Insulated or not?

[Salivanto]

Hello everybody,
I'm getting real close to starting work on my teardrop and I'm suddenly hit with a new thought. Up till now, I'd pretty much assumed that the only choice was to build framed walls with insulation. Now I've been given the suggestion that the walls could be made more simply with 3/4" plywood, no framing, and no insulation. I've also seen statements from people who have built this way who say that their trailers are very comfortable even in cold weather. Part of the reason I wanted to insulate the sides is so I can take it to Vermont in October.

So, my previous thought was to use 1" poplar framing with 1/4" plywood outside and 1/8" inside, and 1" foam insulation in the gaps. (I've seen some designs using 1/2" plywood, but I was going to take my chances with 1/4".) How would my idea compare in weight, cost, and strenth to the alternative -- just using 3/4" plywood unframed and uninsulated?

As a thought experiment, I hit on the idea of using 3/4" plywood in place of the framing (is that called "spars"?) and then cutting out holes in the board big enough for the insulation. (I've seen that described on this message board.) I figured I'd need to cut away roughly 2/3's of the area of the inner board to keep the weight the same. It seems to me, then, that (provided the glue is strong) the thicker wall would be stronger and lighter. Am I on the right track here?

[IraRat]

Hello everybody,
I'm getting real close to starting work on my teardrop and I'm suddenly hit with a new thought. Up till now, I'd pretty much assumed that the only choice was to build framed walls with insulation. Now I've been given the suggestion that the walls could be made more simply with 3/4" plywood, no framing, and no insulation. I've also seen statements from people who have built this way who say that their trailers are very comfortable even in cold weather. Part of the reason I wanted to insulate the sides is so I can take it to Vermont in October.

So, my previous thought was to use 1" poplar framing with 1/4" plywood outside and 1/8" inside, and 1" foam insulation in the gaps. (I've seen some designs using 1/2" plywood, but I was going to take my chances with 1/4".) How would my idea compare in weight, cost, and strenth to the alternative -- just using 3/4" plywood unframed and uninsulated?

As a thought experiment, I hit on the idea of using 3/4" plywood in place of the framing (is that called "spars"?) and then cutting out holes in the board big enough for the insulation. (I've seen that described on this message board.) I figured I'd need to cut away roughly 2/3's of the area of the inner board to keep the weight the same. It seems to me, then, that (provided the glue is strong) the thicker wall would be stronger and lighter. Am I on the right track here?

Hi, Sali.

I think 1/4 sides are pretty thin, even with framing. Even the Cubby, which is tiny, uses 3/8.

If you went 3/4 without framing, what do you envision as the advantage? Less cost and less work? People do it this way, but if you want to get out there in the winter, in VERMONT, I would think you want to do the thinner wall, with the framing and insulation. The framing and insulation is not going to be a big deal, and it will give you more options to run wires. Granted, you're going to have to skin the inside with thin material, but this will give you a bunch of decorating options--your choice of paneling, to stain, etc.

I'm pretty new to this myself, and I've learned there are a lot of "right" ways to do it. A 3/4 wall with no framing or insulation isone of them, but think if that's what you really want for your climate.

As far as taking a sheet of ply, cutting out huge holes for insulation, and using that instead of stick framing...why???

(And FYI: spars are the pieces that connect the side walls. The framing on the walls is just called framing.)

[ALAN GEDDES]

We have been out in the low 30's with only 1/2 in ply walls and insulated roof and floor and have been quite comfortable and I get cold easy. Have not been out in severe weather though.

[lmh222]

I am building my frame with 3/4 ply and holes for insulation. The structure seems a lot sturdier to me than a stick-built frame because the whole frame is one piece rather than a zillion little pieces. Ok, so even if the stability advantage is totally unnecessary, it was MUCH easier. I just grabbed a marker and drew holes wherever I thought they should go and then cut them all out with my jigsaw. I was done with both sides in less than an hour (there's no way that I could put together a stick frame that quickly!). I'm not one for cutting corners but if it would be structurally stronger as well as faster - that just seems to make sense.

The "to insulate or not to insulate" question is one that seems to keep coming up over and over. I don't ever plan to camp in cold weather but I did read something that convinced me to insulate anyway - a temperature difference between the outside and inside causes condensation (even in the summer - dew on grass, etc.). Tents get damp and stinky - so would a teardrop. The insulation will reduce condensation that can, at worst, rot your trailer or at the very least, stink it up.

I have mold allergies so I figured that the tiny investment in insulation would be WELL worth it if it keeps the moisture out.

I skinned my inner sides with 1/8" Lauan. The outter sides will be skinned in 1/8" Okoume. I just got my build journal up online at www.teardrop.myphotoalbum.com.

I'm hoping to weigh my sides sometime before I attach them to the trailer but I don't own a scale so I'll have to think about that one a bit.

I know that I had a really tough time moving the side profile around by myself (5'4" 125lb female - unfourtunately, guys just have more natural upper body strength than us gals - )

Once the holes were cut, I could lift the side over my head with one hand without much effort at all.

OOOh, I just thought of something - I do have a 15lb postal scale, I could weigh all of the cut out shapes individually and add them up.

Lindsey

[Woody]

I would at least insulate the roof if nothing else. Mine is insulated all around for the A/C in south Florida. The sun beating down on the roof and side walls alone would heat up the interior alot without it. The main advantage of it being insulated all around is you never know where you might end up down the road so to speak. It becomes an all weather type of trailer. I've been in the high 90's and down to the low 20's and was comfortable either way

[crankshaft]

I some times bow to the sage wisdom on this forum. But take it from some one that has lived in both cold and hot weather... Insulate!!!!!

What keeps out the cold also keeps out the heat.

