TIMBER FRAMING & HIGH R-VALUE ASSEMBLIES
More insulation, less lumber, fewer thermal bridges.
The R-value printed on a bag of insulation is not the R-value of your wall. Wood conducts heat about three times faster than the insulation beside it, and in a conventionally framed wall the studs, plates, headers and corners are a quarter of the surface. Advanced framing removes the lumber that isn't doing structural work; continuous exterior insulation covers what's left. The tool below shows the gap between what you specify and what you get.
R-13 in a 2x4 wall
DELIVERS R-9
PNNL puts a 2x4 wall at 16 in. on centre with R-13 batts at a whole-wall R-9.4 — 72% of the rated value.
R-19 in a 2x6 at 24 in.
Delivers R-15
The same source puts advanced framing at R-15.2 whole-wall — 80%. Same insulation category, eight points of efficiency.
Insulation outside the studs
COUNTS IN FULL
Continuous exterior insulation is the only R-value in the assembly that nothing interrupts. It is worth more per inch than anything in the cavity.
Three ideas, in the order they pay
TAKE THE LUMBER OUR FIRST
Studs at 24 inches with stacked framing, two-stud corners, ladder tees and right-sized headers. Every one removes wood that carries no load and replaces it with insulation. It is the only efficiency measure on this site that makes the material bill smaller.
THEN COVER WHAT'S LEFT
You cannot frame a wall with no wood in it. What remains — plates, jacks, corners, rim — still short-circuits the insulation. Continuous exterior insulation is the only layer that crosses those members, which is why it moves the effective R more than the same R added inside.
THEN MAKE SURE IT DRIES
A high-R wall is a cold wall on the outside of the insulation, and cold surfaces collect moisture. Enough exterior insulation keeps the sheathing warm enough to stay dry; too little in the wrong ratio makes it worse than the wall you started with. This is the detail that decides whether an assembly lasts.
Frequently Asked Questions
Isn't 24-inch framing weaker?
No — it's engineered rather than habitual. Studs at 24 inches on centre with stacked framing and sized headers is a code-recognised assembly, and the loads land where the members are instead of wherever the tape happened to fall. What it demands is discipline: the floor, wall and roof framing have to line up, so the layout is decided on the drawings rather than on site.
Advanced framing · stack framing required
Doesn't exterior foam trap moisture?
It can, if you use too little of it. Exterior insulation keeps the sheathing warm; a thin layer moves the sheathing into the range where it stays cold and collects condensation. The code sets a minimum ratio of exterior to cavity R for each climate zone for exactly this reason, and we design to it rather than around it. Vapour-open exterior boards give the assembly a second way to dry.
The ratio is the detail, not the material
Should we just use hempcrete?
If the carbon story is the point of the project, it's worth a serious look, and we'll price it. If the goal is the best thermal envelope per dollar in this climate, a 2x6 advanced frame with exterior mineral wool wins on R per inch, on cost, on schedule and on the number of crews who can build it. Both are defensible. They are answers to different questions.
Carbon and R-value are separate objectives
How we build the wall
FRAMING
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2x6 at 24 in. on centre, stacked floor to roof
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Two-stud corners and ladder tees, insulated
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Headers sized to the load, insulated where non-bearing
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Openings ganged to reduce jacks and cripples
ENVELOPE
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Continuous exterior insulation sized to the climate zone ratio
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Dense-pack cavity fill rather than batts where we can
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A named air barrier with one continuous line on the drawings
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A rainscreen gap behind the cladding
WHAT WE WON'T DO
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Quote a cavity R-value as the wall's R-value
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Use exterior foam thinner than the dew-point ratio allows
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Frame at 16 in. out of habit on a wall that doesn't need it
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Specify a material no local crew has installed, without saying so