Kiln Chamber - A Few Questions for the Experts

[YellowHammer]

I used both.  I put the exterior walls on first, metal cladding, and although used trim pieces, did not seal the joints.  It must breath.  Then from the inside I used standard Fiberglas insulation, with no batting, again to not trap moisture.  Then in front of the studs, used 2 in poly foam board.  Then directly on top of that, Tyvek house wrap, to make the waterproof interior liner.  Taped and sealed the seams, especially the roof, wall and floor corners.  This is essentially the swimming pool liner, it must be watertight, no leaks.  Then to the inside of that, more to give it damage protection, I screwed 5/16" plywood, not using lots of screws, because they are penetrating the liner.  Where there are joints in the plywood, I put some silocone and screwed near the edges and covered with furring strips over the sealant.  Any screw holes in the wood thought the Tyveck, penetrating the water proof barrier, I put a bit of sealant.  Then when I double checked all the joints, I used a layer of latex house paint on all surfaces, which will prevent green wood moisture from rapidly getting to the wood but will still allow the wood to breath.  
The key to the whole thing is thinking of building a swimming pool, but not trapping moisture between layers.  So the further out the walls, the more it can breathe to allow moisture out if it even gets in the walls.  It will at some point and you don't want a wet, soggy moldy mess between the walls.

Then because the door seals were closing agaisnt wood, and rough and not perfect seals, I put a strip of aluminum foil tape on the surfaces of the doors where the weather stripping contacted.  These metal strips will be taking the hits and scratches when wood goes in and out of the kiln so do something that is easily fixed and replaceable.  Since tape is a smooth, slick foil, it makes a great sealing surface.  

Seal the concrete floor with a couple coats of sealant, and make sure it gets run somewhat up the walls, again, to make a virtual bathtub floor.  Some methods of fixing kiln drying issues involve pouring many gallons of water on the bottom of the kiln, and I sure didn't want that water getting behind the walls.  Sealing the concrete will also greatly help in shortening the kiln cydle time, as it prevents the concrete from sucking up moisture from the ground, and then forcing the kiln to dry it out.  

Another thing I think is critical is to do a "burn in" or "break in run" where no wood is put in the kiln, but a kiln cycle is run for several days, in essence drying everything and anything out.  Then go back inside and fix all the cracks and leaks that developed as the construction materials shrunk.  

Once the kiln has been broke in, its good to go.  Don't put switches on the inside of the kiln. They will rot out.  Instead run the wires out to the kiln controller box and simply put switches or plugs, there.  Seal any conduit holes through the walls, and run a P trap for the kiln drain line to prevent airflow.  

This may all seem like overkill, especially when the kiln will be venting air during the cycle, but it all pays off when doing a sterilization cycle and otherwise paying for electrical BTU's. A sealed kiln also has a very fast cycle time. 
  

[Mossy Chariot]

Thank you, Robert!!!!!  @YellowHammer 

I've always had a tendency to overkill when constructing. That has been some of my problem here - trying to do the "best possible" job and thinking too much. 

Thanks again!

[123maxbars]

I followed @WDH and @YellowHammer kilns when I built mine. I however went with regular store bought (lowes) garage door gaskets for my doors, they have worked perfectly and were cheap! I always kept the water tight statement Robert made to me when building mine, it paid off in the end.  

[Mossy Chariot]

Thanks for the input Nathan @123maxbars .  I will probably go back and re-review your 10 part video series on your build.  If I remember correctly, either in one of those videos or when we talked in Rentz, you indicated, if had it to do over, you might have sprayed the foam insulation because of it was a major job to do the insulation and seal it with a case or 2 of Great Stuff.  Did you research that any?  Any pros or cons in your mind?  :P

[K-Guy]

@Mossey Chariot 

Be careful on using spray foam. I am starting to get negative reports from customers, absorbing water and degrading. 

[Mossy Chariot]

@K-Guy Is this for both open cell and closed cell foam?  Thanks for the input.

[K-Guy]

Yes it is Mossey Chariot. 

[Mossy Chariot]

Thank you Stan!!  That is what I needed to know.  I will be using the info in your kiln manuals as well as info from YellowHammer, 123maxbars, and others.  As I get closer to builiding, I will call you, as I will be most likely purchasing the L53 and accessories. 

[YellowHammer]

The L53 is a pure workhorse.  @K-Guy can corroborate, I give my L53 no mercy and run it well above and beyond it's expexted norms.  I don't think it has been turned off more than a grand total of a week, in maybe 7 years of continuous, no holds barred, operations.  

