Insulation in garage rafters?

Just looked at a garage that had 4" insulation batts stuffed right up against the sheathing below a garage roof, with the vapor barrier (looked like tar paper) all peeled off with very little left. I know that there should be baffles, but is insulation really needed or effective in a garage? Here’s the thing, the roof is metal and it gets really hot/sunny here in Utah. I assume in summer that metal roof conducts a lot of heat.
Also, its falling down because the vapor barrier is no longer holding it up. What would the ideal solution be?

Metal roofs will often condense and rain water inside. Insulation is often used to control and or prevent it. Solution: qualified contractor should repair the failing insulation.


It sounds like a “hot roof”. You don’t need baffles and there should be no venting. IF, the insulation is installed properly.

Lori, you are there to report defects, not provide solutions, unless you are an expert in the particular defect issue.

What happens if your solution is wrong…money comes from YOUR pocket, is what happens.


Baffles are to cool the roof to protect shingles from heat damage.

as Simon pointed out, metal roofs have a reason for insulation. Too keep the roof temperature up above the dew point.

Insulation was likely installed to keep what heat is in the garage in there. It also blocks radiational cooling when your working in the garage in winter and radiational heating in summer. A radiant barrier is best suited for this application as it also provides better ventilation of the roof deck but it sounds like this house is older than when this practice started and materials were not radially available…

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