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My house is "concrete slab" foundation (no basement). Am I losing heat to the floor?

Post in 'The Green Room' started by NewtownPA, Mar 5, 2007.

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  1. NewtownPA

    NewtownPA New Member

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    I have no basement in my house - sits on a concrete slab. I have tile/hardwood/pergo floors and yes they are cold in the winter. We've got some carpet and rugs covering about 50% of the total area.

    Do you think I loose a lot of heat to the floor? If so, do you have any suggestions?

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  2. Sandor

    Sandor Minister of Fire

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    Concrete slabs are my favorite construction method. LOTS of reasons.

    Yes, you are losing some heat, but the benefits outweigh the losses. (As long as it was constructed properly)

    You are losing way more through your windows, walls and ceilings.

    Be happy.
  3. begreen

    begreen Mooderator Staff Member

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    An uninsulated slab can be very cold and hard on the feet. I lived one winter on an uninsulated slab floor in CT and after developing heel spurs vowed I'd never do that again. The next summer I raised and insulated the entire floor.

    For calculations on the actual heat loss, here is a guide:
    http://www.eminnetonka.com/community_development/permits/documents/heat_loss_calculation.PDF
  4. webbie

    webbie Seasoned Moderator Staff Member

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    Always depends on the climate and how the slab was done - whether it was insulated around the perimeter and sometimes even underneath. Perhaps Elk can enlighten us to the current energy codes for new slab construction if it is the living area.

    Me thinks if Sandor as in Stowe, Vt as opposed to Deltaville,Va his opinion on slabs might change! -or, just put some radiant heat in 'em and all problems are solved.
  5. Sandor

    Sandor Minister of Fire

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    Me thinks u r correct.

    Check Building Science to see how to properly insulate a slab. Lots of thermal mass to work with!
  6. NewtownPA

    NewtownPA New Member

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    What are some of the benefits?
  7. webbie

    webbie Seasoned Moderator Staff Member

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    I'll chime in and say they usually don't sag, don't make noise when you walk on them and don't serve as nesting places for mice and insects! In warmer climates, they can act as a slight cooling agent.
  8. NewtownPA

    NewtownPA New Member

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    Thanks! I have a 180 gallon reef aquarium (~ 6 feet X 2 feet X 1.5 feet) and I am certainly glad I have a concrete slab to put it on! :) Also, I do agree that in summer it's nice to have a cooler floor.
  9. velvetfoot

    velvetfoot Minister of Fire

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    I wonder if Pergo would work over an inch of foam. Of course then the ceiling would be lower. :) Plus, I'm not sure it would conform to code because of the foam needing a fire resistant covering.
  10. NewtownPA

    NewtownPA New Member

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    I used the special "Pergo foam" (it's pretty thin). The problem with thick foam would be if you placed a heavy object on it the compression might snap off the interlocking groove/ridge and you'd have a cracked floor.

    I was thinking that shiny Mylar underneath the Pergo might reflect some heat back into the room, but I don't know if conduction heat transfer is more of an issue than radiation heat transfer. Anyway, there is no way to undo the Pergo now though.
  11. Hogwildz

    Hogwildz Minister of Fire

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    My addition supposedly has 5 foot of stone then a concrete floor over top. I guess I get some benefits of passive heat from the deep stone. I have had a gallon water jug in there on the concrete (yes addition is STILL unfinished) and the water never froze, even in single digits. I guess there is some kind of passive heat from the ground transferring through the stone & concrete? I dunno, but the water ain't freezing sitting right on the concrete.
  12. alfio

    alfio New Member

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    I have read that you do loose sum heat from a slab, if it was not insulated from underneath and the sides. Thats why I'm going to put what they call sleepers with foam insulation in my basement when i finish it . Sleepers are 2x4 laid on the flat then you put your sub floor on top of that.
  13. elkimmeg

    elkimmeg Guest

    Slab sets are the cheap way out of not pouring a foundation. Does not work in the northern climates verry well they don't provide for frost heave protection
    In my zone all foundations have to be 4" in the ground to prevent frost heaves.

    A bigger issue that heat loss is moisture control. before anything goes over cement one had to address moisture that seeps threw concrete
    and yess it is common to find cracks in the slabs.. All cracks should be v chiseled out and filled yith hydraulic cement.

    As for heat loss usless it was properly prepared with a moisture barrier and insulation before pouring you are loosing heat. But prevention is costly

    In basements the sleeper idea with ridgid styrofoam between the sleepers is a vast improvement
  14. slowzuki

    slowzuki Feeling the Heat

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    Frost protected slabs work very well in northern climates, straight poured on the ground ones do not. All concrete will crack, concrete shrinks about 1/2" in 30' from pour to fully cured. This is why basement walls crack and floors crack. You can reinforce with steel to control cracking but it gets costly once you try to keep bigger that about 16 ft dimensions free of open cracks. The steel mesh association has some nice design guidelines.

    Most heat loss in northern climate is from the perimeter of the slab. The exposed part and first 2 ft are the most critical. After that you have loss to the ground below the slab. A bit of insulation will really slow it down. Your 70 f slab is only losing to a 50 f ground in the middle vs your 70 f walls losing to -20 f outside.

    In Canada in coded areas you need vapour barrier and a drainage layer before pouring a slab, otherwise you'd get the same problems basements have with water infiltration.

    I built a pretty unique slab, it has thickened edges like normal but instead of a "frost wall" which is what they call the 4 ft deep footing the contractors like to pour here I have 4 ft deep sloped trenches lined with filter fabric, drain tile at the bottom and filled with compacted crushed rock. The slab lived bare through a winter then with just a roof unheated so the slab had no snow cover. Didn't move and inch in our highly frost suscepible clay till soil.

    Ken

  15. struggle

    struggle Minister of Fire

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    Our basement is poured and 8' 1/2 deep and in the winter if you move a bean bag from a place it has been setting on the floor for a while it will feel cold to step there or sit in that area. SO clearly there is an issu of heat /cold transfer.

    I know in the summer the basement stays very nice and comfortable and all the walls are framed and insulated so the cool we feel is coming from down under the conrete.
  16. slowzuki

    slowzuki Feeling the Heat

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    Yes the mean ground temp almost everywhere is around 50-55 F, which is darned warm compared to -15 F outside in the winter. Unfortunately concrete soaks up heat so well we feel cold touching it even when it is nearly the same temp as us. So heated floors are a real boon to the senses as the concrete can be warmed up enough to actually feel warm. Room temp in concrete feels cold still.
  17. velvetfoot

    velvetfoot Minister of Fire

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    This is interesting to me, especially about the sleepers, as I too am thinking about finishing the basement.
    What would the spacing on the sleepers have to be? I would assume they would be pressure treated?
  18. Highbeam

    Highbeam Minister of Fire

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    Lots of people convert garages to living space. It is common to use sleepers and insulation under a subfloor and then build on top of all of that. If you lay the sleepers on edge like a framed platform then you have more room for insulation. Normally you first fix any water problems, then lay a water resistant layer like poly or tar paper, and then frame up a floor out of non-treated lumber with insulation. I fear fiberglass for this application so I would use XPS. 16" centers just like a real floor and then standard subfloor and then flooring.

    That's how the articles on the net show it done. I use a converted garage for living space in my home and they just carpeted the concrete. Hard and cold so I am really watching this thread too.
  19. slowzuki

    slowzuki Feeling the Heat

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    There is also eps with 3" strapping grooves formed into it that is great for doing basement floors. My old bedroom had this setup but I would have prefered pex attached to the concrete floor with a 3/4" top coat of concrete or gypcrete over top.
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