In reply to Stone_donkey:
I found this
"How to use compression bags for down or feathers without damaging them
Having said why you shouldn’t use vacuum storage for down and feather, we’re now going to tell you how you can do it anyway, as long as you understand that this is at you own risk, and you’ve read what can happen to the duvets.
Pack the bedding into a suitably large vacuum storage bag. Seal it properly and check the zip is fully sealed as normal. Attach the vacuum cleaner to the valve and start removing the air. Pat the bag as you do it to ensure the bedding is packing down evenly. Do not remove all the air. Stop removing the air when the duvet is reduced down in size, but before it has been compacted to the point that the down is being compressed or quills broken. This means leaving in 20-30% of the air.
You should determine how much air exactly to remove on a case by case basis. So, rather than take all the air out at once, do it in small steps, checking the bag and contents as you go to ensure that you don’t overdo it. You will still have a significantly reduced size and an easy way to store the duvets, but you shouldn’t have done any damage to the bedding.
When you take the duvet back out, ensure you fully shake it to get the air back in and re-ventilate the down."