Ah- looking at it 60-80 is flawed. Perhaps the key is looking at it 40-60?? I'll need to play with the numbers. There's probably not a lot of saving on a low IBU beer, but on an IIPA, one could save .25 ounce.
But this does bring up a point- it looks like you make an argument that for additions 60 minutes and longer, the difference is marginal. IOW, one needn't bother applying the chart.
The same hop addition above (1oz of 12AA) will provide a 1.9 IBU difference between 40 and 60 minutes. Keep in mind though that if you are boiling for 60 minutes and DO NOT move that addition (keep it at 60 and get credit for 80), you are only gaining 1.2 IBUs.
To clarify. If you have a recipe that calls for a 60 minute addition of 1oz of 12AA hops for 21.7 IBUs. By NOT moving the addition to 40 minutes in NC wort (according to chart) and keeping at 60 to gain the credit for 80 minutes you are gaining 1.2 IBUs.
To clarify. If you have a recipe that calls for a 40 minute addition of 1oz of 12AA hops for 19.0 IBUs. By NOT moving the addition to 20 minutes in NC wort (according to chart) and keeping at 40 to gain the credit for 60 minutes you are gaining 1.9 IBUs.
In either case you will save .1oz or less. But, if it is worth it to you... I say do it. This chart is just a guideline that I use. Also, as stated previously, these small changes make it almost useless to move move hop additions above 60 minutes in length... right, but it has proven difficult to explain this chart/process as it is... trying to keep it simple and to the point.
You are right though, on an IPA or something, you would save more ounces. But again, when I no chill, I boil for 90 minutes at a minimum, meaning that I extract no more regardless of what I do. This is my chart, depending on how you brew, you could probably make your own chart that fits your needs and works for you. This chart isnt here to be used as THE guidline, it is an example of MY guideline only, that fits how I brew. Someone who boils for 90 minutes at a min. will have a completely different view of bittering hop utilization than someone who boils for 60 min.