Should you choose to install an LPG system in your project this work must by law be carried out by a Qualified Gas Work Licence Holder who will be familiar with the safety requirements as laid out in the Australian Standard AS / NZ 5601.2:2020
One of the requirements relates to Ventilation – which is required in any space where a gas appliance (such as cooker or hot water system) is installed. The calculations are complex and should be worked out by your gas engineer.
This will have implications for your choice of some other purchases such as roof vents, entrance doors with vents since without sufficient ventilation your gas engineer will not be able to install the gas appliance(s).
Please read this document for more information as provided recently in Queensland as a reminder by Resources Safety and Health Queensland or contact your qualified gas engineer to discuss.