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My house has a very small kitchen which is actually an extension of the house with its own roof.

I suspect its roof insulation is old and not effective, because this kitchen is quite cold (8 degres celsius sometimes in winter).

Landlord says the room is cold because the floor is made of concrete with tiles on top of it. I personally find the roof explanation more convincing, but I admit that the floor in this kitchen is extremely cold. Sometimes I get out of the kitchen just because my feet are cold.

So is it possible that the landlord's explanation be correct? Can the floor make a room cold? And if so is there a way to make the room less cold?

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There is something to be said for a cold floor making a room feel colder even though the air temperature is appropriate. If the room is 8 degrees then a major amount of heat is being lost somewhere, as mentioned in the answers. –  bcworkz Dec 10 '13 at 22:39
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If this is a rental property, your landlord probably has legal requirements for providing a habitable living environment, which 8º C probably does not meet. Check your local landlord/tenant laws. Politely reminding the landlord of his legal obligation may prompt some action. –  Henry Jackson Jan 3 at 19:19

2 Answers 2

Yes, the room can be very cold because of the floor.

Concrete slabs do not insulate well (R-value around 0.6!), and they lose most of their heat along the outside edge of the slab (the ground beneath the slab is a decent insulator). Using a Heat Loss Calculator, I assumed you had a 10x10 room with a completely uninsulated floor (concrete), uninsulated walls (stick built w/drywall), and ceiling (drywall ceiling with an uninsulated attic).

Heat loss was 4050 BTU/hour from the floor, 5440 BTU/hr from the walls, and only 1540 BTU/hr from the ceiling.

So, while your ceiling may be a factor, it's probably not the most major factor. Given that your floor is very cold, you probably don't have much (or any) insulation on that slab.

On the outside of the building, see if you can see the edges of the concrete slab. If you can, then it's not insulated. Buying some one-inch R-5 foam insulation and affixing that to the perimeter of the concrete slab drops the heat loss from 4050 BTU/hour in half to 2050 BTU/hour. Two-inch, R-11 insulation drops the heat loss to only 1050 BTU/hour.

Placing a rug on the floor would likely be insufficient, as carpet only gives an R-value of around 1.3 (and an area rug isn't going to cover the entire floor, anyway).


Edit with more information:

Consider a house built on an uninsulated concrete slab. Insulating the slab can lead to a reduction of 10-20% in total heating costs. Of the heat lost through a concrete slab, up to 80% is lost through the exposed outside edges.

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True, I should have noted that the rug was more a 'foot insulator' than it was a 'floor insulator' :) –  DA01 Dec 10 '13 at 3:30
    
True the concrete slabs outside are apparent. But inside there's a layer of tiles on top of them. Can concrete slabs convery outside cold to the kitchen so efficiently? –  drake035 Jan 3 at 17:03
    
Yes. Insulating a concrete slab can reduce total heat costs by up to 20%. Up to 80% of the heat lost from a concrete slab is lost along exposed edges. I'll update my answer with references to the extra information. –  philipthegreat Jan 3 at 18:26

Heat rises. So if you have poor insulation in the roof, yes you can lose a lot of heat their. At the same time, if there is little-to-no heat in the floor, it will never likely get all that warm (given that heat rises).

Ideally when a concrete floor is being used, they'd put insulation under the floor. If that hasn't been done, that's going to be a difficult thing to remedy.

Options:

  • install in-floor heating. For a retrofit, this is typically done as an electrical system under the tile. This would require removing the existing tile, installing the heating mats, then retiling on top.

  • insulate everything else as best you can. Windows, ceiling, walls, etc.

Neither are likely all that doable in a rental, however.

So I think that leave you:

  • crank the heat (not ideal)

  • insulate the floor on top. (perhaps with a rug?)

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Also, don't discount heat losses caused by airflow. Six tubes of caulk can cover a multitude of sins or if you take time to measure it and calculate the surface area, the equivalent of a window being open year round. Once the inner envelope is airtight, ceiling insulation becomes the next big worry. As noted above, heat rises up against that big, flat heat exchanger. –  Fiasco Labs Dec 10 '13 at 3:11

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