SIP garden room?

Hi all, we are thinking about replacing our old shed with a properly insulated garden outbuilding. Have been looking at a few options, from wood frame to brick and blocks to SIP (structurally insulated panels). Seems like SIP is the most cost-effective and efficient build? Especially as nowadays builders are so hard to get hold of (and expensive)... It'll be on a raised concrete platform (site is sloped) facing southwest, so I'm a bit concerned that it may get quite hot in the summer as my partner wants to use it as a gym...

Wondering if anyone's got experience with it please? Any advice and comments are welcomed!