Polytunnel’s should be cleaned at least once a year, maybe more if your Polytunnel is nearer trees as it will probably have algae forming on the outside and debris from the trees falling onto it. There are different ways in which to clean your tunnel. Here are a few helpful tips :-
If you get a bucket of warm water and add a small drop of washing up liquid, you will then be able to use a soft brush to clean the tunnel, for the bits you cannot reach get an old bed sheet and with a person each side of the tunnel gently go along the tunnel. Be careful not to do anything that will scratch the cover as this will reduce the light transparency.