Hot Bed Construction Questions

Discussion in 'HortForum' started by nikdo, Jul 25, 2009.

  1. nikdo

    nikdo Member

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    Location:
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    Hello everyone!

    I am in the process of creating a hot bed inside a home made cold frame. I have not begun the construction yet as I am seeking advice. I live in free hold strata in Coquitlam (Lower Mainland, proximity of Vancouver, BC, Canada), so I own my own land but it is very small.

    The cold box will be constructed on my front lawn for the purpose of it facing south, make use of otherwise useless grass lawn and to educate passersby that indeed gardening is possible next to year round in lower mainland (and what to do with that useless front lawn).

    The basic design I am looking for is loosely adapted from many sources:

    there will be the garden box itself, foot deep, either above ground or within the ground (have not decided yet), filled with mixture of peat moss and various composts. It will be a large box with dimensions of 4' x 12', constructed mainly out of 2x4s. I will be going with the Square Food Gardening methodology as it appeals to me on many levels. The box might have a heating wire below it to help maintain a certain temperature of the soil. On top of this foot deep box, I will build the cold frame (again out of discarded 2x4s). The slant will be 25 degrees (so I can still bend down on the rear, high side of the box and reach the ground. The front height of the cold frame will be one foot above the box with soil.

    In the summer, I will remove the windows on top of it, since this box is meant to be used in the summer as well and allow crops such as tomatoes, cucumbers to climb higher then the box (vertically). In the winter, I will put the windows on, covered with thick transparent plastic. I also intend to insulate the walls of the cold frame with about half a foot thick straw bails.


    I have following questions:

    1) Is a heating wire (forget the exact term) necessary or recommended to use underneath the soil? this question of course pertains specifically to where I live. We get sometimes max -10C, but mainly it hovers between -5 to +7C during winter months.

    What I am trying to understand here with respect to the heating wire is this: if I use it, keeping the temp at around 10C (this is what I read is recommended), will it accelerate maturity of winter plants AND / OR will it also allow me to grow other vegetables, that I would not be able to had I not had the heating wire? I understand I won't be able to grow tomatoes, but perhaps I might be able to grow a wider variety of crops?

    2) Any idea where to buy this heating wire (if you know specific stores in lower mainland)? Would the wire used for de-icing roofs from snow work?

    3) The angle for the cold frame. Some people say where we live you need 45 degrees to get the right sun, others say 30 is fine, yet others say you can live without any angle at all. I am aiming for 25 degrees as a compromise in order to reach into the box on the back side (because my box is long, 12', I have access to some portions only from front and back). So, how much difference does the angle really make?

    4) Wood. Any idea where to get discarded or reclaimed 2x4s or 2x6s or 2x8s?

    5) Insulation. I had the idea of using straw bale, about half a foot thick and line the walls all around it with it. I figured straw bales have insane insulation factor, so this should stop the porous wooden sides. Does this makes sense? Is it overkill for where I live? Again, just like the question with the heating wire, if I insulate it better, is it just to prevent frost, or will it allow me to grow wider array of vegetables? I am not creating a green house, I know that, but would like to know if the extra effort of these measures is worth it.

    6) Any idea where to get cheap straw bale?

    -----

    It is important to me that this project work not only because I want to benefit from it personally, but because I am also an environmental activist and I seek to build stronger and more resilient communities based on the Transition Town concept. As such, the dangers of Peak Oil and Climate Change will necessitate taking food security very seriously. I would like to use my garden and the experience gleaned from it as a platform to build upon and make my community more sustainable and self sufficient.

    I'd like to also mention that I have already a roof top garden on top of my shed that works really nice and also captures excess water to a rain barrel. This cold frame would very nicely complement this existing garden.

    Thank you kindly for your time

    Peter
     
  2. vitog

    vitog Contributor 10 Years

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    Location:
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    What are you planning to grow in your hot bed and during what time of year? It sounds like you plan to use it as a winter greenhouse, but that might not work for typical greenhouse-grown plants because there isn't enough natural light at that time of year. From what I understand, Leafy vegetables, such as lettuce and spinach, are about all that you can grow without supplemental lighting. If that is what you intend to grow, you only need a small amount of heating to keep them from freezing. However, I think that it would be fun to experiment and see what will work. For material you could try Jack's New and Used Building Materials on Still Creek Avenue in Burnaby.
     
  3. Liz

    Liz Well-Known Member 10 Years

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    Location:
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    "5) Insulation. I had the idea of using straw bale, about half a foot thick and line the walls all around it with it. I figured straw bales have insane insulation factor, so this should stop the porous wooden sides. Does this makes sense? Is it overkill for where I live? Again, just like the question with the heating wire, if I insulate it better, is it just to prevent frost, or will it allow me to grow wider array of vegetables? I am not creating a green house, I know that, but would like to know if the extra effort of these measures is worth it.

    6) Any idea where to get cheap straw bale?"

    Straw is not a problem here but I use wood shavings a lot as an insulator. What about the dreaded polystyrene from packing. Newspaper and egg cartons could also be used or bubble wrap or even fiberglass insulation if some how it can be sealed behind a false wall. .

    Liz
     
  4. nikdo

    nikdo Member

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    vitog: I intend to grow leafy and root vegetables only. Indeed you are right that we don't get enough sunlight to be able to grow sun + heat loving vegetables. This is still to be a cold frame, not a greenhouse.

    I was mainly concerned with just how much insulation / heating I needed to grow those leafy vegetables. And if enough insulation was provided, if one could 'extend' the winter season or grow those leafy vegetables faster. It seemed to me I read somewhere that cold slows down how fast those vegetables grow

    As for lumber, jack's new and used - I was always disappointed with them. They are overpriced and don't have much lumber at all. Restore, a block away often has better stuff. But for lumber both suck. I was looking for ideas for free, reclaimed lumber. So far, my only luck has been to find a demolition on craigslist and skids, of which there seems to be unlimited supply! :)

    Liz: great ideas! I think I'll go for the fake wall. I will build the outer wall with the reclaimed 2x4's I already have. Then with planks from skids, I will build another wall inside, and then fill it with some material...I think that straw bale might be best, but I am sure that shreded paper might work as well. Any idea where to get free wood shavings? I'd use it for my compost as well!

    Thanks everyone and cheers

    Peter
     
  5. Liz

    Liz Well-Known Member 10 Years

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    Location:
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    I have been getting mine from a fine furniture place and they only give me the shavings from the planks they are preparing. If you do get onto a place make sure you don't get all the other garbage as well such as laminated boards etc. I load it into large bags from the hopper or at least the boys do. Chaff bags work but the owner made big strong blue platic bags for easy pick up and putting out.
    I took over from my dad yrs ago so the connection with the supply is very long. Also I am in Aust. May be there is a timber mill with clean sawdust.

    Liz
     
  6. nikdo

    nikdo Member

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    Liz: Thanks! I will initiate a search for a similar company. Indeed I know to take only shavings from raw, untreated wood; I don't enjoy feeding my veggies chemicals ;)

    Cheers
     

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