Natural Insulated Door From Scratch- Options?

I've been able to find various mass produced doors for free, but these have proven less than ideal for my building needs. Most doors use some sort of manufactured wood. Others are real wood and suitable to my needs, but are designed as interior doors and not robust enough to last more than a year or two in my environment. Yet others are so heavy that their overkill design stresses the rest of the structure out and make usage inconvenient.

Much of my need is to have something that limits thermal convection and the flow of insect pests like mosquitoes, while being exposed to precipitation and frequent high humidity. Some of the time heavier thermal conductivity reduction would be desired. I have no qualms about using pre-fabricated, all metal hinges and door knobs, but would like to build the rest of the doors from dimensional lumber and natural insulative materials.

I observed construction of the mushroom door at Cooper Cabin, and while impressive, it is overkill for my current needs. Any cohesive guides to DIY doors worth checking out? I think board and batten would be sufficient for a yurt door's basic construction for example, but how to make an airtight jamb to house it?

What thermal materials best make for a middleweight, naturally insulated door? Wool?

You could make a lumber+plywood box and fill it with sheep wool (low quality cut) or compressed straw. If you only have access to hay I would use a rubber ring/gasket or grease seal around the edges

How heavy is acceptable?  A double layer of pine boards (one diagonal one way, the other oriented the other way) would give around R1.5 to R2 by itself and not be terribly heavy.  Especially if it's white/red pine or cedar.  

A good seal on a homemade door is tricky.  If it just closes against the frame it might be easier to manage.

This is for a root cellar entrance- two doors, one horizontal, one vertical. The horizontal should be light as possible because it will be lifted, the other doesn't really matter.

I'm picturing having them close like a refrigerator, the outer panel against the face of the entrance frame. Silicone tubing would be good enough to seal the horizontal one from the weight of the door, but might need a more fancy door latch to ensure a seal on the vertical one.

If using pocketed insulation, I would make a 'box' to fit into the frame like the door shelf space in a refrigerator. Some sort of wool would be an external added acquisition, wondering if moss, pine needles, duff, or some other plentiful woodland product might be made to work? Or I could make the whole door like Mike mentions relying on the insulation of the pine wood that would sit proud to the opening. I think greater than R2 or 3 would be beneficial for the winter here however.

I have a bunch of ~8" boards in both half and 3/4 inch thickness, along with 2Xs of various widths. I think mortise and tenon work is too much for this project, but wondering if a hand router could make a regular enough groove on some boards to do half-laps on them?

Would crisscross diagonal boards be porous where the cracks cross?

Yes you can do a simple half lap with a router and that would fix the criss-cross pin point gaps.

Moss would work fine for insulation in a root cellar I think. Used it around the door frame of one once, and from what I understood it worked okay (it wasn't my own cellar, so no real first-hand info sadly).

All the wooden parts of the door and doorframe could be painted with something pine tar based, to preserve it against the humidity and weather. A mix of pine tar, linseed oil and turpentine works well.

Coydon, since your climate has some major mood swings, you might use some serious insulation in your box door.  Cellulose has the advantage of moisture mitigation plus nsect and mouse defense.  Better than moss I think. Conversely,  you could use moss and treat with a bit of boric acid or Borax, perhaps that is a more Permie solution

Rico Loma wrote:Coydon, since your climate has some major mood swings, you might use some serious insulation in your box door.  Cellulose has the advantage of moisture mitigation plus nsect and mouse defense.  Better than moss I think. Conversely,  you could use moss and treat with a bit of boric acid or Borax, perhaps that is a more Permie solution

Cellulose insulation as I've encountered it has been shredded denim or newspaper recycled from commercial sources. What would a DIY implementation look like?

Have an example of treating moss or anything similar with boric acid in a real world usage case to point to?

Mike Haasl wrote:A double layer of pine boards (one diagonal one way, the other oriented the other way)

Would this produce a decent overall structure, or would some sort of stiles/rails framework be worthwhile?

I'm guessing just the two simple layers direct on one another would work alone, but if I were to put a layer of any sort of insulation between they would need more structure? Although it seems the half lap added in could provide enough structure without 'framing'?

How about filling the 'box' on the door with layers of exactly cut cardboard? Is that likely to prove effective and durable?

Coydon Wallham wrote:

Mike Haasl wrote:A double layer of pine boards (one diagonal one way, the other oriented the other way)

Would this produce a decent overall structure, or would some sort of stiles/rails framework be worthwhile?

I'm guessing just the two simple layers direct on one another would work alone, but if I were to put a layer of any sort of insulation between they would need more structure? Although it seems the half lap added in could provide enough structure without 'framing'?

I think the structure would be pretty solid.  If the boards were thicker (1.5" ea) it would give even more R value without dealing with a layer.  If you have a layer of insulation between the diagonal board layers it probably wouldn't be nearly as solid.

I've always wondered about using slip sawdust as insulation.  Like slip straw but with sawdust or wood shavings...  Bugs may eat cardboard over time.

Mike Haasl wrote:
I've always wondered about using slip sawdust as insulation.  Like slip straw but with sawdust or wood shavings...  Bugs may eat cardboard over time.

In today's BEL post, Stephen mentions he found some slip straw done with pine needles in a structure over there...

As far as cardboard goes, I second that emotion. Bugs seem to be attracted to the glue used, in my experience

However, if you sprayed a borax solution on it, then dried the sheets thoroughly,  it might work. If  I was building the door today, methinks the 1,5 inch space between...filled with your choice of insulation.....would give best results. My 2 pennies.