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Cold cellar question

Troy Stevenson | Posted in Green Building Techniques on

We are building a new home soon and I really want to include a small cold cellar to age a few beers and keep some wine cool in lieu of a beverage refrigerator. I also want keep our chest freezer (we buy full animals to process) in here to lower its run time.

If we have the foundation walls extended to the interior in two directions to create a separate room and then keep those exterior walls uninsulated with no insulation under that part of the floor, is it reasonable to expect that the room would stay a relatively consistent temperature year around? We are in zone 5. Is there anything else we should consider for this room – ventilation, etc.?

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Troy,
    Many people build cold cellars in a section of their basement, so the answer is yes, you can do this. However, I wouldn't do it the way you describe.

    The partitions that separate the heated part of the basement from the cold cellar can be insulated stud walls. You don't need concrete partitions.

    Moreover, you definitely want insulation in the floor framing above the cold cellar (the ceiling of the cold cellar) to separate the warm house above from the cool cellar below.

    To define your thermal boundary well, you need to interrupt your floor slab between the two sections of the basement (the heated section and the unheated section). Vertical rigid foam insulation should be installed at the perimeter of the slab at the heated section of the basement. Then a separate slab should be installed for the cold section of the basement. You probably don't need a special footing under the partition walls.

    Pay close attention to airtightness in all sections of your basement.

    Don't put your chest freezer in the cold cellar. Because the chest freezer gives off heat, it will heat up your cold cellar. To keep things cold, you don't want any electrical appliances in there: no freezer, no water heater, no furnace.

  2. Troy Stevenson | | #2

    Thanks. Less foundation wall equals les $$$. Would you recommend insulation under the slab in the cold cellar?

    Somehow I neglected to remember that appliances produce heat so thanks for the reminder on keeping the chest freezer out of the cellar.

    Lastly, I see some cold cellars implementing ventilation, humidity controls, and other various mechanical components I would rather avoid. Any thoughts?

    By the way Martin, you have responded to many of my posts/questions and your help has been invaluable. If you are ever in the Detroit area (after we get this house done), you must stop by to share a an aged beer in the cellar and maybe some homemade kimchi - we can share recipes.

  3. GBA Editor
    Martin Holladay | | #3

    Troy,
    I don't see why your cellar would require humidity controls. But it makes sense to include one or two windows that can be opened (and that seal tightly). That way you can lower the temperature of the space early in the fall. Once the weather turns really cold, the windows are closed.

    Thanks for the invitation. The homemade kimchi sounds great.

  4. Troy Stevenson | | #4

    One last question. Our back parch is going to be large (approximately 35 ft by 8 ft.) with foundation wall equal to the basement and a cement floor. If building code allows, would it make sense to attempt to use this space under the porch and contiguous with our basement as our cold cellar?

    Although much larger than we need, it seems to make sense. However, I'm an accountant and not a building science guy. Without a window to open, perhaps this just becomes the typical damp, musty basement. Again, thoughts and input appreciated.

  5. GBA Editor
    Martin Holladay | | #5

    Troy,
    The problem with using the space under a porch as a basement extension is that the area has no ceiling or real roof. Most porches are regularly soaked by wind-blown rain and snow. If the porch has a full concrete foundation, the water can drip through the floor boards and be absorbed by the dirt-floored basement below. However, if you want to turn that space into a wine cellar, you need to design a porch with a waterproof floor. This is possible but expensive.

  6. Troy Stevenson | | #6

    The porch floor is going to be concrete concrete so the celing of this below grade space would be concrete. Does this help?

    Anyway, if I am back to using the internal space I want to make sure I have the right idea...

    1. Use under slab insulation but provide break with turned up foam to separate from rest of space
    2. Insulate ceiling
    3. Include a window or 2 for the introduction of cold air in the Fall
    4. Insulate the 2 walls that run to the interior
    5. Are the remaining 2 foundation walls also insulated or is the source of the cold?

  7. GBA Editor
    Martin Holladay | | #7

    Troy,
    I don't know whether the concrete slab that you will be installing as a porch floor will be truly waterproof. It might be waterproof enough -- or your wine cellar might end up with a dripping ceiling.

    The other possible problem with a cold cellar under a porch is that the cellar can freeze. Freezing would be likely in this part of Vermont; where you live in Michigan, however, it might be mild enough in the winter to keep such a space from freezing.

    Concerning your 5 numbered points: the first 4 points make sense. Point #5 raises an interesting question. To avoid thermal bridging through your concrete walls (that is, heat loss from the heated section of the basement sneaking outdoors through the concrete walls of your cold cellar), the concrete walls of your cold cellar need to be insulated in the same manner as the walls of your heated basement. Whether or not the wall insulation will make it harder to keep your cellar cool is an interesting question. Ideally, the lower half of the walls would be uninsulated -- but what works for your cold cellar isn't a good idea for your heated basement. My advice is to insulate the walls.

  8. Guillaume Dumont | | #8

    I am in a similar situation but the cold cellar is in a house built around the 60s. I have 4 inch heating ducts that pass through the cold cellar just below the floor framing. The ceiling of the cold cellar is "finished" with wood and insulated with loosely blown mineral fiber. The interior walls of the cold cellar are insulated but the door is not.

    I was thinking I should remove the mineral fiber and the use rigid or spray foam to insulate the floor framing and somehow insulate the ducts to avoid loosing heat to the cold cellar and insulate the door. Any suggestion on how to insulate the ducts? Or should I just reroute them in the heated area of the basement?

    Another question. During the summer the cellar is not that cold, I would say around 15-18 deg C (sorry about the metric system), and sometimes during the winter I have to open the door so that the cellar does not freeze. I am in Quebec (zone 4 or 5 I guess). I fear that adding more insulation will increase the freezing potential of the cellar. Is this behavior normal? Are there things I should look at to avoid this if it is possible.

    Many thanks.

  9. Guillaume Dumont | | #9

    Troy,

    I don't know if this question is still of interest but this post by Mike Holmes here discusses the subject:

    http://homes.winnipegfreepress.com/winnipeg-real-estate-articles/category-/title-mike-holmes:-take-the-chill-out-of-your-basement's-cold-room/id-1076/

    It basically reiterates Martin's advice with the exception that Holmes advises not to insulate the exterior walls of the cold cellar.

  10. GBA Editor
    Martin Holladay | | #10

    Guillaume,
    If possible, you should re-route the ducts so they don't pass through your cold cellar. If the ducts have to stay where they are, you should insulate them heavily with spray foam or with rigid foam insulation that is taped at the seams.

    Cellars can freeze, especially if there is lots of air leakage at the rim joist area. To reduce the chance of freezing, perform air sealing work.

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