Dear Sir or Madam,
I respectfully disagree with you on all counts. Speaking just to the question of vapor/condensation issues, I intend to have none of that due to fact that I intend to implement an energy recovery ventilation system that should deal with all condensation questions quite handily.
From what I have seen of the pics of the inside of the roof sheet metal of school bus conversions, there doesn't seem to be enough evidence that condensation is as serious of a problem as a lot of people think it is. Most, maybe all, of the roof rust that I saw was from roof leaks (the corrosion from the leaks would probably have been worse if not for the perforated ceiling). The perforated ceiling allows condensation, if any, to dry out fairly quickly in most conditions. I would think that the humidity level in a bus full of children breathing would be pretty high and condensation would happen frequently if it is going to happen. At least the perforated ceiling, fiberglass system seems to work better than the steel, plywood , rubber (vapor barrier) floor system.
However, I can see how skoolies also get used at night as opposed to school buses which are mostly used in the day. Nights being colder than days could increase the amount/incidences of condensation enough to cause a difference. Really cold areas can also be a problem requiring different solutions. Don't know, don't plan on finding out.
Country living vs city - country is cooler but humidity is generally lower than the neighboring city seems to be true?. In Las Vegas (city in a dry desert), 3 times in 17 years I saw it condensate on the bottom side of my aluminum carport cover so badly that I thought it was raining and I had a serious roof leak... It wasn't raining, just 100% humidity, no heat or a/c to consider just different temps/micro climate under the roof than on top (warmer, higher humidity air under the roof than on top, go figure).
Some thoughts
Modern people living on the grid in the city turn their thermostats up in the winter, much higher than people living off grid?. The hotter the air, the more moisture it can hold and when this air cools enough it drops the moisture as rain or condensation. These people
need a vapor barrier on the inside of an exterior wall, especially if they have well sealed, highly insulated homes. Because of the thick insulation (which drops the amount of energy required to maintain a certain temperature) the outside wall surface inside the cavity is as cold as the outdoor temperature (the insulation prevents it getting any heat from the interior). If humidity gets thru from the interior it will condensate on the cold surface. We know this because the people that sell energy, insulation, and vapor barriers have told us that over and over. Heck they even paid for all of the testing to prove it. One thing that they don't tell you is that if it leaks with a vapor barrier and no ventilation then it can't dry out and then it just goes downhill till its gone. But that's ok, you can buy another one.
I'm not even going to talk about summer..... its all backwards....
If you have less insulation in the walls (how dare you) then the outside wall surface inside the cavity is going to be warmer (losing heat energy to the outside) and the interior air is going to have less moisture (humidity) because it is not as warm, therefore there is less opportunity for condensate to form. They don't tell you that because it is contrary to there interests and your comfort. If you don't have a modern inside vapor barrier and if you do get condensation and if the wall is well sealed (if, if, if) then it can't ventilate/dry out and that could be a problem. This was the old way of construction - except the old house walls
were not well sealed so they did have a tendency to dry out.
Most off griders do not turn up their thermostats like the city folk ?? Wood burners maybe an exception??
My point is - it is not cut and dried or easy to figure out. Your behavior, the amount of energy available, the comfort level desired, location , and
use all affect whether condensation is going to be a problem to throw your $$ & time at, or can you just modify your behavior... you are going to have to modify your behavior anyway if your use is to live in a bus. Blah Blah Blah
Use? If you are going to stay put, then spraying urethane foam on the outside roof and coating it with white elastomeric is a proven solution in the mobile home industry. I say foam the sides too, coat it with stucco and paint it to look like a big rock. Pretty stealthy unless you park it in a Walmart parking lot.. "Where did that big rock come from?" LOL
lazy
...:Thanx:
