An Insulation Sandwich to Stand On.

Exterior Shell, Sub-floor

After we finished installing the flashing, we had to close up the seams between all the lengthwise sheets, as well as gaps around hangers and the tongue. To do this, we used a special kind of duct tape IMG_9245made by IPG that is typically used in duct work or on chimneys. It’s heat resistant, which I thought was an added bonus, and it came in a roll of about 45 m (omg, finally something in metric). It also came with a hefty price tag though- $15 per roll, so we bought just one to see how it went. Turned it to be perfect for our needs, and we were able to do the entire trailer with just the one roll! The ‘aggressive adhesive’ lived up to its hype and I feel very confident that we’ve been meticulous enough about moisture and tiny intruder prevention. As a side note, it’s miraculous how well the volume of our purchases have been working out. Little waste makes us happy campers.

There was something very oddly pleasing and enjoyable about peeling the backing off of each strip of this stuff and sticking it to our flashing. Smooth lines, and no more IMG_9266gaps! Simple joys 😀 There was a scattered spot (in the area where we first began our flashing, when we still sucked at it) where the flashing was bowed a bit extra – in those places we beefed up the closure using caulking; PL Premium, to be exact. This stuff worked really well, I’d recommend it. IMG_20150903_154529We also used this stuff all around the perimeter of the axle section, and the hangers belonging to the leaf springs and equalizers. If there’s anywhere on the trailer with a higher risk of water infiltration, we figure it will be around the wheels, so that’s why we did that.

Ready for insulation!

Ready for insulation!

Since the caulking takes a little time to dry, we had to space this out a bit, and did it over two days: September 3rd and 4th. We were going to head straight home for the weekend then to recharge our batteries, but we decided to spend the afternoon on Friday the 4th getting the subfloor insulation started. Now, since I did the post on insulation in the research phase, I’ve learned a good bit more about it all. You might recall that we had said we were planning on rigid board (also known as code board) throughout, but at that time I had no idea how expensive the stuff was. Turns out, a 2″ thick 4′ x 8′ sheet is around $50 a pop. So to cut down costs, we tried to come up with a compromise for our subfloor, since it is probably the lowest risk area for heat loss. A lot more research ensued, and to be honest, I wasn’t really able to get a straight answer on anything.

In the plans we bought, the instructions did not include the seam taping that we did on our flashing. They said to use one layer of 2″ thick rigid board, and another layer on top of the first, of 1.5″ thick rigid board with a radiant barrier (shiny silver backing) on the side facing upward. This would allow for the required air space between the radiant barrier and the plywood subfloor in order to properly reflect radiant heat back into the house. No vapour barrier was used in their method on either side. My issue with all of this was that not taping the seams left the underside of the trailer too vulnerable. Also, using a radiant barrier in the floor didn’t make a whole lot of sense since the majority of heat loss would be happening through the roof – I would consider it up there but not in the floor. And lastly of course, the cost of all the rigid was daunting. So we bought some Roxul mineral wool batts – really cool stuff! IMG_20150827_162456IMG_20150904_140455It’s made from volcanic rock (basalt) and steel slag, spun into a fibrous mass which is basically fireproof, highly moisture resistant, and much healthier and practical than fibreglass. It is recommended to install a vapour barrier with it though.

With all of this insulation research, my biggest concern was vapour barriers and if / when to use them. Theoretically, in a predominantly cold climate, you want to place a single vapour barrier on the warm side of your insulation (towards the inside) in order to block moist air moving from inside the house, into the wall / floor space and condensing on the insulation or exterior sheathing once it meets the cooler temperature towards the exterior. Since we had sealed the bottom, moisture and water vapour were effectively blocked from that side, so if any moisture got in, it would be kinda stuck with a vapour barrier on top as well. I was worried that putting that vapour barrier / retardant on the top would run the risk of turning our subfloor into a big ziplock bag of mould, if any vapour was able to sneak inside somehow. Oh the stresses… we decided against it in the end and went back to plan A to fill the entire trailer with rigid board. IMG_20150904_143856That way we don’t have to vapour barrier, and we’ll be adding extra structural integrity to our base. The rigid board is closed cell foam, and it is petroleum based of course, so it is intrinsically very adept at preventing moisture intrusion (and mould development). It’s printed on each board that at least 20% is recycled material, too. Our floor is going to be R-20!! Hooray for warm feet. The roxul won’t go to waste though because we are going to put it in all our walls 🙂

We have an account at the hardware store now, so we’re feeling very professional and important being able to say “Yes, put it on my account, please”! We bought our stack of insulation and the very nice people working in the yard offered to bring it over to our warehouse with their forklift! Gotta love rural Newfoundland. IMG_9276

Each (standard) bay in the trailer frame is 4″ thick, 23 3/4″ long, and 91″ wide. This meant we would get two pieces from each sheet of rigid board, and each bay would accommodate two pieces stacked on top of one another. There are a few exceptions to this, such as in the axle section, and the two end bays, so we adjusted measurements accordingly. We first started out cutting our pieces to size using our circular saw. This achieved very straight lines, and it was ok, but the IMG_20150904_163058blade spins so fast that it actually burns the foam a bit along the cut, and also, I find it a bit overkill / aggressive for this kind of material. The weight of the saw causes the sheet to bow in the centre along the axis where it is being cut, and this sometimes causes the blade to get pinched by the foam, resulting in the saw kicking from time to time. This is not fun. It is a pretty amazing machine though, I enjoyed using it when it was cutting smoothly, and it will be much better when using it on wood.

On day 2 of insulation, Tuesday September 9th, we incurred a power outage for the majority of the day, so we had to try a different method. As it turns out, using a utility knife blade to score the rigid board and snapping it along that cut works beautifully! I’d say even cleaner and faster than the circular saw, and safer as well. We kept this up even when the power came back on. Getting a really snug fit for these pieces of insulation is really important in order to block drafts and to have an efficient and economic subfloor. Why pay for heat if it’s going to escape out through gaps? I took a segmented video laying out the whole process of preparing a sheet of rigid board to place within the trailer frame- you can watch it below!

Using a regular handsaw works well too, and we used one for some of the smaller, thinner trimming we needed to do on certain pieces. And that bread knife… I gotta say, it was essential for those notches. If you’re a good hand at cutting homemade bread, you’ll be great at slicing insulation with the same knife. We finished insulating on September 9th, and bought our stack of 3/4″ 4′ x 8′ tongue and groove plywood for our subfloor as well. We’ll very soon have something to stand on!

Finished job!

Finished job!

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