Insulation and Mold Links

[jwilcox]

I live in southern TX....its hardly ever cold here so insulation for me is for summer heat more than anything. I plan on using BusKote on the roof at some point and keeping the bus in the shade as well. We'll also use it to tour the country, but not in the winter. Anyway, for our purposes, EPS is the insulation of choice (or rather, the type that the Universe handed us

It sounds like my best bet is to place the vapor barrier directly behind my wall, ceiling, and flooring material, right? The EPS boards do not have any shiny material, which is why I was asking about the plastic. Would 6ml plastic sheeting work, and should it be glued right to the foam? I also plan on sealing any gaps with spray foam and use tape on the seams.
Jamie

[Tedd]

Is there any chance that this thread, or one that serves the subject "Insulation" more effectively, could be turned into a sticky?

Perhaps a creative administrator could join several of the insulation threads found on this forum.

Sometimes its not a bad idea to put all of ones eggs into one basket.

I think it might be helpful/useful to have discussions of this topic on one thread instead of on almost every thread.

[family wagon]

As I recall, vapor barrier belongs on the side of the wall that is typically more humid. For charles_m and myself that's the interior: in the winter the outdoor air here is cold and bone dry while indoor air is warm (capable of holding more moisture), is humidified by breathing and cooking, and often we even run humidifiers to add more moisture to the air. In the summer we do dry the interior air with air conditioning but the humidity isn't all that high outdoors anyway. Heating-dominant climates are often like this and end up with the vapor barrier on the inside.

Your climate in Texas may be different; if the outdoor air is very humid there in the summer and you'll be running air conditioning inside the bus to de-humidify, then the vapor barrier may serve better if it's on the exterior side of the insulation. You might check how regular buildings are done in your area.

In both cases the idea is to put the vapor barrier on the side that is more humid in hopes of keeping the insulation and wall assembly dry. The rest of the wall, toward the side that doesn't have vapor barrier, should usually be built vapor permeable so that whatever water does get inside has an easy path to dry out again.

6 mil polyethylene sheeting ("visqueen" and other brands) is a fine vapor barrier. Most adhesives won't stick to polyethylene very well; usually it's stapled to wood studs. Duct tape kinda-sorta works, but it won't hold long-term. You could probably staple it to the foam to hold it in place long enough to get the final wall covering in place.

[jwilcox]

Well family wagon, you've nailed the reason for my confusion as to where to put the vapor barrier........yes, it is really humid here most of the year but it would certainly be more humid inside the bus during our short winter. I'll ponder this concept and see where it lands in my mind. Great info, plenty to work with!
Jamie

[family wagon]

I was thinking about the vapor barrier a little more this evening. The steel exterior of the bus is already quite good at blocking vapor, if not for all the holes through it... So what about sealing it up? With the interior side of the walls uncovered, maybe the mastic the HVAC trade uses for sealing air ducts could be used to seal the exterior skin to each side of each rib/bow. There's still the issue of all the screw/rivet holes through the center of the ribs too, but maybe those can be plugged with mastic too? I don't recall hearing this idea floated before and I'm interested in pitfalls or drawbacks any of you might see in the idea.

[kwang_yi]

Every automobile, maybe with exception of RV industry, uses vapor barrier (cheap plastic sheet) to prevent mold growth. Homes are built such way that this plastic sheets are readily available from any hardware stores, priced much cheaper than fancy bubble trapped material wrapped in aluminum foils. I've not yet to see anyone using this plastic sheet before installing expensive insulation material, I mean watching youtube crowds. It just amazes me people duplicate other people's work without first using their head to first rationalize their effort and justify all that spending.

[EastCoastCB]

Originally Posted by kwang_yi

Every automobile, maybe with exception of RV industry, uses vapor barrier (cheap plastic sheet) to prevent mold growth. Homes are built such way that this plastic sheets are readily available from any hardware stores, priced much cheaper than fancy bubble trapped material wrapped in aluminum foils. I've not yet to see anyone using this plastic sheet before installing expensive insulation material, I mean watching youtube crowds. It just amazes me people duplicate other people's work without first using their head to first rationalize their effort and justify all that spending.

Everyone has their own wants and needs. The kind of insulation most of us are using is foam based. A plasitc sheet over a bus' insulation and you're going to most certainly have massive amounts of mold. My bus had a default "vapor barrier" and I'm cleaning up the corrosion.
Do you have a bus? post some pics!

