The solar kiln begins

grweldon · July 25, 2013, 01:48:19 PM

Definitely not... AC in the summer isn't a problem because it tends to remove moisture from the air. The vapor barrier is supposed to go toward the living space of the house.

Planman1954 · July 25, 2013, 02:05:14 PM

Maybe everybody is misunderstanding the point I was making. There are many different materials used in walls which aide in controlling the penetration of moisture, inside and out. The outside house wrap used today has replaced impregnated asphalt (IMP) sheathing of yesterday. Styrofoam sheathing is used on the outside of house walls as well. Different combinations of materials are used in different areas of the country to control moisture penetration.

Kraft/foil backed insulation vapor barrier is only one type of moisture barrier, and IS placed on the warm side. (Check out my solar kiln build.) I was speaking of the entire wall system.

But hey, we're building a kiln here! I just used 15# felt on my kilns' outside walls and underneath the floor to control moisture (mainly from escaping so the dehumidifier can catch the moisture and expel it.)

beenthere · July 25, 2013, 02:38:10 PM

Quote from: grweldon on July 25, 2013, 01:48:19 PM
Definitely not... AC in the summer isn't a problem because it tends to remove moisture from the air. The vapor barrier is supposed to go toward the living space of the house.

Better check that one out. The hot, humid outside air will condense on the cold wall cooled by AC, and without a vapor barrier (not talking Tyvek which isn't a vapor barrier) outside of the insulation, there will be condensation in the insulation. I'm thinking..........

grweldon · July 25, 2013, 04:19:21 PM

As far as I know it's not done that way, at least here in the south. Vapor barrier toward the living space. That's the method as of this date using conventional materials. Some builders also use foil-faced rigid foam beneath or on top of the exterior sheathing, but it's not done as a vapor barrier.

isawlogs · July 25, 2013, 06:46:12 PM

I am guessing this is going to be a coin toss. ;D

Might be wether one takes his grits early in there mornign' or later in the evenin' :D

Planman1954 · July 25, 2013, 08:14:10 PM

Sounds like we're trying to call the insulation paper back or foil backing the "vapor barrier." I'm calling many materials vapor barriers. Each material in the wall is rated as to how much moisture is allowed through it. I'm no expert on the ratings, but it is available online.

Handy Andy · July 25, 2013, 10:10:32 PM

Just use the kraft paper faced insulation, and put the paper side on the inside, and staple it so it doesn't slide down in the wall. That black coating on the back side of the paper is the "vapor barrier".

GeneWengert-WoodDoc · July 27, 2013, 11:14:24 AM

The vapor barrier needs to be on the warm side, which is the inside of a solar kiln.

In the South, it would seem that the warm side of a home is the outside of the house, but the small temperature difference in the summer means that a vapor barrier is not essential and if it is on the inside of the house, it will not be serious. The vapor barrier is most important when the inside and outside are more than 30 F difference for long times AND the warm side is humid. So, wintertime is the main factor in almost all cases.

In a solar kiln, or any kiln, never use batt insulation as you will get it wet (by accident, small leaks, etc.), it will lose insulation value and also get heavy and sag and fall down. The best is closed cell, rigid board styrofoam, also called "blue board" and other names. In a kiln that gets really hot, you also must use a product that can take the temperature, or it will melt and disappear. The foam insulation usually cannot withstand much heat.

Planman1954 · July 27, 2013, 09:58:23 PM

I give up. I'm yelling down a well. I guess kraft paper and foil will slow vapor penetration and Styrofoam won't. It's amazing a Styrofoam cup holds water. I fail to understand this discussion.

beenthere · July 27, 2013, 10:01:51 PM

Planman
There is a difference between a vapor barrier and a water proof barrier. That may be what is confusing to your thoughts.

Okrafarmer · July 27, 2013, 10:16:43 PM

Planman, can you link up to your thread about your own kiln? I am hoping to build one within the next year, if all goes well.

Planman1954 · July 27, 2013, 10:24:16 PM

Here it is:

https://forestryforum.com/board/index.php/topic,50281.0.html

Build it. It works like a champ.

