IBU question

[Nola_Brew]

I brewed a NE IPA a month ago. I added a small bittering charge at FWH and the rest all at FO and WP @150 for 30 min. The IBU calculated for the batch was 35 (used BF). There were some IBU's that were contributed during the WP, maybe 10-15. The FO hops contributed zero. The first batch barely had any bitterness so I would have to assume the estimated 35 IBU's were actually under 30. With my next batch I plan on increasing total IBU's to 45.

Question:

Why does FO additions show zero IBU's but WP additions show IBU's?

I entered the same recipe in BF and BS and changed the hops around. The FWH in BF shows 29 and BS shows 44 or 49 (cant remember the exact amt).

Any insight as to why there would be a large difference between the different software?
The only thing I can see is maybe the equipment profile may be a little different between the two. I'll have to verify when I get home but if it is different it isn't by much.

Also, when calculating WP additions what is the best utilization percentage to use?

 

[J A]

I never could make sense of that, either. Why should FO hops in boiling-temp water add fewer IBUs than whirlpool/hopstand additions at a lower temp? And it's safe to assume that the FO hops are still in the wort during the whirlpool as well so if anything ,they should add more.
I usually calculate FO hops at a small fraction of a minute rather than zero - maybe .25 or even .1 so that there's a blip in the IBUs and then set the WP utilization at a really low percentage, maybe 1 or 2. Can't say it's even remotely accurate, but it seems right to me.
I'm not sure exactly how you'd judge the actual IBU contribution other than tasting the beer and guessing that the number seems to match the flavor, but even then, the perceived IBUs would probably vary with variety.

 

[Ozarks Mountain Brewery]

all I can say is Ive done some testing and it really depends on when you add the FW hops, most times its correct, very low if any bitterness and more flavor, thats the whole point so what Ive done is ignore any bitterness in the mash or first wort and use a bittering hop like normal. as for whirlpool it really depends on the temperature, the longer at almost boiling it would be the same as adding it at say 15 minutes and it will add some bitterness just not nearly as much as you think and the lower the temperature the less it adds. I agree with the first wort readings but not the whirlpool % readings its way off in my opinion

 

[Nola_Brew]

I've read if you add WP hops under 170 then there should be no bitterness. I'll have to assume that is correct as most of my WP hops go in at 170 or below, most times at 160. The NE IPA I did was calculated to have 35 IBU's with 20 of that coming from FWH and the rest at WP. I doubt it had more than 20 or 25 IBU's.
Would you think I should go with 35 IBU's at FWH and ignore what the WP IBU's show if I add them at 160?

 

[Ozarks Mountain Brewery]

I would ignore both if it were me and I don't put a utilization percent in for whirl pool its just not accurate "but" a certain water profile can drastically change bitterness in any brew so its really up to you

 

[J A]

all ... as for whirlpool it really depends on the temperature, the longer at almost boiling it would be the same as adding it at say 15 minutes and it will add some bitterness just not nearly as much as you think and the lower the temperature the less it adds.

It seems to me that if the WP hops are going to add any IBUs at all, then the FO/Aroma hops would surely add more. But the 0-minute addition in the calculator - boil or aroma - adds nothing to the IBUs.

If I do a hopstand/whirlpool, I've been just leaving the hop sack in and using the FO hops as the WP hops, anyway. And I never seem to quite have my act together so the chiller doesn't start bringing the temp down for at least a minute or two after I stop the boil. They're in for a minute or so at almost full boil temp, maybe 5 minutes while the temp drops to 160 and then the 20 or 30 minutes of the duration of the hopstand. With most hops, I doubt that the whole process adds more than a point or two the the IBU count, but if you threw in several ounces, it could add up to something more significant.

 

[Nola_Brew]

My plan this time is to ignore the WP hop IBU amt and add enough bittering to get to 35-40. Will start my WP at 160 or 170 and let it ride for 30 min then continue the chill down.

The last NEIPA I did was calculated to have 35 IBU's but that was taking the WP hops into account, which I will not do this time around. Definitely didn't have 35 IBU's but the flavor/aroma was pretty good. I actually expected more from the amount of dry hopping so may increase those on the next batch.