Should I insulate the ceiling of my basement?

shortsJanuary 18, 2012

Hi - Thanks in advance for helping!

I live in a 1906 stone wall foundation home, in NY state. My 1st floor hardwood is pretty cold, and we are thinking about putting some insulation in the basement. I had one "expert" tell me not to insulate the ceiling because it would result in too cold of a basement.

Frankly, I would rather have a cold basement than a cold first floor. Will the basement really get too cold?

Please let me know if there are any strong concerns with this insulation approach!

Thanks,

David

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bus_driver

Yes, do insulate. At least R-13. Put the vapor barrier side up against the floor.

    Bookmark   January 18, 2012 at 4:39PM
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worthy

Usually it makes more sense to insulate the basement walls than the ceiling, according to the U.S. Department of Energy.

    Bookmark   January 18, 2012 at 4:42PM
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shorts

worthy - We have stone walls that weep when it rains. That is a whole can of worms we will tackle in the spring! Until then, I doubt it is wise to insulate the walls, right?

bus_driver - thanks for the confirmation. And yes, I know of too many people who have the paper facing down...I know that is incorrect.

    Bookmark   January 18, 2012 at 6:03PM
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bus_driver

I did not look at the linked website. No doubt at all that insulating the basement walls is helpful. But if the basement is not to be conditioned to the same temperature level as the floors above, the floor insulation will help. My basement walls are at least R-5 every where and are R-24 at most places-- and my floor immediately above it has R-13 between the joists. The basement has no heating or cooling provisions. Winter lows within the basement are about 53 deg and Summer highs are about 78 deg. Temperature changes in the basement are very slow. Not bad at all. But the floor insulation helps keep the upstairs isolated from the basement temperatures.

    Bookmark   January 18, 2012 at 6:10PM
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worthy

We have stone walls that weep when it rains. That is a whole can of worms we will tackle in the spring! Until then, I doubt it is wise to insulate the walls, right?

Handle the leaks first. But you can tackle the rim joist, sills and all above grade areas, where most thermal change occurs.

bus driver confirms the importance of insulating the walls. Once that's done, the basement is essentially part of the conditioned space. The summer/winter differentials are then so minimal there is no problem with vapour drive and no need for a vapor barrier. See Martin Holladay's comments here, for instance.

    Bookmark   January 18, 2012 at 7:32PM
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bus_driver

My basement today is 57 degrees. The floor above it is heated to 70 degrees. I do not consider the basement to be part of the conditioned space. It is an undeniable fact that the heat moves from the warmer to the colder area and the rate of movement is greater when the temperature differential is greater. So my heat loss to the basement would be greater and faster if the basement was 49 degrees rather than 57. But the insulation immediately under the floor does slow the heat loss from the area above to the lower temperature basement below.

    Bookmark   January 19, 2012 at 8:33AM
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shorts

When I put insulation in paper side up, how do I secure the insulation to the joists?

    Bookmark   January 19, 2012 at 10:03AM
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polishqueen

A house my daughter is buying has the insulation paper side down in the basement ceiling. Is it working at all?

    Bookmark   January 19, 2012 at 11:11AM
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shorts

Yes it is working, my research has determined the issue is about trapping moisture, not the effectiveness of the insulation.

    Bookmark   January 19, 2012 at 11:53AM
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worthy

I do not consider the basement to be part of the conditioned space.

Once you insulate and seal the basement from the exterior it is conditioned. That's the point of the insulation and sealing. Most basements would then be warmed in the winter, directly or indirectly, by the heating system in the basement.

A house my daughter is buying has the insulation paper side down in the basement ceiling. Is it working at all?

Probably not doing much at all because of the difficulty of effectively sealing off the basement from the first floor, whether the paper is up or down. That's an important point made in the brief US Department of Energy link above.

    Bookmark   January 19, 2012 at 1:20PM
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bus_driver

I guess that our perception of conditioned space is different. It is indisputable that my basement most of the time has a different temperature from the living space above and for that reason the insulation between the basement and the living space has real value in slowing the loss (Winter) or entry (Summer) of heat from the basement. I do not grasp how the presence or absence of insulation affects the definition of conditioned space. I lived for some years in an uninsulated house heated with wood. No insulation but I considered the living space to be conditioned in the Winter.

    Bookmark   January 19, 2012 at 9:03PM
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