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Much like windows, door units must be a part of the overall strategy for air tightness. A high performance exterior door must have the following:

• Multiple seals across jamb width and threshold
• Insulated door and frame
• Air tightness when closed
• No thermal bridging

A door with all of the required characteristics is going to be a heavy unit = added labour.

Installing this type of door in a retrofit may require inspection and improvement of the rough opening frame and robust hardware for operation.

For retrofits and renovation, door units should be examined to see about the following:

• Weather stripping still in tact? Replace if necessary after scraping away the failed material.
• Are there signs of water damage anywhere? Is the threshold solid or experiencing rot?
• Can you install a sweep or threshold seal?
• Is there room around the rough opening to spray foam? This will require a bit of surgery to remove interior trim.
• Is the door itself air tight or insulated? Consider replacing the door with an insulated unit.
• Glass on the unit (glazing) - does it experience frost or condensation? Seals may be gone. Look into replacing the door or the glazing.
• Interior and exterior caulking around perimeter of door unit.
• If there's room and a budget, consider the addition of a mudroom 'airlock' to the exterior door area. You can then make the addition air tight and performing better than the existing.