Wall Construction

Anything to do with mechanical, construction etc

Re: Wall Construction

Postby lacofdfireman » Sun Aug 19, 2018 3:04 pm

travist wrote:What's RTT?

I also wonder at the weight savings of skeleton and then having to add 1/8" skins on both sides.... that almost seems like zero weight savings.


(RTT) Rooftop Tent

Image


Sent from my iPhone using Tapatalk
lacofdfireman
Teardrop Master
 
Posts: 134
Joined: Thu Mar 17, 2016 5:59 pm

Re: Wall Construction

Postby Andrew Herrick » Sun Aug 19, 2018 3:38 pm

lacofdfireman wrote:Also I figured if I used a solid sheet of 1/2-3/4” that would be plenty of insulation?


I'm one of those odd people who become excited over such mundane topics as thermal insulation. So with that said …

Insulation serves two purposes: acoustic and thermal resistance. If you're talking a 1/2-inch to 3/4-inch of plywood as sufficient insulation, then I would argue the answer is a resounding NO. This is for many different reasons, but a big one is that controlling air temperature is only half the battle. In small campers, controlling the temperature of the walls and ceiling is of equal importance due to all the radiant heat in such a small space.

So I would argue that some form of thermal insulation should ALWAYS be specified. Even something as simple as carpet or foam-backed vinyl on the interior walls will make the camper FEEL much cooler on a hot day. Many fiberglass "eggshell" campers have done this for years.

Obviously, as has been pointed out, vintage campers made do with 1/2-inch plywood walls. So do you need insulation? No. But there's no question that foam insulation makes the camper more comfortable and useful. After having built both construction styles, I would always recommend an insulated shell (minimum an insulated roof).

*Hopping off soapbox*

:)
A few of my builds:

ImageImageImageImage


SEE MORE AT: boondockcampers.com
User avatar
Andrew Herrick
The 300 Club
 
Posts: 390
Images: 15
Joined: Mon Apr 25, 2016 5:39 pm
Location: Cedar City, Utah

Re: Wall Construction

Postby Ottsville » Sun Aug 19, 2018 3:44 pm

lacofdfireman wrote:Also I figured if I used a solid sheet of 1/2-3/4” that would be plenty of insulation?


Sent from my iPhone using Tapatalk


build yourself a plywood box, let it sit in the sun all day, then go sit in it...
My guess is you'll find the wood transfers a surprising amount of heat.

I question the strength of just a 1/2" or even 3/4" wall to support the stress of a RTT on the roof while off-roading. Remember, we are talking about much more than just vertical load. Unless you are going to add some framing, and if you are going to add framing, then why not just go with 1/4"? Or even 1/8"?


I'm excited to see your build though. Your first one was pretty cool.
Ottsville
The 300 Club
 
Posts: 318
Images: 4
Joined: Tue May 08, 2018 2:19 am
Location: Virginia
Top

Re: Wall Construction

Postby lacofdfireman » Sun Aug 19, 2018 10:56 pm

Ottsville wrote:
lacofdfireman wrote:Also I figured if I used a solid sheet of 1/2-3/4” that would be plenty of insulation?


Sent from my iPhone using Tapatalk


build yourself a plywood box, let it sit in the sun all day, then go sit in it...
My guess is you'll find the wood transfers a surprising amount of heat.

I question the strength of just a 1/2" or even 3/4" wall to support the stress of a RTT on the roof while off-roading. Remember, we are talking about much more than just vertical load. Unless you are going to add some framing, and if you are going to add framing, then why not just go with 1/4"? Or even 1/8"?


I'm excited to see your build though. Your first one was pretty cool.


My last build I did 3/4” outer walls with 2x3 framed inner wall with a 1/8” inside wall. And 2” foam board insulation between the outer and inner walls. Was super insulated.

