A small example of worthwhile forward planning

[Bugtownboy]

I’ve got it it all wrong

What was that song by the B52’s

[Moxi]

Lurve ! shack!

Moxi

[Moxi]

Mind you apparently according to the B52's, tin roof leaks! so maybe better of with the felt roof

Moxi

[Mr Gus]

Joe, I have no idea what you intend to grow , nor how tall, bushy etc..
But from my perspective, you likely don't want (& neighbours won't thank you) if you manure heat it, topping up periodically, this brings a lot of extra work but is eco, also may introduce elements you don't want,moulds, rots, etc.

If building from scratch, bear in mind that polytunnels can be colder than your outdoors environment is in winter, so insulation or at least a cloche within a poly tunnel may raise temps by a few degrees.

I'd literally plan from the sub-ground up so it could be switched out & tweaked, such as an insulated foundation bed & sides, heated seedling area, / blitz a complete underfloor micro-mat heating set up.micro mister & drip irrigation, damping down areas of a poly tunnel to beat the excessive heat that was pointless when it simply dribbled into the ground

Whilst not viable for a poly tunnel, this.... some years ago at an agricultural show, some tenting housing cattle got so hot from the sun that the fire brigade cooled the exterior via a low pressure wash on the canvas roof under gets orders.

Felt lined white painted bamboo would be my low tech emergency protecter to raise & power accordingly to reduce peak heat load, but winter is another thing entirely, if in pots you may consider overhead poles for a sunshade ..so you can throw pots outside, to prevent scorch & whoever is keeping things ticking over when you are away isn't chained down & losing a battle.

For winter warm soil can't be beaten, just lost to the atmosphere, so bell jars creating a micro climate around a plant are good, these days it's plastic & wire fold up laundry basket design, no idea how expensive they are.
If you have space for winter, insulate beneath the soil, then vermiculite soil mix, & maybe To direct heat at the plant, thinnish insulation sheet with cut outs around the plant to direct warm air escaping from the soil to help above ground, ..it a plastic bag worked for my Venus fly traps to flower in a cold Victorian house on a single glazed window then anything is possible with a bit of planned planting, a hole cutter, aluminium tape & some large clear heavy duty poly bags, I'd be maybe making support sticks around the plants (with end tips) & bagging the established plants accordingly to see how far I could take it in year one. Chilli bushes to start with I guess?

A few Ali express LCD 99p thermometers to understand temperature variables over the colder months & one for outdoor subsoil.

Maybe skip rat / Freecycle appeal for insulation boards either way.

The annoying thing about polytunnels is their simple form which is also a limiting factor, we can't touch the mainframe integrity, but we can play around with doorspaces as they are often hung on a wooden frame, which is where cut outs for an exterior fan blower could be fitted without much trouble, & draughtproofed for winter too.I

Just some thoughts to toy with mind.

[Joeboy]

Joe, I have no idea what you intend to grow , nor how tall, bushy etc..
But from my perspective, you likely don't want (& neighbours won't thank you) if you manure heat it, topping up periodically, this brings a lot of extra work but is eco, also may introduce elements you don't want,moulds, rots, etc.

If building from scratch, bear in mind that polytunnels can be colder than your outdoors environment is in winter, so insulation or at least a cloche within a poly tunnel may raise temps by a few degrees.

I'd literally plan from the sub-ground up so it could be switched out & tweaked, such as an insulated foundation bed & sides, heated seedling area, / blitz a complete underfloor micro-mat heating set up.micro mister & drip irrigation, damping down areas of a poly tunnel to beat the excessive heat that was pointless when it simply dribbled into the ground

Whilst not viable for a poly tunnel, this.... some years ago at an agricultural show, some tenting housing cattle got so hot from the sun that the fire brigade cooled the exterior via a low pressure wash on the canvas roof under gets orders.

Felt lined white painted bamboo would be my low tech emergency protecter to raise & power accordingly to reduce peak heat load, but winter is another thing entirely, if in pots you may consider overhead poles for a sunshade ..so you can throw pots outside, to prevent scorch & whoever is keeping things ticking over when you are away isn't chained down & losing a battle.

For winter warm soil can't be beaten, just lost to the atmosphere, so bell jars creating a micro climate around a plant are good, these days it's plastic & wire fold up laundry basket design, no idea how expensive they are.
If you have space for winter, insulate beneath the soil, then vermiculite soil mix, & maybe To direct heat at the plant, thinnish insulation sheet with cut outs around the plant to direct warm air escaping from the soil to help above ground, ..it a plastic bag worked for my Venus fly traps to flower in a cold Victorian house on a single glazed window then anything is possible with a bit of planned planting, a hole cutter, aluminium tape & some large clear heavy duty poly bags, I'd be maybe making support sticks around the plants (with end tips) & bagging the established plants accordingly to see how far I could take it in year one. Chilli bushes to start with I guess?

A few Ali express LCD 99p thermometers to understand temperature variables over the colder months & one for outdoor subsoil.

Maybe skip rat / Freecycle appeal for insulation boards either way.

The annoying thing about polytunnels is their simple form which is also a limiting factor, we can't touch the mainframe integrity, but we can play around with doorspaces as they are often hung on a wooden frame, which is where cut outs for an exterior fan blower could be fitted without much trouble, & draughtproofed for winter too.I

Just some thoughts to toy with mind.

Thanks Gus,
I have no idea what we'll grow. Chilli's and tomatoes for sure. Beyond that we'll just go with whatever takes our fancy. Managed to process and freeze 5 kgs of chopped apples and 1kg of chopped Rhubarb today.

I like that, 6 large Winter desserts taken care off. Each lasting two days. There shall be custard.

[Mr Gus]

The world needed a custard tree at point of earths creation, clearly then, there is no god.
Mmm, custard.