Welcome to the forum
I keep mine outside in a shed. I have a 8ftx6ft shed.
I actually find keeping them cool outside in summer is considerably harder than keeping them warm in winter.
Yes a shed would need to be insulated. I have silver foil insulation in my shed.
Winter is pretty easy - it involves plenty of hay as as bedding. Hides stuffed with hay. Thermal hutch covers and blankets on the hutch. And importantly Snugglesafe microwaveable heatpads inside the cages to provide warm spots for them to sit.
In summer is where the issues tend to come and with the weather getting warmer year in year it is becoming even harder.
They should not be exposed to anything over 25 degrees so being outside at all can really be a problem. Hutches and sheds then tend to trap heat and raise the temperature further . When it was 32 degrees here on Saturday, my shed hit 38 degrees. My piggies had to be in the house in temporary enclosures as it was far too unsafe in the shed and also too hot to be on the lawn.
I personally wouldn’t do the one in your link as that is set up for poultry - nest boxes etc. You just need a normal shed.
I had mine made by a local company. It has an external stable door and internal mesh stable doors. That way, I can have the external door open but the mesh door in place for ventilation. Being stable style I can of course have the top half open and bottom door closed on cooler days.
Sizing is obviously a consideration. Two sows need a hutch of 5ft and two boars need a 6ft hutch so you obviously need to make sure your shed can accommodate a hutch of that size.
I posted a few pics of my shed to another older thread which may help you -
How to make sure shed stays cool in summer?