I have been doing a considerable amount of thinking and figuring to come up with a possible Timber enclosure/infill system. I should mention that I do not want to use SIP's. Not because I think they are evil or anything like that, but for a number of other reasons, such as: Do not want the full width of timbers encroaching on the interior of the structure; SIPs seem wasteful and expensive to me, along with the associated problems of off-gassing, etc.; SIPs seem to be contrary to the rest of the structure, that is: a timber frame should be (in my opinion) a structure built to last for generations, SIPs do not seem to fit the bill at all. and there's more.

My idea, in it's current form, is:

Timber framed walls (obviously) normally using timbers of a 9" depth. Between the timbers are placed 2x6 studs 2' on center. It is important to note that the framing timbers are between the studs, and not on the 2' spacing. Sheathing is fastened to the outside on the studs, but not fastened to the timbers so that timber movement will not cause sheathing problems. The sheathing is then covered at least with Tyvek or other housewrap, but possibly also with foam panels.

Now on the inside you have a couple of different options. If you desire the inside wall to be flush with the timbers, then you frame it out and plaster/drywall/panel it flush, probably with some sort of trim piece around the timber edges that will hide any movement. The system was originally designed to have about 3 inches of exposed timber on the inside of the structure, and works best like that. In this case you apply plaster drywall or panels to the 2x6 studs, and apply a wooden trim piece to the edge of the timbers (once again to conceal wood movement. This trim piece can be anything, such as a quarter round or a rectangular piece that sits flush with the inside face of the timbers, and is made of the same wood. Think of this is sort of like door or window trim, which is really there to hide a gap.

Now you have a 5 1/2" cavity inside of your walls, and this is where your insulation goes of course.

One last thing, it may also be beneficial to have a v-groove or a cove on the portions of the timber that face into the wall cavities. The purpose of this is so that if the timbers shrink, any air gap will be convoluted, which discourages airflow to some extent. A V-groove would be the more convoluted path, however it might also provide a weak point where the timbers could easily split. A cove would not create the same weakness.

Now I realize that this isn't going to fit with our drams of a super-insulated home. Really, though, the important thing is whether or not it is as good or better than conventional stick framed wall insulation?

This system is intended to provide a reasonable ALTERNATIVE when price is a major factor, and it is also designed so that it can be reasonably executed by non timber framers. I am a fan of traditional means of enclosing the structure, and things such as straw bales. The thing is not everyone will go for those things, at least not yet, and in order to remain viable we must have a reasonable alternative.

If I could, I would build all frames with an infill system similar to Fachwerk, but that would also be expensive, and would only appeal to a limited customer base (which is not a good thing, especially right now)

So what do you think of this idea? Is it viable? Is it good? Is it economical?

I think the gap at the post will attract moisture with or with out the v-groove. The inside of the post will be warm and the outside of the post will be cold, allowing repeated condensation when the conditions are ripe. Maybe it is of no concern?

I don't know what the minimal amount of insulation needed on the outside of the post is to stop this from happening.

I keep going to clay and straw or wood chip as an answer, with the post partially buried in the wall of clay/wood chip, say half in and half out, half exposed to the inside of the building and completely covered on the outside, with plaster and render applied.

I am starting to get frustrated with all the options, this is what you get if you want a variable, keep looking.

All the regulations coming down the road is a headache. I will just stay home and work on my gardens and stuff. That is probably what They want anyway.

Define economical?

Not everyone will go for a timbered frame either. Why limit yourself? Where do you draw the line? Rhetorical questions.

Tim

I am not limiting myself. In fact, I do not limit myself to the extent that timber framing is not the only kind of construction I am involved in. That's right folks, I still will build a stick frame now and then.

As I said, this is just one option. If I had my way I would do all infills of some form or another, like waddle and daub or clay or brick. But not everyone who wants a timber frame would want that. Really if I could I would build all of my building with super wide eaves and half hip roofs, in a bernese Swiss style -but most people probably won't go for that. (that said, the design of my frames is headed in the direction of Swiss framing in a hurry, although the overall appearance remains faithful to American architecture for those who want it to) I can easily see how someone might get the idea that such a system is dirty or crude. It's not my place to push people into buying something they don't want, let's leave that to car salesmen and government officials. Some people obviously have this idea of a slick, trim, clean house and these methods don't fit their picture.

