, loud speech is not audible at all.
One of the quietest floor construction designs utilizes (from top down) carpet, pad, half-inch underlayment, half-inch sound board, five/eighths-inch subfloor, 2 x 10 floor joists with three-inch fiberglass batt insulation, soundproofing resilient channel, and five/eighths-inch gypsum board ceiling.
Another design, which greatly reduces impact sounds such as footsteps, uses a 1 5/8-inch thickness of special lightweight cellular (foamed) concrete over the subfloor. The mass of the concrete deadens the noise.
Special long-span trusses instead of joists for the floor are effective for soundproofing. You can purchase either all-wood trusses or ones with a steel reinforcing web between the wood support members. Both types of trusses weigh less than standard wood joists.
There are some new materials that you can use during construction or to quiet existing floors. Soundproofing carpet board, in half-inch and five-eighth-inch thicknesses, can be laid under the carpet and pad. There is also some special sound-control matting made of a mesh of extruded nylon filaments that form a three-dimensional geomatrix.
You can write to me at the address below for Utility Bills Update No. 305 showing diagrams and descriptions of 16 different soundproof floor construction designs and the STC and IIC ratings, tips on soundproofing existing floors and walls, and information on the new floor soundproofing products. Please include $1 and a self-addressed stamped business-size envelope.
Film Can Protect Roof From Solar Collectors
Q: I am going to have my house reroofed and I plan to install solar collectors at the same time. What is the best way to install the solar collectors to minimize the possibility of leaks?
A: You should definitely use metal framing to tilt the collectors at the proper angle. Trying to flash wood supports on to a new roof is bound to fail and result in leaks. The wood will not last as long as the new asphalt shingles.
You should consider using an industrial-type of single-ply rubber-like EPDM film roofing system under the solar collectors. The metal frames can be mounted directly over the EPDM film and secured to the roof sheathing below. This should last as long as the rest of your roof.
Letters and questions to Dulley, a Cincinnati-based engineering consultant, may be sent to James Dulley, Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, Ohio 45244.
