If you'll be there for a few years you might want to consider a green wall for that side of the house. Best approach is to build a structure off the wall to train the plant, but you can also just let something like a boston ivy grow and you get the benefit of shady leaves (e.g. transpiration/cooling) during summer, and they lose their leaves over winter so you'll get direct sun again. I experimented on the side of an old house and had temps more than 10deg lower behind the leaves/on the wall than the ambient 35deg. https://www.theguardian.com/lifeandstyle/2019/oct/20/dont-bother-with-living-wall-plant-ivy

I realise this won't help the window issue. The shade cloth will work but I think you'll want something more tensionable than ocky straps.. a big wind could have them whipping round. Edit: see other posts about not attaching to the guttering.

You might also want to look at planting something deciduous to shade the window during summer too.