In respect of building envelopes, we tend to think insulation, as if that were the only option. But the range of other options is much greater than that. The “R” in R-value stands for Resistance, in particular resistance against heat transfer from hot to cold.
There are other options, which can be complimentary or could simply be the better options at times. I recently posted a few things about the InFlector window insulator, pointing out that it functions in several ways, namely by high emissivity, meaning it bounces heat back away from it, by reflectivity, rejecting light and heat, and by insulation as an air barrier is formed between the window and the InFlector. In short it is a pretty comprehensive solution, and it drastically reduces the heat loads from the largest thermal holes in your building envelope. Arguably, windows are the worst problem, as even the best triple glazing, with 1/2″ spaces, achieves only an R-3.23. InFlector can nearly double that.
With walls, it’s a little better, looking at primarily frame constructions, wall spaces can be from 4″, or 6″ all the way up to 10″, as a friend of mind on Long Island did. and the various insulating materials may range from an R-value 2 to 6 per inch. One big question is that in real life we do not achieve the same results as in the lab, so an R-19 insulation may yield R-15 or less. You do the best you can, but in existing construction, adding insulation beyond what is in the walls, is hard. So insulation is not the way to go.
In short, we have a complete line of retrofit options for reducing energy loss through the building envelope. In an apartment building we could apply this when tenants change, and sometimes even while its occupied if the tenants can stay out for a day. The InFlector window insulators can evidently always be hung even while the building is occupied, although your may need to make changes in some other window treatments.
Here is when heat-blocking coatings come to the rescue. We work with a coating called SuperTherm, which offers 91% emissivity and overall it blocks heat in all its forms: emissivity and reflectivity bounce it back, and an inner layer of ceramic simply blocks heat directly. R-value slows down heat transfer, but the coatings block the heat loss directly, and a 91% reduction is not chickenfeed!
Now there are a myriad of special cases. What if there were lead paint? We have an undercoat for that. What if I wanted to have a smooth finish? Check! What if I want to prevent grafitti? Can do that too! Putting it all together, the windows should come first, as they are always the biggest loss. and in typical situations, the reduction in the thermal load is 20-40% with a 2.5-5 year typical payback. Adding the coatings will result in a combined result of 40-70% reduction in normal cases, and the 2.5-5 year payback period will be typical.