I left you hanging in yesterday's post about our skirting decision, and while your thoughtful comments were pouring in, I went outside to start experimenting.  Mark had bought me a four-foot-by-eight-foot-by-two-inch sheet of rigid-foam insulation, unfaced because we wanted to buy from our local hardware store (even though the options there are rather limited) rather than driving an hour to Lowes.  It turned out to be simple to cut the insulation sheet to size with our hand saw (much easier than using the utility knife I tried first).  Digging out a little bit of dirt where the insulation was going to go made it relatively easy to slide the cut pieces into place.

From my perusal of the internet before beginning, I'd thought I'd need to make a bottom rail for the insulation to attach to and to use button nails to attach the top of the insulation to the underside of the trailer.  But once I got the insulation wedged into place, it became clear it wasn't going anywhere, so I skipped that step.  I did use a bit of scrap wood to push one piece back so it lined up with the other, though.

The corrugated pipe we're using to send water from our (as-yet-hypothetical) downspout to our greywater wetland goes under the trailer, and I'd originally planned to cut a hole in the insulation to let the pipe through.  But as I worked, I figured it would be simpler to dig down a bit and send the pipe underneath (as you can see in the photo below).  As I type this, though, I'm wondering if that's a good idea, since the pipe will go down and then slightly up, meaning a bit of water will pool in the lowest point and will probably freeze in the winter.  I guess we'll wait and see if that's an issue, or maybe I'll fix the problem before Mark installs the downspout.

You'll notice there are a few small cracks between the sheets of foam in the photo above.  I went back and forth on these, at first thinking I'd seal them with reflective tape, but then realizing that the flashing I planned on putting on the outside would do the same job.  When I finally crawl underneath to deal with the problematic insulation under the floor (one of these days...), I may use some spray-foam insulation to fill in these gaps.

Rigid-foam insulation isn't supposed to deal well with either UV damage or water, so it needs some kind of outer layer.  We could have bought skirting made for trailers, but flashing is so easy to work with (and is always on hand), so I decided to give that a try instead.  After I took this photo, I backfilled some earth around the base (and will add even more dirt later to increase the height of the planting bed), so the gap at the bottom shown in the photo above is already long gone.

This small part of the skirting project was so fun and easy, it made me wonder why we've been putting off skirting for so long.  Then I remembered that I want to replace the disintegrating insulation under the trailer floor before we make it even harder to work under there by closing the space in.  We may need to bite the bullet and do that before summer, though, since the back of the insulation sheets I installed this week are currently exposed under the trailer, and free-range chicks adore pecking at styrofoam....