[kwang_yi]

I have no bus to prove my points, but gained valuable experience on a mini-van's passenger panel. I neglected to place vapor barrier back after doing some work in that area, and I noticed the evidence of mold few years later. Fungus just cannot have enough of plastic material used for vehicle's interior materials.

Fungus are easily managed once you know its presence; all you need is bottle of vinegar. The problem with fungus is that you can't tell its presence unless panels are removed, while it's contaminating and spreading toxic air for human to breadth in, that is known to cause cancer and rapidly consuming healthy human cells. Fungus is highly beneficial, only after you're dead, not when you're alive.

Imagine if I had used lots of insulation material, providing warmth and ideal condition to encourage fungus spread, this would have been a heaven for mold to prosper. Long time ago, someone told me about this barrier while I was working on the boat project. Due to marine environment and the material used for hauls, it's impossible to completely eliminate fungus growth, but this cheap plastic sheeting worked like a magic for a long time.

I would use plastic sheeting before insulation, not after. Bus's metal skin, vapor barrier, insulation, then paneling in that order.

[EastCoastCB]

A bus sweats. If you trap that behind plastic, you're gonna have a bad time, man.

[kwang_yi]

You need to remember why damp condition exists. It's not the leaky barrier (bus's metal skin), but the condensation of air that forms the moisture and eventually the molds.

[Scooternj]

Mold Growth, from the University of Central Florida's Florida Solar Energy Center:

There are 4 critical requirements for mold growth – available mold spores, available mold food, appropriate temperatures and considerable moisture. The removal of any one of these items will prohibit mold growth. Let's examine each requirement, one-by-one.

Mold Spores. Ranging in size from 3 to 40 microns (human hair is 100-150 microns), mold spores are ubiquitous – they are literally everywhere. There is no reasonable, reliable and cost-effective means of eliminating them from environments that humans inhabit. So, trying to control mold growth through the elimination of mold spores is not feasible.

Mold Food. If all three other requirements are met, almost any substance that contains carbon atoms (organic substance) will provide sufficient nutrients to support mold growth. Even the oil from your skin that is left when you touch an otherwise unsuitable surface, like stainless steel, or the soap residue left from a good cleaning will provide sufficient nutrients to support the growth of some molds. And many of the most common materials found in homes like wood, paper and organic fibers are among the most preferred of mold nutrients. Thus, eliminating mold food from your environment is a virtually impossible task.

Appropriate Temperatures. Unfortunately, most molds grow very well at the same temperatures that humans prefer. In addition, anyone who has cleaned out their refrigerator quickly realizes that temperatures close to freezing are not cold enough to prevent mold growth and temperatures that are much warmer than humans prefer, like those of the tropics, will grow abundant quantities of mold. Therefore, it is not feasible to control mold growth in our home environment through the control of temperature.

Considerable Moisture. Most molds requires the presence of considerable moisture for growth. Obviously, the word "considerable" is key here. The mycologists (fungi scientists) refer to "water activity" when describing the required conditions for mold growth. The various species of mold have different water activity requirements. A material's "water activity" is equivalent to the relative humidity of the air that would be in equilibrium with the material at that material moisture content. The vast majority of mold species require "water activity" levels that are equivalent to material equilibrium moisture contents corresponding to relative humidities of at least 70%. In fact, the great majority of serious, large mold outbreaks inside buildings occur where porous, cellulose-type materials have literally been kept wet by liquid water or sustained condensation.

By using closed cell foam, either spray on or rigid board (installed properly), bus conversions remove the potential for those conditions. Spray foam will act as it's own vapor barrier.

[Jolly Roger]

Love it, for our application I would like to add? No introduction of outside air? I have tried to seal all seams,rivets, and everything else with a silicone based caulking and loose fibre insulation that can twist and move with the body of the bus as going down the road or wherever I want to try? I ain't a bus builder and think buses (at least mine were built for there purpose) I did better the insulation in areas during construction/destruction but I chose fiberglass. I used board type and blanket as needed. I think (in my head) that the spray on foam stuff after going going down the road is going to break loose. It will still be there in the shape or form but itis still going to let go and the air pocket is there again unless it is done thicker than the ribs and you sandwich it with your new material?
All of this is a rigid material with great insulation values but (correct me if I am wrong) is not made to flex,twist. There is probably something new I don't no about ?
Build for your location and expectation.

