Insulating windows involves sealing and insulating gaps to prevent air leakage and improve energy efficiency. Caulk and weatherstripping seal cracks, while foam insulation fills larger voids. Window film reduces heat transfer. A staple gun, caulk gun, and weatherstripping tool are necessary for installation. Professionals such as installers, contractors, and inspectors can assist in insulation and inspection. Organizations provide standards and ratings for window efficiency. Concepts like thermal insulation, air leakage, and heat gain/loss are crucial in understanding energy efficiency.