Cary Winch wrote: I don't consider what you are doing as an insulated floor as much as it is a lightweight composite floor. If all voids are filled and it is well sealed I think you will have something really cool there.Cary
Cary: I was going to respond to your earlier post until I saw you 2nd post! I was going to ask what the difference was between an insulated floor and insulated sidewalls/roof in terms of moisture infiltration potential, and why you seemed to be saying that an insulated floor was a big problem but that insulated sidewalls/roof weren't. Seems like you addressed that.
My new modified question is while I understand that a "belly pan" would be a bad idea for the floor, how is this different from the aluminum applied to the roof and sidewalls. Doesn't the air gap between the plywood and aluminum on the sidewalls and roof allow for condensation to form and premature rotting to take place? This question has been bothering me for a while, and I haven't seen anybody address it in any forum. Does anybody have any thoughts on the matter?
I agree with you 100% about not using fiberglass insulation.
Finally, I have to respectfully disagree with you regarding your statement that "if you are building a wall 1" or thinner you will not see a significant enough difference in R value over 3/4" plywood to justify insulating sidewalls."
As far as relative R-values, plywood has an R-value of about 1.25 per inch thickness. 3/4" plywood thus has an R-value of about 0.94. In comparison, with Styrofoam having an R-value of about 5 per inch thickness, the composite sidewalls on my trailer (5/32" ply/3/4' Styrofoam/5/32" ply) have an R-value of about 4.14 (not counting reduced insulation because of thermal bridging where there is wood framing). That's about 4 1/2 times the insulating value of 3/4 plywood. That's a big difference. But does that translate into a real-life difference in terms?
The answer is YES! Since my front storage box (top half is accessible from the inside) has uninsulated sidewalls (only 1/4" thick, but still comparable to 3/4" ply in terms of R-value), but my main body has insulated sidewalls, I have been able to conduct real-life experiments with a direct comparison.
The result: in cold weather (I have been in the trailer down to mid-20s F), the insulated sidewalls (even just 3/4" insulation) make a HUGE difference. The storage box sidewalls become very cold to ther touch and because of this, LOTS of condensation forms on them (so much so that I will probably retrofit some insulation to them). The main body side walls stay warm and get no condensation.
Also, in hot weather when the trailer is in the sun, you get similar benefits from the insulated sidewalls. The thermal gain on the inside is reduced tremendously.
Of course, it is a lot more labor intensive and expensive to construct composite insulated sidewalls. For a lot of people who aren't camping in extreme conditions, the benefits probably aren't going to be worth it.
Keep up the great discussion!
Rik