R-values
matched to Tennessee.

R-value measures thermal resistance: how well insulation slows the transfer of heat through it. Higher R-value means better insulating performance. R-13 is the typical value for 2x4 stud-wall batts; R-19 to R-21 for 2x6 walls; R-30 to R-38 for attic ceilings; R-30 to R-49 for cathedral ceilings. R-value is additive in continuous insulation (R-13 + R-5 continuous = R-18 effective). Midway Supply Co. stocks fiberglass batts in R-13 through R-38 across 16-inch and 24-inch widths for Middle Tennessee builders.

Mineral wool (also called rock wool or stone wool) is insulation made by spinning molten rock and steel slag into fine fibers and binding them with resin. It's denser than fiberglass, naturally fire-resistant up to 2,150°F without melting, and significantly better at sound dampening (typical wall STC 45 to 52). Common applications include party walls, sound-isolation walls between bedrooms, fire-rated assemblies, mechanical room walls, and continuous insulation behind cladding. Rockwool is the dominant brand, available at Midway Supply.

Tennessee adopted the 2018 IECC for houses on July 16, 2020, with an amendment that swapped the insulation table for the older 2009 one. Under that statewide floor, climate zone 4 (Nashville, Ashland City, Franklin, Clarksville) is R-13 in a wood-frame wall, R-38 in the ceiling, R-19 in the floor, and R-13 or R-10 continuous on basement and crawlspace walls. The unamended 2018 model table, which energy raters and some jurisdictions use, is R-20 in the wall or R-13 plus R-5 continuous, R-49 in the ceiling, and R-19 in the floor. Ask your building department which it enforces. Midway stocks the batts for either path and reads the wall section with you at the counter.

Faced batts have a paper or foil vapor retarder bonded to one side. The facing goes toward the heated side of the wall (toward the room interior in cold-climate exterior walls). The facing reduces vapor migration into the wall cavity and provides a stapling flange. Unfaced batts are bare fiberglass, used where a separate vapor barrier (poly sheeting) goes over the studs, in interior partition walls without vapor concerns, and stacked over existing insulation in attics. Both are stocked at Midway Supply.

Rigid foam board is a dimensionally stable insulation panel. Three main types: EPS (expanded polystyrene, white beadboard, R-3.6 to R-4.2 per inch), XPS (extruded polystyrene, pink/blue/green, R-5 per inch), and polyiso (foil-faced, R-6 to R-6.5 per inch). Used for foundation insulation, continuous insulation over wall sheathing, roof deck insulation, and crawl-space encapsulation. Polyiso has the highest R-value per inch but loses some R at very cold temperatures. Midway carries all three types.

Blown-in insulation (loose-fill fiberglass or cellulose) typically provides better coverage in irregular attic spaces. It fills around top plates, electrical penetrations, and odd geometries that batts can't conform to. Batts go faster on flat, accessible attic floors with consistent joist spacing. Blown-in cellulose has slightly higher R-value per inch and better air-sealing than fiberglass. Many attics combine both: batt-cap over a bottom layer of blown-in. Midway sells loose-fill bags and refers the install crew.