Thermal mass as temperature control

[Jwood0123]

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)

[Jimny14]

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.

[veggiechicken]

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.

[ESBkevin]

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.

[Jwood0123]

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.

[veggiechicken]

How big is your GH?

[MyWifesBrassicas]

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.

[veggiechicken]

This thread about heating a GH may be of interest https://www.growfruitandveg.co.uk/gr...-no_96070.html

and this one https://www.growfruitandveg.co.uk/gr...use_56181.html

[Mark_Riga]

The same principle can be used for individual plants. e.g. If a series of cold nights are threatened in spring and your courgettes are out then putting a couple of 4pint milk bottles full of water either side and covering them with fleece/polythene/newspaper can protect them.

[Jwood0123]

How big is your GH?

Its only 2mtr x 2mtr, it has a good position for catching sunlight though so I think I can use almost all of the space inside effectively. I have considered using water containers underground, although this would only be marginally better at regulating temp compared to soil, and I will need to make the floor dark to improve the rate of heat absorption (plus the added bonus of less sun scorch on plants maybe?)

As this is all theoretical though, I haven't got much clue on how well it will work.

P.S thanks for the link to the other thread, il have a look now.

[Jwood0123]

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.

This may actually be a possibility for me, I have my compost bin directly behind the greenhouse. Once I have managed to sustain a decent compost temp, I may be able to feed a pipe from the bin into the greenhouse. even if it doesn't last all the way into winter, I imagine it could still extend the growing period.

[veggiechicken]

To be honest with you, I think you'd do better to concentrate on growing winter hardy crops in your GH than giving up valuable space to water containers that may not make much difference to the temperature.

[MyWifesBrassicas]

This may actually be a possibility for me, I have my compost bin directly behind the greenhouse. Once I have managed to sustain a decent compost temp, I may be able to feed a pipe from the bin into the greenhouse. even if it doesn't last all the way into winter, I imagine it could still extend the growing period.

I've been composting a large pile of wood chips since Dec 18 and it's only just started to cool down.
Stayed at around 60C for the majority of that time, it's now 40C, that's 9 months of heat.
However, if what i use to store the heat, say water barrels in the greenhouse, then loosing space for valuable winter growing is a little counter productive just as VC say's.

[Jwood0123]

To be honest with you, I think you'd do better to concentrate on growing winter hardy crops in your GH than giving up valuable space to water containers that may not make much difference to the temperature.

I think I probably will. But while I'm still designing my greenhouse layout, if I can figure out a way to stabilise temperature without sacrificing too much grow space, I'm hoping it'll help even with winter crops anyway.

[veggiechicken]

Line it with bubblewrap - doesn't take up any growing space. I used to do it when I first had a GH and thought I should try to keep the temperature up if possible.................Now I have 5 GHs and just grow whatever I can with whatever the temperature may be.