Bello Haus — insulation R-values | bellohaus.net
The ordered selection procedure for attic, walls and floors, using the R per inch table and the target-to-thickness method.
Start each space with its own assembly R target. The attic, the walls and the floors are separate barriers with separate targets, and the R quoted for one does not transfer to another; write the target for the space you are working on before you open the material table.
Step 1 — write the target as an assembly R for that space. Step 2 — subtract the R of sheathing, glazing, finishes and any framing that already contributes. Step 3 — divide the remainder by the R per inch of the candidate material from the table to obtain the required thickness in inches. Step 4 — compare those inches with the available cavity or roof depth and change material if the thickness does not fit.
Typical failures in this procedure are unit mixing, where an RSI target is divided by a US R per inch and the 5.68 factor is missed; linearity assumptions, where a thickness is doubled and the R is expected to double although R per inch generally decreases as thickness increases; and quoting the insulation's R alone without subtracting the other layers, which lands the assembly off target in either direction.
On narrow screens, swipe or scroll the plate sideways.
Where the space is tight — a wall cavity of fixed depth, a floor build-up with limited clearance — pick the material whose R per inch delivers the needed R inside that depth. Closed-cell polyurethane at R-5.5 to R-6.5 per inch needs the least thickness of the materials measured here; Thinsulate at R-1.6 to R-2.9 per inch needs the most.
Where the space is deep — an attic floor or a vented roof — thickness is cheap and the per-inch figure matters less than the total. Even there, apply the reduction: R per inch generally decreases as thickness increases, so the last inches of a deep layer contribute less than the first, with foil-faced polyisocyanurate as the documented exception whose R per inch increases with thickness.
Finish each selection by checking the U-factor: take the reciprocal of the assembly R you have just built up and confirm it matches the U written in the plan, if one is given. Then, in the field, read the rated R printed on the facing of any batt — a faced fiberglass batt carries R-21 visibly — and reconcile it with the number in your calculation.
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