Re: Is the Holman shade house suitable for use in the subtropics?
Welcome to the Bunnings Workshop community @rexwickes. It's great to have you join us and many thanks for your question.
Was this Holman Walk-In Greenhouse With Misting Kit similar to what you were looking at? Any clear or semitransparent covering on a frame is going to heat up the interior to a hotter temperature than what is outside. These are commonly called hothouses or labelled as greenhouses. A greenhouse works by converting light energy into heat energy. Light rays from the sun enter the greenhouse, where they are absorbed by plants and objects and converted to heat.
If you were wanting to protect the plants from the sun, you would need to provide shade to the plants and not have an enclosed environment. If you were to use the frame of the Holman greenhouse, you could remove the plastic cover and replace it with shade cloth. This would give you a shade house.