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Terms - Construction 101 & Greenhouse stuff

  • 4 season harvest 4 season harvest means that there's a lot of growing in the fall, not much growth, but a lot of harvest in the winter, and then as the days begin to get longer, growth takes off. Elliot Coleman is the 4 season harvest guru -see his books.
  • Anchor bolts Those are long bolts with an L at the bottom that you push down into the concrete, and use to fasten the wall plates) - to be placed after the concrete was poured.
  • Caulk When caulking - latex caulk can be used outside, but pure silicon caulk must be used inside since it will get wet. ie, there's plenty of condensation inside, and for the planting beds, they will always be damp. Of course the waterline connections to the rain barrels have to be caulked with silicone.
  • Concrete beam - Instead of a full foundation, you can use at least 6" of compacted gravel with say, a 12x8" concrete reinforced with rebar. This'll do just fine for a greenhouse and will keep rodents out.
  • Hardware cloth 1/4", 1/2" and larger wire screening, very heavy duty, galvanized, excellent for sifting compost, etc.
  • Insulation #s 4 x 8 foil faced foam insulation, 1/2" thick is bendable, R value about 3.4, 7.2 RValue per inch
    4' x 8' 2" rigid insulation, 12 Rvalue. 6.2 Rv per inch
    fiberglass fiber insulation, 3" thick (for 2x4 wall) R13
  • Let ins Diagonal pieces of wood, at least 1"x2" go diagonally from one corner of a stud wall to another, to stabilize it endwise. When the stud wall has been assembled and is lying a flat surface, ie, your flat garage floor, and you've made sure the corners are square, then they are laid on top of the wall, the wall is carefully marked, slots cut from the studs to accommodate the let-in, and the let-in fits down into each slot, so that the surface is all flush.
  • Plates Bottom and top plates. Bottom plates go between the stud wall and the foundation. They are bolted to the foundation with anchor bolts, and then the stud wall is nailed to them from above. Long top plates go on top of the sections of stud wall to stabilize it.
  • Polycarbonate twinwall Polycarbonate, tho more expensive than plain plastic provides good R value, lasts probably 20-25 years (it is guaranteed for 8 years). By comparison, plain non-UV plastic will have to be replaced annually and has pretty much zilch R value. UV plastic also has little R value and will need to be replaced every couple of years.
  • Rainwater collection 1" of rain on 1000 square feet of roof will collect 640 gallons of water. So our 125 sq foot roof more than fills 1 barrel with an inch of rain.
  • Rebar Steel, various sizes, 1/4" 3/8" etc - used to reinforce concrete. Generally 10' or 20' long. The place where you get your concrete supplies both rebar and the 'feet' to hold the rebar up off the bottom.
  • Shallow foundation system Developed by designers in Scandinavia, the idea is to have insulation around the outside of the foundation - since a great deal of heat loss takes place there. You can have insulation going all the depth of the foundation, down to frost line, ie 3-4', or have it going out laterally various distances - 1-3' depending on the zone. For a greenhouse, we compromised with 24" of insulation going down to the bottom of our shallow concrete beam.
  • Skin Material #s (Material, R-Factor, U-Factor)
    5mm Solexx Panels, 2.3, 0.43
    3.5mm Solexx Panels, 2.1, 0.48
    8mm Triple Wall Polycarbonate, 2, 0.5
    Double Pane Storm Windows, 2, 0.5
    10mm Double Wall Polycarbonate, 1.89, 0.53
    8mm Double Wall Polycarbonate, 1.6, 0.63
    6mm Double Wall Polycarbonate, 1.54, 0.65
    4mm Double Wall Polycarbonate, 1.43, 0.7
    Single Pane Glass, 3mm, 0.95, 1.05
    Poly Film, 0.83, 1.2
  • Skin: Clear versus opaque skin. Ambient light is better for a greenhouse. With direct light, ie, glass or clear plastic - what you get is what you get. But with a opaque skin the ambient light bounces around, especially with a good reflective surface or at least white on then north wall. In essence, it gets 'recycled.'
  • Soil/gravel #s Earth, moist, excavated - 90 pounds/cubic foot
    Earth, wet, excavated - 100 pounds/cubic foot
    Earth, dense - 125 pounds/cubic foot
    gravel - 100 #/cu ft
    Dry sand has a density of 100 pounds/cubic foot
    1.18 tons yard - limestone .75"
  • Stud wall A standard stud wall is composed of 2x4s or 2x6s (for thicker insulation), the center of each vertical is 16" ("o.c., or on-center") and top and bottom members connecting them. It is nailed to the bottom plate and topped by a top plate.
  • Sun: Summer/winter sun In the summer, the sun rises and sets north of due east/west (and in the summer you have more sun than you need). In the winter, the sun rises and sets south of due east/west, and the angle of the sun is lower than in the winter. Thus the sun rises in the SE, crosses the southern sky, and sets in the SW. Therefore, you need to make sure that there are no trees or buildings blocking your winter sun. (Some blocking summer sun is ok)
  • R Factor - the measurement of ‘insulating ability’ of the material. The higher the R Factor number the greater the insulation value.
  • U Value - the measurement of ‘heat loss’ through the material. The lower the U Value the less heat is escaping.
  • Univent a self-opening window, using a tube of wax which expands when it warms up (ie, 85 degrees) allowing ventilation windows to open. The tubes only last 2-3 years, but if you remove them and bring them in for the summer (leaving the windows wide open all summer) then they last longer.

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