Small House, Big Heater
This article first appeared in Fine Home Building in September, 1992, issue #76. We have added to it several more drawings and photos to show the full layout of the masonry heater and a view of the exterior of the house.
Viola Rothschild was 79 when she moved into her new center-chimney cape on wind-swept Tory Hill in Strong, Maine. She previously had lived for 47 years in Bangor. But when her mother died at the age of 102, Viola asked her son Michael what she should do. Michael said that she should move to Strong, where he and his family would build a house for her within sight of their 18th century Federal farmhouse.
Michael paced the fields across the road from the farmhouse, relying on his heart and his artist’s eye to tell him where Viola’s house should be. He called and wrote to architect friends, inviting comment and design ideas. He also called on me, an old family friend, for advice. We had worked together before, having fashioned with the help of his family and friends a handmade soapstone complex consisting of a fireplace, a bake oven, a cookstove, a bench, shelves and a sink. That masonry centerpiece transformed a new timberframed wing off the farmhouse into a family room for banquets, violin and piano concerts, ping-pong tournaments and art shows.
But that wasn’t Michael’s only experience with masonry heaters. Michael had just returned from several months of lecturing on art and sculpture in the People’s Republic of China. During the tour, he and his son Harry visited a remote village whose houses were carved out of stone cliffs. Inside one house, Michael and Harry were surrounded by three or four generations of bright-eyed villagers who had never seen the likes before of this large, dark-haired, white American or his larger, red-haired son. The two men were invited to sit on a wood-heated, carved-stone bed-bench-table called a kang, probably the most ancient form of masonry heater known. Inspired, Michael decided upon his return from China to build Viola’s new home around a wood-fired masonry heater that would include a heated bench to give comfort to her arthritic joints.
The Cape Cod style of house was born in the Massachusetts Bay Colony during the late 17th and early 18th centuries. A hedge against the blustery weather of the Cape, the traditional version was one story high and two rooms deep, with a symmetrical facade and a steeply pitched, side-gabled roof for maximum headroom on the second floor. Communal rooms (foyer, living room, parlor, kitchen and pantry) were placed on the first floor, and bedrooms on the second. All the rooms were comfortably arranged around a central fireplace and chimney of stone, brick or both. A pair of stairs–a main one in the foyer and a utility stair in the kitchen–united the first and second floors.
We decided, with Viola, to build a personalized cape. The house frame would include four timber-framed bents (complete sections, or gable-end profiles, of the house that consist of two or more posts linked by horizontal girts and supporting a pair of rafters). The two center bents would be spaced about 11 ft. apart, sufficient for accommodating a substantial masonry heater. Like its forebears, the heater would provide thermal mass, fire-viewing, heating and cooking. We would, however, seek our design inspiration from Finnish and Chinese roots rather than American. Finnish masonry heaters, in particular, are known for their exceptional flexibility, efficiency and heat-storing capability. They also burn cleaner than any other type of fireplace or wood burning appliance available, including the latest wood stoves rated by the Environmental Protection Agency. Besides, for years I have designed, built and conducted workshops on Finnish-style masonry heaters, so I was on familiar turf. Finnish heaters can be finished in stone, tile or brick. The Rothschilds picked brick for a traditional look.
Respecting Viola’s age, Michael and I devised a floor plan that would allow her to live almost exclusively on one floor. On the first floor, a kitchen, a dining room, a living room, a bedroom and a bathroom all pinwheel around the masonry mass. We also tucked a laundry room into the northeast corner, where it is warmed by convection and by heat from the laundry appliances. A fully enclosed 14-ft. by 16-ft. sunroom is attached to the east gable end.
The bathroom lies between the foyer and the back of the masonry heater, displacing the traditional main stair. This layout called for an unusual hallway into the house. A traditional centered front door opens into an ample foyer flanked by a coat closet. From the foyer, however, the entry hall doglegs clockwise around the bathroom and into the kitchen, the beehive of activity. Off this same hallway, against the east gable end, switchback stairs lead to a full basement and to the second floor. The stair design offers minimal intrusion at all three levels of the house.
The second floor houses two bedrooms and a full bathroom. Grandchildren or other guests sleeping upstairs could enter and leave the house with little interruption of the main living area or turn a hard left into the kitchen to nab some of Viola’s hot cookies as they came out of the oven. Grandchildren could also easily march down to a wood-storage area beneath the porch to restock the wood bins in the kitchen and the living room.
But there was more to the design process than arranging rooms around a masonry core. For example, facing the road to the north, Michael and I called for traditionally sized windows and a custom raised-panel front door. But toward the spectacular mountains to the south, out of the public eye, we called for large contemporary sliding windows to capture the view and to encourage maximum passive heating and cooling.
The kitchen is in the southeast corner of the house, where it basks in the warmth of the rising sun. As the winter sun tracks across the southern sky, it strikes the 10-1/2 ft. long masonry core, which stores heat and radiates it gradually into the living spaces.
Viola wanted the bedroom to be relatively cool, so we placed it in the northwest corner of the house to shade it from direct sunlight. Two modest windows capture the cool summer evening breezes.