Planman1954 · July 27, 2013, 10:47:48 PM

Thanks Beenthere. I think you are correct in my misunderstanding a lot of the posts. I was discussing permeance. I was using water and water vapor interchangeably. Permeability is the rate that water or vapor will pass through a membrane. It is expressed in perms. This relates to my earlier post of the combination of wall materials used establishing the dewpoint of penetrating moisture.

Kingcha · July 31, 2013, 07:03:24 PM

pineywoods or anyone else I have ? about attaching black metal siding on the bottom of the rafters. Does it do a better job then just putting it on top of the pile. Also If I do it that way I plan on leaving a gap at the top and the bottom of about a foot to allow for airflow from the fans to force it down and back thru the stack.

Thanks in advance.

Got a little done today but no pics. I should have all the interior plywood up tomorrow as well as the insulation panels in place. Then it will be time to coat the walls.

matt

Planman1954 · July 31, 2013, 07:52:31 PM

Use metal roofing. Paint one side black, and install it under the rafters with the black painted side facing up. I left about 6" at the top and bottom....not a foot, since this allowed for more surface area to heat up. You are creating a chute that the air will flow through. Take a look at my thread "Solar Dry Kiln Construction," and there are photos of it.

Kingcha · July 31, 2013, 08:23:54 PM

Thanks Planman, I will go with the 6" then.

matt

Kingcha · August 04, 2013, 05:59:44 PM

Well progress has been slow but I have chosen to paint the entire inside with that rubberized rood coating and I found a nice exterior flat black paint for the trusses and anything the sun will shine on.

I will get one last white coat(making it 3 coats) tomorrow and put on a 2nd coat of black until it runs out. Thinking I will need 1-2 more gallons. Some of the white will need to be top coated with black plus I got the metal to paint.

I almost order my fans, found some all metal one on sale. I think I will be going with 3 14" fans.

Matt

Kingcha · August 07, 2013, 06:47:44 PM

Flooring is in, just have to get 3 coats of that rubber roofing stuff on it. We also got the clear panels installed.

Hopefully I will have time to get the steel up tomorrow before having to head out of town.
Fans our ordered. 3 - 14 inch all metal fans.
The goal is to start cutting the trees down for the exterior siding by Tuesday. I think I need a little over 220 bf of siding.

I have not decided if I am going to use hinged doors or lift off doors yet, I will decide that next week.
Matt

Planman1954 · August 07, 2013, 08:06:07 PM

I'm proud of it!! Lookin' good... 8)

pineywoods · August 07, 2013, 09:56:32 PM

Quote from: Planman1954 on August 07, 2013, 08:06:07 PM
I'm proud of it!! Lookin' good... 8)

Me too... Put a thermometer inside up near the top, then tell us how ~~warm~~ hot it gets. ;D

WDH · August 07, 2013, 10:11:21 PM

You are doing good!

Kingcha · August 08, 2013, 08:31:22 AM

Thanks guys. I have a thermometer that I use in my smoker that has an extra 2 foot lead that I was going put inside. That way I can just plug it in when need to check the temp.

Matt

SPD748 · August 08, 2013, 11:13:45 AM

Matt,

Looking great! I'm pretty stoked about getting started on mine.

Looking at your pictures, are the roof rafters 2 x 6 or 2 x 4? They look like 6's and if so, did you go with a wider board for any particular reason? I was considering using 6's thinking that it would create a larger area between the metal collector and the poly panels. I'm thinking, more area = more hot air however I'm not sure it works that way.

-lee

Kingcha · August 08, 2013, 11:33:13 AM

Thanks Lee, they are 2x6's. I used 6's mainly for strength, originally I did not plan on attaching the metal to the bottom of the joist. I was just going to paint everything black and put the metal on top of the stack of wood. After reading how the others where attaching it to the joist it just made more sense. If I had know I was doing it this way when I began I might have used 8's.

I got the metal hung this morning. I left a 6 inch gap at the bottom and a bite larger at the top. The way I plan on mounting my fans, they will blow down on both sides of the metal and the baffle I will install will force the air through the wood pile.