Klins & Barns
British practice strongly influenced American architecture for hop production, though practices in other countries also played a role and Americans also devised their own designs and building practices. A 16th century publication documented a three-room masonry structure that continued in use in Britain through the 18th century. In the 19th century, British hop kilns (where hops are dried) and hop houses (buildings incorporating rooms for cooling, baling, and storage as well as drying) evolved with larger buildings and different fuels and .construction details for the furnace.
Although some early American hop kilns were constructed of masonry and used open furnaces to dry the hops (usually introducing issues of the effect the combustion gases on the hops), the trend in America was to buildings of wood with masonry, or somewhat later, iron or steel heating apparatus. In America, the easy abundance and low cost of wood, or charcoal made from wood, eliminated challenges that fuel posed to British hop farmers. While a description from the 1830s of a Massachusetts kiln documented the practice of building the structure into the side of a hill so that the furnace was accessible from below and the drying floor from the uphill side, the only mention of a roof was that it "would be a further improvement." While ventilation to dissipate the moisture from the hops was essential to successful operation of an enclosed kiln, American practice quickly evolved to roofed kilns, which retained heat better than an open drying floor and also provided protection from rain. The hip roof form associated with hop kilns in the West was said to have been introduced in New York around 1850; it takes advantage of the stack effect to induce a draft from the furnace below, through the drying floor, at out the open cupola. Although there are examples of round hop kilns in the East and Midwest, this form did not take hold in the West and ultimately faded from use.
Once they reach the necessary moisture level, hops must be cooled and then baled for shipping. In Britain and America, a variety of architectural solutions provided spaces for these operations, with associated sub-types of the hop house. The earliest approach, documented in Britain in the 16th century, was to build a simple, gabled structure and subdivide the interior. The drying floor had to be separated from the furnace (especially where the fire was open) to avoid scorching the hops; this necessity, along with the construction of the firebox and flue (if used) and the benefit of the stack effect led to building forms for the kiln which were tall but compact in footprint. Although the cooling room needed some ventilation, it did not necessitate a specialized building form, nor did storage of the green hops or baling. As a result, many hop houses consisted of a kiln of specialized form and construction, and a more conventional, barn- like building for the other operations. Two other factors affected the building forms for hop kilns and hop houses: the short harvest season and fragile crop required that each farm process its annual output within about two weeks, making it desirable to keep the drying floor in continuous operation and thus putting a premium on easy of loading and unloading the kiln; and even with masonry construction, hop kilns were always vulnerable to building fires because their function was to heat a large quantity of hops to about 160 degrees F. for a long period.
Overall, these influences resulted in varying building forms in America with some common, though not universal, traits:
- The kiln itself was a compact, tall building form with a tapering roof profile
- The kiln form was not scalable; larger farms had multiple kilns instead of a larger, single kiln The kiln was set on a sloping site, providing access from grade to the furnace at the downhill side and the drying floor at the uphill side
- The cooling room, baling room, and store rooms were in a building form similar to a barn the kiln somewhat distinct from the rest of the hop house, though it was connected to it.
- Building forms and mechanical devices which allowed quick movement of the hops from one stage to the next increased output and could reduce fuel use.
Although other construction materials continued in use, and experiments with new materials such as steel and concrete could be found, wood came to dominate construction of hop kilns and hop houses in the U.S. during the 19th century. Balloon framing became common for hop kilns, even in the East. (Balloon framing was a structural technique introduced in the United States as industrial production of lumber and standardized use of wood framing instead of masonry influenced the growing construction industry. It frames the full height of a building's walls with continuous studs, nailing the framing for intermediate floors onto the side of the wall studs, instead of framing the walls at each level independently like interposed but independent blocks.)
In Sonoma County, hop kilns like the subject building supplanted the earlier type that dominated in 1875 when the crop was introduced locally.67 Daniel Flint (whose brother Wilson brought the first hop roots to California) built the first kiln in the state, a frame building erected by 1861. It had a brick furnace, with pipes that heated the air below the drying floor.68 California practice was notable for continuing the developments begun in the Midwest to speed movement of hops, including the use of cars and trestles to move hops from the kiln to a cooling room in a separate building; it also experimented with a wire screen for the drying floor instead of wood lath, and multiple kilns were found on many hop farms.69 In the 20th century, electric fans were introduced to ventilate kilns, and oil and gas replaced wood as the fuel for drying. After World War I, these and other developments led to a new design more similar to generic agricultural processing facilities than hip-roofed hop kilns of previous generations