Sat here watching the snow coming down reminds me of the easy, and cheap, way to check out attic insulation.
Have a look around your neighborhood and see which roof melts off first, a sure sign that there is excess air leakage into the attic, not enough insulation, or both.
This can have many adverse effects. Large heating bills, moisture in the attic space and not to mention roof damage from the inevitable ice damming, caused by the snow melting from the warmed roof and then refreezing when it reaches the eaves. Yes, the resulting icicles do sometimes look quite spectacular but, really, not what you want.
And the moral of the story, seal up the ceiling as well as you can and add plenty of insulation to the attic. Keep those heating bills low.