Efficiency is affected by a number of things. Different types of pale malt produce different yields. A fine grain crush helps, and is possible with BIAB. A mashout helps, I believe, because hotter water removes more sugars. And a full length sparge with water at sparge temperature helps too. But a lot of BIABers put all their water in the mash and get very good efficiency. I think if you do that then raising the temperature of the mash to mashout temperature before removing the grains will help efficiency.
But efficiency isn't the be all and end all. It's most important to be able to predict your efficiency pretty accurately, so you can hit your numbers. You can add a bit more grain, which won't cost much, if you are not hitting your OG. Adjust your efficiency setting on your software and use a consistent method that works for you. The amount of water you use should be similar every time, it should only vary according to how much grain you mash with and how much beer you are making. If you use tons of hops you will lose some to the hops, too, of course. But if you make the same batch size every time there should be little if any difference in the amount of water required. If you end up 3 litres short, use an extra 3 litres next time.
But efficiency isn't the be all and end all. It's most important to be able to predict your efficiency pretty accurately, so you can hit your numbers. You can add a bit more grain, which won't cost much, if you are not hitting your OG. Adjust your efficiency setting on your software and use a consistent method that works for you. The amount of water you use should be similar every time, it should only vary according to how much grain you mash with and how much beer you are making. If you use tons of hops you will lose some to the hops, too, of course. But if you make the same batch size every time there should be little if any difference in the amount of water required. If you end up 3 litres short, use an extra 3 litres next time.
