September 23, 1911 



HORTICULTURE 



430c 



GREENHOUSE CONSTRUCTION AND HEATING 



An Illustrated Address before the Vegetable Growers' Association of America at Boston, Mass., by W. R. Cobb of the 



The subject which I have been as- 

 signed to speak on this evening, is a 

 most interesting and extensive one. 

 It is so extensive that it is impossible 

 in one evening to touch other than 

 briefly on the various parts and the 

 part each of the various details plays 

 in the finished structure of an up-to- 

 date greenhouse. Each of these parts, 

 such as the superstructure, ventila- 

 tion, plant benches and heating, are 

 capable and worthy of considering 

 separately. 



But as it is not possible for us to 

 have more than one session, I shall 

 try to cover the subject in a general 

 way and trust that our time together 

 may be profitable. I shall not try to 

 go into mathematics and other of the 

 various sciences which are called into 

 requisition in designing an up-to-date 

 greenhouse, but simply present In a 

 pictorial way, the results that have 

 been obtained and progress made. 



The Old Type of Greenhouse. 



It is a long step from the cumber- 

 some greenhouse of 50 years ago, to 

 the modern cobwebby structure of to- 

 day. The illustration which we have 

 before us on the screen, is typical of 

 the early greenhouse. They were gen- 

 erally built against a high wall, the 

 wall being on the north side. This 

 wall was quite a factor in supplying 

 heat during the night. You know how 

 a piece of masonry will absorb heat 

 with the sun shining on same, and 

 how it feels warm for a long time 

 after the sun has ceased to shine 

 upon it. So these high walls absorbed 

 the heat and gave it up to the green- 

 house during the night. In those days, 

 the only method of heating was to 

 have a stove or a long flue either of 

 pipe or masonry running the length of 

 the greenhouse, through which heated 

 air generated by a furnace was at- 

 tempted to be carried. 



Now as the construction of the 

 superstructure, a heavy wooden sill 

 was placed on top of the front wall. 

 Heavy wooden rafters were placed 

 about 3 feet apart and sash glazed 

 with glass only 6 inches wide, were 

 placed in the roof. The top sash was 

 arranged to slide down for ventilation 

 and was operated with a system of 

 ropes and pulleys. 



The crops raised in houses of this 

 type were far from satisfactory as 

 you can readily realize, as with the 

 amount of wood used in their con- 

 struction and the narrow glass the 

 percentage of light admitted was very 

 small, to say nothing of the cold air 

 admitted through imperfect construc- 

 tion. 



Later, full span houses were built 

 of similar construction. 



Mr. Lord, who was the founder of 

 the L. & B. Co., was a great lover of 

 flowers and also a thorough mechanic. 

 He had a small greenhouse in his yard 

 built similar to the last one I have 

 shown you. Mr. Lord became dissat- 

 isfied with the results obtained and 

 made up his mind that if horticulture 



Lord & Burnham Company. 



was to make any progress it would be 

 necessary to greatly improve the con- 

 struction of the greenhouses, so he 

 built himself a house which proved to 

 be so far ahead of anything yet built, 

 that his services were soon in demand 

 among the local community. It was 

 not long before the success attained in 

 these new houses spread beyond these 

 narrow limits and the greenhouse 

 business, as a business by itself, was 

 launched. It has continued from that 

 time to grow until it has reached its 

 present proportions. The outlook for 

 its continued expansion, improvement 

 and stability is bright. 



Construction and Principle. 



The house adopted and built by Mr. 

 Lord was the same as is universally 

 used today, namely building the roof 

 as a permanent sash, with separate 

 small ventilating sash at the ridge. 

 This method increased the amount of 

 light in the greenhouse as well as 

 furnishing a weather proof construc- 

 tion. Methods of supporting the roof 

 members are today numerous, but 

 they all are simply a means of mak- 

 ing the principle stated above, stable 

 and lasting. In the early days there 

 was no glass on the sides. Walls of 

 brick or stone were built and the roof 

 sprang directly from the top of these 

 walls. The inside level of the green- 

 house was generally on a lower level 

 than the outside grade. This was done 

 so as to "reduce the surfaces exposed 

 to the outside air as much as possible. 

 Most of the houses were narrow and 

 the plant benches were so close to the 

 glass that it was impossible to grow 

 plants of any size except on the outer 

 edge of the benches. 



