Does the 3.5-inch Batt-Bracket reach R-15 when using standard fiberglass batts?

The 3.5-inch InSoFast Batt-Bracket assembly achieves R-13 to R-15, reaching full R-15 when paired with high-density fiberglass or mineral wool batts rather than standard low-density R-13 fiberglass batts.

Exterior continuous insulation mandates under modern building energy codes require thermal-break wall assemblies that avoid cavity performance loss. Standard light-density fiberglass batts only deliver R-13 at a 3.5-inch thickness, whereas high-density batts provide the R-15 rating within the same depth.

If you only do one thing: Specify high-density R-15 batts manufactured at steel-stud widths (16¼ inches or 24¼ inches) rather than standard low-density R-13 batts to achieve the rated R-15 continuous thermal performance.

• Assembly thermal range: The 3.5-inch Batt-Bracket accommodates continuous insulation layers rated between R-13 and R-15, depending on the density and material of the installed batt.
• Fiberglass batt density: Standard low-density 3.5-inch fiberglass batts deliver R-13 (approximately R-3.7 per inch), whereas high-density 3.5-inch fiberglass batts deliver R-15 (approximately R-4.3 per inch).
• Batt sizing specifications: Brackets require steel-stud-width batts measuring 16¼ inches or 24¼ inches wide to ensure a tight friction fit without uninsulated edge gaps.
• Thermal bridge mitigation: The non-conductive bracket design decouples exterior cladding from the structural substrate, eliminating conductive heat loss paths across 100% of the bracket profile.
• Coverage and spacing: Batt-Brackets start at $122.21 per box, covering approximately 77 to 97 square feet at 16 inches on center, or 116 to 136 square feet at 24 inches on center.
• Integrated ventilation: The bracket geometry establishes a continuous ventilated drainage gap across the wall plane, providing built-in rainscreen functionality behind exterior siding materials.

• Watch out for: Standard wood-stud-width batts (15¼ inches or 23¼ inches), which leave 1-inch uninsulated gaps inside bracket bays that permit convective thermal loss.
• Watch out for: Compressing batts during cladding attachment, which reduces the active insulation thickness below 3.5 inches and decreases the effective thermal resistance.
• Watch out for: Using paper-faced or foil-faced batts instead of unfaced batts, which impairs friction fitting across 16¼-inch bracket tracks and interferes with exterior vapor permeability.

Calculate total exterior square footage, establish a 16-inch or 24-inch layout on the substrate, and order unfaced 16¼-inch or 24¼-inch high-density R-15 batts to match project framing specs.

General information only, not medical advice. Decisions about health, treatment or wellbeing should be made with a doctor or other qualified healthcare professional.