Can I put rigid foam insulation overtop an existing low pitch roof?  The existing roof is torch on.  I’d like to cover with metal roofing.  My plan is to put 1×4 strapping over the existing roof, put rigid foam insulation panels between the strapping with an air gap along one edge, and then new metal roofing overtop fastened to the strapping.  My questions:  will this work? Can I put it over the old roofing without stripping it down to the sheathing?  Would I use underlayment and if so, over the rigid foam or under?

thanks!

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