How big (dimensions) would a solar hot box have to be to keep a 6000 cf. room warm enough to dry lumber?

Question

Hot box made from plywood, glass, and tin roofing painted black.
I live in New England. 1000ft up.
Any other ideas to help dry this stuff without having to buy a kiln.
I am thing of one 4x8ft to start, then more if I need them.

Answer 1

This question brought back a whole lot of memories! We ran a small fine woodworking business back in the early 1980's and had access to free oak, walnut, maple and cherry which needed kiln drying after we felled the trees and had it sawn into lumber.

We built an A frame kiln in our backyard which measured 12'Lx10'Hx8'W or so. The glazing material was Lexan dual wall plastic sheets which were commonly sold at lumber yards at the time for homemade solar air heating units. I believe it took 3 of them across, though I'm going from memory. We put rubber gasket material between panels and around the edges of the Lexan where it met the plywood to seal the south side.

The other leg of the triangle (facing north) was plywood, and the kiln sat on a plywood base on 2x4s. The inside of the kiln, except for the inside of the Lexan, was painted flat black. The ends of the kiln were plywood and the door just sat in the opening on a lip, with flip latches to hold it in place. We did not seal around the door or the opposite end, though it did fit tightly.

There was a small circular ventilation fan on the top of the door near the peak to let humid air out. I believe it was solar operated. We stickered the lumber all the way to the top of the A, sealed the door and left it.

Even though we live in central west Michigan, with a freezing winter the kiln took about 4 months or less to dry a load from green sawn to usable lumber.

Outside of the building costs, running the kiln was free. I planted a lilac hedge on the west and north sides to conceal it from the neighbors. The whole thing worked very very well.

Answer 2

you'll never get hot enough to get the quality of kiln dry studs.... so air dry - fan & open winder... or just open winder - there going to bow & twist - deal with it when you frame!