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Author Topic: Insulation questions  (Read 2851 times)
Mex-Busnut
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« on: August 09, 2011, 08:08:25 PM »

Dear Friends,

I hope you guys and gals are not getting tired of my millions of questions!

 Grin

Today my carpenter friend Beto and I went over to the Home Depot in our state capital, about 35 miles away, to locate some insulation for the bus. There was only one option, which was Owens Corning R-19 fiberglass rolls. It is the stuff that has the Pink Panther on it. We are planning to do a carefull sealing to waterproof the roof (We have the ceiling removed!).

1. Do I need to place some protection between this stuff and the engine, such as more sheet metal, or maybe the heavy tin foil stuff airconditioning people use on their ducts? (This will go under 5/8" plywood floor in the engine area.)

2. Does this stuff catch fire? If so, how do we protect it?

3. Does it need to be protected from humidity? How do we do that? The stuff we removed from the ceiling appeared to be very rotten.

4. My paint and body shop guy is suggesting adding some undercoating-type paint to the under-roof before putting in the fiberglass and the ceiling, to increase protection. Does this sound like a good idea?

Thanks in advance!
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robertglines1
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« Reply #1 on: August 09, 2011, 08:17:56 PM »

no foam board?  fiberglass gets wet= mush  will melt in fire.& burn must stay fluffy to = r value
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« Reply #2 on: August 09, 2011, 08:43:54 PM »

A layer of 6 mil visqueen properly installed between the insulation and the finished ceiling/walls of the coach will isolate the water vapor to some extent - HTH
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« Reply #3 on: August 09, 2011, 09:29:19 PM »

no foam board?  fiberglass gets wet= mush  will melt in fire.& burn must stay fluffy to = r value

Yes, Bob: We also got 10 sheets of 4 by 8 foam board, but the R value is way down. So maybe put this foam board under the fiberglass, and seal it carefully against moisture?
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Dr. Steve, San Juan del Río, Querétaro, Mexico, North America, Planet Earth, Milky Way.
1981 Dina Olímpico (Flxible Flxliner clone), 6V92TA Detroit Diesel
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100 miles North West of Mexico City, Mexico. 6,800 feet altitude.
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« Reply #4 on: August 09, 2011, 10:36:04 PM »

I don't exactly reccomend this for a bus, but instead of plastic sheeting, i now use house wrap (like tyvek). I'm not getting into the mositure questions here, but i have used it while repairing a travel trailer.
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« Reply #5 on: August 10, 2011, 05:14:41 AM »

We used 1 1/2" closed cell roofing insulation, tar paper both sides. Then went over the top with 3/4" foil two sides from Lowes. It has worked very well and in this hot Texas heat, we stay mighty cool.

Check a roofing supplier, hoping you find one in your area.

If you check our blog, there is some information along with pictures. Go here http://www.uniquebusconversion.com/2008/11/these-pictures-show-installation-of.html

Note: We did ours before I even knew about bus boards! Might have done it differently, but it is what it is. Grin
« Last Edit: August 10, 2011, 06:36:57 AM by Dreamscape » Logged

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« Reply #6 on: August 10, 2011, 06:06:28 AM »

Biggest (one of) thing is the thermal break between the outside steel/alum skin and inside. that said ; make sure no metal is exposed to interior that it is all covered by insulation and or wood -a non heat/cold conductive material. Heavy shades or drapes for windows when not in use will help also.   Yes I no all material will conduct some heat or cold but at a lower rate.
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« Reply #7 on: August 10, 2011, 06:33:08 AM »

I did a lot of research before deciding on which type of insulation to use on my conversion.  The conclusion was the fiberglass batting was out because of condensation getting it wet and ending up with absolutely no R value.  I didn't think I could totally eliminate condensation in a bus environment no matter how hard I tried.  The best choice is blown in expanding foam, but it only has a slight advantage in R value over pink, or blue board and cost a lot more.  I decided to go with Styrofoam board, packing in as much as possible and filling in any gaps and tightening it all up with expanding foam in a can. Now condensation is no longer a worry as far as R value is concerned.  I may have a little less R value than fiberglass and a little less than spray in expanding foam, but it's only about 1 or 2 R's.  Also take into consideration that huge hole in the front called a windshield, maybe the dash, or the whole front end depending on how difficult your particular bus is to insulate there, can you really take full advantage of the R value your insulation has to offer. Remember that R value is calculated in a laboratory setting under perfect condition, a bus does not even come close to that.  For me I feel I made the right choice for my budget and my intended use for the bus. 
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« Reply #8 on: August 10, 2011, 07:38:49 AM »

Regarding the foam board insulation, how do you attach it to the metal roof? What type adhesive?

