weather skirting

Hi,

You don't have to skirt but it will make heating very much easier to do.

Besides some very good skirting and perhaps a heat source under the rig (light bulb or a heater....be careful if you put a heat source under an enclosed RV of fire danger!!)You should do the following:
put throw rugs on the floor (even if you have carpeting, every where you can); put windshield sunshades between the drapes/blinds etc. and the windows, especially in the bedroom; put heavy insulation panels in all of the ceiling vents...they are all standard sizes in RVs usually 14 1/2" square, I use Aluminum foil insulated material available at any home improvement store. There is a great heat loss from these vents; Use your internal water tank and refill when necessary...do not attach a hose to a faucet, it will freeze solid unless you can locate a heated hose you can plug into electric; if you have slides they are a tremendous heat loss, so it's a tossup of room over heat...you can always pull them in at night or on very cold days; keep the doors/cabinets open where you have plumbing to keep them from freezing; if you can place a heavy tarp over your roof and tie it down very well to keep the snow & freezing rain water directly off of the roof; buy some tire covers; place cardboard or some other form of insulation in behind the grill to the engine compartment to help keep the cold out. Got luck and make Hot Toddies all winter!

I have read where some use hay bales to skirt the sides of the RV. The rear of the DP will require a different approach.

Live up in the northeast and most folks who stick around and are full timers use rigid foam board from ground to underside.
The 2 inch thick panel has a R rating of 7.2 or so. typically used for foundations as a thermo break. I guess you can double them up to get a better R value. I think that a SIPs panel(structural insulated panel) could be had from a good lumber company, a lot of times you can get cuts from a mill (if one was in your area) they have nice hi R values and will help keep the snow and cold at bay.
We have some real cold weather at times in upstate NY. Don;t no what the typical temps are over in Oregon, but when it goes below zero you need all Rs you can get and keep the propane filled
Good Luck,

Here's a commercial RV Skirting website. Maybe you can get some ideas of how to make your own skirting.

In that harsh weather I would make my own skirting to put around your coach it will keep the coach warmer!