I think I’ve convinced myself to do this one with a 1/4”outer wall and a 2x3 inner wall and 1/8” inner wall and then I’ll also do the 2” insulation between the studs again. Should be sturdy enough to hold my RTT. Then I’ll do 1/2” roof so I can stand on it. Sound good?
lacofdfireman
Teardrop Master
 
Posts: 134
Joined: Thu Mar 17, 2016 5:59 pm
Top

Re: Wall Construction

Postby Ottsville » Mon Aug 20, 2018 7:21 am

That sounds reasonable. Strong, yet lighter than last build, which is what you were looking for.
Ottsville
The 300 Club
 
Posts: 318
Images: 4
Joined: Tue May 08, 2018 2:19 am
Location: Virginia
Top

Re: Wall Construction

Postby aggie79 » Mon Aug 20, 2018 4:45 pm

lacofdfireman wrote:Also I figured if I used a solid sheet of 1/2-3/4” that would be plenty of insulation?


Sent from my iPhone using Tapatalk


It's hard to quantify "plenty". EPS has about three times the insulation value per thickness of plywood. XPS has about 3-1/2 times the value of plywood. Granted, stick framing is a thermal bridge, so you don't get the true value of insulation only.

Insulation does provide both thermal and acoustical insulation benefits.
Tom (& Linda)
For build info on our former Silver Beatle teardrop:
Build Thread

93503
User avatar
aggie79
Super Duper Lifetime Member
 
Posts: 5405
Images: 686
Joined: Tue Aug 07, 2007 5:42 pm
Location: Watauga, Texas
Top

Re: Wall Construction

Postby Jeepertrains » Fri Aug 24, 2018 8:40 am

TD Wall structure.jpg
TD Wall structure.jpg (26.97 KiB) Viewed 1824 times
This is the structure I'm considering using on my TD.
Has anyone tried this?
Jeepertrains
Teardrop Inspector
 
Posts: 2
Images: 2
Joined: Tue Aug 22, 2017 4:28 pm
Top

Re: Wall Construction

Postby Esteban » Fri Aug 24, 2018 6:59 pm

homeconstructionimprovement.com/foam-board-insulation-values indicates that:
!) Expanded polystyrene foam (EPS) typically has an R value of 3.6 to 4.0 per inch of thickness.
2) Extruded polystyrene foam (XPS) typically has an R value of 4.5 to 5.0 per inch of thickness.
3) Polyisocyanurate (polyiso) often has a foil facing and typically has R values of 7.0 to 8.0 per inch of thickness.

My teardrop will be insulated with polyiso foam boards to achieve higher R values (which will be reduced by the wood framing):

Floor. The floor will have 3/4" thick polyiso in it. The floor's rigid foam R value will be about R 5.25 to R 6.0. I'll use 3/8" plywood for the top of the floor and 1/8" plywood on the bottom of the floor.

Walls. The cabin side walls will have 1" thick polyiso. The walls rigid foam R value will be about R 6.0 to R 8.0. I'll use 1/8" plywood inside and outside the cabin.
The bulkhead between the sleeping cabin and the galley will have 3/4" polyiso with a rigid foam R value of about R 5.25 to R 6.0. The bulkhead will have 1/8" plywood on both sides.

Roof. The roof and front wall will have 1-1/2" polyiso. The roof and front walls rigid foam R value will be about R 10.5 to R 12.0. I'll use 1/8" plywood for the cabin ceiling and the roof skin.

The outside of the teardrop will be fiberglassed (and painted) to add strength, rigidity and waterproofing.
Last edited by Esteban on Wed Nov 28, 2018 5:23 pm, edited 1 time in total.
Steve - SLO, CA
Esteban
Donating Member
 
Posts: 1684
Images: 15
Joined: Fri Jul 28, 2006 4:39 pm
Location: California, San Luis Obispo
Top

Re: Wall Construction

Postby greygoos » Fri Aug 24, 2018 9:34 pm

Jeepertrains wrote:
TD Wall structure.jpg
This is the structure I'm considering using on my TD.
Has anyone tried this?

