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Old 08-18-2021, 05:17 AM   #1
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Skip furring strips??

I’ve found only one video with people who skipped furring strips all together. Has anyone else done this??

Some background:

I will be using spray foam insulation
Will use Wood for ceiling
Wood burning stove for heat
Living in Minnesota where it gets crazy cold and crazy hot
I’m tall and hoping to keep as much head room as I can (without a roof raise)

Can I just screw the wood ceiling directly to the ribs? It seems like a useless step to screw wood onto each side of the ribs just to connect more Wood. Putting furring strips under the ribs, there would still be large spaces without them. What’s the point??

So in this situation, would it be reasonable to skip furring strips all together??

Side note, suggestions for types of wood are welcome and appreciated.

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Old 08-18-2021, 05:46 AM   #2
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Originally Posted by olivemartini View Post
Can I just screw the wood ceiling directly to the ribs? It seems like a useless step to screw wood onto each side of the ribs just to connect more Wood.
You can of course do whatever you want - it's your bus. But furring strips are not a useless step at all. Steel conducts heat much better than wood (and much, much better than foam insulation - about 300X and 1500X, respectively), so the closer your steel ribs are to your living space, the more rapidly you will lose heat to the outside.

Furring strips are not actually used as commonly as you think in the skoolie world, and people who apply their ceiling panels directly to the ribs always report that those areas are much colder than the rest of the ceiling, resulting in greater heat loss and (perhaps just as importantly) condensation problems with your fasteners which will tend to be wet in cold weather.

Quote:
Originally Posted by olivemartini View Post
Putting furring strips under the ribs, there would still be large spaces without them.
This sounds like you're planning to do the thing where people spray just a thin coating of foam on the inside of the roof panels, leaving most of the cavities between ribs empty. This is inadvisable, especially in Minnesota - the effectiveness of any form of insulation is a function of its thickness (R-value is literally the thickness of the material divided by its thermal conductivity), so you should completely fill the cavity with spray foam in order to maximize the insulation value.

Furring strips, in addition to providing more separation between your living space and the steel ribs, allow you to have even thicker insulation, since you apply the spray foam flush with the inside of the furring strips. A bus typically has 1.5" deep ribs, so 1X furring strips (0.75") used in this way will increase your effective R-value by 50%.

Wood stoves provide a large amount of heat and they tend to dry out the air inside, so perhaps you can survive a winter without furring strips and with just a thin layer of spray foam, but I personally don't like being cold and I would do (and have done with my bus) everything possible to make my insulation as effective as possible.
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Old 08-18-2021, 02:01 PM   #3
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Perfect answer from Music, above.
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Old 08-18-2021, 02:36 PM   #4
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I did not use firing strips. I was going to use 1/4 plywood for my ceiling but after seeing some condensation issues with my plywood lower side panels during construction over the winter, I opted to use FRP sheet for the ceiling. I riveted it to the ribs with aluminum pop rivets. Now I know when it starts getting cold as I can see a light condensation where it contacts the ribs. With my diesel heater, much like a wood stove, running it puts out plenty of warm dry air to clear it right up. I think over time plywood would delaminate in that application.
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Old 08-18-2021, 03:35 PM   #5
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Quote:
Originally Posted by musigenesis View Post
Furring strips are not actually used as commonly as you think in the skoolie world, and people who apply their ceiling panels directly to the ribs always report that those areas are much colder than the rest of the ceiling, resulting in greater heat loss and (perhaps just as importantly) condensation problems with your fasteners which will tend to be wet in cold weather.
I often here of this issue but haven't convinced myself yet. "always report those areas are much colder than the rest of the ceiling", are we talking the area being the 1.5" wide rib? The typical space between ribs in my bus 1020 square inches surrounded by 211 square inches of ribbing. Are you saying the 1020 insulated inches will be dramatically cooler because the covering is directly connected to a metal rib? I seriously doubt it. What makes that screw sweat anymore than the screw that was removed from that rib. While I often "hear" the theory, I've never seen the issue actually documented, let alone reported as "always". My ceiling is attached directly to the ribs, I have no sweating fastener issue.
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Old 08-18-2021, 04:18 PM   #6
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01marc,
We just don't have many opportunities in the south. Are you in Southern GA?

I have seen condensation, on a cold ac vent, inside a hot car. Or the outside of cold, single pane glass, all summer long. Or on my sunglasses, when moving from AC inside to outdoors, in the Florida humidity.

The water separates from the warm air side onto the cold surface. Central FL has 11 months of summer. Our condensation usually appears on the exterior, here.
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Old 08-18-2021, 06:54 PM   #7
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01marc,
We just don't have many opportunities in the south. Are you in Southern GA?

I have seen condensation, on a cold ac vent, inside a hot car. Or the outside of cold, single pane glass, all summer long. Or on my sunglasses, when moving from AC inside to outdoors, in the Florida humidity.

