Hi @Denia,
Thank you for your question and welcome to the Bunnings Workshop community, it is fantastic to have you with us.
This question comes up frequently on Workshop and a number of solutions have been offered. You might like to check out some of the following discussions for information that would be useful to you.
Foilboard is a good choice for patios like this as there is no need for sheeting to be installed to keep it in place.
Alternatively, insulation batts will offer a higher R rating, but you will need to install sheeting to keep them in place and contain any fibres.
Please note that the use of foil insulation products is prohibited in New Zealand due to safety and compliance regulations. Ensure all insulation materials meet local building standards.
Let me know what you think and if you have further questions, please don't hesitate to ask.
Jacob
