Correct way to insulate the roof of a horse run-in shed?

It is an open run-in shed, no soffits but has ridge vent with white shingle roofing. Wanted to use blue board. Do I place it in between the joists, right against the back side of the roof sheeting or do I need to place it on top of the joists so there is air space?

You need to leave a small air channel, running from where the soffett should be, to the peak, between each rafter. There is a product on the market that is made for this type of application, when using batt insulation. But you can easily achieve the desired result, by simply applying a furring strip to either side of the rafters, to nail the blue board up against.

If you applied the blue board directly to the underside of the sheathing.... it would heat up enough to, literally, 'cook it'... causing the sheathing to warp, and would shorten the life span of your roof. So, you need some air movement there to cool it off. An inch or inch and half should be plenty of space.

I would recommend splitting some 2x materials to make the strips to nail/screw to either side of the rafters. These strips could even have some gaps in them, as long as you have enough in place to support the blueboard. (I would go with 2 inch blueboard too... its stiffer, provides a bit more insulation, if blueboard is what you want)

Once you have the insulation up... you need to cover the ends of the openings, so you dont get a bunch of birds trying to nest in the space, hehehe..... you can do this by stapling some vent, or even screen, in place.

Good Luck!

I'd use 2 inch blue construction foam, between each joist, and depending on the space you have, NOT directly against the underside of the roof base material.

Rev. Steven