§ 22.22.030. Twenty-five decibel noise level reduction standards.

(A) General. All structures subject to the noise level reduction requirements must conform to this section unless it can be shown by documented tests, or other appropriate information acceptable to the building official, that equivalent performance can be accomplished by other means or methods.

(1)

Brick veneer, masonry blocks or stucco exterior walls shall be constructed airtight. All joints shall be grouted or caulked airtight.

(2)

At the penetration of exterior walls by pipes, ducts or conduits, the space between the wall and pipes, ducts or conduits shall be caulked or filled with mortar.

(3)

Window and/or through-the-wall ventilation units shall not be used.

(4)

Through-the-wall or door mailboxes shall not be used.

(5)

Fireplaces shall comply with the Clark County building code.

(B)

Exterior Walls.

(1)

Performance Standard. Exterior walls shall have a laboratory sound transmission class (STC) rating of at least thirty.

(2)

Prescriptive Standard.

(a)

Masonry walls having a weight of at least twenty-five pounds per square foot do not require a furred (stud) interior wall. At least one surface of concrete block walls shall be of one-half-inch gypsum board or plastered.

(b)

Stud walls shall be at least four inches in nominal depth and shall be finished on the outside with siding-on-sheathing, stucco or brick veneer.

(i)

Interior surface of the exterior walls shall be of gypsum board or plaster at least one-half-inch thick, installed on the studs.

(ii)

In addition to exterior wall covering, continuous composition board, plywood or gypsum board sheathing at least one-half-inch thick shall cover the exterior side of the wall studs.

(iii)

Sheathing panels shall be covered on the exterior with overlapping building paper.

(iv)

Insulation material of at least R-11 shall be installed throughout the cavity space behind the exterior sheathing and between all studs.

(C)

Windows.

(1)

Performance Standard. Windows shall have a laboratory sound transmission class (STC) rating of at least twenty-eight.

(2)

Prescriptive Standard.

(a)

Glass shall be at least three-sixteenths-inches thick.

(b)

All operable windows shall be weatherstripped.

(c)

Glass of fixed-sash windows shall be sealed with a non-hardening sealant or a soft elastomer gasket tape.

(d)

The perimeter of window frames shall be sealed to the exterior wall construction with a weather-resistant sealant.

(D)

Doors.

(1)

Performance Standard. Doors shall have a laboratory sound transmission class (STC) rating of at least twenty-six.

(2)

Prescriptive Standard.

(a)

All exterior side-hinged doors shall be solid core wood or insulated hollow metal at least one and three-fourths-inches thick and shall be weatherstripped.

(b)

Exterior sliding doors shall be weatherstripped. Glass installed in doors shall be at least three-sixteenths-inches total thickness.

(c)

Glass in doors shall be sealed in an airtight nonhardening sealant or in a soft elastomer gasket or glazing tape.

(d)

The perimeter of door frames shall be sealed to the exterior wall construction with a weather-resistant sealant.

(E)

Roofs.

(1)

Performance Standard.

(a)

Combined roof and ceiling construction other than described in this section and the following section (Ceilings) shall have a laboratory sound transmission class (STC) rating of at least thirty-nine.

(b)

Skylights shall conform to an STC rating of at least twenty-eight.

(2)

Prescriptive Standard.

(a)

With an attic or rafter space at least six inches deep, and with a ceiling below, the roof shall consist of one-half-inch composition board, plywood or gypsum board sheathing topped by roofing as required.

(b)

Open beam roof construction shall follow the energy insulation standard method for batt insulation.

(F)

Ceilings.

(1)

Prescriptive Standard.

(a)

Gypsum board or plaster ceilings at least one-half-inch thick shall be provided.

(b)

Insulation at least R-19 shall be provided above the ceiling between joists.

(G)

Floors.

(1)

Performance and Prescriptive Standard. Openings to any crawl spaces below the floor of the lowest occupied rooms shall not exceed two percent of the floor area of the occupied rooms.

(H)

Ventilation.

(1)

Performance and Prescriptive Standard.

(a)

A mechanical ventilation system shall be installed that will provide the minimum air circulation and fresh air supply requirements for various uses in occupied rooms without the need to open any windows, doors or other openings to the exterior. The supply and return ducts serving all conditioned air equipment shall have the first five feet from the exterior of twenty-gauge steel duct including one ninety-degree bend and shall be lined with one-inch-thick coated glass fiber insulation. (Includes attic-mounted equipment.)

(b)

Gravity vent openings in attics shall not exceed code minimums in size and number.

(c)

All vent ducts (except kitchen exhaust ducts) including bathroom and dryer exhaust ducts connecting the interior space to the outdoors, shall contain in the last five-foot length to the exterior a minimum of twenty-gauge steel duct. Each duct shall be provided with a ninety-degree bend in the duct such that there is no direct line of sight through the duct.

(d)

Listed factory-made ducts specifically designed to meet the twenty-five decibel noise/sound attenuation requirement may be substituted for twenty- gauge steel duct.

(e)

Domestic range exhaust ducts connecting the interior space to the outdoors shall contain a back draft damper.

(Ord. 1749 § 2, 1995)