CPES inside the walls?

[Aint2Proud]

I am building sandwich walls with 1/8 inch Baltic Birch outside and 1/8th Maple inside. I will skin it with aluminum. My question is with CPES, should I apply it to the wall frame and inside of the plywood and then glue foam down once it is dry or is that overkill?

I should clarify that I am going to apply it to the outside of the plywood as well and am planning to epoxy and tape the roof/wall joint.

[afreegreek]

hey, why not? overkill is the name of the game on this site..

[planovet]

I put CPES on both surfaces and all edges of my inside and outside ply. Overkill? Maybe but I doubt my ply will ever fail due to moisture. I did not CPES the framing of my walls though...

[afreegreek]

the truth is with all the sealing and glueing you're making it as hard for moisture to escape as it is to penetrate and the fact is moisture will get in no matter what you do.. the more you seal the better as far as surfaces go but vent your cavities so the moisture that will get in can also get out. avoid metal to wood contact and all this insulation BS does more harm than good. buy a bigger heater and forget the insulation.

[Miriam C.]

CPES is on only a waterproofer, it is also a wood hardener. It was created to repair damaged wood on boats. If you get too much hard wood you might have a dandy time getting screws and such in......

[48Rob]

avoid metal to wood contact and all this insulation BS does more harm than good. buy a bigger heater and forget the insulation.

While I agree that minimizing wood to metal contact is wise, I don't understand the "all this insulation BS does more harm than good"

Can you explain why?

Proper use of vapor barriers is key to avoiding trapped moisture in wall cavities from vapor transfer, and of course preventing leaks is rather important too...

Rob

[Aint2Proud]

By minimizing metal to wood contact I assume you mean trim surfaces, but I am not sure how you minimize those? You have doors, a hatch and the bottom of the walls where trim will be used. I am planning on using the butyl tape underneath that trim. How does that statement relate to aluminum skins floated on plywood? Is there a barrier I should be putting between them? Also the insulation factor is kind of secondary. While I will be camping in spring and fall, the biggest factor for me was the weight. I am building a 5 wide, 54 inch tall by 11ft long Diner style with aluminum skin. To find 60x144 inch aluminum it looks like I will be going with .063 thickness, which add a bit of weight. Thanks for the feedback - I am paranoid about moisture!

[Arne]

CPES is a good stiffener as well as sealer. If I used 1/8", I would do both sides. As far as moisture, it would only be a problem if you got a leak. Even then, the cpes would be good protection and would save you from more serious damage.

Personally, I would not worry about normal moisture in a sealed wall system. Sealed or unsealed, the moisture level would be the same.

I've built 2 in the past 7 years and never had a leak in the walls/ceiling, and no cracks (which is why I never had a leak)...

[afreegreek]

avoid metal to wood contact and all this insulation BS does more harm than good. buy a bigger heater and forget the insulation.

While I agree that minimizing wood to metal contact is wise, I don't understand the "all this insulation BS does more harm than good"

Can you explain why?

Proper use of vapor barriers is key to avoiding trapped moisture in wall cavities from vapor transfer, and of course preventing leaks is rather important too...

Rob

over the years I've done a lot of renos and repairs to homes both old and new and if there's one consistent thing I've seen is insulation traps moisture (like a sponge) and prevents air movement causing rot and mold. I haven't seen this is old homes before insulating the hell out of them and installing vapour barrier was the norm. I can't tell you how many times I've pulled drywall to find insulation full of mold. I've even seen wall cavities full of water for the first few inches too. I suppose in a perfect world you could seal out all moisture but in reality, you can't and must make allowances for the water to escape. it's not the water getting in that's the problem, it's water that can't escape. in the Province where I live we've had so much trouble from this "insulation/energy conservation" of late. homes only 15 years old are rotting away while 70 year old home next door are dry as a bone. the only difference is the insulation/vapour barrier. personally I don't see an advantage in setting your house up to rot in a few years just to save a few bucks on heating.

