Quote:
Originally Posted by rvmaker
When you speak of ventilation, are you talking about between the insulation and the outer skin of the box?
Can You explain this with a pic? and I was planning on notching a hole at the ends of each joist and alternating the holes, then having a fan that can be snapped on, or run on a timer.
This is not a good idea: to coat the original wood floor of the truck with fiberglass resin to help prevent moisture damage to the floor decking. Am I on the right path in my thinking?
In structures, water flows down, but also from warm to cool, thick to thin. Plywood is problematic because it is layered thin-thick-thin-thick, thick glue between layers of wood. When creating a temperature difference of at least 2°C the water starts to flow towards the cold. Steam pressure is higher in warm than cold. In case of barriers, it will be stuck and stay for prolonged periods - to reach temperature or pressure difference to flow again. For this reason, flooded houses are tough to dry. Standing moist feeds all kinds of fungi and other micro-organisms and they tend to cause problems. Not to mention the freeze-thaw cycle in a colder climate. Water expands when it freezes causing moist structures to break.
For example, freight containers or vans have this problem - the density is reversed, the thick side is outermost layer and water has nowhere to go. Therefore it condensates and drips down. The worst possible mistake is to use mineral- or other kinds of wool insulation inside. I see this a lot.
Spray Foam PU attaches seamlessly to metal surface leaving no space for water. It also mutes the temperature difference from the surface, so the moist (steam) stays in the air and then that needs to be vented out. |
RV maker, I'm intrigued by what you're saying, but have a few concerns.....
My first concern is the introduction of water in the form of a potential leak. I remain committed to trying to prevent this from happening, but would like to build with the possibility that if ever I did get rain water inside the enclosure, that I can get it out. That being said....... I'm especially concerned where the sprayed in closed cell insulation is utilized, and the insulation begins to deteriorate from the heat hitting the roof. I know that just a small little break in paint coatings such as a rock chip in a vehicles paint for instance, is an entry point for water to get under the paint. So I'm thinking that any point where water can actually reach the sprayed in foam, via a gap or hole in the box (which is going to be more likely to happen than not, lets face it.) I'd just be concerned that this water will be working at the bond between the foam and aluminum, and becoming a source of trapped water. So I was planning (although still researching) on using sheets of rigid closed cell, and leaving a 1/2 inch gap between this insulation, and the box at all points..... floor, walls and ceiling. On the inside, I would of course be applying a vapor barrier to prevent moisture from the living space, from getting to the cooler environment outside the insulation, and creating condensation. This was also the reason I was considering a fan, to circulate air throughout the gapped areas I was talking about, to assist in equalizing the temperature between the gap, and the outside of the box, as well as serving as ventilation should water (from rain or melting snow ever get in the box. I plan on doing routine checks and maintenance to prevent it, but just in case.......
By the way..... photos or sketches are forthcoming..........