Using a shed or playhouse is always a brilliant thing to do for outdoor piggies. However, I would be hesitant to use a c&c in a shed, and would always (and do) go for a hutch inside the shed, for a few reasons.
You would like to think the shed would be entirely predator proof but caution is always needed. Even if a fox couldn’t get in, rats can chew wood and can get through tiny gaps. A c&c would not offer them any protection if something was to get inside.
Keeping then warm in a c&c may not be easy.
Many people with outdoor shed piggies do use oiled filled radiators, but it’s going to be shed dependent on how well it heats it up in the first place and if and how quickly the temperature drops if you turn it off or when the thermostat turns it off - you don’t want piggies exposed to fluctuations in temperature. Some say the oil filled radiators work well, others say it does little more than take the edge off. Being in a c&c, you would need a heater to fully heat the entire space and keep it consistent between 18 and 22 degrees for months on end all day and night. Just taking the edge off will likely not be good enough if they are in a c&c as you cannot trap the warmth inside the cage. It would most likely be fine if they were in a hutch given hutches can be insulated and covered which keeps warmth inside, probably allowing you to turn the heater off at night.
For summer you would also need an alternative plan for living and be very aware of what happens in the playhouse. Sheds are brilliant in winter as they offer protection against the elements but can be death traps in summer (and this includes hutches and runs outside). They tend to get hot quickly and you would need to be prepared to move them out.
Tunnel from shed to run is a great idea but keep in mind that they should ideally not be on grass/in a run unless you are there supervising them.
What sex are the piggies?
Two sows can be in a cage with the measurements of a 4x2 c&c, but two boars need a 5x2 (basically boars would need the whole floor space of your playhouse).
This is also where having a hutch in the space will be problematic though because boars need a 180x60cm hutch which wouldn’t fit.
Sows need a 150x60cm hutch, this will also take up almost all the floor space and may not even leave enough room for the hutch doors to be properly opened.
Hides - I would recommend you only use double exit wooden hides outside. Nothing plastic as they get too hot in summer and can condensate in winter exposing piggies to damp. Bendy log bridges work very well
Bedding - no fleecey items or bedding as in winter particularly, as they wont dry properly and can absorb moisture from the air which will leave piggies in wet bedding
My personal experience - my piggies live in a 8ft x 6ft insulated shed with a stable door, and also an internal mesh door so the outer door can be left open and they are still secure inside. I have a hutch in the shed. The shed does not have electricity but even so it remains around 5-10 degrees warmer than outside temperatures which is a godsend in winter and really makes all the difference. The hutch door is left open from May until October and they come and go between hutch and shed as they please. In winter, they have access to the shed floor to play during the day but are locked into the hutch at night for warmth and protection.
For winter the hutch is also insulated and has a thermal hutch cover and blankets to keep warmth inside, with several snugglesafes being used. I’ve never had any issues keeping them warm enough in winter (all winter) and at night using this method. Inside the hutch itself always remains at their comfort zone, even if it gets a bit cooler in the shed itself (and this is why they are locked in the hutch at winter nights - I am certain they are warm enough).
Summer is where the problems are. It gets far too hot, far too quickly, so they have to move into the house during any hot weather in summer. They’ve just gone back out to the shed after having had to move inside for the past week of just over 30 degree temperatures where the shed hit 42 inside.
Even if I had electricity out there, fans still wouldn’t work and would just draw hot air in and blow hot air around, air con also isn’t designed to be used in sheds.