Clean, two-step combustion is the key to the effciency and flexibility of Finnish masonry heaters. Primary combustion occurs in the firebox, the same as in conventional masonry fireplaces. But instead of exiting straight up the chimney, heated gases from the firebox enter a secondary combustion chamber, where they burn at temperatures reaching 1,800° F or more. The gases that emerge from this secondary chamber (mostly carbon dioxide, water vapor and air) are so clean that they can be routed in any direction through heat-exchange channels en route to the chimney, with little danger of soot or creosote buildup. The heat-exchange channels dump heat into the masonry mass, which in turn radiates it gradually into adjacent rooms. This contraflow design not only allows a great deal of design flexibility, but it also offers 80% or higher combustion efficiency. Two small firings, one in the morning and one in the evening, deliver a day’s worth of heat.
I designed Viola’s intricate masonry heater for comfort and convenience, but I counted on her intelligence and commitment to make the system work. Supported by a concrete-block foundation, the masonry mass consists of a heater in the living room, an oven and stove-top in the kitchen and a heated black-serpentine bench in between.
I wanted Viola’s heater to allow fire-viewing during the summer without heating the masonry mass, so I installed a bypass damper. When opened, this damper routes gases from the secondary combustion chamber directly into a primary chimney flue, bypassing the heat-exchange channels. Opening this damper also encourages smoke-free start-ups year round. Once the draft is established, the bypass damper is closed, pushing the heater into a downdraft mode. On Viola’s unit, heated gases then travel down heat-exchange channels on either side of the heater before rising up a third rear channel that feeds into the chimney flue. But that’s not the only option. Once this flow is established, a bench damper and a second chimney-flue damper can be opened and the primary flue closed, drawing the heated gases through heat-exchange channels beneath the bench, then out the secondary flue. A turn of still another damper routes the exhaust through a pair of vertical heat-exchange channels behind the bench before it enters the secondary flue.
On the kitchen end, the stove-top firebox and the oven can be fired independently with quick access to the secondary chimney flue. Or dampers can be manipulated to send the combustion gases around the cookstove, then either under the bench, up and out or under the bench or up and down through the vertical heat-exchange channels and out.
Neither of the two kitchen fireboxes has a secondary combustion chamber because the fireboxes are small enough to achieve efficient combustion on their own. For added energy efficiency, the cookstove is equipped with a stainless steel hot-water jacket that thermosyphons domestic hot water to an 80 gallon tank in the upstairs bathroom. Just in case the masonry heater wasn’t enough, Michael mounted an externally vented kerosene heater in the basement. This backup heater has proved unnecessary as long as the masonry heater is fired daily.
The complete masonry-heater system has seven dampers, and Michael was worried that Viola might not be able to master them all. A month or so after she moved in, he wanted to review with Viola how to use the system and which dampers to open first. But she told him to back off because she had already mastered the dampers and created her own efficient and tidy firing ritual.
Money alone did not design or build Viola’s home and heater. The family brought to the project incredible diligence, love and attention to detail.
Hemlock, spruce and pine logs for the timber frame were cut from the Rothschilds’ wood lot by local woodsman Troy Romanoski. After a local sawmill sawed the timbers, they were planed, cut and assembled on site by family members Michael, Harry and Wendy Fleming with help from builder Chris Brown. Juliana Rothschild, Michael’s daughter, reproduced an exquisite Chinese painting of household gods on the heater foundation.
It took me three weeks to build the first-floor masonry complex. I built the living-room heater as part of a 10 day hands-on workshop, then finished the rest with Aaron Moore, a high school helper. Brown then built the chimney up through the second floor and the roof. The chimney emerges from the roof at the exact center of the ridge and measures 36 in. by 28 in., virtually mirroring the proportions of the house.
In the meantime, Michael, Wendy and Juliana laid black-slate floor tiles at the front entry and in the sunroom. In the kitchen, native white-pine plank flooring was installed for its warm honey tone. Maple strip flooring was installed in the hallway, the dining area and the living area. To emphasize boundaries, a strip of black cherry was inlaid between the hall and the kitchen, as well as between the kitchen and dining room. Around the heater complex, we laid pieces of slate cut by Michael and friend David Randall from antique sinks and a water trough that I had collected. The slate also was trimmed in cherry.
At the bathroom threshold, the cherry strip appears again, introducing 1-ft. square tiles of white Carrerea marble, reminiscent of Viola’s Italian roots. The bathroom vanity and towel closets (made by local cabinetmaker Tenney Gavaza) are of black cherry, and the vanity top is white marble to match the floor.
With the house completed, the family set about furnishing and decorating it. Jeff Audet, a cabinetmaker from Lewiston, Maine, was at work on a final surprise piece of furniture for the house, a set of cherry book shelves, when Viola died while on vacation in California. Viola made a final, silent visit to her home in a handmade redwood coffin, which was set above the slate-covered floor of the porch and surrounded by flowers, family and friends, including the logger, the cabinet maker, the tile setter, the plumber and the mason.
Shortly after Viola died, a great granddaughter, Viola Lou Lan was born to Harry Rothschild and his wife, Liu Cheng Mei. Viola and her parents moved into the house.