(extracted from H. Goldbach 1979)
Construction Details of the new Storage/Drying Unit
Because the available funds did not allow the purchase of a prefabricated room which would meet the program's needs, it was decided to construct the main building by direct labour.
The Unit (see Figures A 3.1 to A 3.5) consists of the following parts:
a foundation raised 50 cm (minimum) above ground level. Two-inch diameter PVC tubes are embedded in compacted coarse gravel below the freezing room, and spaced about 50 cm apart to provide drainage and subfloor ventilation.
a separate roof on 30 × 30 cm reinforced concrete columns, consisting of fibrous cement sheets (Ricalit (R)) on steel trusses. All sides were left open to provide good air circulation and to avoid heat build-up beneath the roof.
a drying room (inside dimensions about 7 × 3 × 3 m) built as an antechamber to the store.
a cold store (dimensions within the insulation, about 6 × 7 × 2.5 m).
The joint structure consists of:
reinforced concrete floor on heavily compacted coarse gravel.
walls of reinforced concrete columns, spaced about 3 m apart and in-filled with high resistance concrete blocks. In order to provide additional strength and resistance to earthquakes, the block work is reinforced by a lattice of 1/2" iron rods, embedded in cement, between every second course of blocks and at vertical intervals of 80 cm.
a ceiling of reinforced concrete 20 cm thick is suspended from beams (20 × 30 cm with 3/4" iron rods) extending from column to column. Reinforcement between the beams consists of 1/2" rods criss-crossed at 20 cm spacing.
The ceiling was poured directly onto the insulation, which was held in place by temporary supports.
All the concrete was kept moist to give a slow drying effect which results in higher strength. Finally, a cement plaster was applied on both sides of the walls.
Vapour-barrier: This consists of a layer of paper/glass fiber coated aluminum foil between two layers of generously applied asphalt. The individual sheets of foil are overlapped at least 10 cm on each side. The vapour barrier on floor and ceiling extends at least 50 cm onto the walls to avoid possible gaps. The asphalt provides an elastic and vapour-proof connection between the foil sheets, so that thermal expansion and contraction of the walls will not damage the vapour barrier.
In the drying room the vapour barrier of the walls and ceiling is protected by sheets of fibrous cement mounted on a wooden frame.
The inside floor consists of reinforced concrete ‘floating’ on the vapour barrier.
Thermal insulation: common polystyrene foam is used to insulate the walls and ceiling of the cold room, and high density polystyrene for the floor. For walls and ceiling, 40 cm thick sheets (1.2 × 2.4 m) were used, cut in a way that provided an overlap of at least 20 cm on all sides. The sheets are kept in place by wires fixed to the walls and also by a wooden lattice on the inside. For the ceiling insulation, curved iron rods were pressed into the styrofoam (at least 40 cm deep) and hung from the ceiling reinforcement. Floor insulation consists of two layers of 20 cm thick high density styrofoam, with a 20 cm overlap.
All seams were grouted with asphalt, and occasional wider gaps were filled with polyurethane, foamed into place.
The wall insulation is protected by asbestos cement sheets fastened to the internal wooden framework, and the ceiling has an additional layer of ornamental styrofoam.
The floor consists of 10 cm reinforced concrete with a smooth finish, sufficiently resistant to bear the expected load. The insulation is sufficient to maintain temperatures below freezing point for at least one week, should the cooling equipment fail, provided the door is kept closed.
Cooling and drying equipment
Cooling: Cooling compressors of the semihermetic type are used. A 5 HP compressor and a 16800 BTU/h evaporator are sufficient to cool the chamber and maintain the temperature at -20°C. Freon (R12) is used as refrigerant.
A second identical cooling unit is provided as stand-by equipment.
The main equipment is controlled by a thermostat set at -20°C (± 1°); the stand-by equipment is controlled by another thermostat set at -17° C (± 1°), so that this latter will switch on automatically should the temperature rise to -16°C. This is the simplest and safest way to control the stand-by device. A switchboard with control lamps indicates whether the emergency equipment is working or not. Once a month the functions of the two units are exchanged, so that each receives equal wear as “main” and “stand-by” equipment. An alarm bell, controlled by a third thermostat, switches on at -15°C.
Drying: For the drying room a silica-gel type dryer, which maintains an RH of less than 15 % at +25°C was installed outside the building and ducted into the antechamber. It is controlled by an electronic humidistat set at 20 % RH.
Uniform humidity distribution in the room is provided by remote installation of the air-inlet of the drier.
To compensate for the heating effect of the drier, a household type airconditioner (9000 BTU/h) was installed. The gaps between the wall and the air-conditioner are filled with an elastic filling, and the apparatus has been slightly modified to prevent the entrance of moist air.
A 30 KW electric power plant provides the whole system (as well as the short-term storage room and the laboratory) with electric current in case the main supply fails. A control unit switches the plant on automatically when the power fails or if the voltage varies by more than 10 %.
Short-term storage room (used jointly with the Latin-American Forest Seed Bank)
At Turrialba, seeds obtained from recent collection trips or by introduction, which normally come in very limited quantities, are kept in the so-called short-term Storage Room. It is run at +5°C and at about 30% RH. Seeds are kept in paper bags and maintain their viability, under these conditions, without any significant reduction for between 5 and 10 years.
The chamber (internal dimensions: 4.5 × 5.5 × 2.2 m) is built like the long-term storage room but with less insulation. The cooling equipment consists of a semihermetic-type 3 HP compressor, a 10400 BTU/h evaporator and a standby compressor. A silica-gel type drier maintains the low relative humidity.
A room for seed preparation and a laboratory for routine seed testing (germination, viability, moisture content), as well as for experimental work on seed storage and germination, are located close to the storage units. The labequipment includes various incubators, 4 Copenhagen-tanks, a small germinator, a two-way thermogradient table, an air-circulated drying oven, an analytical balance and other items. A walk-in germinator is in use since the second half of 1979.
A 3.1 Plan for longterm storage unit at CATIE, front view.
A 3.2. Plan for longterm storage unit at CATIE, side view, roof construction not shown.
* = not shown on floor and ceiling; applied throughout on the warm side of the thermic.
A 3.3. Plan for longterm storage unit at CATIE.
(installation of vapour barrier applied on all sides of both rooms not shown)
A 3.4. Wall and floor construction, details not in scale.
(* vapour barrier consisting of aluminum-foil between two layers of asphalt)
A 3.5. Wall and ceiling construction, details.