A warm bathroom floor is a something to look forward to on a chilly winter morning, and C.L. is poking around for ideas on the best way of accomplishing that.
One option is installing a grid of electric cables beneath the finish floor in tandem with a polyethylene underlayment manufactured by Schluter Systems called Ditra. These installations are often topped with ceramic tile, which is impervious to water damage and readily transmits heat from the buried cables.
But C.L. has another idea.
“In regards to finish flooring over the heated floor in the non-shower part of the bath, cork looks like an interesting product,” C.L. says in a recent Q&A post. “Although cork is sometimes discussed as an insulator, the [manufacturers] of solid cork flooring propose it as an ideal finish floor for a heated floor; supposedly it heats fast.
“Does this sound reasonable, or is this just marketing hype?”
That’s the topic for this Q&A Spotlight.
First, how efficient is electric heat?
C.L. begins his post with a question on whether there’s a recognized metric for measuring the efficiency of electrically heated bathroom floors. Actually, there is, points out GBA Editor Martin Holladay.
“Yes,” he writes. “The metric is called ‘efficiency.’ It describes the conversion of electrical energy into heat energy. All electric-resistance floors have the same efficiency, namely 100%.”
This is technically true of all electric resistance heat, whether it’s in the floor or not. But Jon R suggests that definition doesn’t go far enough.
“A reasonable definition of efficiency would involve useful work,” he says, “so I’d exclude any heat lost to the underside of the floor. This efficiency will be less than 100% and cork will lower it (as compared to something more thermally conductive…