Insulating odd shaped garage

[tyme2par4]

This spring I bought a house built in the 70's. It's quite odd in a number of ways, including the garage. It's currently uninuslated, and I would like to insulate it next spring to help keep it above freezing during the winter, and not so hot during the summer.
My question is, what would be the best way to insulate it?
The rafters are not level, as the garage is lower than the house, so the door to the house is about 4-5ft above the garage floor. That alone isn't a big deal. What really throws me is that there is a door from the garage attic to the second floor of the house. So from the landing, there is another set of stairs that goes up to the attic. There is currently a plywood floor on the right half (from the web to the house), but open on the left. Obviously there's an opening for the stairs.
If I close in the rest of the rafters, am I going to lose too much heat up the stairs to the uninuslated area? Should I insulate the roof instead?

What are your thoughts?

 

[bczygan]

Please put your location in your profile.

What sizes are the structural members and their spans? Need to know if the attic is adequate space for storage or other uses. Need to know depth of rafters and joists.

If you insulate at the roof deck, it must be foam.

What uses do you intend for the spaces?

Bill

 

[tyme2par4]

I live in NH and the temps are already below freezing at night.

The rafters are all 2x6 and the webs are 1x6.
The attic height is 8-8 feet, depending on where you are. I use it for a little bit of storage, but there isn't much up there.
The garage space will mainly be used for parking the cars. And of course working on the cars when they need work.
There's also a door that goes down into the basement where I'm working on a small 12x17 shop, so most of my tools will live there.

 

[Firebrick43]

So you have access to the garage attic from the house? Is that enough/acceptable access for you? I would close it off and put in pull down stairs. Insulating roofs causes many issues best avoided if possible and keeping the heat down will be much more efficient and comfortable.

 

[Perrorojo]

Hire someone to come spray on expanding foam insulation.

 

[tyme2par4]

So you have access to the garage attic from the house? Is that enough/acceptable access for you? I would close it off and put in pull down stairs. Insulating roofs causes many issues best avoided if possible and keeping the heat down will be much more efficient and comfortable.

I would like to keep the access from the garage. But I could possibly build a lightweight, insulated door, as it doesn't get used all that often.

 

[bczygan]

If the garage attic is only going to be used for light storage, and not as a work space, then there is no reason to condition or insulate it.

I would insulate the envelope of the garage space only.

The question remains whether you can install a finished ceiling though.

You need to look at the spans of the ceiling joists in the garage to see if you can install a drywall ceiling.

Please post photos and dimensions and I can tell you how to proceed.

Bill