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Greenhouse

S

Spikeanator

hey i finnally get to build a greenhouse/sunhouse. it will be 12 ft by 12 ft. Going from 8 ft in the back to 6 ft in the front. the back and at least one side will have plywood for a wood. the top and front will by a double layer of 4 mil plastic stuff. how many btu's do u think it will take to heat it. it can get to 0 degrees F. pretty often here. i want it to be a warm house as decribed in the Savage Garden. staying at least 50 degrees F.

Thanks

Brad
 
i am going to build it lol, so i got it from the the local lumber store. i am going to build it as a shop project. the lumber and the plastic cost me lil over $239.
can u guess how mant btu's i will need to heat it at 50 degrees year round?

thanks

Brad
 
4mil plastic sheeting?? Or do you mean like a rigid plastic? If your talking plastic sheeting in a roll, I would suggest 6mil Greenhouse film. It is capable of handling the sun for several years.

To get a rough idea on heating. Charlies Greenhouse has a calculator. Heat will depend on the lowest outside temperature you might experience, the square feet exposed to the cold, the type of covering material, and the differential temperature between the warmest temperature you would like to reach on the coldest night.

Tony
 
where is the calculator? yes i mean 4mil plasic sheeting in a roll. will it work for a year or 2? or should i get higher? thanks


Brad
 
The plastic poly in a roll will get brittle and break up within a few months out in the sun.. roughly. Greenhouse poly film is made with UV blockers.

Charlies basic heat calculator

IGC calculator

The first one is very basic. The second is much more involved but probably more accurate.
 
can you buy this green house film online?

I'd like to make a miniture green house to experiment with something.....
 
yea 6 mil poly film will last you about 4-5 years... I also reccomend using the air bubble meathod.
 
sure Jess.  Although if you want only a small piece maybe you can find someone that has some they can cut off for you.
IGC poly films

(oops I should add) The overwintering film is not for more than one season use. While much superior to the poly film in a roll in your hardware store. It doen't have the UV protection that a 4 year all season polyfilm has. The cost of a good poly film is very insignificant to the effort to install and cost of the plants if it rips and all your plants die! Don't skimp on the poly film!!

One more thing Brad.  You would get much more insulation value if you used 2 layers and inflated them.

Tony
 
  • #10
ok so i need to use a Greenhouse poly film of at least 6 mil? and it need to be 4 season film?

how to i attach them and inflate?

thanks, all the help is apreciated

Brad
 
  • #11
Whether you inflate 2 layers or not is up to you.  The greenhouse polyfilm will work without inflating.  But you will have less insulation rating.  You would know better how long your cold season is and how warm you want to heat it as well as your utility costs.  

If you decide you want to look into 2 layer inflated, click on the IGC poly film link and you will also see other things such as inflation blowers and aluminum rails with clips that lock the 2 edges of the poly together.  These rails go around the entire perimeter on the outside of the structure so the 2 layers can then be inflated like a pillow.  You can do it less fancy and simply overhang the plastic and then roll up the excess around a piece of wood like a windowshade.. and then secure that down. As long as the edges are sealed to keep air from escaping.

Of course your other options would be a clear fiberglass panel or more fancy.. twin wall polycarbonate.  Fiberglass is not too expensive.  It would be a bit more than the polyvinyl sheet but might look a little nicer and won't flap around in the wind (a potential problem if you use uninflated polyvinyl sheet that is not pulled snug enough).  Twinwall polycarbonate looks great and has higher insulating value than inflated polyvinyl but is ALOT more expensive.  Fiberglass and polycarbonate will also last about twice as long compared to polyvinyl sheet.

Tony
 
  • #12
well the double b mil poly panels dont save me much for heating, so i think i will go double poly sheets with an air space. the blower must be used right, i mean there isnt any other way to put air in it is there?  also does the blower run continueally?  and the tube locks they have to put the poly on 1) do u just screw the base part to the frame, 2)  what about the gaps between the 6' long locks?  i think that is all my questions.

thanks

Brad
 
  • #13
Thanks Tony,

This air pocket method is most interesting. Would the insulation value be futher increases by placing some type of bubble insulation inbetween the two layers? Also the method in which you seal these pockets would be simielar to say a autoclave clamp? Would one be able to create a frames out of 2x4's and then secure them together with something like hinge latches?

This is most helpful I'm planing out my greenhouse for a build this summer and I think I like this pillow method.

thanks,
JEss
 
  • #14
Brad-
The inflation blower runs continuously. Not sure what you mean by gaps between the sections of aluminum locks. Each section butts up to the each other so that when the top clips are installed it is one continuous run all the way around the edge. The base piece is secured down to the frame. The two layers of poly are placed over the frame with some extra extending beyond the base sections and then the top clips are snapped on. The inflation blower is installed on the inside so the air is blown between the two layers.

Jess - I guess you could put a layer of bubble wrap in there? Only problem I see is that unless it was secured, there would be nothing really holding it in place. And if you needed to get to it for some reason... you wouldn't be able to. Not sure what you mean by autoclave clamp or hinged thing.. The aluminum 2 part locking clips are nice but really anything that will form an airtight seal around the perimeter would work.

Tony
 
  • #15
but now after looking into it, it might be cheaper to just buy the double 8mil poly panels and screw them onto the frame after u pay for the blower running continuesly and the blower. thanks


Brad
 
  • #16
well i finally desided what to do. i went out and bought some corragated plastic. thanks for the help


Brad
 
  • #17
I just bought one of these for a greenhouse. Haven't put it up yet but I just don't have the patience anymore to build one lol.

pseudoGreenhouse
 
  • #19
Gonna start with the tarp and see how the light is. It's mainly for my neps.
 
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