I've had good results with the Thermofor gas pressure automatic vent
openers on pre-existing conservatory roof vents. I got them from Jade
Mountain. I still need to put up double shadecloth during the summer.

Mike

In article , Jan
wrote:

Does anyone have any recommendations for a particular one or any
problems with using one?

We have an 8x6 aluminium greenhouse in a very sunny position so any
ideas on shading materials would probably be helpful too.

Thanks - never had a greenhouse before as you can tell :-)