What do I need to know before selecting and installing a cat/pet door in a door?
Questions you need to answer:


Does your cat fit? we ended up buying a small dog door for our enormous cat.
Can your cat figure out how to go through the door? Ours eventually was able to get through, but would bolt in/out because his tail would get caught otherwise. Some cats never figure out the flap-kind. Try it out in a local store if they'll let you (bring food as encouragement).
Do you mind other cats coming in through the door, too? If you do, you can get some assistance from the proximity-sensing collars, but your cat can still lead other cats inside if s/he wants.


Every cat door is going to leak wind somewhat, except the super high-end powered ones. Rain/snow can be mitigated by building a hood around the exterior of the door if you're handy; I haven't seen a product for this but that doesn't mean it's not out there. 

You may be able to get away with simply having an extra doormat on the inside of the door, and keeping the laundry room door closed. Yeah, it'll be colder in there...the price of some extra sleep at night.