My wife and I recently bought a home with an unfinished attic that we want to turn into an office. Right now there is insulation under the floor, but not in the rafters. I would like to put insulation in the rafters. The attic currently has gable vents on each side at the peak, but the house does not have any soffit vents. Should I still run rafter baffle vents between all the rafters? Should I run a radiant barrier between each rafter? I want to do it right, but I don't want to waste money installing something I don't need. Thanks!
Charley, it sounds like the only form of ventilation your unfinished attic presently has are the gable vents. If that is the case, I suspect that even now there is insufficient air flow in the area. It's not at all unusual for older homes to have attics that are poorly ventilated and that can lead to higher energy costs. It may even cause the roof sheathing to fail over time.
I'm not sure how much of the attic the new office will occupy, but the finished walls and ceiling will more than likely restrict the air circulation even further. In my opinion, installing ventilated soffit would be a very good idea.
If the current soffits are wood, round vents should be able to be installed between the rafter tails fairly easily. It will have to be done from the exterior and you'll need a hole saw that's the same size as the vents. It may be a good idea to hire a contractor for the project if you've never done this type of project or the soffits require more than a stepladder to reach. If you have vinyl or aluminum soffit panels, switching out the solid pieces for ventilated can be done by most siding contractors.
Once the soffit is set up to allow air flow, baffles should be installed between the rafters prior to the insulation. If you're using fiberglass batts, the baffles should be long enough to permit air to get past them and up to the open area above the new ceiling.
As far as installing radiant barriers between the rafters, I suggest consulting with a local insulation contractor to get their opinion. My experience is that they work better in unfinished attics and in regions that have very warm summers. If you live in an area that has cold winters, increasing the R-value of your insulation might be a better choice. A local contractor should have the knowledge as to which route might be best for making your home more energy-efficient.