Boyce
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Boyce Rampey
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« Reply #9 on: August 10, 2011, 07:40:21 AM »

A foam adhesive would work, won't burn through. Any hardware or box store has it.
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« Reply #10 on: August 10, 2011, 07:44:42 AM »

tip   plastic sheet on some foam board will seperate from board and stay glued to roof without board. lesson learned  da   foam to metal 
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Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
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« Reply #11 on: August 10, 2011, 07:58:03 AM »

No one has bothered to mention that if you compress the fiberglas R-19 you'll lose the majority of your insulating value.
If you have an extra 6"+ in your ceiling for the fiberglas, you'll still be better off with foam board at R-7 per inch.. three inches would give you an R-21 rating, and as mentioned, seal all the seams and cracks with expanding foam insulation.
I went one step farther and used Reflectix between the finished ceiling and the foam board.
I could keep the front third of the bus cool with an 8Kbtu window air and a box fan when ambient was 85°

Do it your way, and good luck.
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« Reply #12 on: August 10, 2011, 08:04:27 AM »

Any preference to which foam board? I see some that are foil backed on both sides, some that are not lined on either side, and I think I saw one with a foam liner on one side only....
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Boyce Rampey
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« Reply #13 on: August 10, 2011, 08:19:54 AM »

I like the most r-valve for thickness  which is either pink or blue.    The white bead board I stay away from.  The blue had the plastic on it. Removed it on one side and adhesive held to ceiling just fine.
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Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
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« Reply #14 on: August 10, 2011, 08:22:10 AM »

The best insulation in dead air space!

Build accordingly.
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gary t'berry
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« Reply #15 on: August 10, 2011, 08:27:22 AM »

Gary, be careful in recommending dead air space, one of the best is a vacuum.  The problem with a dead air space, is that it is not dead.  There are thermal currents set up by sun and shade, light and dark paint etc.  This moving air then transfers heat by convection on the various surfaces involved.  "Dead air space" is one of the reasons that bubble foil R values should be carefully looked at to determine the testing protocol used.

fyi chuckd
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« Reply #16 on: August 10, 2011, 09:56:35 AM »

I think what I did works well, as well. I bought foam board in 1/2", 3/4', and 1" thicknesses with the foil back. I cut it to fit snug in all the different spaces and would use whatever thicknesses, combined, to get as much in as possible. Then if there were voids, I used the expanding foam. That will also "glue" the board to the ribs, etc. (nasty sticky stuff! It's basically Gorilla glue that expands)
By doing it that way, I "think" it is "just about" as good as spray foam (I have that in my house) and for a LOT less money!!! I think the foil is a plus.
Just my way. Your mileage may vary.
  Chaz
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« Reply #17 on: August 10, 2011, 10:41:31 AM »

 Fiberglass inside a Bus is bad? I scrapped over 20 Buses back in the late 80's, including a 1947 GMC 3751, and a 1953 GMC 4104, and a bunch of Transits, GMC Fishbowls and AM Generals. All those Buses had fiberglass batt insulation, I never saw a single one that had rust or corrosion from condensation. I currently have a 1975 MCI MC5B, that still has all of its original fiberglass batt insulation and the only place ive found corrosion is where a hole was drilled through the outside skin and water soaked the insulation. It hasnt caused trouble in 36 years, why tear it out?

  I have also read that spray foam insulation is not recommended for metal buildings because of high cndensation/corrosion issues, and that potential damage will remain unseen until it at an advanced stage which could lead to structural failure. I cant see that foam boards would be any different, the stuff just sweats and soaks anything its in contact with. Honestly, foam may well be to Buses what fiberglass was to wood boats in the 1950's. Time will tell.

