most efficient way to insulate ceiling of garag

What is best way to insulate the ceiling of a garage as far as cost and effectiveness? Do I add insulation rolls between the rafters before drywall goes in or blown in after or?

I'm in Texas where we get brutal heat during the summer and moderate cold winter. A whole lot of what's being done nowadays is spray foam. I had my shop done with it and it was a 100% positive experience. The price is great and it flat works. I personally won't consider any other methods.

In reply to Cousin_Eddie (Forum Supporter) :

Did you use closed or open cell?

In reply to Slippery :

closed cell

Spray foam.

In reply to Cousin_Eddie (Forum Supporter) :

Did you do Spray foam on just the roof line or the walls too?

In reply to 93EXCivic :

I had the entire walls and roof done. Including the roll up door. 

Is DIY spray foam a thing, or am I going to have to have the pros come and do it?

Spray foam is pretty awesome when done well because it air seals and insulates at the same time. So you essentially get a higher R value per inch of thickness then the foam alone is rated at. But, it's pricey, and if it's not done well it can have some issues like shrinkage or off gassing. Blown cellulose is usually the cheapest way to get the desired R value in a ceiling.

I was interested in foaming my attic a few years ago and talked to someone that mentioned that open cell was preferable in case you had roof leaks as it would be easier to spot. Is that true?

Also, would foam add any strength to the roof? Like bracing? 

I think the most cost effective is to have cellulose blown in after the ceiling is done. Next is to staple batts to the underside of your rafters, then drywall. I found I can have the blow in stuff done for the price of buying rolls and I don't have to sweat during the install process.

The spray foam will give a bit better performance though. Check local pricing and flip your coin.