I recently moved into a house where the previous owner built an extra room on the back of the house, and expanded the basement underneath that. The addition room is noticeably colder than the rest of the house. Using an infrared thermometer I discovered the floor of that room is about 4-5 degrees colder than the rest of the room, as well as the floor of other rooms. Should I insulate the ceiling of the basement below this room?

  • Insulation will keep the temp of the upper room warmer since the floor is so much cooler,
    – Ed Beal
    Feb 18, 2017 at 20:24

1 Answer 1


What type of heating is used in that added on room? That will make a difference in how you solve the problem of the room being cooler than the rest of the house. Answer #1; yes insulate the floor if the basement under that room is unheated or cooler than the rest of the house. Answer #2; If the added room has 3 sides exposed to the weather, that is probably 1 or 2 more walls than any other single room in the house. If this is the case the room should have been built with more insulation than the rest of the house, since it will loose more heat due to the number of walls exposured. The type of heating system will determine how you correct the heating deficiency. You may have to add a separate heating device to solve the problem.

  • I have baseboard water heat in that room, and the rest of the house. The added room does have 3 sides. Side 1 has a regular window and baseboard heater along 2/3 of the wall. Side 2 has a regular window, a 3 pane bay window, and baseboard heater under the bay window (only about 1/3 of the wall). Side 3 has a patio door.
    – JCB
    Feb 19, 2017 at 16:06
  • 1
    When you say a regular window do you mean thermopane glass or single pane glass? Thermopane is a must and could be double glass or triple glass .If you want that room to be about the same temperature as the rest of the house you have 2 options after you insulate the floor. Option 1: add more finned coil heating element. Increase side 1 and side 2 two full wall.length finned tubing. Option 2: this is the better way and probably much more expensive. Add zone valves so this room can have its own thermostat. You may need an HVAC co. to do this but it will give you the best results
    – d.george
    Feb 19, 2017 at 19:19

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