[Don P]

Tyvek is a water barrier but is not a vapor barrier, it is designed to pass vapor. In home construction it is referred to as a weather resistive barrier, we use it to block airflow and rainwater but allow the wall assembly to dry out, google Dow on this.

 Moisture drive is normally from the warm side which is the inside of a kiln and that is where the vapor is coming from. I'm wondering if something with a lower perm rating, a true vapor retarder like poly wouldn't be a better choice just under the interior sheathing? In my way of thinking that would let less vapor into the wall. From that poly layer out let the wall materials dry to the outside. Let the kiln dry the interior sheathing from the poly inwards.

[YellowHammer]

Interesting on the Tyvek, buts its worked fine for me.  Maybe use a thick plastic instead, but I would be worried about the plasticizers breaking down from the heat and time.

A buddy of mine had a leaky riveted boat and he spent lots of time trying to seal it up.  He eventually brought it to a LineX bed liner dealer, they sprayed it and it hasn't leaked since.

I think if I was going to build another one, I would investigate spraying the inside of the kiln, in its entirety, with a pickup truck bed liner material, a thick, total, "rubberized" waterproof proof liner, walls, floors, and ceilings, assuming it would take the heat.  It would also provide inpact and damage protection which is a real problem and also address all the issues with calling and sealing floors and ceiling joints.  A true "swimming pool" liner.

It might also be a solution for covering the spray foam.  

[doc henderson]

My BIL does bed liners and tried to spruce up his 5 x 10 utility trailer and the coating did not adhere long term to wood.  good thought though.

[123maxbars]

A spray in liner material would be a cool looking kiln atleast @YellowHammer  8)

[YellowHammer]

I think I would apply sheet metal to skin the inside of the chamber, then spray that to get good adhesion.  

[GeneWengert-WoodDoc]

A product called Silverliner made by Pace Products has been used on interior kiln walls, roof  and baffles for years to seal the wall.  Sticks well, lasts for many, many years, reflects light compared to black coatings.  The silver (really aluminum flakes) form a continuous layer as it dries. And the "tar" helps seal as well.

[doc henderson]

MC  @Mossey Chariot , this has been a great thread helping us all share our ideas not only with you but each other.  I hope to have a few more things figured out before I begin my kiln.  Thanks @GeneWengert-WoodDoc   &  @YellowHammer   &  @123maxbars 

[Mossy Chariot]

You know @doc henderson. The members of this forum are a real world "Think Tank." For those that listen, the knowledge of the collective can be brought to bear to best solve the most difficult problems.....

I'd better stop there before I get off topic and start ranting about other areas of our society that have no understanding of this concept. 

[doc henderson]

Amen my brother!

[scsmith42]

Mossy, have you thought about an L200 instead of the 53?

[Mossy Chariot]

Actually, that was my original plan.  However, I've talked myself out of it being a one man operation, limited space, and limited support equipment to move logs and lumber. Didn't think I could keep a bigger one up running efficiently.  

[scsmith42]

Actually, that was my original plan.  However, I've talked myself out of it being a one man operation, limited space, and limited support equipment to move logs and lumber. Didn't think I could keep a bigger one up running efficiently.  

One thing to keep in mind is that kiln capacity varies depending upon species, thickness and MC%.
For instance, my L200 is sized for 4K bd ft of 4/4 oak.  However, if I load it with green 1" SYP I have to reduce the load down to around 1250 bd ft in order to maximize the drying rate.
If I load it with air dried material (15% MC) that I only need to do a finish off and sterilization run on, then I can put 6K bd ft + in it.
4/4 poplar is around 1500 bd ft if I want maximum drying rate.
4/4 black walnut is around 2,500 bd ft.
One trick that I learned years ago was to either air dry below 25% first, or if I wanted to go in with green material load the kiln so that the maximum number of gallons of water removed daily matches up with the safe drying rate for the lumber.  
Said differently, If I put 4.5K bd ft of green 4/4 oak in the kiln I don't really need to worry about it drying too quickly.  My main concern is to be sure that the temps don't get out of hand during the initial drying phases.  Usually the RH% will remain above the targeted drying rate for the first couple of weeks, which is when the greatest risk of degrade occurs.
However, if I load 2K bd ft of green 4/4 oak I have to pay a lot more attention to the daily drying rate.
For that reason, an L53 may be a better choice for you. 
Lots of pro's and con's on each side.