Insulation Takeoff Guide

An insulation takeoff measures every surface of the thermal envelope by assembly (exterior walls, ceilings or roof deck, floors over unconditioned space, foundation walls, slab edges, rim joists), assigns each one the R-value and product the drawings call for, and converts area into the unit the product is sold in. Batts and rolls convert by square feet of insulation per bag. Blown-in converts by bags per 1,000 square feet at a stated installed depth. Spray foam converts to board feet (square feet times inches of thickness) and then to drum sets. Rigid board converts to sheets.

The step most takeoffs get wrong is the area itself. For walls there are three different areas: the gross wall area (length times height), the net wall area (gross minus windows and doors), and the cavity area (net minus the framing). Batt and dense-pack quantities follow the cavity area, which on a typical 16 inch on center wall is about 75 percent of the net wall area. That comes from the framing factor published in the ASHRAE Handbook of Fundamentals. Continuous rigid insulation and most spray foam pricing follow the net wall area. Mix them up and the wall bag count runs a third high, or the foam bid runs short.

The Order That Works

1. Find the envelope before you measure. Mark the line between conditioned and unconditioned space on a section or wall section. Insulation goes on that line and nowhere else, unless the spec adds sound batts in interior walls or floors.

2. Read the energy notes and the wall sections. The R-value by assembly, the product type, any continuous insulation, the air barrier, and whether the design used the prescriptive table or a performance path are all there. They are usually not on the floor plan.

3. Measure each assembly separately. Exterior 2x4 walls, 2x6 walls, knee walls, the wall between house and garage, flat ceilings, vaulted ceilings, floors over garages or crawlspaces, rim joists, basement walls. Each can carry a different R-value and product.

4. Take gross area, deduct openings, then apply the framing factor where the product fills cavities.

5. Convert to purchase units with the manufacturer's chart, not a generic rule. A bag of one loose-fill product can cover twice the area of a bag of another at the same R-value.

6. Count the accessories last. Baffles, attic hatch dams, depth markers, fire and ignition barriers, sealant, tape, fasteners and the installer certificate. This is where scope disappears.

Two Rules That Decide Most Quantities

The first is federal. Under the FTC's R-value Rule (16 CFR 460.12), a batt or blanket package has to list the square feet of insulation in the package. That is the area of the batts themselves, not the wall area they cover. A loose-fill bag has to list the maximum net coverage area and the number of bags per 1,000 square feet at each R-value, along with the minimum installed thickness and settled thickness. So the label is always telling you insulation area, and it is your job to get from wall area to insulation area.

The second is the energy code. The 2021 IECC's Table R402.1.3 sets the prescriptive minimum R-value by climate zone and component: R-60 ceilings in climate zones 4 through 8, for example, and a wood frame wall requirement that can be met several different ways with cavity plus continuous insulation. The drawings should already reflect it. When they do not, that is an RFI before bid day, not a guess.

Every argument about "do you deduct the studs" comes down to which of the three areas a number is based on. Here is how they relate on a wall.

The Framing Factor

The framing factor is the projected area of all the framing divided by the total opaque wall area. The American Wood Council's DCA 7 describes what counts: studs, headers, jack and king studs, top and bottom plates, and corner studs. Citing the ASHRAE Handbook of Fundamentals, it gives 25 percent at 16 inches on center and 22 percent at 24 inches on center. APA's IECC compliance document breaks the 25 percent down further: headers are typically about 4 percent of the wall area and the rest is studs, plates and full-cavity blocking. It also notes that the IECC's own wood wall U-factors assume 25 percent framing and 75 percent insulation.

Advanced framing moves the number. Building Science Corporation's BSI-030 says advanced framing (24 inch spacing, stacked framing, single top plates, insulated or eliminated headers) cuts the framing factor from 25 percent to about 15 percent. If the drawings show advanced framing details, use the lower number.

Why "Just Deduct the Studs" Undercounts the Framing

A stud is 1-1/2 inches in a 16 inch bay, so studs alone are about 9 percent of the wall. That is the number people have in their heads when they say deducting framing is not worth it. But the studs are only part of the framing. Three plates on a standard wall take another 4-1/2 inches of height, headers take their 4 percent, and every opening adds kings, jacks, cripples and sills. That is how 9 percent turns into 25 percent.

A long-running thread on the SprayFoam Magazine forum shows how this plays out in practice. A newer applicator asked whether he should deduct the studs, because customers kept asking. A veteran answered "Deduct for studs? Never heard of anything so dumb." For spray foam priced per square foot of wall, the veteran is right. You pay for overspray on the stud faces, trimming and the time to fill small bays, and that eats the difference. For batts and dense pack, the framing factor is exactly the difference between a correct bag count and a bag count that is a third too high.

What the Label Already Does for You

Batts for wood framing are sized to fit between the framing. 15 inch batts go in 16 inch on center bays and 23 inch batts go in 24 inch bays. Batts for steel studs come 16 and 24 inches wide, because steel stud cavities are measured differently. Since the label reports the batt area, a bag of 15 inch batts covers 16/15 of its label in wall area, about 6.7 percent more, before you account for plates, headers and openings. Some estimators treat that gap as built-in waste. That works on a simple wall, but it does not hold up on a wall full of windows, where the short pieces above and below the openings generate real cutoffs.