Look at this build. He did the same if not similar to what you are asking about. viewtopic.php?f=50&t=66930
greygoos
Silver Donating Member
 
Posts: 630
Joined: Sun Sep 27, 2015 6:15 am
Location: Syracuse NY
Top

Re: Wall Construction

Postby QueticoBill » Sat Aug 25, 2018 6:17 pm

I'm not keen on polyiso . By many reports it looses r value as it outgasses and ages. You might check https://buildingscience.com/documents/i ... nt-r-value

Its also seems hard to get a structural bond between foam and skin, if you plan on any strength from the composite panel. And it's always seemed a little more brittle and less able to bend.
QB
A tear with no name: viewtopic.php?f=50&t=67624
QueticoBill
Silver Donating Member
 
Posts: 1183
Images: 22
Joined: Sun Apr 14, 2013 7:22 am
Location: Clayton NY
Top

Re: Wall Construction

Postby Ottsville » Sat Aug 25, 2018 9:53 pm

I don't believe you can get polyiso without a facing of some sort, usually foil or tarpaper, so composite panels will be limited by the strength of that facing. Polyiso also absorbs water more readily than eps or xps. Performance of Polyiso also drops with temperature, and some builders in colder climates give it a lesser R value because of that.
Ottsville
The 300 Club
 
Posts: 318
Images: 4
Joined: Tue May 08, 2018 2:19 am
Location: Virginia
Top

Re: Wall Construction

Postby Andrew Herrick » Wed Nov 28, 2018 4:28 pm

lacofdfireman wrote:Also I figured if I used a solid sheet of 1/2-3/4” that would be plenty of insulation?


Sent from my iPhone using Tapatalk


Plywood and solid wood has an R-value (insulation effectiveness) of approximately 1 per inch. While much better than aluminum or steel, that's not much compared to any other insulation material, such as fiberglass strand, cellulose, mineral wool, EPS/XPS/Polyiso foam, spray polyurethane foam, etc., which boast R-values between 3.3 and 7.5 per inch. To put that into a perspective: Adding 1-inch of EPS insulation to a wall assembly reduces the conductive heat transfer about 5x. Denser forms of insulation may also help mitigate sound transmission, making for a quieter and more relaxing camper.

Yes, old school camper bodies were made with solid plywood. If you pay attention to building an airtight shell, this will retain heat decently. If you want something that stays comfortable in all seasons, though, and has a quieter interior, then you'll want insulation. You get what you pay for :)
A few of my builds:

ImageImageImageImage


SEE MORE AT: boondockcampers.com
User avatar
Andrew Herrick
The 300 Club
 
Posts: 390
Images: 15
Joined: Mon Apr 25, 2016 5:39 pm
Location: Cedar City, Utah
Top

Re: Wall Construction

Postby noseoil » Fri Nov 30, 2018 8:40 am

"I also wonder at the weight savings of skeleton and then having to add 1/8" skins on both sides.... that almost seems like zero weight savings." Sorry to get back to this comment so late, been a bit busy with the move.

3/4" plywood is about 1.91 pounds per square foot. 1/8" Baltic birch is about .44 pounds per square foot. If you look at a Benroy that is 4' tall X 9' long (like we made), the original 3/4" sheet-weight is about 85 pounds before cutting, due to the type of exterior plywood used & the added foot of length. The Baltic birch weight is about 31# for both sides before any trimming, door cut-outs, etc. Once you remove most of the 3/4" plywood to make the skeleton, whittle out the doors & windows, trim the curves & remove the extras, it's much less weight, stronger & easier to insulate.

Here's the skeleton panel, trimmed of excess weight it tips the scales at 17#, quite a bit less than the original one. It's actually about half the weight of a solid panel, with the two 1/8" skins attached & finish applied & sealed. Could it be less weight? Yes, less labor? Yes. Better for what we wanted? Nope!
137818
Build log: viewtopic.php?f=50&t=60248
The time you spend planning is more important than the time you spend building.........

137905
User avatar
noseoil
1000 Club
1000 Club
 
Posts: 1820
Images: 669
Joined: Sun Apr 27, 2014 8:46 am
Location: Raton, New Mexico, living the good life!
Top

Previous

Return to Teardrop Construction Tips & Techniques

Who is online

Users browsing this forum: 1KCLC and 10 guests