Polytunnel 1

PT1 or Polytunnel 1.


Is the Project Name of my initial Designing and creation of my 6 Metre by 3 Metre “Off the grid” internal grow space.

Let me first start by explaining a few words and things that follow.


What is a Polytunnel.

Why do you need or use a Polytunnel?

What does “Off the Grid mean?”


A covered grow space, much like a Greenhouse but using plastics and various transmission or thickness of Cover to provide more controllable Temperatures, Humidity or Moisture Control.

You can use a Polytunnel for the same reasons a Greenhouse is used, to boost plant growth or keep a certain set of conditions or needs met in a selected space.  From a small-scale Polytunnel to a much larger grow space if required.

“Off the Grid” in this case means.  There is no Electricity Source and only Water in by Watering Can from a Stop tap within 25 Metres or more to bring in Water to the Polytunnel and Plants or Stock inside it.


As for Why do I need or use a Polytunnel?

It extends the season or allows you to start it early.  & in the middle it can give you a boost for heat and overnight Frost protection as well as somewhere to go when the weather is not as you wished or need.

While even being “Off Grid” I fully intend this Polytunnel and Section of this Land to have some form of Automated Hydration and Feeding systems in place eventually.

As well as In House or On Station Electric production to allow Temperature and Humidity Control as well as Ventilation and Exhausting Air from the Polytunnel.

This is where the true Design stage and serious Trial and error comes into play.

Picking the Site and placement of this Polytunnel wasn’t hard; basic Gardening Know how and tracking the Sun aspect was all that was needed.  It’s only when the considerations and needs of what was to happen in this polytunnel are introduced the task really shows itself.


In the Spring/Summer:

Initially a Surface below the required levels of Tender stock to be stored on and allow moisture retention to provide H20 or aid with Humidity and Moisture.  So a Sunken Storage or a “False Bottom System; as in layer or layers of sands, gravels or other means such as Bark Chippings, Coco or Hydroponic Materials” Which can have water and potentially Feed poured on into it and be accessible by Stock stored on this bed.

Then the addition when practical and possible Automated flowing water that requires to be in some manner pumped from Harvested Rain on Site and Close by.

Then dispersed through either Flood and Drain Hydro system or Micro Irrigation system in an enclosed loop.

Much as it’d be nice, a full on spray misting system is unlikely to be viable.

Leading to diversification into Aquaponics when Power and Water Supply requirements meets safety Levels required to keep Fish safe and Healthy.

Ah, and it has to be powered by/run off/through Solar or Wind Power…

Let alone be a viable workspace for mass Seed Sowing and Pricking Out, Potting on, Hardening off stock and storing seed trays if they need to be brought under cover due to poor weather conditions.  It’s going to be a busy place and space is at a premium given the volume of items intended to be brought to life and cared for in this Polytunnel.

Several Hundred Thousand Plants and Seedlings in spring.

Thousands of Bonsai Seeds and Trees brought to life and cared for 12 Months of the Year.

Hundreds of other Varieties or In House grown Stock for SOTG & RBT Requirements.

Prepare several ton of Compost and Materials processed through the working year.

Provide all year round internal workspace and Shelter for a Work Group, Detail or Visitors.

Enable Indoor Refreshments and Breaks are viable.  Subject to weather and Season.


It’s a lot of fundamental stuff in Gardening, those needs are hard to not want, let alone require for basic plant care.

Replicating them on an Allotment or Green Space without the home comforts of Easily accessed Hose Pipe or Main grid support for Power and Water, make your wish list change somewhat from the next plush expensive Hose pipe Head for Precision Spraying to “Where are the next 10000 Litres of water coming in from or Stock dies!”


It’s going to have a lot asked of it and be expected to perform and at least offer basic protection for plants and Humans alike at times.



In the Winter:

Be heated or at least allowed to stay Frost Free via either harvested and Stored Heat through natural means, or by use of Rocket Mass Heating or some other alternative.

It’d be nice to have Hot Water production in place during the Cold and Wet months/seasons or spells.


No matter the season, it should always be easy to store and place large volumes of Seed Trays or Trays filled with Pots that can easily be irrigated.  Internal Staging will need to be several layers high and easy to use to get seed trays with tender and fragile Seedlings and plants in them.


Large Potting and Compost Prep area and Workstations.

This is one of the areas Time and Motion aspects of Design creep in further.  Large volumes if Soils must be processed or mixed to spec and be easy to add too and remove the final mix for use at another station or to be collected and bagged then removed to use.

Constant process of Sieving and sifting soil is a chore and something that would be desirable to reduce the effort and time required through system or process.  Mechanical would be viable if possible.

Sliding the Seed trays around Sowing Area through to Pricking out/Potting on Work Areas would be an advantage – Hard but smooth and non wearing Metal or tracked system?


Internal Grow beds or raised bed with Cloche Enclosures for double insulated Cold Frames inside the Polytunnel and External Hot Boxes using Bricks and Recycled Plastic Bottles for Thermal Banking Sunlight and Natural Heat as well as Glass Lids.


Water Reclamations system using the Polytunnels Ventilation System and Rain Collection Feature on the chosen Polytunnel.

A Waterbutt either side and alternate ends to store the Water that will be used in the Polytunnel.


Possible ideas of a Sump below the Polytunnel floor level to be supplied by Harvested rainwater and used as Store of Internal Water and Thermal Properties to Cool or Humidify the Polytunnel and Hydrate if required.


Not much of a shopping list to get your Design teeth stuck into; right?



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