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While insulation is required for all exterior walls in a house, it is not typically required for interior walls. Local and state building codes mandate that new construction homes have adequate insulation in exterior walls and ceilings to suit the local climate.

However, there are several benefits to adding insulation to interior walls. It is excellent for sound-dampening between rooms and can help with temperature control by maintaining a regulated temperature in specific rooms and lowering heat transfer between adjacent areas. Insulating interior walls can also contribute to the overall energy efficiency of your home.

Open-cell foam insulation has a life span ranging between 15 to 25 years when well cared for. However, the material may degrade sooner in areas with high humidity or after prolonged water exposure. Proper installation and maintenance can maximize its longevity but requires close monitoring. Closed-cell foam insulation has a longer life span of 30 to 50 years.

Installing insulation helps reduce energy usage, improve home comfort, and lower utility bills by maintaining stable indoor temperatures year-round.

You do not always need to remove old insulation before adding new. If the existing insulation is in good condition—not wet, physically damaged, moldy, or infested with pests—you can add new insulation directly on top of it for a compounding effect. You can also mix different types, such as adding blown-in insulation around existing fiberglass batts.

However, removal is recommended if the old insulation is compromised by water damage or pests. You should also remove it if you plan to install a different type of insulation, like switching from roll or batt insulation to spray foam. If the existing insulation is very old or damaged, you will likely get more benefit from removing it and starting fresh.