ROBERT JOHNSON

Greenhouse - What would you differently now?

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I am building a solar greenhouse, mainly for sundews, 6x3m, 1m underground, front will be doubleglass, top 16mm lexan. Front is 17deg to maximize light and heat from sun in winter and reduce in summer. The construction will be from Larch, treated by Osmo oils.54712e06e2049e2248154059606f1cdc.jpgdb215e4764cdf5b34504d9002594f6bb.jpg

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On 22/09/2017 at 10:28 PM, Fero said:

I am building a solar greenhouse, mainly for sundews, 6x3m, 1m underground, front will be doubleglass, top 16mm lexan. Front is 17deg to maximize light and heat from sun in winter and reduce in summer. The construction will be from Larch, treated by Osmo oils.54712e06e2049e2248154059606f1cdc.jpgdb215e4764cdf5b34504d9002594f6bb.jpg

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Really interesting to know how much winter heating you will need for it.

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Really interesting to know how much winter heating you will need for it.
according to my calculation, which include 10 year historical daily data heating to +10 degrees should cost 150 eur per year, but I did not include solar gains and vent losses - these could be +-0. Half I plan to heat to +15, half +5.

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1 hour ago, Fero said:

according to my calculation, which include 10 year historical daily data heating to +10 degrees should cost 150 eur per year, but I did not include solar gains and vent losses - these could be +-0. Half I plan to heat to +15, half +5.

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Sounds very optimstic, but will be interesting to see how well it works.

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On 8/16/2017 at 10:44 PM, Gaz said:

To start the ball rolling I would say...

  1. make sure you have a good level base down
  2. while you're putting the base in make some provision to get power in the GH.
  3. decide where your water butts will be going.  Does the base need to be big enough to accommodate them as well as the GH

There has been some talk in greenhouse cirlces of using water butts as a sort of heat sink, to provide passive heating of a greenhouse. The maths don't work. The water cannot absorb sufficient heat during the day to make up for the heat loss during the colder nights.

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21 hours ago, Sunscript said:

There has been some talk in greenhouse cirlces of using water butts as a sort of heat sink, to provide passive heating of a greenhouse. The maths don't work. The water cannot absorb sufficient heat during the day to make up for the heat loss during the colder nights.

The problem is heating the water up quickly enough in the daytime, 1 te of warm water stores a decent amount of heat but heating up a water butt would take a long time.  Same with cooling it down.  It would really need a system of pipes, radiators and pumps, and then your using power to pump the water around.  It just not practical in a small greenhouse.  Big industrial greenhouses use a variety of methods to store heat, sometimes underground.

Same issue with dick’s solar powered system for pumping hot air through water filled bottles underground, if you could get a decent amount of water stored, at least 1te, preferably more, it has a chance of being usefull.

 

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Thanks for the great question.

 

1) If you have digging machines, then consider installing pipes for a ground source heat pump. Once you reach a couple of meters underground, the temperature doesn't vary much, regardless of what happens on the surface. It is about 12Celsius.

2) Have a place and space for a hammock in your greenhouse. It would be a waste to leave such a lovely place solely to plants.

3) Consider hanging some LED growlights to keep things going during Winter.

4) The North side will likely lose such heat that it might be worth using multi-panel polycarbonate there.

5) You can use a water feature like a pond in front of the South side to bounce light into the greenhouse. If the water is saline, it wouldn't freeze during winter.

6) Consider a geodesic dome. Check out ziptiedomes.com and the brilliant Paul Robinson channel.

7) Space is often limited. If digging, dig deep and use trap doors to allow storage under the green house.

8) 6mm Polycarbonate twin wall is the best balance for allowing light and retaining heat, iirc. There are UV protection coatings now available. Frosted polycarbonate will disperse light and reduce "hot spots".

9) Plan for and automate ventilation and irrigation.

10) Consider a hydroponics setup.

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Considering 6mm polycarbonate on a new build poly tunnel (13ft x 32ft) Will this material allow sufficient light for Sarracenia ? Also will 6mm polycarbonate require shading material in the summer ?

kind regards

Sean

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