The Inside Outside Guys: Those, Cold, Cold Basement Floors

By Ken Calverley and Chuck Breidenstein

DETROIT, March 10, 2022 ~ Every Midwesterner knows the issue. You invest thousands of dollars in finishing that lower-level space only to realize your feet are cold whenever you spend time enjoying it.

We really shouldn’t be surprised. That floor is 4 inches of concrete, known for its ability to absorb and conduct both moisture and heat.

The floor likely rests on raw soil, which will periodically carry moisture and maybe even active water that will also “steal” heat. In fact, the soils below your home are a huge “heat sink” with the ability to conduct large amounts of heat energy away from the basement.

The presence of water in the soil only exacerbates this heat exchange since the water will both absorb heat and carry it away.

The concrete sitting on that soil sets up the perfect scenario for conducting any heat in the basement into the earth beneath the floor and that makes for a cold floor.

Remember, while warm air rises, heat goes to cold in any direction. It will certainly go from your feet into the cold floor.

In commercial construction, which is often slab-on-grade as described above, we normally place rigid foam insulation below the concrete to slow or stop the conduction of heat from the conditioned space above to the ground below.

In newer homes, when the specification is called for, we do the same thing beneath the basement floor.

Good thermal insulation below the slab is the most effective, standardized, method of providing for warm floors in that space.

In some hybrid applications, we have substituted the concrete slab during construction for a treated wood frame floor spaced slightly above rigid foam insulation that rests on a layer of pea gravel. This stone drainage layer can effectively eliminate water/moisture from the equation and the lack of direct contact between the wood floor frame and the insulation further reduces heat conduction.

A more popular hybrid solution in new construction includes installation of the same stone and insulation layers topped by a hydronic heating system composed of loops of PEX type piping embedded in gypcrete, which is a high cement, small aggregate like material that is used to make custom pools.

But what do you do if you occupy a 20- or 50-year-old home that was built as we first described?

If you have some extra height in the basement, you can have that hydronic heating system installed over the existing concrete floor. You will lose 3 to 4  inches of height to the gypcrete floor but will have a fantastic heating system and warm floors in your lower-level space.

You could install a “sleeper” floor system using treated 2 by 4s laid flat with rigid foam either between or under them and plywood or OSB on top as the sub floor.

There are also some 2-foot square modular panel floor systems that consist of a dimpled plastic layer on the bottom, a rigid foam insulation layer, and a layer of plywood or OSB on which you will then lay your carpeting or other finish flooring. They are tongue and groove and provide for quick installation.

All of these can be somewhat pricey, but effective, in your quest for warm toes.

The alternative to installing systems like those just discussed is to generate enough heat through various methods to eliminate the issue from concern.

One suggestion for anyone finishing a basement space is to have an HVAC professional design and install additional supply registers nearer the floor in the new wall frames for forced-air heating.

Another possibility is to have radiant heating panels installed in the ceiling of the space, though this is an electric source heat and could be expensive to operate. The most common system is a series of “drop-in” panels made to fit standard suspended ceiling frames. A variant is the radiant ceiling heating systems that are installed behind the drywall finish, so they are concealed from view.

For housing advice and more, listen to “The Inside Outside Guys” every Saturday and Sunday on 760 WJR, from 10 a.m. to noon or contact us at InsideOutsideGuys.com.