Typically you are not deciding to use glass for thermal performance but for other reason like aesthetics. https://www.lowes.com/pd/SEVES-Glass-Block-Glass-Block-Common-8-in-H-x-8-in-W-x-4-in-D-Actual-7-75-in-H-x-7-75-in-W-x-3-875-in-D/1000095299This window is R-0 but I think the info is not provided here. https://www.lowes.com/pd/Project-Source-30001-Series-Tilting-Vinyl-Double-Pane-Double-Strength-Replacement-Basement-Hopper-Window-Rough-Opening-32-25-in-x-14-25-in-Actual-31-75-in-x-13-75-in/3683856This window is R-3.33   (U-value is reciprocal of the R-value)  1/0.3 = 3.33https://www.lowes.com/pd/ThermaStar-by-Pella-Vinyl-Double-Pane-Annealed-Replacement-Double-Hung-Window-Rough-Opening-27-75-in-x-45-75-in-Actual-27-5-in-x-45-5-in/3119077

My rentals down the street, 3/1/1 each about 900 sq ft, built in the 50's, vinyl siding, original single pane windows with storm windows on them....I have about $55,000 in each of them.  

One was a just a broken window pane.

Break them out by item:          8 windows; installed in existing openings:  Anderson series 70, double-hung, double-pane, low-e, with grids.  

In your house, if it's an option, the answer is obvious - put the front door under the gable roof where you've got the three-paned window mock-up and the windows become much less important.

Are the windows old, single pane? 

Improvements:  ADDING new features or upgrading an existing feature.eg:  Old window may be a single pane casement style (crank to open) and the upgrade may be to a dual or triple pane, eGlass with Argon fill replacement.That's an improvement, a capital expenditure and amortized.

Hi Jeremy,The building has some potential, and with a few simple changes could look amazingly different.First, I like the large ground floor windows, the multi-panes look good and not "storefront" at all.

One end panel IS beside the dishwasher, the other is at the other end of the row of cabinets.

FYI, windows will be replaced with dual-pane, and we'll get rid of some of the ones above that little table.