Cooling Loss in water volume calculation

[mgarofan]

New to AG brewing and have a question re: calculating total water volume needed.

I read everywhere that a cooling loss factor (typically recommended to be 4% loss from boiling to room temp) should be considered when calculating the volume of water to be used for a batch. As this 4% volume decrease is due to cooling of the wort from boiling to room temp, I can see why it would need to be known when monitoring the volume of the boil (so that you don't end up with less wort than you'd planned), but I don't understand why it should be used as a factor in initially calculating the volume of water needed for a batch...

Put another way, if I start the brew process with 68 deg water and end the brew process with 68 degree wort, how can there have been any volume lost due to cooling? Thus, why would one factor in cooling loss when calculating the total water needed for a batch?

I know...I'm anal...but this has been bugging me. Thanks.

 

[ayoungrad]

Not sure, but my guess is that people are talking about accounting for 4% volume loss if you are trying to estimate final volume by measuring volume at the time of the boil.

 

[StinkyVp]

I need to figure this out because I stopped my boil with 5.4 Gal of water in my pot. Once it was cooled and in the ferminter I had much less. I estimate only 4 Gal of water. My plan is to pad my boil with +1 Gal extra.