In extreme temps, we have found that the side walls and glass can transmit a fair amount of coolness, as the R value is minimal. There are ideas out there to combat this chill, products like Reflectex, that have been used as sun shields, but we were mostly hoping to improve the warmth inside.
We ended up finding a material at the Scout Store that is intended to reflect heat or cold waves. It came in the shape of a large sleeping bag, so this meant it needed to be taken apart. It is silver on one side, and a poly type material on the other. We used the side curtains as templates and fashioned up a set of reflective panels. These are velcroed in place, silver side out, and the interior curtains are then pulled over them as normal. For the back window, we used the same material, but sandwiched an extra layer of polyester mat insulation in between. We sleep with our heads by this rear window, so it warranted a little extra insulation.
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| a little extra insulation built into this one |
We have tested the effectiveness, and quite frankly, it feels warmer. Less cool spots, and certainly less cold radiating from the side wall. We only made the panels for the back half of the Alto, thinking the sleeping area is what needed the extra comfort.
