Solar Mike wrote:

What version of basic is this, looks like GWBasic...

Yup. IIRC, gwbasic.exe is still available free from a web site and runs from
a DOS prompt. BWbasic is almost identical and runs with Ubuntu linux. The new
ASHRAE comfort spec also contains a gwbasic program.

It's not easy to estimate the US R-value of a reflective insulation system.
It varies from about 1 to 10, depending on emissivities, airspace thickness,
mean temperature, temperature difference, and the direction of heatflow.
The complex table in the ASHRAE HOF rarely matches real situations, but
this program can help with that.

Nick