After we sold the business, the first major trip we took was to visit friends in Norway. As we toured the country, one of the things that I really loved was warm bathroom floors. Many places had radiant heat in the bathrooms, and there’s nothing like getting out of bed in the middle of the night to find your feet warmed by the bathroom floor. So, when we began to design our cabin in Colorado, one of the criteria became incorporating radiant floor heat.

Radiant Heating since the 1970’s

For 25 years, I had experience with radiant heat at work. We were a heavy equipment dealer, and our shop had bays with doors that were 20 feet tall and 15 feet wide. When we built the building in 1973, we installed piping in the floor slab and heated the place with a boiler. The amazing thing is that you would open the doors for twenty minutes while moving a tractor in or out, and wind would blow through in the winter and chill you to the bone. As soon as the doors were closed, if felt warm again, because the heat was rising from the floor. I realized that if your feet are warm, most everything else feels warm.

Building with Logs

As we worked with the builder to design our cabin, we realized it is very difficult to put a typical forced air heat system into a log cabin, because you cannot run duct work in the outside walls. With a log home, the outside wall is also the inside wall. Here you can see my son Andy helping put up the log walls.

So, you have to drill holes in the logs for electric wires, telephone wires, and cable for TV and computer. There is no place for heating ducts. Many people heat log homes in Colorado with electric wall units that are not very effective. There are wall units that use radiant heat, but again, not very effective or efficient. We chose to install in-floor hot water radiant heat. This technique was first employed by the Romans 2000 years ago, and is today one of the most efficient ways to heat a home. Here you can see the plastic tubing that was later enclosed in our basement floor slab.

All of our mechanical equipment for both the solar electric system and the heating system are located in our garage. So, all the utilities have to be piped underground over to the house. Because we are heating several floors, we poured a thin layer of light weight concrete on the upper floors, and put the heat tubing in the concrete. Here you can see the pipes and wiring being routed between the two structures.

5 Foundations

Floor Surfaces Matter

In the basement of the house, we installed ceramic tile, because it does not impede the flow of heat from the floor. Because the basement slab is at least a foot thick, once the slab warms in the fall, it is very efficient to keep it warm all winter.

On the main floor, we have a combination of hardwood and slate. We wanted to use the 3” hardwood flooring, but found out it can buckle with the uneven heat between the floor tubes. So, we installed laminated hardwood that eliminates this problem. Wood, however, is an insulator, so pushing the heat up through wood is not the most efficient. We discovered that the slate floor was the best material for radiant heat. The slate is thicker than ceramic tile, and has the characteristic of having thermal mass, the ability to store heat and release it over time.

Log walls are the same way. They do not have the same R-factor as fiberglass insulation, but they have significant thermal mass. Once the logs warm up, from sunlight or fire or thermal heat, they store heat, which dissapates slowly when it cools off. So, into the evening, the logs are giving off heat they stored up during the warmer daylight hours. That makes logs efficient as an insulator.

Upstairs, we installed carpeting, which, like hardwood, is really an insulator, and not the best floor surface for radiant. We could only afford so much slate, so we satisficed with the other floors. That’s a fancy term my statistics professor taught us that means it is not optimal, but given the constraints of time and budget, it will suffice.

Controlling the Heat

Each room has its own has valves that control the flow of water in that room’s floor, and its own thermostat. The challenge is that the floors are slow to respond, given the method of heating them. So, you don’t put in programmable thermostats which significantly lower settings at night and when you are away. These systems like a constant heat point.

Passive Solar Assist

We have large south-facing windows and like to have a fire in the wood-stove in our fireplace. With our prow roof, the summer sun does not come flowing in overheating the place. The roof is designed to keep out the rays of the sun when it is high in the sky. In the winter, the lower trajectory of the sun works with the roof to allow sun to stream in during the day, warming the floor and log walls. In this picture, you can see the prow roof on the south side of the house, which offers shade in summer, sun in winter.

Southeast View

So, we keep the heat set at 65 degrees in the living/dining area, where we have a cathedral ceiling. On sunny days, by 9 AM, it will be above 70 in the room from the passive solar heating. On cloudy, snowy days, I set a fire in the fireplace and supplement the radiant heat with a high efficiency wood stove.

This past fall, we installed a new Viessman Modulating, Condensing Boiler which replaced two original boilers that were not high efficiency. I was looking at the possibility of installing solar thermal panels on the roof to preheat the boiler water, but when I looked into it, the best return on investment was to upgrade to a high efficiency boiler. It is hardly bigger than a suitcase, and provides domestic hot water and heat for 5000 square feet under roof. And, there’s nothing like walking around barefooted on warm floors in the winter. Ahhhhh!!!!!