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In order to know the building's true thermal performance, you must calculate overall R-values for assemblies like walls, roofs, floors, and glazing. Thermal resistance adds differently if it is in series or parallel.
Thermal insulation is a material that blocks or slows the flow of heat through the building envelope. Insulation is vital to most green building design because it allows spaces to retain what heat they have, while avoid gaining excess heat from outside. Learn how to measure insulation and about different types of insulation.