Wednesday, April 23, 2014

calculations for heating and venting the greenhouse

using some helpful internet calculators, i've figured out this much:

fan calculator:
9' length
5' width
7' height
W x L x (H x 1.2) = 378 CFM fan needed (cubic foot per minute of air moved)

heater calculator:
exposed Surface Area of greenhouse
north wall = 9' x 7' = 63
south wall = 9' x 6' = 54
west wall = 5' x 6' = 30 (estimated because the east and west walls are actually ...
east wall = 5' x 6' = 30 (a square with a triangle on top and i'm not doing that much math)
roof = 9' x 5' = 45
exposed Surface Area = 222
internet calculator said 226, so i'm going with that number.

DR = degree rise, minimum nighttime temp you want to keep inside the greenhouse minus the coldest outside temp you'll be heating against (in Fahrenheit). 55-15=40
226 x 40 = 9040 BTU heater needed

alternately, SA x DR x HL = BTU
HL = heat loss thru single pane 1/4" thick (6 mm) glass. the chart said .9
226 x 40 x .9 = 8136 BTU heater needed

heating cost calculator:
used SA, DR, HL, and # of heating months

cost per month based on needing 8136 BTU heater:
(based on the nighttime temp being constantly 15` outside and 55` inside the greenhouse)
927 KWH of Electricity (kilowatt hours)
35 gallons of propane (per freaking month, that is more than one gallon tank per night!)
3101 cu ft of natural gas

cost per year, estimating 4 months of heating required (guessing march, april, sept, october)
3706 KWH of electricity
138 gallons of propane
12405 cu ft of natural gas

927 KWH of electricity in one month is more than my entire march electric bill use was! (660, feb-700, jan-830 KWH).

i looked around online at some greenhouse heaters.

of the 120v variety (can plug in directly to any outlet), most only rated 1500 watts and 5120 BTU's, which is less than what i supposedly need. googling around to understand volts and watts and amps reveals that 120v on a 20 amp circuit gives 1500 watts. 120v on a 30 amp circuit gives 3600 watts. i dont know what the circuit for the garage is rated. i'll have to go downstairs and look at the circuit breakers. i was hoping to be able to just run an extension cord from an outlet in the garage to the greenhouse. i didnt see any plug in heaters rated for 3600 watts. these 1500 watt heaters tend to run $50-100.

of the 240v variety (needs to be wired to its own dedicated circuit and its own outlet, like a stove, dryer, or air conditioner require). they tend to be rated for 19000 BTU's. which is over twice what i need. aaaaand these heaters tend to run in the $200-500 range.

Friday, April 4, 2014

the shelves go up in the greenhouse

some quick painting was done to the bottoms of the boards
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it was only 40'F outside the day i did the painting, but it was 60 in the greenhouse!
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on a nice sunshiny 60' day, we set up my saw and installed the shelves. there was still snow on the ground in places.
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a front post for the shelving was installed
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some cross bars were installed from the front post to the back post, to support the shelving
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the front and back posts at the other end were located in such a way that they could be attached to the roof rafter for extra support and sturdiness.
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one middle support front post installed, also attached to a roof rafter
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the second middle support front post installed and attached to a roof rafter
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Tuesday, April 1, 2014

rainbow step afghan

an interesting but super easy pattern. its worked in steps. first color is only 6 dc. next color is 6, step up, and 6 more. and on and on. the afghan is rather triangle shaped until you finish it.
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close up of the stitches, and wow did the red and orange over-saturate (i think thats what that is). all the yarn colors are really bright bright colors.
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puppy said there is an afghan? i must try to lay on it!
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why wont you let me lay on it!
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the finished afghans without the fringe
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adding the fringe. i'd never done fringe before.
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fringe added. its not square. but its still really pretty.
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the pattern is here
found it thru