Air duct insulation typically lasts for 10 to 15 years or even longer, depending on the material and maintenance. It's important to conduct periodic inspections to check for signs of deterioration, such as water damage, tears, or general wear. If you find any of these issues, it may be time for repairs or a full replacement. You might also consider upgrading your insulation even if it's in good shape to improve your home's energy efficiency and enhance your HVAC system's performance with newer, more effective materials.

Spray foam insulation can last between 80 and 100 years, depending on the type. Closed-cell spray foam is more durable, while open-cell foam is more susceptible to moisture damage and deterioration. It's important to consult a professional installer to understand which type of foam will be used and its specific longevity. Additionally, be aware that some spray foams can damage plastic piping, so if you have PVC or CPVC pipes, discuss this with your installer.

According to a report from Energy.gov, radiant barrier installations can save between 5% and 10% on your energy bill each month that your HVAC cooling is in operation. That fact can mean savings of up to more than $325 per year for homes that experience frequent direct sunlight and high summer temperatures. 

Don’t install insulation near water heaters, oil burners, or any other object that gets hot. Many insulation materials are fire-resistant, but not entirely fire-proof, so you should take precautions to keep hot things away from fiberglass. This is also why it is imperative to box off lighting fixtures and breaker boxes.