Condensation Question

[lrrowe]

Now this is a first. I replied to Hank's question and I hit submit and then went to see my post in the forum. It was gone and MtnDon's was there. Is it possible that we did it exactly at the same time and somehow mine got over ridden? Oh well, I will try again and I do not about others, but I never can duplicate the first wording the second time. It never comes out the same.

Hank, I was going to comment about the air space but MtnDon sort of hit on what I was going to question. And in my case, I do not want to give up the 1/4" or more for anything but insulation. And in my case again, I have the plywood on the outside, so I have another barrier between the inside plywood and the aluminum siding. I also have heard before and MtnDon mentions it also, that if the insulation is installed with no gaps, then the air/moisture has no way of getting through. I also heard that Blue Foam itself is a moisture barrier. But I do not know how true that is.

[MtnDon]

Blue and pink rigid foam, as well as the polyiso, are closed cell and do not absorb moisture. That does not apply to the white expanded polystyrene foam... the cheaper stuff. Pink, blue and polyiso are used on bare earth with concrete poured over it for an insulated slab. That is commonplace these days.

Having plywood exterior skins is ideal. Glue the foam in place between the ribs; foam adhesive or foam in a can around the edges will seal out any moisture/air from getting in there from the interior. Do a careful job. If desired a second layer on the inside over all the ribs removes any potential cold spots the framing would make.

[lrrowe]

Good, thanks MtnDon.

I also think I will apply polyurethane or something similar to that to the inside part of the exterior plywood. Just another point of possible protection for rot, etc. Is there a trick to the glue (i.e. get it all over the foam or just enough to hold it in place). My uninformed approach would be to put it all the way around the edges and then maybe an "X" in the middle.

[MtnDon]

Cut the panels to be a pretty good fit, not too tight that they are difficult to place, not so loose that they want to fall out of the wall before the adhesive sets. My thinking is to apply a bead all around the perimeter at the plywood / stud corner. Maybe a few lines of adhesive in the field of the opening. Press into place. Loctite has some good foam friendly adhesives in caulk tubes. Some require blocking / bracing to hold in place while the adhesive cures. That is in part because the adhesive expands somewhat like Gorilla glue. I used 1 x 2 ish material from ripped 2x material, cut to the length required to span the trailer. Pieces of scrap 2x, 1x or plywood were used to spread out the forces against the insulation panel and protect the foam from being crushed.

A spritz of water on the foam or wall with the adhesive in place speeds up the cure of a polyurethane adhesive. Though you have more air humidity there than we hardly ever see here in NM.

I don't know if it is necessary to coat the plywood with polyurethane. Probably won't hurt but may not be of any benefit either.

BTW, are you anywhere near Elk Creek?

[lrrowe]

MtnDon, good hints on the boards to hold the foam in place. Thanks.
I will overdue things and coat the plywood with a poly varnish.

My ISP server is crashing today and I complained. Will be 24 hours to fix it. Anyway, I could not get Mapquest nor Google Maps to search Elk Creek for me. But I was able to find an Elk Creek close to Wytheville, VA and if so, then yes, I am fairly close. I am counting 2 1/2 to 3 hours close.

[OverTheTopCargoTrailer]

Then I should be in great shape for hunting camp this November. I am used to sleeping with temps as low as 20 degrees .

The only way you would get me to sleep in 20 deg is in between two big native Alaskin girls - wrapped in walrus fur inside a 6ft thick iglo.

[hankaye]

MtnDon, & lrrowe, Howdy;

I worked on old military aircraft when I first went into the Service (1968), and it
got me thinking that I could use some aircraft drain grommets;
http://www.univair.com/hardware/grommet ... -seaplane/
They are used to help drain seaplanes and some older types of aircraft of the
condensation that accumulates in non-pressurized aircraft. Only needs a 1/16th inch hole,
and you glue the grommet over the top with either some silicone or rubber cement.
At the cost I can get 100 and have plenty for spares as they do blow off every once in awhile.
I can put one at the top and bottom of each 'cell', and the screen trim between the blue board
and the exterior skin. Then a piece of screen trim over the ribs to stop the bridge effect.

hank

[lrrowe]

Then I should be in great shape for hunting camp this November. I am used to sleeping with temps as low as 20 degrees .

The only way you would get me to sleep in 20 deg is in between two big native Alaskin girls - wrapped in walrus fur inside a 6ft thick iglo.

It is really not that bad if you do not have to get out of your sleeping bags (yes bags).

[lrrowe]

MtnDon, & lrrowe, Howdy;

I worked on old military aircraft when I first went into the Service (1968), and it
got me thinking that I could use some aircraft drain grommets;
http://www.univair.com/hardware/grommet ... -seaplane/
They are used to help drain seaplanes and some older types of aircraft of the
condensation that accumulates in non-pressurized aircraft. Only needs a 1/16th inch hole,
and you glue the grommet over the top with either some silicone or rubber cement.
At the cost I can get 100 and have plenty for spares as they do blow off every once in awhile.
I can put one at the top and bottom of each 'cell', and the screen trim between the blue board
and the exterior skin. Then a piece of screen trim over the ribs to stop the bridge effect.

hank

Hank, if you are saying the screen trim is your 1/4" air gap provider and then you offer a place for the condensation, should there be any, to escape by, it makes sense to me. Sort of like putting the air baffles in the attic between the insulation and roofing plywood. Are you thinking about it, or are you going to try it?

But to play Devils Advocate if I can, if you were to adhere your blue foam to the aluminum siding with adhesive and spray foam like MtnDon suggests, would that not be easier and less obtrusive to the outside siding?

[hankaye]

lrrowe, Howdy;

After measuring and fitting the foam for each cell, I'd stick the trim pieces to the foam then both to the exterior.
If I get some foam that is thick enough to extend past the ribs by the 1/4" then I'm sittin' in tall clover. If not then
I'll have to give up some interior space to make things mate up smartly.

hank

[AZ_Desert_Rat]

AZ_Desert_Rat

I just noticed - you need to change your name to

MN_Mountain_Rat



Prem ....... I'm never getting inside another moldie Airstream ever again

Hi Over the Top,
Not many mountains in MN until you get up in the northern Iron Range; however, there are plenty of lakes here ... I'll have think what I might change the handle to, but I'm not sure I really want to yet ... my roots are still in Arizona ...

Later my friend...

[chiefb711]

So I went to the box store today and got some polypropylene tape and vapor barrier. I covered all my wires in the poly tape and used what was left to seal off my vapor barrier. I went with the 3.5 mil in between the polystyrene R5.0 insulation and my 3/8" wood panels. Should keep moisture out of the walls, now I just need to focus on ventilation and heat/air. I spent a good hour putting the finishing touches on my re-use ceiling mount A/C.