IMG_5483

Polytunnel Passive Solar Heater

My attempt at solving the heat loss in winter in my polytunnel.

Building a passive solar heater for the polytunnel

My attempt at solving the heat loss in winter in my polytunnel.

Notes: I used materials I had around a block of thick insulating polystyrene, some left over underfloor underlay, lots of my guilty pleasure tin cans. I work with building materials so I had some left over plumbing pipe but had to buy the elbows. I purchased, outdoor black spray paint and hard as nails glue. 

I also brought a solar fan for about £15 so the warm air could be blown back into the polytunnel. This isn’t strictly necessary but once thought had entered my head I wanted to do it. I purchased some twin wall sheeting for the front.

Typically the people who have attempted this build their boxes out of wood then put a foil lining and glaze with glass. I went for the materials I had and used them because of the ease of use as in I just needed my saw and glue gun.


The story begins with a lot of tin cans

A hole drill bit

You’ll need a drill

They all need holes

Align and glue on a thermal base

Build an insulated box, cover the inside with foil

Spray all box internals black

Cut a template to build a wall at the base

Secure the wall and make sure air cant escape

Cut a whole for the fan and a pipe piece at the back

Insert fan

Internal polytunnel inlet and outlet

The lower pipe takes polytunnel air out to the passive solar heater. It then travels up through the cans and then is pushed fout the heater by the solar fan and through the grey vent back into the polytunnel.

outdoor piping

Pipes linking outdoor heater to polytunnel inlets and outlets

Passive solar heater

Regretting my use of no nails glue to hold down the twin wall glazing. It’s plain ugly. I could put a border around it in the future. So far the air coming out has been quite warm. I’ll report back at the end of winter.

Building a passive solar heater for the polytunnel

My attempt at solving the heat loss in winter in my polytunnel.

Notes: I used materials I had around a block of thick insulating polystyrene, some left over underfloor underlay, lots of my guilty pleasure tin cans. I work with building materials so I had some left over plumbing pipe but had to buy the elbows. I purchased, outdoor black spray paint and hard as nails glue. 

I also brought a solar fan for about £15 so the warm air could be blown back into the polytunnel. This isn’t strictly necessary but once thought had entered my head I wanted to do it. I purchased some twin wall sheeting for the front.

Typically the people who have attempted this build their boxes out of wood then put a foil lining and glaze with glass. I went for the materials I had and used them because of the ease of use as in I just needed my saw and glue gun.

The story begins with a lot of tin cans
A hole drill bit
You’ll need a drill
They all need holes
Align and glue on a thermal base
Build an insulated box, cover the inside with foil
Spray all box internals black
Cut a template to build a wall at the base
Secure the wall and make sure air cant escape
Cut a whole for the fan and a pipe piece at the back
Insert fan

Internal polytunnel inlet and outlet

The lower pipe takes polytunnel air out to the passive solar heater. It then travels up through the cans and then is pushed fout the heater by the solar fan and through the grey vent back into the polytunnel.

outdoor piping

Pipes linking outdoor heater to polytunnel inlets and outlets

Passive solar heater

Regretting my use of no nails glue to hold down the twin wall glazing. It’s plain ugly. I could put a border around it in the future. So far the air coming out has been quite warm. I’ll report back at the end of winter.