Pretty much all insulation products are harmful if inhaled, and every time a ball hits that stuff, what you are not seeing is small particulate being broken loose and sent airborne… to drift down over your kiddies heads. Probably not life threatening in limited exposure, but definitely not beneficial!

If it were me, I’d screw up the cheapest sheet good I could lay my hands on, or as others have suggested, staple up some 6mm poly and tape the seams with tyvek tape (the red plastic-y stuff). 6mm is pretty robust, so it should stand up to some abuse, but if you go too thin somebody is bound to poke holes in it eventually.

I don’t think it’s dangerous at all. Based on all I’m reading here, I think OP is fairly well informed and is merely confirming his own suspicions, and I’m not the only person commenting in any case, so I’m sure he’s well aware that he can’t just go hacking holes in a 2x6 wall. Another commenter suggested backframing the wall to accommodate the duct, and OP seemed up to the task, so he appears to have at least some basic general knowledge about construction and/or carpentry.

One 90 is not insignificant, but probably not the end of the world. If your run is especially long, consider adding a small booster fan somewhere. Some other commenter’s solution of backframing to accommodate the duct would work too, but sounds like it might be more work…

Either way, good luck to you sir!

There’s no foundation behind OP’s wall, he’s either on a 2nd floor or above a crawl space. Laundry rooms are a prime candidate for 2x6 partitions because the walls hold a lot of services. But obviously we don’t know the exact layout of OP’s house, the wall in question could be holding up the roof, or maybe there’s a third floor master ensuite jacuzzi tub right above there.

Me too, I’ve definitely seen more 2x6 partition walls than I have seen houses with specially built utility chases.

Pretty much, but not absolutely. Sometimes a wall will be framed in 6” studs so that there is room for the utilities inside it, such as a 4” dryer vent pipe.

15 years in hvac sheet metal here. If you are opening up the wall to drill through two studs, you should also be able to drill a fresh hole in the floor where you actually want your duct. This is by far the better option, but of course you would also need access to below where the duct stubs through. It’s not a great idea to add extra bends, length, or transitions to dryer vent, as you are typically relying on the dryer’s internal blower to void all that air and they are not designed to overcome excess static pressure. If you do run the vent in the wall, avoid transitioning to square as that will not be nice for airflow and that square part will fill up with lint faster and be harder to clean properly. Also, connect the duct pipe with foil tape, no screws, as the screws act as little hooks to catch lint, which will also cause faster clogging and difficulty in cleaning.