Define economical? Well for this discussion I guess I mean efficient in terms of construction. I want to develop a system that can be executed by people who are not experts at doing it. In other words, I want a way to enclose my walls that can be done by a non timber framer, a non specialized carpenter. This allows me to outsource a lot of work, freeing me up to focus on joinery and things like that. What if I were to build a frame that was to be shipped across the country for example? Would it be a good business practice if I had to ship my workers with it, paying for their hotels, food, etc. not to mention inconveniencing them (and probably myself too) by separating them from their families for a long period of time?
I want a system that can be done by people who don't need paid a lot of money, because they are readily available. -Efficient use of available labor

There is no single answer to the enclosure question in my opinion. It's all a case-by-case thing. I will do things like straw bales and clay and waddle and lime plaster whenever it fits the project and the customer. For example, I am currently building myself a small building for some extra space, this building will be a chance for me to use whatever I want. So what am I doing? I am siding the whole thing with wood, because I am emulating a specific style (one from outside of this country)

The v-groove probably will attract moisture, that is a flaw in the design I know. But will it sweat? Will it result in much heat loss? I thought about having a flexible foam or plastic stip of some sort attach to the post (in lieu of v-groove) or perhaps a series of them. Maybe a plastic half-tube deal with a foam core (just mulling over the idea in my head right now, dont mind my rambling)Something that insulates, is attached rigidly to the post, and can move through or along whatever insulation is there (I am envisioning cellulose)
Another concern is the thermal properties of the post itself. The wooden post has a lower r value than a corresponding cavity filled with insulation, and hardwoods can actually become heat conductors during the winter (as I understand it, the harder the wood the poorer its insulation value)

My 2 cents: I like the idea of using locally sourced materials as much as possible for all phases of construction. With all the problems related to oil based transport, this can be more sustainable. If the materials are local it is much easier to track down how they were obtained; ie: were they obtained in a responsible manner? Also, aesthetically, local materials simply tend to blend in to the natural environment better than "exotic" materials. For example, a log home looks strange in LA. And an adobe home looks even stranger in Alaska. As an amateur owner builder, local materials can be appealing for several reasons - simple, cheap, efficient, and attractive. Possibly quite labor intensive however (strawbale, adobe, cordwood masonry, etc) So, for the NW use lots of wood - for the SW use lots of soil (adobe).

Economics is a very important factor to consider when you are building for others, and even more important when you are marketing your services. I can sit here and go on about my ideal system and how it is vastly superior and all that good stuff, but sometimes as businessmen we simply have to compromise.

There is a difference between the owner/builder who is building his own timber frame and has the freedom to use any method he can dream up and the professional timber framer who has to find the balance between quality and cost. That balance is different for every structure and we do well to remember that.

This system I proposed is not intended to be the perfect system with absolute seal and everything else we have dreams about now and then. Rather, this system is designed to be competitive. It is designed to be practical and open up the world of Timber homes to those who would never afford a spacious open design house clad with SIPs, or would never be able to pay me to give them a traditional infill or whatever else you might see as ideal.

SO back to the main point: Aside from the problem of moisture around the post, what other flaws are there that need to be addressed? What is the widest stud spacing I could reasonably use and still clad the inside with drywall? I need to review Indiana building codes again, sigh...

You could try 2x4@24" O.C. on the vertical with a 2x2@16" O.C inside run horizontally with 2" rigid SM foam on the exterior. If you spray foam the 2x4 walls, you'll have approximately an R-35, except at the timbers. But, by spanning the rigid foam on the exterior, to incorporate the infill into the the exterior shell, I don't see anyway that your house wouldn't perform as a 'super-home' based on it's thermal efficiency. Don't forget to tape the rigid foam with sheathing tape and to save money, google tiger foam for DIY application. Do price it out locally first, at least for comparison. To insulate between the posts and the sticks, use friction fit insulation and backer rod to stop convection drafts. Also leave about 1-2" of space between the post and the rigid foam so that movement of that post doesn't buckle your exterior finish.
Hope this gives you some more idea's for your home. Thanks for the tip on the pitch!

