Answers

Depending on the application, spray foam is oftentimes preferable.  Closed cell spray foam, applied properly, can also help reduce or eliminate the growth of mold, as long as it doesn't exist already.  Spray foam is typically more costly, but has many benefits to include an excellent R value.

Spray Foam. Much better insulator and fills any gaps that might otherwise be missed.

I would encourage you to read up on SPF and if you do go that route, make sure you get a great and insured installer.  SPF does have additional benefit from and air sealing standpoint but beyond the airtightness improvements, does not (in the case of OC SPF) have any greater R-Value than traditional batting assuming that both are in an static air environment.  Best thing you can do from a real high performance wall assembly is to thermally uncouple the exterior wall from the framing.  This will net you a much higher performance assembly than SPF alone but should be done by someone that is familiar with this approach and applications. 

SPF is great but I prefer it to be used as an air sealant first and foremost. 

Educate yourself on the pros and cons before you engage in an insulation schedule. 

Eric Novotny

Hey Alex, 

?I would say that close cell spray foam insulation is the way to go if your budget allows for it.  Although it's much more expensive than batt insulation, the long term savings on your energy bills will be far greater.? Hope this helps! 

Cheers, 

Eric Consuegra, AROCON Roofing and Construction, LLC