Questions pertaining to creation of hot bed inside cold frame (Coquitlam)

Discussion in 'Small Space Gardening' started by nikdo, Jul 22, 2009.

  1. nikdo

    nikdo Member

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    Coquitlam, Canada
    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


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