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Insulation R-Values by Climate Zone
Zone 5A: Ceiling R-49, Wall R-20 or R-13+5ci, Floor R-30
Air Barrier & Insulation Installation
Requires continuous air barrier, tested ≤ 3 ACH50 for new construction
Fenestration U-Factor
Zone 5A: U-0.30 max
Vapor Retarders
Class I or II required on warm side in Zone 5A
Basement Wall Insulation
R-15ci or R-19 cavity
Duct Sizing & Installation
Return air must equal supply, max 0.05" static per 100ft
Dryer Exhaust
Max 35ft equivalent, 4" smooth metal duct
Bath Fan Requirements
50 CFM intermittent or 20 CFM continuous
Whole-House Ventilation
0.03 × floor area + 7.5 × bedrooms + 1
Duct Sealing
≤ 4 CFM25/100 sq ft for new, ≤ 8 for existing
Emergency Escape
Min 5.7 sq ft, 24" min height, 20" min width, max 44" sill
Stairway Requirements
Max 7.75" riser, min 10" tread, min 36" width
Guards Required
At 30"+ above grade, min 36" high
Automatic Fire Sprinklers
Required in new 1- and 2-family per MA adoption
Carbon Monoxide Alarms
Required on every level + near bedrooms
Commercial Envelope
Prescriptive R-values by assembly type
Enhanced Requirements for Stretch/Specialized Communities
15% more stringent than base 780 CMR
Performance Path
Simulated performance ≥ standard reference design
Energy Rating Index
ERI ≤ 55 for Zone 5A
Blower Door Testing
CFM50, ACH50, NACH calculations
Combustion Safety
CAZ depressurization test, CO limits
Air Sealing Work Scope
Priority list: attic bypasses, rim joist, etc.
Insulation Standards
Grade I/II/III installation quality