With the mercury already having dipped down to the lower 40s at night, I’ve already had to turn on the heat at night.
Or in my case—and the apartment I am living in now—turning on the floor.
My apartment uses a Korean-style of heating called ondol (translated as “warm stone”) that is a traditional Korean underfloor heating system for indoor climate control. This system of heating rooms that dates back to the Three Kingdoms 37BC-AD668 period in Korea, is similar to a Roman hypocaust (in a hypocaust heat comes from an underground source, a furnace—the word literally means “heat from below”).
The main components of this traditional system of underfloor heating are a fireplace or stove (also used for cooking) located below floor level, a heated floor underplayed by horizontal smoke passages, and a vertical chimney to provide draft. In traditional Korean homes, stone piers, covered by stone slabs, clay, support the heated floor and an impervious layer such as oiled paper. The latter gave the floor a warm, yellow color that is still popular in modern homes.
Problems with the ondol system included overheating, which could last for hours because of the heavy stone masonry as well as carbon monoxide poisoning from cracks in the floor surface. In the past, yontan—cylinder-shaped charcoal briquettes were used for heating the ondol system—which also contributed to some of that carbon monoxide poisoning).
(When I first came to Korea in 1990, yontan was used a lot for heating and cooking and in winter there would be a layer of fine black dust everywhere. Sort of reminded of growing up back in the American Midwest back in the 1960s when many homes and business still burned coal. And these days, given the high cost of fuel for heating homes in Korea, yontan is in demand again.)
In modern homes and apartments the ondol system is heated by circulating hot water or an electrical cable located beneath the floor. In my apartment, I have a wooden floor with the ondol system located underneath. I can control the temperature of the floor by a thermostat, which also controls the hot water temperature. You have to admit it’s a pretty ingenious and practical system to heat a room. I’d rank it right up there with solar heating in terms of its energy efficiency.
And it has been one of those uniquely Korean things that have always been an interesting part of a conversation when I have had to try and explain it to someone back home or someone not familiar with something like ondol.
“So when you turn on the heat, you are actually turning on the floor. Is that right?’’
“Yup, that’s what you do.’’
“And the floor heats the room?’’
Interestingly, the custom of removing one’s shoes when entering a Korean home and sitting down on the floor can be attributed to ondol. Likewise, this “sitting culture” also influenced traditional Korean clothing—the Hanbok that was loose enough and had enough room to bend one’s knees and legs when sitting on the floor for long periods of time. Likewise, the warmer areas were reserved for elders—grandparents and parents as well as guests as an expression of respect.
Although some modern apartments do not have the ondol system, you can buy these huge carpet-like heating pads to put on the floor to simulate ondol heating. Some of my former colleagues and friends who had one these heating pads on their floors said it was the next best thing.
It was really cool (or should I say nice and toasty) when I lived in this one apartment many years ago and slept on the floor on traditional Korean bedding called a yo (kind of like a futon) or sat on cushions around a traditional Korean-style table (like a square coffee table). It was a small apartment so it was quite cozy and toasty in the winter. However, the apartment was a little drafty so even though my bum and legs were toasty, the rest of my body from the chest up was a little on the cool side.
And speaking of heating pads and sleeping on a yo—if one is ever troubled by any kind of back pain, sleeping on a yo on a warm ondol is like sleeping on a heating pad. It worked for me a couple of times.
It’s supposed to get down in the lower 30’s tonight—looks like I’ll be sleeping with the floor on.