Polytunnel and heat rentention

[gengis]

HI I have a 6 x 2m polytunnel. The highest temp recorded is 40 celsius but can drop to minus 1 during the night. I am in the north west by the coast. What can i do to retain the heat?

I was thinking about a candle heat retainer using tealights ant suggestions would be welcome thanks

[Bren In Pots]

I've found an older post hope this helps.

https://www.growfruitandveg.co.uk/gr...erracotta-pots

[Nicos]

I’ve seen water containers in polytunnels specifically used to heat up during the day and slow release heat during the night.
On a small scale you could fill water bottles and leave them dotted around the plants?

[rary]

If using poly containers they absorb more heat if they are black or a darker colour