New insulated doors are usually foam-filled and are more efficient than solid wood doors. Weatherstripping should be a high-performance durable material that forms a continuous tight barrier against air leakage.
In retrofit applications, the door and frame can be replaced with a factory-made, core-insulated, pre-hung unit. As a rule, these units have air seals that are tighter and more durable, have a thermally broken sill assembly, and are easier to install on site.
Glass inserts and side lights should be at least double glazed. Performance comparisons should be based on the complete door system.
