On Mon, 25 May 2020 08:29:01 -0700 (PDT), polygonum_on_google
wrote:

We have a small, nay, very small lean-to greenhouse.

Trouble is, we are getting quiet a lot of powdery, mildew-like, mould inside it. It is bare treated timber.

Despite opening the doors as much as possible, it has got worse.

I have now given it a good scrub and the sun is drying it out. But I would like to do something to stop it happening again and again. Any suggestions? My suggestions so far have not gone down well. :-(

I've found benzalkonium chloride works well for moss, algae and mold.
It's what's used in a lot of patio cleaners, but it's a lot less
expensive to buy it in more concentrated form as "BAC 50".