Thermal barrier for bus framing

[Scott & Heather]

On our 102, I and considering doing two things:

1. Install wood studs next to metal framing of coach (vertically) so that I can screw my interior knotty pine walls to said wood and provide thermal barrier. In cold conditions our 9 wall screws would frost up.

2. Install some sort of rubber or felt on the metal framing to provide thermal break between metal framing and wood. In cold conditions wood would be cold to the touch where it came in contact with the metal frame of the coach.


Are there easier ways to do this? Restudding the coach with parallel wood is going to be a pain


Edit: one last question. My spray foam guy insists I don't need to fill the framing flush with spray foam. I want it flush and then I'll grind off extra. Am I crazy for wanting this?

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[sledhead]

I used 1/4" ply strips 2" wide glued and screwed to the ribs then installed the 1/4" sheets of ply ( 4 x 8 ) to that , only thing I forgot was I should have used spray foam inside all the closed post on the bus framing by drilling 5/16 holes in it to put the spray foam in it .
dave   

[Scott & Heather]

Dave so your screws were short then...going into 1/4" ply strips. I'm using 3/4" knotty pine tongue and groove again on this coach cause we love it so much in our 9. That would add a 1/4" to each side netting us a width loss of 1/2". I guess I could live with that. Would it be strong though? I am hanging heavy cabinetry off the walls..


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[buswarrior]

re-studding parallel gives you that much more thickness for insulation? Practical result with spray foam, since it will really have insulation thickness in it, theoretical with other hand installed methods, likely won't achieve any result.

Otherwise, twinning the verticals with wood sounds like a good way to stop the "screw sweat", which if leaving in the metal, also risks water marking/rust marks at each screw, ruining your pleasant decor.

I've wondered about that caulk that is used on studs/joists for sound deadening, as an easy to use separator? It is supposed to stay flexible?

For mounting locations for cabinets, one of the best tricks I've read over the years is to bury a thicker metal plate/skin inside the wall in the general area, well secured, in order to drive your supporting hardware into it once the other layers are installed over it. No careful measuring to hit a thing stud, just drive 'em in to the plate. These might conduct, but would likely be inside, out of sight?

happy coaching!
buswarior

[Scott & Heather]

Nice thoughts BW. Another idea I might use, is wife and I are seriously considering using 1/4 log as our interior siding. At its thickest place, it is 1-3/8" thick. If I countersunk screws as deep as necessary into the center thickest portion of the log, I could then tap a 3/4" plug into the hole on top of the screw head and then putty to blend. This should do the trick too if we are using 1/4 log siding anyway for the look. A thermal foam adhesive strip on the metal ribbing would provide thermal break between log siding and metal rib.


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[brmax]

That's my understanding with the wood, its the break between bus metal and interior.
In looking around here and there a bit, I noticed attachment to metal through wood was separate and or possibly counter sunk.
Some follow up articles I found interesting mention the attachment of interior wall board or what ever was to the areas in the wood and non contact to metal coach structure.
I had noticed some underlayment types with my mci and their plywood some just clear looking, probably several different for areas they found from experience, I will soon see more.
I thought it all sounded pretty cool and makes perfect sense, and as you mention a wool or roofing paper or many super rubber/ice roofing substrates are great ideas.
Totally interested in any of your findings, man would it be great finding 1-2" strips /rolls.
I think some good non hardening but flex and hi temp stuff would be worth looking into, will keep an eye out.
good idea there
Floyd

[Scott & Heather]

Here's what I think I'll do with my 1/4 log interior siding which is 1-3/8" thick:



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[sledhead]

I pl glued ply to the stud and 1/4 " strips + used longer self drilling screws any were I needed them . I used a lot of stay put spray glue ( like 3m 77 ) on all of my paneling when I added to it ( I used solid oak wainscoting   1/4" x 32" h  front to back but not behind any wall cabinets ) spray glued on to the 1/4 " ply )
using the sheets of 1/4 " ply on the walls just made it easier to add any thing to the sides with out making the inside size any smaller . some spots I just used long 3 / 16 rivets in to the 1 / 4 " ply to hold things . to this day I have not had any problems . maybe because I spray foamed the complete inside shell for insulation , added support . on all my upper cabinets there is a pantry or a floor to ceiling panel that is screwed to the upper cabinets for added support . I did this in the design of the cabinets , with all my sliding pocket doors . I tried very hard as to not use up any extra space for inside walls ( all dividing walls are 3/4: ply with veiner glued to each side or 3/4 " foam board with 1/8 " ven. panels glued to them .
dave   

[flynbanjo]

Soundown has a product called tuff-max.  It is designed as a sound barrier and weighs anywhere between 1 to 2 pounds per square foot.  It is effectively a large roll of rubber that can be secured to the walls.

[Tikvah]

Scott,
I glued and screwed 3/4" boards horizontally 12"o.c. to the steel frame throughout the bus, and even the ceiling.  Then it was spray foamed to the level of the boards (3/4" beyond the steel frame).  Then my interior plywood was glued and screwed to the horizontal boards.  We have absolutely no "cold spots" from screws or condensation from framing.

We do get some minor condensation from our roof vents, wish I could find a cure for that.

[Scott & Heather]

Yeah our roof vents soak our bed cover and front carpet when we winter up north. I was using beach towels to deal with it. The new coach is going to have something more drastic like a complete door rr. Maybe pull the hatch out completely. Not sure yet.


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[Skykingrob]

Scott
There is a product sold at any lumber yard/big box lumber stores called "sill plate". It goes below the stud walls of homes as they are being built to seal gaps between the walls and the foundation and is a thermal break. It is a roll of 1/8" thick closed cell foam that is 6" wide, usually blue in color. Take a band saw and cut it down from 6" wide to 1.5" wide strips, then simply roll in over your bus wall uprights before you screw the wood to the bus upright frame. It adds minimal amount of thickness, is a thermal/sound break and is very light weight. I used it and the things you mentioned as objections are not an issue plus it stops squeaking as the bus frame flexes.

Rob
Missouri

[Seangie]

Scott,

That's exactly what we have.  We used reflectix for a thermal barrier.  The screws for the firring strips are covered by the 1/2" plywood.  It works fantastic.


What fails in our bus is the windows.  They make up about a quarter of the total wall surface.  There is no thermal break with the window frames (original bus windows) and the heat and cold walk right through the window frames regardless of what we put in the windows to block the heat/cold.  Its not the glass but the frames that carry the energy.  Double pane glass will help as well.

[Seangie]

Scott -

Here is a napkin CAD of a cross section of bus wall showing where the reflectix would be used as the thermal barrier.

One thing I did as well was to clear coat the underside of the plywood on the interior walls.  This was just a preventive measure to prevent mold growth from water leaks or condensation build up should any section of the thermal barrier fail.  Maybe an overkill but hey...thats what bus conversions all about

You can spray foam between the bus frame.  For the space between the furring strips, use 3/4 foamboard and trim it about a 1/4" short.  Then sprayfoam the foam board into the space you are insulating.  This is much faster and easier (less mess) then respraying between the furring strips.  I think you can get better insulation with the closed cell foam board as well.  The spray foam around the edges helps to hold the foam board in place and fills all the little gaps as you can't get the foam board cut exact every time unless you have a ridiculous amount of patience and skill (I have neither)

When does the said project begin?  Also - We are here in Texas....where are you??

-Sean

[Scott Crosby]

I have a flir infrared camera and it can see and find imeadiatly every screw that goes into the bus metal.  Having a vapor barrier to prevent condensation from clinging to the screw heads I would say is very important.  I'll see if I can post a pic but it's amazing what the thermal camera sees.