[teambadass]

I'm still not convinced that tearing out the walls is the best idea, esp. if the bus will be moving a lot or being used for a different purpose in the future... I forget which thread I read where someone brought up the idea of the skin of the bus (both interior and exterior) being integral to the structural integrity of the bus as a whole. When I was reading through some of the "completed conversion" thread, I read about owner/drivers completely losing screws in their panelling and having to retighten and refix, which in my mind is due to the structural integrity of the vehicle being compromised. Yes, I think insulation is super important in terms of temperature control, resource conservation, etc., but if installing stellar insulation means one has to compromise the structural integrity of something that is meant to move, I don't know that it's worth it. I recently saw this vid on youtube of a skoolie with a tent-style wood stove, parked for solar gain. This was in Colorado, in the snow.. Here's the link:

https://www.youtube.com/watch?v=X1SK_SUIRNI

Any thoughts on this are appreciated.

[EastCoastCB]

Removing the interior panels doesn't harm stuctural integrity.
Gotta break eggs to make an omelette.

[kwang_yi]

Originally Posted by EastCoastCB

Removing the interior panels doesn't harm stuctural integrity.
Gotta break eggs to make an omelette.

I agree. Sheet metals are never meant to provide structural support but for the appearance. It's a low maintenance item, kids spill something, just hose it off.

However, ribs across the ceiling beam, I wouldn't touch unless I have some fancy software that will calculate complex equation of stress analysis and experienced with dealing with it.

Currently, I'm running Autodesk Inventor software, it just amazes me what it can do, more like billion dollar CATIA software we used to build a commercial aircraft. I'm not a mechanical but even dogs can emulate after hearing so many every freaken' day.

[EastCoastCB]

Yeah its meant to be "kid proof industrial grade interior paneling". And to that end its very functional. But it makes for a horrible living area.

[Tango]

Here we go again. And I promise this will be the last time I post this. According to a retired Blue Bird engineer I consulted with years ago...both the exterior AND interior sheet metal panels are necessary to maintain overall structural integrity. Together they form a box beam effect in conjunction with the ribs.

I really would like to hear a real professional position on this subject and not more opinions or conjecture.

[kwang_yi]

Originally Posted by Tango

Here we go again. And I promise this will be the last time I post this. According to a retired Blue Bird engineer I consulted with years ago...both the exterior AND interior sheet metal panels are necessary to maintain overall structural integrity. Together they form a box beam effect in conjunction with the ribs.

I really would like to hear a real professional position on this subject and not more opinions or conjecture.

How many engineer do Bluebird have? Probably thousand, majority of them, old folks who are not useful to rapidly evolving technical advancement.

I worked in a Customer Engineering department for ages, directly interfacing with FAA and carriers for safty and modification works. From my own experience, those who directly interface with public are the typically low ranked, not usually important staff, otherwise their talent would be placed where they're needed to develop a killer product to reign over competition.

I recently had completly wasteful pissing match with Amazon customer service group, apparently someone of very low intelligence and low education, who bluntly claimed, oh no mr. yi we have many doctors and lawyers as our customer, not just bunch of zombies... Over the course of my life experience, I learned these two group of professions are the worst, contributing nothing but headaches and regress human civilization back to cages.

there is nothing more bitter than having to spend hours talking to an idiot.

[cbear]

I'm going to have to go with Tango on sheet metal argument. Kwang, are you asserting the an aircraft's wing or fuselage has the same strength whether it has it's skin or not?

[kwang_yi]

I'm speaking of paneling, not the outer skin of aircraft.

My guess is that additional sheet metal to form a box will enhance its structure rigidity, but the absence of it should not significantly degrade the overall strength to endanger in any form. The super-structure, a beam alone, should have been fabricated to withstand all kinds of stress that was given to engineering as a design criteria.

If I was to design that shell, I will just make sure outer skin of the bus will be able to withstand known variable such as thermal deformation, mechanical strength such as pounding with unimaginable hail etc. but not to meet minimum structural requirement. I wouldn't want to be constrained in interior wall in same criteria as outer wall, preferably polyurethane board or equally light material, but then I know my targeted load can be more destructive than normal crowd, so the sheet metal would be my natural choice.