Our roof structure uses double insulation and an additional vapor barrier to insure our 4 seasons insulation capability. A majority of fifthwheels are built without this exacting insulation spec and you can understand why the fellow's fifthwheel in the above picture just couldn't handle the Las Vegas heat and why 2 roof airs and 2 furnaces have become a norm for other brands.
Also, remember that windows have an “R” value of 1 - its like having nothing there, dual pane windows have an R value of 2, almost ike having nothing there. So the larger your windows, the less well insulated your coach will be. Therefore, one of the parts of our RT Specification is window size control. We make our windows just big enough to allow for good viewing and ventilation and to let light in, but no bigger. Huge windows designed to sell RVs at RV shows, look great, and they really don’t cost very much up front sometimes they cost less per square foot than our laminated sidewall material, but they cost you more down the road. When windows are too big: well greenhouses are difficult to heat and air-condition.
Our window coverings are extremely important for keeping out the hot or cold. Pulling down the day and night pleated shades behind the side cornices creates an excellent air damn that impedes convection currents and drafts. Our window coverings act just like storm windows or thermal pane windows in that they increase the R value of the window opening.
Another way we control the quality of comfort during temperaure extremes is to keep the slide-outs down to a minimum size. Long and high slide-outs are easy enough to make, but when they get too big the total outside exposed area of the slide-out may increase to a point where we would have to add a second furnace and/or roof air. None of our customers have told us that a second furnace or roof air is a good idea, and most of our customers are full-timers who end up in the Western desert in the hot summer or don’t get out of Michigan in time to avoid the beginnings of winter.
Size control of slide-outs also helps maintain the beam effect of our sidewall structure over the slide-out space. Long unsupported spans create a tendency for the beam area over the slide-out to twist or deflect under compression or torsional loads. To Save costs, most RV manufacturers, DO NOT insulate their big main slide-out floors. That is a large area to expose to heat and cold without insulation. Our RT spec. calls for the big main slide-out floor to be insulated with space age insulation material with an insulation efficiency similar to our RT spec. for our vacuum bonded foam slide-out walls and main side-walls. None of our customers have reported inside wall condensation or frost, as could happen in the cold, if the walls weren't up to the job.
The goal is to allow our bonded sidewalls, made of one and one half inches of block foam, to do their job and keep the inside toasty warm in the winter and cool in the summer.
The bonding process allows us to use the same foam that is in coffee cups. Even though a coffee cup may be only 1/8 of an inch thick, it can make a scalding cup of coffee a handleable commodity. Our RT spec for bonded walls with with block foam gives us fantastic insulation roughly equal to at least four inches of fiberglass bat insulation.
RVs built to a less costly specification are often disappointing performers in temperature extremes. As an example, two inch fiberglass bat insulation is normally used by most manufacturers in their hung fiberglass, non-laminated sidewalls or aluminum skin non laminated products.
The standards of our industry require testing data to support R value claims. We are aware of only two RV manufacturers who have paid to have their R values laboratory tested, and both are out of business today. Therefore, most of the R values quoted in brochures by RV companies are cooked up by the sales manager or by an ad agency. As they see it, the bigger the numbers, the better.
Very frankly, we haven’t paid for R value testing either, because to do so is quite expensive. We will, from time to time, quote R values which are printed on materials that we use, but not the total constructional composite R value. All we can tell you is that our R values are good enough for one tank of propane to keep our RT model with living-room and bedroom slide-out at room temperature for four days and four nights of sub zero weather, and at the other end of the spectrum, our roof air blows cold in the Kitchen, Living-room, and Bedroom on hot summer afternoons in the Mojave.