  I'm sticking with fiberglass and other types of porous breathable insulation as well as to keep the cavities well ventilated. May not be as sound proof or offer the greatest R value, but the Bus might still be around 10 or 20 years from now.

 
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robertglines1
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« Reply #18 on: August 10, 2011, 10:58:47 AM »

Main reason for their reasoning in metal buildings is all the UN sealed seams every few feet. eliminate water entry/seams and no problem.
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Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
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« Reply #19 on: August 10, 2011, 11:03:59 AM »

House wrap (Tyvek) is a selective barrier - while it is resistent to water it is not resistant to water vapor - this is the reason it is on the exterior of the structure - if water or water vapor gets into the wall cavity from another source (plumbing or structural leak) the house wrap allows the water vapor to escape - visqueen (polyethylene) when properly installed (ceiling sheets applied first then tucked under wall sections and sealed with tape) is an absolute water and water vapor barrier and should only be applied on the climate controlled/conditioned side of the wall - FWIW

When you say "dead air space" what your really refering to is "isolated" dead air space - a frame structure with 2x4's foam sealed drywall on one side and foam sealed sheathing on the other with no insulation is also considered "dead air space" by definition - that insulation you add in the cavity is isolated or encapsulated air pockets encased in a nonconductive material - that is what gives you the R value - FWIW

































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« Reply #20 on: August 10, 2011, 11:48:11 AM »

Main reason for their reasoning in metal buildings is all the UN sealed seams every few feet. eliminate water entry/seams and no problem.
 

  But your forgetting condensation from living inside breathing, cooking, showering, and heating. Every RV ive owned had warnings that the vehicle was not designed for long term use. They are built too tight and condensation cant escape past the metal skin, so instead the interior walls get saturated and they rot and mildew from the inside out if used that way. As long as they dont stay too closed up and you air them out after use they last for years. That was actually a discussion when they started handing out trailers to the refugees after Katrina, those trailers wernt designed to be used as long term living quarters.
 
  Certainly the majority of Bus conversions are for limited use, spending most of the time parked and empty. But for those living in them as a home they could see problems down the road. I know many have used spray foam and foam boards, and it may not ever be a problem, but I dont think we know enough about it one way or the other. I know fiberglass is not any problem at all as long as it can breath, and thats what I intend to use. At least until I see more data on foam to show its safe.
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« Reply #21 on: August 10, 2011, 01:12:32 PM »

I am not a very big fan of foam over the engine compartment.  I have it in the top of all my bays but not over the negine.  Throw a piece in a fire and you might change your mind.  It is one thing to have a fire but another to have a fire with extra fuel.  When I burned the scraps after my project they burned like a Christmas tree.
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« Reply #22 on: August 10, 2011, 02:43:48 PM »

Before we pink 1.5 inch foam boarded everything, we laid down a layer of Reflectix in the ceiling, walls, etc. Was well well worth it. Been in 100 degree temps this summer and a 13,500 BTU Coleman Mach III kept it at 75 degrees or less in here. Right now it's 84, and the thing is set to low about half way on the thermostat, and we're chilly. As for the engine compartment, I used actual firerock sheetrock over the plywood we laid. Sound proofed, and gives us 90 minutes to figure out we're on fire down there before it toasts us.
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Scott & Heather
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« Reply #23 on: August 10, 2011, 07:24:01 PM »

  Throw a piece in a fire and you might change your mind.  It is one thing to have a fire but another to have a fire with extra fuel.  When I burned the scraps after my project they burned like a Christmas tree.

  Thats something I forgot about. I know Celotex and some of the other foam type insulation boards have fire warnings, and state they are only to be used as exterior sheathing. I have no idea about spray in foam, but it is urethane so I assume it would burn.
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« Reply #24 on: August 10, 2011, 07:35:04 PM »

Normal spray foam from a can will go up like gas!!!  Nasty stuff!
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« Reply #25 on: August 10, 2011, 07:41:30 PM »

