Conductor wall with internal/external insulation

[Donna14]

Homework Statement

Doing my homework I came across the question:
why it would be better to have styrofoam on the inside of the house
And why it could be better to have it on the outsideThe answer is
The steady state will be the same for both but
inside: warm and cold quickly
Outside: temperature will be more stableIm just not understanding why it is like this... Can someone explane this to me?

 

[BvU]

Typically schoolbook. What they are after: heating and cooling the house itself also requires heat. So with the insulation on the inside, the interior doesn't have to provide that heat (/cold). With the insulation on the outside, once the steady state is established, the house walls provide a buffer.

In practice nobody in his right mind has styrofoam on the outside: birds nest in it, it's vulnerable, etc. Inside idem: not sturdy enough. So isolate between walls or under floors, under roof tiles. But variations are imaginable: with a protective layer of wood or gypsum.