Hi, apoligize if this has been discussed, but search did not find anything useful...

We have a simple 1152 sq ft ranch house rectangle. Off part of one side we have an enclosed porch with about 300 additional sq ft. Previous owners put up 2x4 walls with about 1/12 pitched, 2x4 roof. The walls seems to be insulated with fiberglass batt. We have 1 velux skylight in the roof of the enclosed porch. The porch is seperated with a wall between a small mudroom and larger area.

So what types of SIP solutions are available for installing on top of the existing roof that would meet structural needs and better insultion that could be installed/flashed around the skylight?  I haven't looked up our county snow load yet, but we live at 7000 ft elevation in Northern Colorado.

The reason I am considering SIP here is: high insulation in small height (maybe 4 inches), structure capabilities and hopefully relative low cost without doing rip off of existing roof.

Specific solutions and thoughts?

Thanks,
Storm

Applying SIPS over the existing roof would not be hard to do. However, I would worry about the very low pitch on the roof. Does this addition have a gabled roof with a ridge beam or is it a shed type roof where the top of the rafters are attached to the main house? What is the span of the existing 2x4 rafters? Is it possible to increase the roof pitch on the new roof without major problems when tieing in to the main house roof? This information would help better determine a correct solution.

You should also consider the benefits the different construction types offer, before you consider costs. The possible benefits will also depend on how the rest of your house is built, and how the living accommodation is arranged.

Once again polljimmy offers succinct and poignant advice. Well done!