A polytunnel (as the word is used in New England) is just a light duty
greenhouse. They are not really designed for winter use in places that
get significant snow loads, but they would work in a mild climate.
However, you will have to put double poly with inflation on them if you
want to keep your heating costs reasonable. Otherwise you will be
spending the difference between the greenhouse and the tunnel on heat.
The extra poly cost is worth it in the long run.

Note that whichever you choose, ventilation is essential to keep
temperatures reasonable inside the structure. You can easily cook your
plants on a sunny day even in fairly cold weather.

You can make your own with PVC pipe if you are really limited
financially. However, the commercially built structures are more likely
to hold up to snow, ice and wind. Be sure to use the UV stabilized
plastic covering. Rated lifetimes are in the 3-4 year range, depending
on the amount of sun you get.



browfish wrote:
Hi, new here so go easy

i very nearly ordered a polytunnel the other day but read that they are
not suitable for overwintering plants such as palms, bannanas etc that i
currently put in a small greenhouse. I understand they are slightly less
efficient at heat retaining but by how much.

I wanted a large 20' x 10' (around £300) and the equivalent greenhouse
would cost me a fortune. Do you think a ploy tunnel would be ok? I plan
on adding some heat and can always line with bubble wrap etc but then i
do that in the small greenhouse. Im in southampton by the way

cheers