Good on both points.

Installing on the outside is a complete pain in the arse however. The superfoil is reflective enough that the extra gain wasn’t worth the extra hassle. It also looks a lot better from the outside (if it matters to you what the neighbours think).

As for the foil. It works, but is very hard to apply. Milar space blankets are a bit easier, but not much. That’s how I ended up with the super foil. It’s stiff enough to handle, but flexible enough to roll up for storage. A cardboard backing also makes sense, though it would have made storage harder for me.

It’s also worth noting to not leave it up for too long. Cannabis growers use a similar method to try and hide drug labs. You might get a visit from the police (hopefully politely) if it’s up for too long.