We want to replace the sliding door that leads from our family room to our sunroom with French double doors. Can we replace it with indoor doors? Or do we need outdoor doors? The sun room has other doors that lead to out to the yard that won’t be replaced.

  • Are the other doors that lead outside exterior, well insulated doors? Are the walls and ceiling properly insulated? Are the windows of quality (double-pane, low-e etc)? What's the floor like, insulated? What climate are you in? If the room is well protected from the elements (including cold/moist air), then an indoor door will be fine. Also consider security though. If you're to use an indoor setup, you'll want everything to be secured on the perimeter of the sunroom.
    – stevieb
    Commented Sep 27, 2018 at 19:16
  • The doors leading to the outside are glass doors like the one that you see on the front door in lieu of storm doors. The sliding door that we want to replace is double panel though. The windows seem to be single panel and the flooring is carpet that we want to replace with tile. We don't have any idea of what is the insulation underneath because we just bought the house last winter. Commented Sep 27, 2018 at 19:23
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    Ok, a couple of other questions: Was it cold in the sunroom throughout last winter? Is there heat in there? If no is the answer to both questions, it's likely the sunroom is just that; not a winterized area. If that's the case, I'd go with an exterior door. That said, we have no idea of where you live or what the climate is like. For example, where I am in Northern British Columbia Canada, it can get to -35c for days/weeks on end.
    – stevieb
    Commented Sep 27, 2018 at 19:25
  • Yes, Im In NJ so in winter is more like an Ice room rather than sun room...Thanks for the advice Commented Sep 27, 2018 at 20:05

1 Answer 1


If your sun room is really a three-season room, you need an insulated door between it and your heated space as part of what's known as the "building envelope". Interior doors not only don't insulate as well, but they don't offer the seals that prevent airflow (which is actually a greater source of heat loss).

If your sun room stays within say 20 degrees of the heated space year round, you can probably go ahead and use interior doors, but I'd still consider adding bristle-type air gaskets.

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