A home windows installation rep gave me a quote today and conducted the following temperature differential demonstration.
Alice pointed a heat gun (with a surface temperature of 165F) at the interior surface of a window.
Bob measured the exterior surface of the window (with a no-contact laser thermometer) to be 45F.
Is there any way to calculate R-value (or any other standard thermal insulation reference) given the temperature differentials resulting from the above setup and procedure? Can the setup or procedure be improved in order to get an R-value or any other standard and useful benchmark or metric? If so, how?Fig. 1. Test Setup
Edit: Per one of the answers, let's make the simplifying assumption the temperature of the window's interior surface is equal to the temperature of the heat gun.