re: Finishing bonus room - insulation question

It could just be the picture, but those rafters look bigger than 2x6 (in comparison to the 2x4 collar bracing and other framing). If 2x8's you could go up to r30 batts with the baffles assuming you have soffit vents and ridge venting. If 2x6's then do the r19 with baffles. DO NOT spray foam in your rafters AND try to vent your attic. When foaming, you are trying to create a yeti icechest out of your home. You need a different type of HVAC system that dehumidifies the air in the home, only allows for minimal introduction of outside air, and allows for certain air (gas from heating) to escape. You can cause way more problems than it is worth if you don't account for all of these variables and then some. What happens when you close an ice chest with just a little bit of heat and moisture in it and no way for it to escape? After a few weeks it is full of mildew. Venting an attic space with foam (in our climate) just introduces humid air to an area that it cannot escape from.