I am planning a long term relationship with a woman I love very much but combine we have 5 in the household and only a two bedroom house. 2 are grown and hopefully sprout wings and become independant but still would want enough space to accomodate everyone when needed.

I will start with two questions and see if this is the sight that will help me out.

i have a large garage with a loft above (its like a stop sign cut horizontaly in half, the upper is the roof shape and loft then is squared off at the bottom for the vehicles).

I want to insulate the roof, the ceiling is only 2x4, I am under the impression that you have to have (working down) Shingles, roofing osb/plywood, some sort of airgap, insulation, ceiling (sheet rock). Is this correct?

question 2 how do I get the air flow as my 2x4 runs horizontaly from the peak down the roof every 18 inches, so even if i created a gap between the insulation and the osb roof, the 2x4 on either side will prevent any passive airflow to push the heat out.

This is a show stopper and I have yet to figure out this dillema. my friend said put shims on the 2x4 and place the sheetrock onto them allowing air to pass above the sheetrock but doesnt the air need to pass above the insulation below the roofing osb?

How I am I going to insulate that dam ceiling...

I am not concerned about Anything else at the moment, just that ceiling, I will be putting in a ridge type peak vent for the whole roof but I am sure I need much more and somehow move this air I can put saffet vents down the whole left and right side.

I live in Michigan yes its cold up there in winter and hot in the summer. I am just starting this to get an idea. Please help me get this ball rolling if only in my head