I should clarify. This system is not for me personally. If I were building for myself I would definitely do a 'down and dirty' system, probably with waddle and daub infill between timber posts that are exposed on the outside. This is a system I am trying to develop as an alternative to SIP's for commercial timber framing. It's a part of my long quest to make timber framing available to people that aren't fabulously wealthy. It is my dream to make timber framing something that the common man can afford, because I believe it is something that our society should return to and we will not return to it unless it is available to the majority. (Sorry, I rambled again. just slap me upside the head next time)

Blake, you have some great ideas there. I hadn't thought about having the stud wall offset to the outside of the timbers to have an insulation gap behind the posts! Thanks a lot, that right there solves my biggest problem! Not only that, it allows me to have a little more exposed timber for those who want that look.

The actual insulating material is not so important, that is something that can be decided on a case-for-case basis.

I should also mention that I am a fan of having rigid OSB sheathing on the outside for the sake of nailing and attaching things, like siding. I despise doing remodel work on a house that has only foam or blackboard sheathing and no plywood or anything rigid.

So here is what I am thinking at this point:

Standard Timber Framed structure, with a large space between posts, fully braced so that the frame itself is self-supporting. I.e. it does not rely on sheathing or panels for stiffness and bracing.

The sills and top plates extend past the posts on the outside wall by 2 or 3 inches.

2x6 studs are framed in either 16" or 24" o.c., with the studs placed so that the posts will fall between studs without interrupting their spacing. This can be done easily by starting the stud layout at the outside corner of the sill, since it is out 2 or 3 inches from the post, assuming that the post spacing matches up with the 16" or 24" stud spacing. These studs are lined up with the outside of the sills, so that the exterior wall will be out 2 or 3 inches from the posts, allowing for at least some insulation on 3 sides of the posts.

No sheathing material is applied directly to the timber posts, it is attached to the 9non-structural) studs, and to the sills and plates above and below.

Drywall, lathe ad plaster, or paneling is applied to the interior walls. The cavity between the inside and outside walls can be insulated as if it were a stick framed walls, with the space between the post and exterior wall insulated as well. The insulation material depends on the customer and their budget.

Or option 2, which is what Blake described (option 1 is a hybrid of Blake's idea and my original idea)So I won't repost it, since it was the last post anyway! (I think that would seem kind of disrespectful too)

Both have their advantages, and their disadvantages. I should run up some figures to see which is the winner.

By the way, r-35 sounds pretty good to me!

It seems to me that Blake's idea would make a good super-insulated system, but could potentially be a bit on the expensive side (which isn't always a bad thing either) whereas my modification of the original system, inspired by Blake's idea, might be a bit more affordable (which isn't always a good thing) I think it would be wise to have both as options. I should make up some drawings, because it's always hard to describe things like this with just words...

Thanks again, guys! This is the reason we bring our questions to places like this

I have a modification of my design (and then I really need to go to bed)

The spacing between post and exterior wall should be 2", and between the post and the sheathing you should put a piece of 2" foam board. The foam should probably extend past the post edge on either side like 1/4 or 1/2 of an inch or so to ensure a good seal is made.

Here we are then


picture quality ain't the greatest, but I think you can see everything good enough.

The stuff between the posts and the exterior sheathing can be the good stuff, with like r-7 or r-8 per inch (for a total of around r-15, which is acceptable) or you could use the regular r-5 per inch stuff if you want. fiberglass insulation for a 2x6 wall has an r-value of r-19, so that's the minimum for my system as currently designed. This picture shows studs 16" o.c.

I would leave some room for movement that will occur within the 9x9 over time. I made that mistake once before and when the post started to check (and it didn't take much) the stucco finish cracked and I wasn't very popular with that particular home owner! In lieu of the 2x6 in the corner, you could try a drywallers structural galv. metal corner in order to eliminate the thermal bridging at the corner. Just cut the plumb line at your corner, screw the piece of corner on, and sheet up the other side.
Have you ever tried the Simpson let -in straps instead of sheathing? It's a method that we used instead of sheathing, when we used to build homes with a brick or stone veneer. It's easy to use, effective and saves you a lot of money on sheathing an sheathing labour.
I apologize for the confusion in which home this system is being used for. I build houses for myself from time to time and tend to call everything my home until I pass over the keys!
I'll see if I can get my scanner working and I'll try to post a drawing of what I was trying to describe. Unfortunately, this forum is the extent of my computer ability, but I'll try.