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Thread: Thermal mass as temperature control

  1. #1
    Jwood0123 is offline Germinator
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    Default Thermal mass as temperature control

    In my frantic research to learn as much as possible about gardening early on, I once read about temperature regulation using large containers of water.

    While the science behind it is sound, does anyone have any personal experience in doing this. Is it possible to prevent frost inside a greenhouse using this method?

    Im not particularly keen on using any electrical/fueled heating.

    (in case anyone seeing this isn't aware of what I'm talking about - thermal mass is the amount of heat material can contain, water is one of the best materials for this, so it takes a lot of energy to heat up and releases that stored heat energy over a long period of time, this helps cool in hot weather and heat on cold nights.....in theory)
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    Jimny14 is offline Tuber
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    It will definitely help give you some frost protection, I'm not sure how hard a frost or prolonged cold snap it would protect in a greenhouse. The main problems are going to be how much space you are able to give over to this (as you note the containers are going to be in place for a big portion of the year). February is going to be a struggle I think as in a greenhouse which is relatively small and uninsulated most of the thermal mass will be lost by then.

  3. #3
    veggiechicken's Avatar
    veggiechicken is offline Gardening Guru
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    Let's go back to the BIG question - what will you be growing in your GH over winter that you want to protect from frost?

    I don't heat mine at all. If there's a cold snap on the way I cover plants with bubblewrap or fleece. GH space is too precious to give it over to water storage.
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    ESBkevin is offline Cropper
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    There are several yootoob videos of people (mainly off grid in the USA) using earthbank/car tyres and or black water butts for just this purpose. They are also able to build decent sized spaces to half fill with mass and still leave room to manover yourself and grow stuff. My little 6x8 greenhouse would be all but useless once filled with a couple of water barrels.
    The other popular unpowered heating is an adaptation of the Victorian scheme of Hot bedding.
    Essentially they build a large deep bed (5ftx5ftx4ft deep) of fresh manure. They place a collar around the top and a glass cover accross the lot. You can dig a hole and fill with compost to grow plants direct, or place seed trays and pots on top. I have seen people do this in a greenhouse too. The issues are 1) it must be at least 4x4x3 feet minimum for the natural microbial action to create enough heat. 2) It lasts with decreasing effect between 9-16 weeks. Not a problem if you haul it all out and replace it with fresh after 2 months, but you find that harder if you planted directly into it. 3) Make sure the roots of anything don't get burned. 4) make sure the localised air temp doesn'y get low and damage the leaves.

    Lots of detailed info online, Charles Dowding here in the UK uses the hot bed scheme iirc.

  5. #5
    Jwood0123 is offline Germinator
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    Quote Originally Posted by veggiechicken View Post
    Let's go back to the BIG question - what will you be growing in your GH over winter that you want to protect from frost?

    I don't heat mine at all. If there's a cold snap on the way I cover plants with bubblewrap or fleece. GH space is too precious to give it over to water storage.
    I haven’t planned anything yet, as I’m still very much new to gardening I’m still working out what I can/aim to grow. As you stated as well my GH space is very limited at the moment until I have built more storage space and planters inside.

    The reason I’m considering thermal storage now is that once I’m into next year I will be building a lot of GH furniture so the water barrels could be incorporated into that.
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    veggiechicken's Avatar
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    How big is your GH?
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    Hi,

    Back in the 50's and 60's, Jean Pain did this through composting wood chips.
    He create a complete heating system of self sufficiency, this heated his home and all the hot water he needed to 60C
    Of course he used tons of woodchips, but this can be down scaled to heat a greenhouse, thinking of trying this very principal to slightly raise the temp of my greenhouse over winter.
    The woodchip build is outside my greenhouse with a piping system providing heat to the greenhouse, just not too sure which system to use to pump the heat (no power supply at the allotment)
    This also gives me a great supply of compost.
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    veggiechicken's Avatar
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    Last edited by veggiechicken; 03-10-2019 at 06:35 PM.
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