The water separates from the warm air side onto the cold surface. Central FL has 11 months of summer. Our condensation usually appears on the exterior, here.
Seems like a normal occurance that is much ado about nothing. I'm in far north Ga.
Why does it become a problem in a Skoolie, but wasn't an issue in the bus?
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Old 08-18-2021, 09:57 PM   #8
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Originally Posted by o1marc View Post
I often here of this issue but haven't convinced myself yet. "always report those areas are much colder than the rest of the ceiling", are we talking the area being the 1.5" wide rib? The typical space between ribs in my bus 1020 square inches surrounded by 211 square inches of ribbing. Are you saying the 1020 insulated inches will be dramatically cooler because the covering is directly connected to a metal rib? I seriously doubt it. What makes that screw sweat anymore than the screw that was removed from that rib. While I often "hear" the theory, I've never seen the issue actually documented, let alone reported as "always". My ceiling is attached directly to the ribs, I have no sweating fastener issue.
This is why I’m confused. It just seems like an extra step. I plan on using some sort of tongue and groove method with real wood, around an inch thick. I’m not understanding how the furring strips would change anything. Either way it would be wood attached to metal with screws, surrounded by spray foam. I don’t know if that would actually make a difference as far as warmth or condensation. Would anyone mind explaining a bit more in depth?? In words that even dummies with no experience can understand?
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Old 08-18-2021, 11:20 PM   #9
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It's not a belief or faith. It's physical science. Convection, conduction & radiation work together to cause condensation.
Musigenesis provided an excellent description & mhaisten a testimonial.

I hate sleeping in a damp bed....camper, tent, boat, cabin, hotel room....

Your bus, choose for you & your environment.
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Old 08-19-2021, 09:38 PM   #10
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I think I get it… idk why it took me so long lol!

So the furring strips are attached to the ribs with screws, which could cause condensation. Then the ceiling wood is attached only by screwing to the furring strips??

So it would be ceiling metal, add furring strips with metal screws, cover those screws with actual wood. So there would be spots with metal touching wood, but no spots with metal touching metal directly inside the bus…..

Did I get that right?? ��
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Old 08-19-2021, 10:10 PM   #11
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Exactly! Fur strip could be attached to any of the three faces of the hat channel. Insulated from the warm air inside. Keeping the humidity low, with the wood stove, will make a huge difference, for you.


(Edited)
I remember, the Sticky Windows. You have the window convection info covered.
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Old 08-19-2021, 10:42 PM   #12
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[QUOTE=DeMac;450165]

Not trying to add to your projects list... just bonus info.
Sealing all convection leaks, will also lower condensation. Above IC windows, there's gap between the steel coach and aluminum window frame.



Section of 1-1/2" dia backer rod (closed cell) to demonstrate the gap. Note the light peering in, from above the factory installed window.

I have been dreading windows… If I remember correctly, you used butyl tape around all sides of the windows? Did you also use backer rod along the top where the gap is, or just the tape?

Mine were not held together with any screws. Only tar. Will butyl tape stick enough to hold them in or will I have to use screws?? And will those screws cause more condensation issues??
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Old 08-19-2021, 10:52 PM   #13
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I did leave one window, for a few days, without the trim plate or screws, just the factory butyl. We found it on the floor, one morning. Luckily, no dings in the aluminum or cracked glass.

Ours are pulled tight to the coach by two 30" aluminum plates with 4 main screws each. Some buses have a round disk/washer or flat U brackets. We did add 1-1/2" dia ccbr over the top. Rope butyl, pressed into the upper crevice, from outside.
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Old 08-19-2021, 11:21 PM   #14
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I did leave one window, for a few days, without the trim plate or screws, just the factory butyl. We found it on the floor, one morning. Luckily, no dings in the aluminum or cracked glass.

I have a 30" aluminum plate with 4 screws. Some buses have a round disk/washer or flat U brackets. We added 1-1/2" dia ccbr over the top.
Gotcha. That seems doable.

Follow up question about the ceiling… thoughts on bamboo instead of wood? It seems to have close to the same insulation properties. Specifically found this, which looks like it would make putting the ceiling together a hell of a lot easier.

https://foreverbamboo.com/bamboo-wall-paneling-carbonized-finish-4-x-8/?gclid=EAIaIQobChMIiIPPndm-8gIVy2pvBB1-xgKhEAQYCCABEgKlp_D_BwE

Thank you, btw. This info is helping me a lot.
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Old 08-20-2021, 03:04 AM   #15
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Gotcha. That seems doable.

Follow up question about the ceiling… thoughts on bamboo instead of wood? It seems to have close to the same insulation properties. Specifically found this, which looks like it would make putting the ceiling together a hell of a lot easier.

https://foreverbamboo.com/bamboo-wal...CABEgKlp_D_BwE

Thank you, btw. This info is helping me a lot.

YIKES that's some spendy stuff.
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