All fuel-fired appliances must be direct-vent / sealed-combustion / power-vent (no atmospheric-draft inside the envelope)

Description

All combustion appliances within the conditioned space must be direct-vent, sealed combustion, OR power-vented (not atmospheric or natural-draft). Atmospheric water heaters and furnaces are NOT compliant inside the air barrier. Solid-fuel-burning appliances (wood stoves, fireplaces) must be EPA-certified AND have outside combustion air ducted directly to the firebox. Garage-attached homes require a tightly sealed door + air barrier between the garage and dwelling.

Why this exists

Atmospheric-draft appliances backdraft in tight homes, pulling CO + combustion gases into the dwelling. Direct-vent appliances eliminate the issue entirely. Architects designing modern tight envelopes should specify direct-vent water heaters + furnaces by default; the small first-cost premium pays back through eliminated CO risk and simpler combustion-air design.

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Source

Solver enforcement

Browsable only — the solver does not currently enforce this directive (no spec-level data to check against). This entry exists so the architect personas can cite it in conversation and the user can read what the rule says.

Related directives

• Cathedral ceilings: gable-end wall stud must extend to roofline (no hinge at top plate) · HUD RSDG §5.6.2
• In high-wind zones, soffits need solid blocking at exterior walls · HUD RSDG §5.6.5
• Sill-plate anchor bolts: 1/2" diameter @ 6 ft on-center, max 12 inches from corners/splices · HUD RSDG §7.4.3
• Ramps over 6 inches rise must have handrails on both sides · HUD FHA Design Manual Chapter Two §2.8
• Floor surface vertical changes: 1/4 inch max vertical; 1/2 inch max with 1:2 bevel · HUD FHA Design Manual Chapter Four §4.2