Before we dive in, it's important to cover off on an idea that many people miss out on: a bug out bag should be built for fast movement towards an area of safety, with capabilities to overcome any obstacles in your way.
An evac is not a camping trip or a backpacking trip--it's not a happy, leisurely thing. You're running for your life. If it's safe for you to be moving, and you have the physical ability to do so, then you should be getting out of dodge, not hanging out bushcrafting or whatever. A lot of people get confused here.
We also often overlook our primary form of transportation - the ol' family bug out vehicle. The BOV will to get us to our safe location faster than on foot, and should only be ditched if absolutely necessary - ambush, utterly impassable roads, out of fuel with no hope of refueling or broken down with no hope of repair. These are the kinds of dire situations that would push us to abandon our vehicles, extra gear and bail out on foot.
This all helps shape our choices for shelter. We should attempt to have something that is:
- Light and compact enough to allow for fast movement
- Quick to set up/take down
- Multipurpose if possible
- Robust enough to provide life saving shelter in killer weather conditions
- Subdued color or camouflage pattern
Setup and take down times on these kinds of shelter can vary, and improve with practice. Bivy bags are mostly just roll out and jump into. Tarps can be a bit trickier. I would not hesitate to add shortcuts like bungie cords to help ease setup - yes, you should know the knots, but if you can save time/effort for a minimal weight savings. Worry more about set up times than about how fancy or perfect of a shelter you can pitch. From packed to under shelter in 5 minutes is a good baseline.
Robustness on tarps and bivy bags is going to vary fairly greatly - I would be cautious about going with too thin/lightweight of material. But, you probably don't need the item to last for months of use - it needs to hold the weather at bay for as long as it takes you to move from your point of danger to your targeted safe zone.
The old USGI poncho used to be the no-brain option, but they are getting scarce and running up in price. Many use the bivy bag from the military sleep system. There are numerous tarp, poncho tarps and bivy bags on the market, though - Go Lite, Seek Outside, Kifaru, SnugPak, Dave Canterbury's Patherfinder School, Bushcraft Outfitters USA and others all have solid options in their product lineups. A green, brown or tan hardware store tarp can work in a pinch, too. Not ideal, but not much money, either.
A tarps, poncho tarps or bivy bags are the common answer to the survival shelter problem, and it's a good one. If you need to go really fast and light or find yourself without your kit, here are a couple options to consider:
Having the tools and know-how to build primitive shelter, ala the Discovery survival TV shows. A fixed blade knife, saw and cordage are go bag staples, and they're all you need to build a variety of primitive shelters that will keep you alive in nasty weather. Throw in an axe and you can do even more. And, these tools are useful for more than just shelter building, too.
This "Bear Grylls" approach has a major downside to it - shelter building is time and calorie intensive, and your time and energy would probably be better spent moving to your final destination. It also exposes you to greater risk of going without shelter - if you're injured, don't have adequate materials, run out of time in the day, etc.
Use Existing Shelter
Most areas of the U.S. are populated and developed - lots of existing buildings and other hidey holes. In a bug out level disaster scenario, a large number of buildings are likely to be completely abandoned -- office buildings, unimportant stores (not many people shop for furniture during the apocalypse), barns and utility buildings and so on. All certainly potential options.
Private residences will be hit-or-miss--hard to determine if they're actually abandoned, potentially deadly if you barge into someone's occupied home by accident. Certainly risky.
The home of a friend or acquaintance would be another matter - if they are home, you may be able to hunker down in the basement or garage for an evening. If they aren't, well, at least they might not shoot you if they show up while you're riding out the storm in their living room.
And, of course, lots of other options - access tunnels, bridges and overpasses, etc.
Either of the above - primitive shelter or leveraging existing shelter - can also of course be combined with any shelter that you have with you. For example - a tarp can do a considerable amount to reinforce a debris hut or lean-to.
Anyways, quick overview of some of the options that are out there and how to think about your selection when packing shelter for your bail out bag.
What shelter do you carry in your bug out bag? Let us know!