Reducing cold floors in winter with a house built on a concrete slab.
Last Post 25 Mar 2011 06:44 PM by toddm. 4 Replies.
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Fernwood176User is Offline
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14 Mar 2011 05:00 PM
I am currently living on a two story house built on a slab and am hoping to add some additional warmth to the flooring.
Unfortunately, the floors were just completely installed with engineereed hardwood floors so I can't install any radiant heating.
Wondering if there is a cost effective method to insulate the exterior of the foundation to reduce the cold floors in winter.  Anyone have any experience with those foundation wraps?
If not, any other suggestions to heat up the first floor?  Electric baseboad heat, fireplace insert, etc.?  Just looking to be more comfortable.

McFishUser is Offline
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14 Mar 2011 11:50 PM
Read up on frost protected shallow footings. These will keep more of the heat in the slab, less heat is allowed to go direct to cold outside air. The insulation board can be added after the construction. This might be less cost than an insert or baseboard, with no fuel cost after it is installed.
RosalindaUser is Offline
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18 Mar 2011 11:31 AM
Do you know how thick the slab is? I would say dig a trench around the perimeter of the slab down at least 2 feet and insulate from the top edge of the slab down with R20 or so blue board, depending on where you live. You might need to use something like grace shield compatible with foam, and a metal flashing for termite and/or rodent protection on the foam.

The FPSF guidelines can give you specific depth, and R value for vertical and horizontal foam depending on your climate. If you search google you should be able to find the PDF with all the details, though your State Code will probably also have the details.

Also think about ways to expand the dry soil around the perimeter of the house, as water sucks up and carries heat away. Maybe a 2 foot or greater impermeable cover sloped to drain away from the house.

Sum total of my experience - Designed, GCed and built my own home, hybrid - stick built & modular on FPSF. 2798 ft2 2 story, propane fired condensing HWH DIY designed and installed radiant heat in GF. $71.20/ft2 completely furnished and finished, 5Star plus eStar rated and NAHB Gold certified
ecoarchitectUser is Offline
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19 Mar 2011 01:26 PM
I agree with Rosalinda. perimeter blue board rigid insulation 2ft deep is the best. up to 20% of heat loss in the building can go out the uninsulated slab on grade floor edge. see
toddmUser is Offline
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25 Mar 2011 06:44 PM
You may well need to insulate your slab, but I'd put a thermometer on the floor first. Absent radiant, the floor will never be warmer in winter than your Tstat setting, and 70 degree wood flooring will never be as comfortable as 70 degree carpet (or area rugs.) If the problem is an uncomfortable air temp downstairs I assume you've done the easy stuff, like resetting Tstats or forced air vents and searching out and sealing air leaks. Convection moves heat upstairs, so you'll want to favor the first floor vents in an open house.
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