The garage kiln

[Osric]

I'm in the process of building my garage kiln.  It is 5' wide, 13' long, and 6' high.  I've put the studs together (metal) and sealed the garage walls so there is no water seepage.  The garage is 2 floors, so I'm going to run some duct work up to the attic area down to the kiln, put a duct circulation fan in there and let it blow into the kiln for some added heat in addition to the dehumidifier I plan on running.

As I was about to insulate the walls before drywalling, I had to wonder if it was worth insulating.  With a constant source of heat coming into the kiln, and I assume I'll need to put a vent in the kiln as well to allow for air circulation, I began to think that this would just be wasted money.

Do I need to insulate this?  Would it make a significant difference one way or the other.  The more I think about it, the less it would seem that insulation is needed.

[brdmkr]

Maybe not.  I have not gotten my home DH kiln working yet, but I know that the compressor is designed to kick off at high temps.  I think above 100 or 110 F, the compressor shuts down.  You may want to check the owner's manual of your DH unit.

[Osric]

got the box built, drywalled and spackled.  Still need to figure out a door for it...probably make one out of plywood.

World's worst spackle job, though...that'll teach me to use old mud  ;D


Next step...get a dehumidifier...then, get some lumber to load the sucker up

[TexasTimbers]

I would insulate it. I did insulate mine in fact and I live in Texas. I don't need insulation 8 months out of the year but those other 4 - especially 2.5 to 3 of them, it gets miserably cold. I hear it gets downright frigid in Ohio sometimes too. ;)

Don't understand why you do not want to insulate it. Your compressor is not going to heat the box appreciably in the cold months without insulation, and supplemental heat will be even more inefficient during the cold months too. Insulation is your friend.

[Osric]

Don't understand why you do not want to insulate it.

Short answer:

$$$$$$$$$

[Don_Papenburg]

That is also the short answer for why you should insulate.  If it is a small garage kiln it will be emty at times .  In the summer that means to much heat convecting into the garage and in the winter way to much convecting out of tha garage.

[Osric]

loaded it up today, even though I'm short some duct work and a door for the front of the kiln.  I picked up 800 bd. ft of sycamore 'outs' and they fit nicely in the kiln with a little room to spare.  Looks like I could get a full 1000 bd. ft. in there if not a little more.

Tomorrow, I get some plywood to make a door, run an outlet into it and at least get a fan blowing on the stack.  I'm still looking for a used dehumidifier for this...I'd really rather not spend $150 on a new one.

[TexasTimbers]

Find a way to get your hands on some insulation. Talk to some of the remodelers there in Athens and tell them next time they tear out some walls you want the old insualtion. That's something they don't recycle. You need insulation for a kiln, especially where you live.

You don't need much really, so get industrious!

[beenthere]

Osric
Looks pretty cozy in there.

Must be real tough to load it and keep the stickers straight, one over the other.
And wondering if you are planning to have air circulate through the load?  If so, how?

Curious here. 

[Osric]

details...details... :D

The next project is to have a cart built that fits inside the kiln that I can roll in and out.  Never done any welding, so maybe I'll ask the local shop teacher if he wants to have one of his classes tackle that project for me.

As the kiln is now, I'm not entirely certain how well air circulation is going to work.  I do have a couple options to help improve things, though.  The duct work that I run can either be run to the top of the kiln, or down the side in the back of it depending on whether it would be better to have the air enter from the top or the bottom.  I assume I'll also need to cut a vent for air to escape, and I can locate that pretty much anywhere I want.

Any suggestions?

[TexasTimbers]

Getting  ample, evenly-distributed airflow across the boards might be a challenge the way you have it laid out.

You are defiinately going to have to install baffles on the top and sides to force the air across the your boards. If you pull air from the top, locate 3 or 4 fans/ducts in the baffles spaced evenly apart the length of the kiln so that you don't get uneven flow. The only return air you want is what comes across the boards.

Air flow in a kiln is critical. Sort of like retaining heat in the winter. ;D

[Osric]

Correct me if I"m wrong here...

This kiln was designed to be a dehumidification kiln.  I was under the assumption that you do NOT want a lot of fresh air coming into a dehumidification kiln because that will bring in added moisture as well.  A dehumidification kiln worked on sucking all the moisture out of the air and when it was done with that, it would start sucking it out of the wood.

No?

[TexasTimbers]

You are right. No one is saying you want alot of fresh air. You want to recycle the inside air over and over again while the DH removes the mositure. But you also need a vent to be able to control moisture. Some species such as white oak can be dried too fast and cause defects, so you need to be able to control the mositure removal rate both ways.

A DH unit like you are running is pretty foolproof though. It's real hard to ruin a load in them, unless you do not have proper airflow, proper tempurature control within reason, and the proper rate of mositure removal. other than that it's a walk in the park. ;D

I've said about all I can say.