I did a lot of research before deciding on which type of insulation to use on my conversion.  The conclusion was the fiberglass batting was out because of condensation getting it wet and ending up with absolutely no R value.  I didn't think I could totally eliminate condensation in a bus environment no matter how hard I tried.  The best choice is blown in expanding foam, but it only has a slight advantage in R value over pink, or blue board and cost a lot more.  I decided to go with Styrofoam board, packing in as much as possible and filling in any gaps and tightening it all up with expanding foam in a can. Now condensation is no longer a worry as far as R value is concerned.  I may have a little less R value than fiberglass and a little less than spray in expanding foam, but it's only about 1 or 2 R's.  Also take into consideration that huge hole in the front called a windshield, maybe the dash, or the whole front end depending on how difficult your particular bus is to insulate there, can you really take full advantage of the R value your insulation has to offer. Remember that R value is calculated in a laboratory setting under perfect condition, a bus does not even come close to that.  For me I feel I made the right choice for my budget and my intended use for the bus. 

What Mike said....all of it.  You could install fibre bats under the floor where no interior air will get into it.  I would still use foam board, though.  I put fibre glass bats in the little spaces between the foam boards and such in my roof.  I built a roof on top of my roof and that chamber is isolated from the interior and is sealled to weather.
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« Reply #26 on: August 10, 2011, 07:43:30 PM »

Regarding the foam board insulation, how do you attach it to the metal roof? What type adhesive?

Boyce

Be careful here.  Many cemenbts/glues have solvents that disolve different foams.  Consult the mfr fo the cement that works.  I used contact cement cause it is dry when you press the parts in place.

John
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« Reply #27 on: August 10, 2011, 10:15:15 PM »

Normal spray foam from a can will go up like gas!!!  Nasty stuff!

  I imagine it would right out of the can, but what about after its dry/cured??
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« Reply #28 on: August 12, 2011, 09:01:14 AM »

Normal spray foam from a can will go up like gas!!!  Nasty stuff!


  I imagine it would right out of the can, but what about after its dry/cured??


Not sure it really goes up like a gas...this guy has a hard time keeping it lit with a torch!

Burning Spray Foam Insulation
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Scott & Heather
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« Reply #29 on: August 12, 2011, 12:01:59 PM »

There are three families of this stuff that i can think of off hand.  One uses "two parts" and seems to cure like epoxy.....fast and it out gasses highly toxic when curing.  Second comes from a can and that stuff needs to out-gas it's solvent to cure and if shot into a confined space, pipe or plastic bag or some such, it stays wet "forever".  The third is a new stuff that is water based and that is water absorbent after it cures/drys.  I think there are also variants within each category.  I probably have some of these angles off but you need to either do all your homework or follow what others have done.  Whether it actually flames violently or not, much of this stuff will out-gas toxic stuff when subjected to extreme heat(fire) that will kill you in seconds or render you unconscious in less time.  In a motor home/bus it is the heat that kills in mere seconds.  You need to be out before you take your next breath after discovering a fire regardless of how nourishing the gas might happen to be. Tongue

John
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« Reply #30 on: August 12, 2011, 02:25:26 PM »

Dr Steve -

Before you get totally into the fiberglass (hope you haven't bought it yet!), do you have any 18-wheeler repair facilities in your neighborhood or nearby?  Especially ones that repair the reefer trailers?

If so, go talk to the shop foreman.  See if he can put you in contact with the guy who comes by and spray foams the trailers after they've been repaired.  Try and schedule a visit with your coach's interior all prepped so all he has to do is shoot it while he's there doing some trailers.  Might also be able to get him to shave it smooth after shooting.  Win-win.

More expensive, yes.  But THE BEST for our applications.  And you, living that much closer to the Equator than the rest of us, really need to have good insulation in your coach. 

This is one area of your conversion that you shouldn't peso-pinch!

FWIW & HTH. . .

 Wink
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« Reply #31 on: August 12, 2011, 03:15:56 PM »

The advice RJ is giving is sworn to by so very many.  Foam board works but fibreglass does not.  MCI had the fibreglass they used sealed in plastic packets that eventually ruptured after 30 years and then just became mildew repositories that stank and rusted stuff.   Put the fibreglass bats under the floor if anywhere but foam is preferred there also.

To track down people that do this contact the wholsaler of the foam cylinders that the factory or jobber uses.

Good luck Doc,


John
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