I got out of it a while ago because the government says.. you'll build it like this, with this and that,.. AND you'll go good for it if something goes wrong. (AKA ..the New Home Warrantee) well, we have 20 plus years of evidence that it is not quite right and "if" becomes "when" in this part of the country.

now the thing is to drill 2 holes at the top and 2 holes at the bottom of the sheeting at every cavity between the studs and use 1/2" thick strapping to attach the siding to (called.. rain screen) this keeps the siding from transferring moisture to the sheeting and allows air to move through the cavities. we've also gone from 2x4 to 2x6 studs to get the R factor insulation in and still leave room for a gap between the insulation and the sheeting.


a good thing to observe is the water vapour that will get in and condense between the two panes of glass on double pane window if the seal is broken and the inert gas escapes to allow air in. every time the sun hits it, the air expands and gets forced out, then the sun goes down and the window cools and sucks more air in the equalize the pressure, with it is moisture. moisture that will condense from vapour to liquid. this moisture is not likely to escape either, it will just continue to accumulate. same thing happens to your walls but they are made of wood and will rot with a moisture content over 20%. you won't see this happen like with glass either, you won't know until it's too late because they will rot from the inside out.

anyway, if you're going to insulate, make sure you don't stuff the cavity full. leave some space between it and the outer panel and keep it up a 1/2 inch from the bottom too.

[teardrop_focus]

Auntie M

CPES is on only a waterproofer, it is also a wood hardener.

You're right, Miriam; most epoxys have hardening qualities...

CPES, though, claims to be altogether different in that dept:

Steve Smith, CPES Inventor

The kind of resins I use will have a toughness and flexibility comparable to that of the original wood. Those other kind of resins just don't. The reason I use what I do is because I want the treated wood to have similar mechanical properties to natural wood. If you look in Section Three of www.woodrestoration.com you will see mechanical tests that prove the untreated wood and treated wood bend in almost an identical manner, although the treated wood is actually stronger, by an average 41%.

http://tnttt.com/viewto ... ht=#619734

From the thread, One more time... CPES

[afreegreek]

Auntie M

CPES is on only a waterproofer, it is also a wood hardener.

You're right, Miriam; most epoxys have hardening qualities...

CPES, though, claims to be altogether different in that dept:

Steve Smith, CPES Inventor

The kind of resins I use will have a toughness and flexibility comparable to that of the original wood. Those other kind of resins just don't. The reason I use what I do is because I want the treated wood to have similar mechanical properties to natural wood. If you look in Section Three of www.woodrestoration.com you will see mechanical tests that prove the untreated wood and treated wood bend in almost an identical manner, although the treated wood is actually stronger, by an average 41%.

http://tnttt.com/viewto ... ht=#619734

From the thread, One more time... CPES

a wood cell is like a hollow grain of rice with a little hole at each end. a piece of wood is a bunch of cells stacked one on top of the other forming tubes, these tubes are bundled together like a bundle of straws. filling the walls of the cell with CPES or anything else will not change the way these cells react in relation to one another due to the compression/tension forces cause by bending the structure (piece of wood) as a whole. what makes CPES different from most other epoxies is solvent content that makes the resin thinner allowing it to penetrate more cell walls by capillary action without filling the hollow part of the cell that thicker epoxies will do. filling the cells beyond FSP (fibre saturation point) will make the wood brittle because it will make the cell a solid object rather than a hollow one and will no longer let the cell expand and contract under load like it would normally. all the force will be transferred to the bond between the cells. (the lignin)

CPES is designed to repair rotten (wet wood) and will penetrate further in wet wood than it will in dry wood (as will all the others). if you are using dry wood you won't get anywhere near the penetration you will on wet wood. without the effect of the water, the epoxy will gel up too fast to penetrate as far.

CPES will not do anything different than any other epoxy will do with an equal amount of a similar solvent added to it..

West Systems and other manufacturers will warn against adding solvent because it will reduce the ultimate strength of the epoxy which is true but they are assuming you're using it as an adhesive and not as a penetrating sealer. in that case the ultimate strength is irrelevant as the ability to penetrate is what you're looking for.

