timberwrestler wrote,

"When I was raising my first timber frame (my house), my friend said wait, you're going to build a whole separate wall outside of the frame? The only way it can make sense is to justify it in terms of the whole open building concept, that the structure is distinct from the enclosure."

What do you mean, the only way it can make sense? Why is the 'open building concept' the only answer 'making sense'? Apply the same logic to single vs double pane windows and see how far it gets you. Obviously having a full timber frame and then a full stick frame exterior to it is using far too much material for the loads to be borne, however, that's where a reassessment of design comes in handy - refer again to your final comment in your piece.

"I've come up with all sorts of design questions in trying to insulate spaces including (but not at all limited to):

-what is really local? Are the SIPS made 100 miles away local?"

I'll go with that. I suspect defining 'local' is a bit difficult, but it surely is within a day's drive. Some would argue walking distance, others would suggest horse and cart distance. I think when we get into sea freight, air lift, and trucking from the other side of the continent, we are beyond 'local', no?

Perhaps 'local' could refer to a general climatic and ecological zone??

"The cellulose from local newspapers with studs from Siberia?"

Hah - where'd the pulp for that newspaper come from? And definitely 'no', the studs from Siberia aren't 'local' in New England.

"How about studs sawn from the site?"

Can't get much more local than that.

"What if you then sheath it with plywood?"

Depends upon the source, both of the material and the plywood mill.

"Clay from the site?"

What's more local than that?


"They don't grow much straw in my neighborhood."

Well they are starting to - a CSA for grain just started in Amherst, MA, and there are grain producers up in Quebec, which is within a day's drive. Further, straw can be replaced very well with wood chips, which are abundant where you live, and are superior in some respects, especially in wetter areas.

I think an over-emphasis on the transportation equation is a little misleading. Most products I have looked at, if you look at the overall environmental impact, the transportation component, even if the stuff comes from overseas, is not a large percentage of the footprint -well under 10% for a lot of products from what I understand. I would say that embedded energy in manufacture is at least as big a component. That factor, for me, rules out SIPS, even if they are made next door. I don't want the factory to take over my trade, so I can't support that industry. I can't find a way to accept the landfill problem at the end of their usable lifespan either. SIPS suck.

"What kind of foundation can I use to support a timber frame and an 18" straw bale?'

Easily solved problem.

What if they want a full basement?

then they can have one too.

Alaskan slabs? And keeping the base of the wall dry? And they can't afford a stone stem wall...'

There's concrete and vapor break between wood and concrete.

"What is the real performance of the insulation? The ICF industry somehow gets to claim R48 on their 3" of foam and 10" of concrete. I don't think so."

Neither do I. Who needs R48 foundation anyhow?

"The thermal mass argument needs to be taken with a big grain of salt in New England. If it's 25 degrees outside on the north side of your house for 3 months, and 65 inside, what's that thermal mass doing for you?

I guess that if one lived in a house with only one wall, this might be a concern.

"I very much like the straw/woodchip clay walls, but I don't think their R-value will ever approach cellulose or foam."

Inch for inch, no, however the clay woodchip wall can be made thicker to suit - at 12", apparently R24 - isn't that adequate? Besides, the benefits of having clay in the wall run to more than simple R-value, and you know that I'm sure.


"I've seen the numbers somewhere, and they are pretty good, but I'm not sure if they'd meet code where I live. As much as codes are a downer, the insulation standards may actually be worthwhile. Maybe. Depends on how uncomfortable you're willing to be.

If one is masochistic, that is one thing, but there's no reason one can't be quite comfortable in a house with light clay/woodchip walls, or straw bale walls. And code, well, that serves industry and the insurance companies more than anything else. There is possibility of amendments and special green building codes if consumers demand it and builders promote it - it's happening in some places.

"How do you insulate the roof? You need LOTS of insulation in Mass. Are you going to put 3' of loose fill straw/clay up there, and how do you frame around that?"

That is a good question, and one of the design challenges to using alternative insulative materials. I can think of any number of solutions, but perhaps some use of conventional insulation products in the ceiling and roof space might well be justified for a lot of folks, especially if they are greatly reducing the use of those materials in the rest of their structure. I don't know about 3' of insulative material being necessary, though I can certainly think of ways to frame that in if that was the objective, and I'm sure you could too timberwrestler.

"I don't think the TF industry standard (SIPS) deserves all of the props they get in the marketing literature, but I also don't think they're evil."

I guess you hadn't heard, that at Lord Vader's command, the entire Death Star was built from SIPS? Saved a lot of labor time - they put the Death Star up in little over a week and are getting R100 from the custom 60 sq. km size panels....

"I also don't think you'll be karmically reincarnated as a newt if you build your walls with straw/clay and put rigid foam on the roof."

What would be wrong with a newt? Certainly smarter than some folks I heard on talk radio lately. Kidding aside, you are right that it isn't always practical to be totally purist, and having walls that are light clay and foam in the roof is going to be an acceptable compromise to most folks, I would think

"And just like every other design problem, you've got to come up with a solution."

Exactly.