Research News

Masonry heater warms space with no mechanical HVAC system

Masonry heater

This wood-burning, masonry heater keeps the café warm without any additional heat source. Photo: Florian Holzherr


Published March 12, 2015

Upstate New York is known for brutal winters, but sometimes beauty and creativity can be born from harsh conditions.

That’s the case in snowy Buffalo, where a new café prompts us to rethink how we heat — and use — the space we occupy in winter.

The century-old storefront on the city’s West Side was renovated recently by a pair of UB architects and their design is an awesome innovation for frosty northern climes.

The space has no mechanical heating or cooling systems.

During the winter, it’s warmed by a specially engineered masonry heater, a wood stove that radiates heat for 24 hours after a single, hour-long burn. This device, developed through two years of research and testing, makes it possible to keep the 880-square-foot café comfortable an entire day using just six logs.

In the summer, the café is ventilated by huge, folding windows that slide open to take in the breeze,and skylights that draw warm air out.


The interior of this century-old storefront at Fargo Avenue and Jersey Street on Buffalo’s West Side was recently renovated by a pair of University at Buffalo architects. Photo: Florian Holzherr

The entire establishment is configured to change with the weather. When the mercury drops, tables and chairs move inward, away from windows and toward the giant masonry heater. Overhead lamps that hang from a tin ceiling via magnets follow the furniture.

The shifting arrangement has a message, say architects Stephanie Davidson and Georg Rafailidis, faculty members in the Department of Architecture and owners of the practice Davidson Rafailidis Architecture, which completed the project.

“When you come into this café, you suddenly experience something you never think about — you’re intimately engaged with the heating and cooling systems,” says Rafailidis, assistant professor of architecture. “These mechanisms are usually hidden, but in our design, we bring it out.”

The café, which sits at the corner of Fargo Avenue and Jersey Street, is expected to open soon after building owner Giles Kavanagh decides on a tenant. Kavanagh commissioned the renovation and says the inventive architecture has helped attract the interest of multiple business operators.

Two years of research and development

Masonry heaters, which rely on bricks or stones to absorb and slowly emanate heat, have been used around the world for centuries. The concept dates to antiquity.

But Davidson and Rafailidis’ creation is unusual in that it uses contemporary materials and implements a design that many masons they contacted thought would be impossible.

The heater, also called a kachelofen (ka-hell-oh-fen), burns wood in a super-heated firebox. From there, hot smoke travels sideways into a rectangular chamber called a flue and out through a chimney.

The flue, which is horizontal, is where the innovation lies. This is the part of the contraption that stores and radiates heat, and it consists of a 15-foot-long box that houses a looped passageway twice that length. The whole device warms up as exhaust from the fire flows through.

“Very long horizontal flues are unusual because smoke wants to go up, so it’s very challenging to keep it from stagnating,” says Davidson, a clinical assistant professor of architecture. “Many of the masons we talked to said they couldn’t do a horizontal flue longer than 8 feet.”

To bring their idea to life, Davidson and Rafailidis partnered with Empire Masonry Heaters in Rochester to research the feasibility of their design and test materials in a kiln.

The end product is both utilitarian and beautiful.

The flue chamber is built from contemporary materials: refractory cement clad with intricately patterned cement tiles. This carefully chosen combination allows the flue to absorb the fire’s heat and release it at just the right pace — fast enough to provide ample heat, but slow enough to radiate for a long period of time. And, at 15 feet long, the ornamental chamber doubles as a café bench.

“We’re encouraging people to cuddle up to the kachelofen,” Davidson says. “It’s an experience and it’s surprising. It asks people to rethink the status quo about how a space is heated.”

A cozy antidote to cold

With the northeast coming off a February that saw record-setting cold, it may be hard to imagine a building surviving in a place like Buffalo without mechanical systems to control the environment.

But the masonry oven works: It was tested in the winter of 2013-14, during which the city endured two blizzards and more than 120 inches of snow.

Rafailidis fired the device regularly during that period to make sure it could warm the café to a comfortable temperature. He says that in subzero weather, more than one burn per day might be necessary, but that on the vast majority of days, a single burn is enough.