This was an asphalt and gravel roof, with a recovery board and a torched modified bitumen and finally a 1" SPF overlay.... No HAAG Engineering needed on this one!
That is a strange looking house. What is that? Shingles on a flat-near flat roof?
SPF is very popular in the Southwest- down here in Texas not so much. In Arizona and New Mexico SPF the competition is fierce. A large percentage of contractors have their own rigs.
3.0 lbs with 3 gallons per square is common- two passes of 1.5 gallons per square- add the Shasta #9's and you have a beautiful roof. If a contractor is using 2.5lbs they usually only apply just 1.5 gallons per square of coating. (they are considered sub par) Not to mention most of the time had under 1/2" per pass of SPF.
I only used the chopped glass a couple of times over SPF but it was difficult to sell against others offering 4-5 gallons per sq with 20 year warranties.... just remember hail was not a huge factor like it is down here.
It was bought and the claim was approved. The adjuster didn't even blink an eye; the ratio appeared to be correct which this adjuster could careless.
Where I come from 3 lb foam is standard for roofing, anything less is for insulation. 3 gallons per square is also standard (about 27-30 dry mills)- in addition, broadcasting Shasta #9 granules adds to the resilience.
My favorite elastomeric coating is mfg by KM Coatings. It has a thermal resistance of .91, reflectivity of .86 with almost 70% solids and is Title 24 compliant-