[Radar67]

If you don't allow enough airflow, you have effectively built a mold breeder. As TT said, the inside air has to be recycled continuously for the dehumidifier to work. The air is the transport mechanism for the moisture to make it to the dehumidifier.

[Osric]

can't do it on this load, but would a couple fans say, 6" from the back of the box, be a good idea to help this?  Keep the air cycling forward towards the dehumidifier through the wood?

[bck]

Seems like to me if you put fans at the end, when the air reaches the stickers it will just go around the pile instead of going through it ? No where for the air to go??

Can you get fans above stack? You will need to get the air to go through the stack. Do you have as much room at the back of the stack as you do the front? Might help to close that off with something or most of your air will take that route instead of going between boards.

Let us know how the sheet rock holds up, I am curious about that??

[TexasTimbers]

No.

If you don't allow enough airflow *[ across the surface of the wood], you have effectively built a mold breeder.

* Added by me but Radar knows this and just thought you'd know what he meant I am sure.


TProvided the chamber is tight, the DH will eventually remove the moisture from the air even without airflow, eventually. But without airflow across the boards themselves, mold has a chance to grow because the same moisture sits there on the surface of the wood with no means to be caried to the DH. Radar did say this.

As air flows across the wood (this means the all the surfaces of each board, not the pile in general), the moisture that is coming out of the wood, the "free" mositure that comes out just from sitting there and not being fed water anymore, just wants to hover there and hang around. With airflow across the wood, ALL of the wood, the airstream takes it away immediately and mold doesn't have one of the necessary ingredients to grow . . . moisture sitting on the surface long periods of time.

As the DH starts to remove the bound water,  the airflow is critical in the finakl stages to get the wood down to the 7% range. You might not ever hit 6% in your kiln where you live, maybe you won't even hit 7% most of the year because you are taking shortcuts which simply can't be taken and expect to have good qulity dry lumber.


You must have sufficient airflow across the lumber. Your arrangement even with fans in the back won't allow for it IMHO.
You must have insulation most times of the year where you live. Your lack of it won't allow your kiln to maintain temperatures in the necessary range to properly dry most species . . . IMHO.

[TexasTimbers]

One thing I didn't mention is that I am referring to really wet wood. You can still get mold on air dried wood, but if you are going to air dry your wood before sticking it in the kiln (sufficient air movement is just as critical when air drying) then you might get by with the fans in the back but it still not optimal when with just a little extra work you could do something like below.

Make a plywood box and stick an old used AC squriel cage type fan in there. You can get one cheap if you scrouge. Run some flex duct, the cheapest kind, down one side and branch them off so you have about 3. Stick some starting collars through the side of your chamber and run the duct to them. Do this on each side. You can probably get the flex duct free or next to nothing from a jobsite or a buddy who works in AC/heating/plimbing contractor.

One supply and return boot would be better than nothing but you may as well install 3 on each side since it won't be that much more trouble or expense. What the highly technical diagram does not shjow, is that remember you need end baffles too. You have to force the air throught the stickered pile of boards.

[Radar67]

Let us know how the sheet rock holds up,

I meant to comment on that last night as well. I don't think the normal sheetrock is going to hold up to the moisture content very well. In all my years of construction, green rock has always been used in "Wet/moist" enviornments. (ie bathrooms). While the green rock is touted as being moisture and mold resistant, there is still a chance it will allow mold to grow. The white rock will definitely grow mold if it stays moist long enough. There is a new paperless sheet rock available that is suppose to be 100% mold resistant. It hasn't been out long enough to know for sure if that is the case though. It is about twice the price of regular sheetrock.

IMO masonite would be the sheet stock covering of choice for this enviornment. The reason I say this is, I have several pieces of old masonite that has been painted on one side that I use to cover air drying lumber. It has been subjected to the weather for over 20 months now with no noticable signs of degrade or of mold growing. A sign maker gave it to me after he removed it.

Osric, I know it sounds like we are ganging up on you, but that is not the case. I can fully understand needing to build for as little as possible.

[bck]

TT, great idea on how he can add the fan . I wish I could make drawings like that.

As for mold growing , would the mold just be on the surface where he can run it through the planer and clean it up or will the mold grow deep??

[metalspinner]

As for mold growing , would the mold just be on the surface where he can run it through the planer and clean it up or will the mold grow deep??

Depends on the species.  White oak should stay near the surface, but soft maple will stain all the way through.  And not the good kind of stain, either. :(

[bck]

I'm still looking for a used dehumidifier for this...I'd really rather not spend $150 on a new one.

 

Try searching craigslist for one. Worked for my first one.

[Radar67]

The mold would mostly be on the surface, but can get deep if it stays there long enough.

IMO running a moldy board through the planer would not be a good idea. You will contaminate your machine, your dust collection system (if you have one), and send the spores airborne where you could breath them in if not wearing a respirator. It would also contaminate the area surrounding your machine.

Many of the members use a bleach solution to kill mold and clean it up, some use distilled white vinegar, and some just pressure wash. All time consuming methods. Prevention is the best option.