Insulation by pack from the area, layers and thickness you are fitting.
Painting, tiling and finishes. 5 questions answered below, each with the arithmetic behind it and the limits of what the tool decides. Open the Insulation Takeoff tool.
Insulation is bought in packs covering a stated area at a stated thickness, which makes the order simple and the layers the tricky part. A wall with two layers has twice the material of a wall with one, and the second layer is often a different product at a different thickness and a different coverage. The takeoff measures insulation area by element, converts it into packs at the coverage the product states, and counts the vapour barrier and the fixings the specification calls for. It does not calculate thermal performance: U values belong to a thermal calculation with the full build up, including the studs, the cavity and the surface resistances, and a quantity tool that reported one would be reporting a number it cannot support. What it does report is exactly what the specification asks for in material, so the thermal calculation can be priced without re measuring the building.
A loft of ninety square metres at two hundred millimetres, in rolls covering eight square metres at that thickness, is twelve rolls, and a cross layer of a hundred millimetres on top adds another six. A wall of a hundred and forty square metres in a hundred millimetre boards covering two point eight eight square metres each is forty nine boards. Vapour barrier at the wall and ceiling areas, with laps, comes to about two hundred and sixty square metres of membrane. The second layer doubled the loft material and changed nothing on the wall, which is why layers are counted one at a time.
Insulation area by element, converted into packs at the product's coverage, plus vapour barriers, membranes and fixings. It handles more than one layer, because a specification often calls for two: one between the studs and one across them. What it does not do is judge the specification, since the thickness and the product follow from a thermal calculation rather than from a quantity takeoff.
No. Thermal performance comes from the whole build up: the insulation, the structure, the cavity, the surface resistances and the thermal bridges, and it is calculated with those in front of you. The takeoff measures material. Reporting a U value from an insulation area alone would produce a figure that looks authoritative and ignores the timber studs every six hundred millimetres, which is where most of the heat actually goes.
Each layer is counted as its own material with its own coverage, so a hundred millimetre layer between the studs and a second layer across them are two orders rather than one doubled figure. That matters because the second layer is frequently a different product at a different thickness, and because the fixings and the tapes change when a layer is added.
Yes. Rolls and packs cover a stated area at a stated thickness, so the takeoff divides and rounds up to whole packs, which is what a merchant sells. Where the coverage differs by thickness, as it does with mineral wool, the coverage for the thickness you selected is used rather than a figure for a different product.
Vapour barriers, membranes, tapes and fixings are counted where the specification calls for them, each at its own coverage. A vapour barrier is measured over the area it covers with the laps you allow, and fixings follow the spacing you enter. They are small items that decide whether the insulation performs as designed, which is why they are lines rather than an allowance.