Ducts in attics/crawlspaces: sealing and insulation
Avoid losses, condensation and poor comfort when heating/cooling ducts pass through cold or unconditioned spaces.
VERT / GREEN
Map routing, joints, returns and sections outside conditioned space.
JAUNE / YELLOW
Leaky or poorly insulated ductwork can hurt comfort and efficiency even when equipment operates correctly.
ROUGE / RED
Active condensation, wet insulation, crushed/disconnected duct or contaminated crawlspace air drawn into return: correct the cause before simply adding insulation.
Quick triage
What the professional checks
The HVAC professional checks leakage, insulation, jacket vapour control, pressure, airflow, returns, condensation and envelope interaction.
Official sources
Checked 2026-08-23
Continue with the right tools
These links connect this page to the next useful checks and decisions without repeating the full content.
Systems to check before closing the work
V14 connects envelope, air, fire, structure, water and code instead of treating each project in isolation.
Remaining system checks not to miss
V15 covers issues that can block a project, cause a loss or become expensive once concealed.
Advanced diagnostics to cross-check
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Specialized systems to cross-check
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Specialized diagnostics to verify
V18 connects systems that become costly or regulated when a primary project triggers them.
Edge systems to integrate into the project
V19 covers interfaces that become important when multiple home systems interact.
Often-overlooked service interfaces
V26 connects systems that cross utility, plumbing, HVAC, envelope and metering boundaries.
Finish and service details to verify
V28 connects small details that become costly once finishes are closed.