Does your attic need more insulation ? (snow on the roof test)

Here is a simple way to see if you need more attic insulation.

Below is a picture of a house that defiantly needs insulation, above the heated living area the snow is melted. Above the non heated garage the snow is still on the roof.

What's happening here...

The heat from the living area is escaping through the under insulated roof and melting the snow above.

Since the garage isn't heated there isn't any heat to escape up, therefore there is still snow on the roof.