Attic insulation and airtightness work together to improve comfort, reduce energy bills, and extend HVAC life. Proper insulation minimizes heat transfer through the attic floor or roof, while airtightness prevents conditioned air from escaping and unconditioned air from infiltrating. Seal gaps around chimneys, vents, recessed lights, and attic access to stop drafts. Choose insulation type and R-value based on climate and local code; ensure continuous coverage without compression. Combine insulation with a controlled ventilation strategy and a professional blower-door or infrared inspection to verify performance. Together they stabilize indoor temperatures, lower moisture risks, and enhance overall home efficiency.