by Jeff Feldman

“How’s the house?”

I am asked this a lot. In winter, this question is often followed with another question, either asked or implied: “Staying warm?”

These might seem unusual questions to ask the average homeowner. But factor in an unusual house—strawbale-insulated with no conventional heating system, and an unusually chilly winter with January and February lows regularly dipping to the single digits—and the curiosity makes sense.

I can’t always tell if people are asking these questions with genuine interest or suspicious skepticism. Sometimes I wonder if their real question is, “Do you roam the house thickly layered in fleece and wool,” or “how many blankets are piled onto your bed?” In other words, “How does your grand experiment in green living hold up against the ravages of winter?”

In some ways the doubts of others do reflect a few of my own. The truth of wintertime comfort in our house of straw is not exactly what I’d like it to be. Straw is a wonderful insulator, but comfortable wintertime warmth requires an even distribution of heat within that well-insulated shell and proper air sealing to prevent heat loss and drafts. The thermal dynamics of our simple strawbale house are more complex than we thought.

Keeping warm in our house is not a factor of indoor air temperature. It has more to do with radiant warmth, the warmth emitted by physical things. Our house uses three complementary sources of radiant heat: the Sun, a wood-fired heater, and an in-floor hydronic heat system.

The Sun makes a world of difference in our home’s overall comfort. We designed the house to maximize passive-solar heat gain. The Sun shines its warming rays on the thermal mass built into the house—concrete floor, clay-plastered walls, and stonework around the wood heater. These capture and hold that warmth, gradually radiating it out once the Sun has moved on. On bright sunny days, even when the mercury barely rises, the house feels warm with little or no additional heat input.

Of course, the Sun does not always shine. On gray winter days we rely more heavily on our masonry heater. It’s essentially a woodstove encased in stonework we light and load twice a day, morning and evening. The fire burns hot and fast, lasting for only an hour and a half or so each burn. The intensity of this hot fire is tempered by the masonry surrounding the firebox: The stonework absorbs much of the heat. Once the fire is out and the chimney damper is pulled closed, the captured heat gently radiates out of the stone over the next 24 or more hours.

The masonry heater occupies center stage in the open floor plan of our home’s main level. Its heat effect reaches everything and everyone within a visual sightline of its warm stone mass. The heater’s stone chimney extends all the way up through our house, creating a column of warmth in the core of our second story. Our second floor is a bit more cut up, though, with bathrooms around corners and out of “view” of the warm chimney. In bathrooms one tends to wear the fewest clothes, and it’s here on chilly mornings that I am reminded we could have planned this arrangement more carefully.

The flooring surface of the main level of our house is concrete. We laid loops of tubing in this floor before pouring, with plans to eventually connect this tubing to a water heating and pumping system for in-floor radiant heat. We thought of this as a future project, a future back-up heating system for when we’d be away several days or if we wearied of processing firewood for the masonry heater. We thought wrong.

Thermal mass like a concrete floor tends to be cold if not warmed by the Sun or by heated water flowing through tubing buried in it. Large cold objects pull heat from anything nearby that generates it. And so our cold concrete floor pulls heat from us. We were reluctant to admit this at first. Kristin and I both wandered around that first winter merely pretending that our straw house was keeping us as warm and cozy as we had dreamed it would. When we finally gave in to the truth, and scrounged the money to have the floor’s mechanical system installed, our comfort level rose. And our electric bill rose right along with it. We accepted the cost of comfort though, and finally, with a heated floor underfoot, the sun beaming through the windows, and a massive stone heater radiating its warmth upon us, we were warm in our strawbale home. Almost.

Despite the high insulation values and various sources of heat working in harmony in the house, we’ve discovered that air leaks are still an issue. The wooden doors we loved for their aesthetic qualities are prone to wintertime shrinkage. Light creeping in along the perimeter of the door is not a welcome sight. The dryer vent behaves like a wind tunnel at times. At places along the edges of walls the interior clay plaster has shrunk, leaving a gap through which cold breezes can sometimes be felt. We still have tightening up to do.

There are simple fixes for all of these issues. And at times I feel a bit hypocritical promoting energy conserving practices that I can be slow to implement myself. Perhaps I’m still too caught up in the lofty notion that keeping warm in a strawbale house should be effortless. As our friend Satch put it, predicting the insulating power of our strawbale walls: “I imagine one day, Jeff, Kristin will say to you, ‘I’m chilly . . . light a candle.’” If only it were that easy!

Jeff Feldman runs GreenPath Consulting, a green building consulting firm. He and his wife Kristin Alexander live in a strawbale home in Berkeley County. Reach Jeff at GreenPathConsulting@gmail.com.