As summer wanes and night time temperatures remind me that my insulation deadline is not some arbitrary date, I have begun that project in earnest. Having completed my degree in Thermal Engineering at the University of Tube, I now feel marginally competent to the task. While there are tons of opinions out there about the relative value of different insulation options, I have gleaned from them a few key guidelines for my project. They are:
- The hierarchy of importance for insulating a trailer goes from top to bottom. The ceiling is the most important surface to maintain year-round comfort in a trailer. In the winter, heat wants to escape from the ceiling. In summer, the roof becomes a flat-iron grill and wants to bake you alive. That is where you should spend your money.
- Spartans have narrow wall bafffles – 2 inches in the case of my ’57 IM. That is insufficient for batt insulation (where thickness is key) to be of much value. Cramming 5 inch thick pink insulation (rated at R -13) into a narrow gap negates its effectiveness and renders you maybe R – 5.
- A radiant barrier is only effective when used in concert with an air void. If you place a shiny aluminum surface (the foil) against another shiny aluminum surface (your trailer walls), you will not get a radiant barrier. You will have installed a conductor which will do a nice job of inviting that scorching summer heat into your dwelling.
So, armed with these guiding principles I drove on down to Home Depot (yes, I checked other sources online, and any pricing advantage I found was negated by shipping costs – as much as $10/sheet for solid foam). I purchased two 2″ 8′ X 4′ sheets of R-Max Thermasheath (closed cell polyisocyanurate), rated at R-13.1 for my bedroom ceiling. It was $31.67 per sheet. I splurged on the bedroom for obvious reasons and it may become my refuge when weather extremes occur. I also purchased two rolls of Reflectix foiled bubble-wrap radiant barrier. Although R-Max is foiled on both sides and one could argue the bubble wrap is redundant at $16 per roll, I decided to go with the extra layer of protection. Even with these two layers, the slightly pitched roof of the trailer affords an additional 2″ of air space, giving the radiant barrier plenty of room to do its thing. Also purchased was foil tape, a long knife for cutting the sheets (forget the box knife) and a cool toy – a infared spot thermometer. The installation was a breeze.