The next step forward was to make 

 the roof curved instead of straight. 



The roof was constructed with two 

 radii, the lower one being about 8 

 feet radius, the upper 45 feet. This 

 gave more room for the plants on the 

 outside of the plant beds. The glass 

 was not bent, but short lights were 

 used and as the radius was large com- 

 pared to the length of each light, the 

 difficulty was solved the same as in 

 building a curved part to a brick 

 house with ordinary straight bricks. 



With the introduction of hot water 

 and steam as a heating medium, it 

 became possible to increase the width 

 of greenhouses, and houses of 20 to 25 

 feet in width became common. This 

 gave room for a centre plant bench. 



Then came the introduction of 

 glass on the sides increasing the 

 height from the walk level to the gut- 

 ter line. By doing this it was possible 

 to build the roofs without the curves 

 and still have room on the side 

 benches for medium sized plants. The 

 masonry wall was cut down to almost 

 grade and wooden vent panels about 

 two feet high placed on the sides be- 

 low the top of the plant bench. This 

 in a measure is an ideal way of ven- 

 tilating a house where side ventilation 

 is required, as the cool air from out- 

 side has to first pass over and around 

 the heating pipes, which takes the 

 sting from the air. 



Iron Construction Introduced. 

 At this time commercial houses 

 were built with locust posts set about 



three feet in the ground and four feet 

 above, and boarded up to the eaves. 

 As the tendency towards wider houses 

 increased and wood decreased in qual- 

 ity it became necessary to find some 

 construction that would take the place 

 of that then in use. The use of iron 

 as a building medium was at this time 

 attracting attention, and to this metal 

 attention in the construction of green- 

 houses was turned. Cast iron sills 

 were substituted for the three-piece 

 wooden sill and iron rafters and pur- 

 lin. 



The first iron frame greenhouses to 

 be built were those for Mr. Jay Gould, 

 at Irvington, N. Y. Here a cast iron 

 sill capped the masonry walls and iron 

 rafters and purlins capped with wood 

 were used to support the superstruc- 

 ture. The principle of this construc- 

 tion todav is still used in all iron or 

 steel greenhouses. The details may 

 be changed but the principle of hav- 

 ing the iron or steel framework on 

 the inside of the greenhouses, while 

 all members which receive the glass 

 are of wood. This construction after 

 repeated experiments has proved the 

 most suitable to our variable climate 

 and has stood the test well. 



The next important step in the 

 construction of commercial houses 

 was the introduction of what is known 

 as the Cast Iron Foot Piece Con- 

 struction. A post or foot piece made 

 of cast iron was placed in the ground 

 about 30 inches, and to these the steel 

 rafters were bolted. The sides up to 

 within two feet of the eaves, were 

 built of two thicknesses of boards 

 with paper between. This made a 

 cheap and substantial construction. 



Next wooden gutters and eave plates 

 were dropped out and angle iron used 

 in their place. The bars and rafter 

 caps were fastened to this angle iron 

 with a small cast iron fitting. The 

 eave nlate having part of its surface 

 exposed to the inside temperature of 

 the greenhouse conveys the heat to 

 the outside surfaces and to a certain 

 extent prevents the formation of 

 icicles on the outside. Certainly it 

 was and is a great improvement over 

 the wood plate and gutter, which 

 were the first members in a green- 

 house to decay. 



Use of Concrete and Hollow Tile. 



Concrete and hollow tile are now 

 being used for the sides instead of 

 double boarding. Where hollow tile 

 is used, it is necessary to plaster the 

 outside and inside surfaces of same 

 with Portland cement mortar. Then, 

 too, the tile have to be cut, and it re- 

 quires more or less time and ingenuity 

 to use the tile to the best advantage 

 without waste. From observation 

 and tests it seems as if concrete made 

 with clean cinders was the cheapest 

 ,-ind best to use. The cinders being 

 more or less porous, makes a concrete 

 full of air cells which accomplishes 

 the same results as the hollow spaces 

 in the tile. The walls need only to be 

 four inches thick, and when a light 

 cast iron sill is placed on top of same 

 you have a construction which is 

 practically indestructible, and as the 

 upkeep is small, this form of con- 

 struction is the cheapest in the end. 