[teardrop_focus]

afreegeek

CPES is designed to repair rotten (wet wood) and will penetrate further in wet wood than it will in dry wood (as will all the others). if you are using dry wood you won't get anywhere near the penetration you will on wet wood. without the effect of the water, the epoxy will gel up too fast to penetrate as far.

CPES will not do anything different than any other epoxy will do with an equal amount of a similar solvent added to it..

West Systems and other manufacturers will warn against adding solvent because it will reduce the ultimate strength of the epoxy which is true but they are assuming you're using it as an adhesive and not as a penetrating sealer. in that case the ultimate strength is irrelevant as the ability to penetrate is what you're looking for.

Not quite. CPES is also intended to be used as a 'primer' for varnish on good, dry wood.

As for flexibility, am I to assume that you're saying that Mr. Smith is making a false claim?

Steve Smith

The reason I use what I do is because I want the treated wood to have similar mechanical properties to natural wood.

Is the point of your post to contradict the following?

Steve Smith

The reason I use what I do is because I want the treated wood to have similar mechanical properties to natural wood. If you look in Section Three of www.woodrestoration.com you will see mechanical tests that prove the untreated wood and treated wood bend in almost an identical manner, although the treated wood is actually stronger, by an average 41%.

[48Rob]

over the years I've done a lot of renos and repairs to homes both old and new and if there's one consistent thing I've seen is insulation traps moisture (like a sponge) and prevents air movement causing rot and mold. I haven't seen this is old homes before insulating the hell out of them and installing vapour barrier was the norm. I can't tell you how many times I've pulled drywall to find insulation full of mold. I've even seen wall cavities full of water for the first few inches too. I suppose in a perfect world you could seal out all moisture but in reality, you can't and must make allowances for the water to escape. it's not the water getting in that's the problem, it's water that can't escape. in the Province where I live we've had so much trouble from this "insulation/energy conservation" of late. homes only 15 years old are rotting away while 70 year old home next door are dry as a bone. the only difference is the insulation/vapour barrier. personally I don't see an advantage in setting your house up to rot in a few years just to save a few bucks on heating.

I got out of it a while ago because the government says.. you'll build it like this, with this and that,.. AND you'll go good for it if something goes wrong. (AKA ..the New Home Warrantee) well, we have 20 plus years of evidence that it is not quite right and "if" becomes "when" in this part of the country.

now the thing is to drill 2 holes at the top and 2 holes at the bottom of the sheeting at every cavity between the studs and use 1/2" thick strapping to attach the siding to (called.. rain screen) this keeps the siding from transferring moisture to the sheeting and allows air to move through the cavities. we've also gone from 2x4 to 2x6 studs to get the R factor insulation in and still leave room for a gap between the insulation and the sheeting.


a good thing to observe is the water vapour that will get in and condense between the two panes of glass on double pane window if the seal is broken and the inert gas escapes to allow air in. every time the sun hits it, the air expands and gets forced out, then the sun goes down and the window cools and sucks more air in the equalize the pressure, with it is moisture. moisture that will condense from vapour to liquid. this moisture is not likely to escape either, it will just continue to accumulate. same thing happens to your walls but they are made of wood and will rot with a moisture content over 20%. you won't see this happen like with glass either, you won't know until it's too late because they will rot from the inside out.

anyway, if you're going to insulate, make sure you don't stuff the cavity full. leave some space between it and the outer panel and keep it up a 1/2 inch from the bottom too

Thank you for taking the time to post such a detailed answer to my question!

I'm in the same general business, and moisture control is the #1 goal with every new home we place.
We struggle too, with the insulation "craze" (more is better, make everything airtight).
Every structure we find that has moisture problems has a leak, has poor perimeter drainage, or is "too tight".

I asked the question because on reading your original post, it seemed you we offering a general "do not insulate period" sort of opinion.

I understand now where you are coming from, and why you posted as you did.

Insulation is good, but moisture control is WAY more important.

Rob