Crankshaft

[Salivanto]

Thanks for all the replies so far. BTW, I have never been called "Sali" before.

I've been going to Vermont every year for years at the same time in October. It's not *quite* winter, but yes, it can be frosty at times. I was suprised to hear so many people say that they've been out in the 20's and 30's in a tear with only the roof insulated... but there ya go -- can't argue with someone who's done it.

> If you went 3/4 without framing, what do you envision
> as the advantage?

I don't know. That was my question. Clearly it could be less work -- but it's not clear to me that it would be less cost. After posting my note I went to Home Depot and started pricing things. The cost difference did not seem prohibitive. It starts getting more confusing when you factor in other things like the possibility of using wood that I already have for the framing (is it OK to frame with pine?) or asking my neighbor if he'd like to part with some of his unused wood. I also am starting to think that the insulation is the least expensive part of an insulated wall.

Although cost is an issue (I'm unemployed), my bigger concern is weight. How strong is a plywood wall compared to a framed wall of the same weight? I would like to be able to finish the project quickly -- at least to the point where I can start using the tear, even if it needs some detail work later, but if a framed wall is lighter and stronger for a comparable cost, that's what I'll do -- especially since that allows for insulation.

> As far as taking a sheet of ply, cutting out huge holes for
> insulation, and using that instead of stick framing...why???

I don't know. I've seen pictures of people doing it that way. I would not do it that way myself. I said I just did it as a "thought experiment." That is, as a way of trying to understand which weighs more -- a thin-sided wall with framing or a thick sided wall with out one. I suppose the thought experiment would only work if solid wood weighed the same as plywood -- which I'm not sure about.

Anybody here every been too cold in an uninsulated tear? How about one with an insulated roof but uninsulated walls?

[len19070]

Previous Post, Same Topic


Joined: 17 Aug 2004
Posts: 154
Location: S.E Pa. Morton
Posted: Mon Apr 25, 2005 5:14 am Post subject:

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I build a 3/4" side that covers the frame. You can have the best of both, 3/4" wall and insulation. Just make the inside wall finish a "Foam backed Rug". Granted its not as good as foam insulation but it is something, and you have to finish the walls anyway. I live in Pa. and camp from April to mid November and the cold has never been an issue. In the summer I have a 12volt fan (pictured) and a full door screen. If you do this put the rug on before you put the roof on, it makes things a lot easier. The photos below are of a foam backed Vinyl (same theory).

http://pg.photos.yahoo.com/ph/len19070/ ... pg&.src=ph

http://pg.photos.yahoo.com/ph/len19070/ ... pg&.src=ph

And Yes.. it is easy and fast.

Happy Trails

Len

[IraRat]

Insulation is gonna work both ways--helping keep it COOL in the summer. The foil backing reflects heat away from the TD, which is a good thing when it's 90.

Also, Lindsey (LMH) did a great job on hers--but I just don't see how it's any easier to cut big holes into a thicker wall, insulate those holes anyway, and have no option to insulate the doors and limited wiring options. Any cheap pine is fine for framing, and if you don't have a curved door, even THAT'S a cinch with straight lumber.

[Salivanto]

Len,

Thanks for taking the time to repost that message.
I'd actually seen it before - that's part of the reason I
asked the question -- namely, how a framed, three layer
wall compares in weight, cost, and strenth to unframed
3/4" plywood wall.

[Salivanto]

Here's another related question -- if I can frame with pine, can I use pine plywood -- or should at least one of these be hardwood/poplar/birch?

[IraRat]

Here's another related question -- if I can frame with pine, can I use pine plywood -- or should at least one of these be hardwood/poplar/birch?

You can PROBABLY cut plywood into strips for this, but I don't know if I would want to. Also, you do indeed use 3/4 plywood to frame around curves, like around the doors. (You trace the door profile onto 3/4 ply, cut that out, and use that as the framing around the curves.)

The only reason I wouldn't use ply for the straight framing, and I could be wrong, is because I think you would get a lot of flex out of this, like it would be susceptible to bending in the middle. Again, this might not be true at ALL because it's attached to the inner skin, but why take the chance?

[toypusher]

You might get some flex, but the biggest reason not to use plywood (at least on the hinge side of the door) is that it does not usually hold screws in the end grain very well.

Kerry

[GregJ]

Just my 2 cents, having never built a tear. Please consider the source.

Both methods appear to have been used and work, so that’s not really an issue…

Cost- a sheet of ¾ ply is about $22 around here, enough hardwood to
frame a side maybe twice that (? or more).

Time- I can cut holes a lot faster than cut and fit for a stick frame.
Those “skilled in the art” may be able to frame as fast. Lindsey
says an hour for the holes, that’s about 3 sticks for me.

Strength- Depends on the structure but with the ply you can beef up the
areas you are concerned about. Also much easier to do a 2D
web with the ply and no joints.

Weight- Either can be over or under done. In our world stick is probably
lighter. Well Engineered, the ply probably is (more design
freedom) but I am guessing here. I’d call it a wash or give the
edge to stick and bow to an ME with data.

Hinges- Wouldn’t use edge mounted hinges directly in ply myself, but
epoxy on the end grain would help a lot. Would be easy to let in
a piece of hardwood for the door hinges: T&G and covered both
sides with sheathing would be as strong as stick. A hinge that
through mounts should be fine, again, I’ll bow to those
experienced. Ply tends to warp less.

Wiring- A ½” hole in ¾ material will not help either; I really don’t see
an advantage either way.

[toypusher]

If you are talking sidewalls, after you get in bulkheads, cabinets, and spars, there should be no warping in the side walls. Just make sure that they are straight and plumb when you put them up. IMHO!

Kerry