My favorite topic! Well... not really. Not at all.
I spent so many hours of research...
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[approximately 60,000 words deleted for brevity]
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All in all, I...
...your insulation, why, and whether or not you like it.
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Our answer is in two parts...
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a)
2003, we converted a 1996 Ford CF8000 commercial truck to our concept of an ExpeditionVehicle.
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Insulation:
Against the outside wall, we used:
* adhesive-back acoustic, a gap, then
* one-inch pink-board, another air-gap, then
* two-inch foil-side poly.
This is also the ceiling system.
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On the floor of the box, we laid one-inch pink-board, then half-inch marine plywood painted on all surfaces to seal.
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Our Reasons:
After a half-century of camping in lesser rigs, we realized we need:
* better insulation than is installed by a factory RecreateVehicle manufacturer...
...and...
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b)
We realized we need
* smaller windows than a factory RecreateVehicle.
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Our Reasons:
Glass is incredibly temperature-transient.
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In a skoolie or van with enormous acres of glass in the quarters, maintaining a stable environment is nigh on impossible.
Accordingly, we installed 3010 (three feet wide by a foot tall) dual-pane sliders designed for a stand-still house.
We installed these at our eye-level standing inside, about eight feet above pavement.
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Obsessively excessive insulation plus small windows.
We like this combination because:
* window height discourages peepers
* temperature stability.
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Stability?
Indeed!
We heat with one Wave 3 catalytic heater set on LOW.
Leaving the rig for several hours, we shut off the heater.
Returning several hours later, the rig is still comfortable.
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But wait, LM, how is that even possible!
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Heat Sink:
I grew-up on a farm.
Our home was/is adobe with a concrete floor.
Cooler weather, sun pouring in the windows warmed the concrete.
After dark, the floor radiated the stored warmth into the interior.
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In our rig, I simulated a concrete floor by using slate.
The Wave 3 sits on its stubby legs and heats the slate, then the slate releases the heat slowly anytime the heater is off.
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This's simple and fool-resistant.
Our rig is constantly evolving, but the insulation seems at its peak.
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We achieved Peak Insulation.
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To reduce humidity and odors, we open two windows on opposite walls 24/7/360°.
To further reduce humidity, we shower on the porch.
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To further further reduce humidity, we built with No! Holes! In! The! Roof!.