[edstrong]

Am ordering a polytunnel soon and need to decide on the type of polythene. The company offers two: Lumisol Clear and Lumisol Diffused. I'm thinking about the Diffused as I want to try to limit the maximum temperatures in the middle of summer and this one will help by letting slightly less light in. I'll be growing veg, live in the Midlands.

Does anyone have any experience of both types, any hints or tips to help me decide?

[Fleecewife]

I think our cover is Visqueen, the thickest and semi-opaque.  The previous one was clear.  My first observation is that I can no longer see out with the opaque cover and as we have an amazing view from our hilltop, I really miss that when working inside the tunnel, so when this cover needs replacing I shall probably go for a clear one.
I suspect that the opaque cover might help with reducing heat loss at night when it's very cold, but I've not seen that mentioned so far. I have though seen it advised ( I think by the late Bernard Salt in his polytunnel growing book) to allow the condensation to build up on the inside of the cover on nights when frost is forecast, and that will help reduce heat loss.  I assume that the opaque cover may act in the same way
We live in a very cold, windy area so summer heat is rarely a problem, and we deal with any build-up which does occur by good ventilation - we have large louvres at both ends and can stand the double doors open. More important for us is to get sufficient light in to ripen crops such as tomatoes. You probably won't have this problem in the Midlands.
I think all told, for our situation, I prefer the clear cover.

[Anke]

Wether clear or opaque - you want a cover that has UV/photo stablisers added. Usually the more expensive one. Ours came from First Tunnels and is still on its first cover (14 years old). You can compensate for high temperatures by having both a side vent and doors at both ends. I wouldn't think temperature is important, I have never found the tunel to be much warmer - if it is frosty outside, it will be inside the tunnel too. In order to keep it a bit warmer you have to use fleece covers on any plants in there in winter.


First Tunnels provide some of the best polytunnels in the UK, only trumped by Keders in my opinion. But you get an awful lot more tunnel for the same money as for a decent site Keder. Still wouldn't be without mine!

[Fleecewife]

Speaking of excess heat, don't skimp on the anti-hot-spot tape between the hoops and the polythene.  Without it, over the years, the extra heat from the metal does denature the polythene and cause it to crack. As Anke has pointed out, a good quality cover can last for many more years than quoted (which is usually about 7 years).  I can't remember exactly when our current  cover went on, but it was definitely more than 15 years ago.