The Three Numbers on One Wall

Take a 60 foot long exterior wall, 8 feet tall, with four 3 by 5 windows and one 3 by 6'-8" door, framed 2x4 at 16 inches on center.

• -Gross: 60 x 8 = 480 SF
• -Openings: 4 x 15 = 60 SF of windows, plus 3 x 6.67 = 20 SF of door, for 80 SF
• -Net: 480 - 80 = 400 SF
• -Cavity at a 25 percent framing factor: 400 x 0.75 = 300 SF

Buy batts off 480 and you have 60 percent more than the cavities hold. Buy off 400 and you are a third over. Off 300 plus a cutting allowance, the bags come out close to what goes in the wall.

(Pulling wall lengths, heights and every opening off a PDF plan set is the part Tectonic automates. It hands you the net areas by wall type. Do this three-number exercise by hand on one wall anyway, so you know what a gross-versus-net mistake looks like when a number comes back wrong.)

A batt takeoff has two honest methods, and on a real job you want both, because they check each other.

Method 1: Area

Cavity area, plus a cutting allowance, divided by the square feet per bag on the label.

Bags = cavity SF x (1 + cutting allowance) / labeled SF per bag

The cutting allowance for batts is small compared with most materials. The pieces are pre-cut to wall height and the offcuts from one bay fill the next short bay. An allowance of roughly 5 to 10 percent is typical, toward the top of that range on walls with many openings, bump-outs or odd heights, and near the bottom on long plain walls.

Method 2: Piece Count

Count the stud bays. Every full-height bay on an 8 foot wall with precut 92-5/8 inch studs takes one 93 inch batt. Bays above headers and below sills take short pieces that you cut from full ones. Divide by pieces per bag.

On a long wall at 16 inches on center, the full bays are roughly wall length in feet x 12 / 16, minus the bays that land in openings. It is slower than the area method. It is also much more accurate on walls chopped up by openings, and it catches mistakes in the area method.

Reading an Actual Bag

Two real Owens Corning R-13 kraft-faced listings show how a label works. A 15 x 93 inch R-13 batt is 15 x 93 / 144 = 9.69 SF. One retail bag lists 106.56 SF, which is exactly 11 batts at 9.69 SF. The contractor M90 pack from a supply house lists 125.94 SF, exactly 13 batts. Both labels are counting the batts themselves, the way 16 CFR 460.12 requires. Neither is telling you how much wall a bag covers.

Batt Widths and Where They Go

Always confirm width and length on the submittal. Lengths are sold precut for common wall heights and in longer rolls for ceilings and floors, and the length changes pieces per bag.

Compression Costs R-Value

A batt squeezed into a cavity shallower than its label thickness loses R-value. The Insulation Institute's (NAIMA) chart of compressed fiber glass batt R-values, built for inspectors, shows a few cases every estimator should know:

NAIMA says manufacturer data always takes precedence and warns not to interpolate between its values. The takeoff point is simple. When the spec says R-21 in a 2x6 wall, R-19 batts do not meet it. The 2021 IECC table notes also say that when insulation goes in a cavity shallower than its label thickness, the installed R-value, not the label R-value, has to meet the table. Price the product that meets the number in the cavity you actually have.

Faced or Unfaced

Kraft facing is a vapor retarder, and whether it is required, allowed or prohibited depends on the climate zone and the wall assembly. Take the facing from the wall section or the spec, not from habit. Unfaced batts in a wall that calls for a separate vapor retarder add a poly or smart-membrane line to the takeoff. Kraft-faced batts in a wall that calls for none are a change you will be asked to eat.

Floors and Ceilings

Batts between floor joists over a garage or crawlspace follow the same cavity logic with one extra count: supports. Wire supports, strapping or netting hold the batts against the subfloor, and they are a per-bay or per-foot count that is easy to leave off. In ceilings with batts, a vaulted ceiling can only hold what fits in the rafter depth minus any vent space, which is often where the compression table matters.

Blown-in insulation is the one product where the manufacturer does most of the takeoff for you. The FTC rule requires every loose-fill bag to carry a coverage chart. At each R-value, the chart gives the minimum installed thickness, the settled thickness, the maximum net coverage per bag, the number of bags per 1,000 square feet, and the minimum weight per square foot. Your job is to measure the attic floor area, pick the row, and multiply.

Bags = attic SF / 1,000 x bags per 1,000 SF (from that product's chart), rounded up

A Fiber Glass Chart

Here is the Johns Manville Attic Protector blow-in fiber glass fact sheet:

A Cellulose Chart

And the National Fiber cellulose expanded coverage chart, per 25 lb bag, loose-fill attic columns:

Put the two charts side by side and you can see the three mistakes that cause most blown-in shortfalls.

Mistake 1: Treating Bags as Interchangeable

At R-49, this fiber glass takes 28.4 bags per 1,000 SF and this cellulose takes 62.5. Cellulose is not worse. The bags weigh differently and the product blows to a different density. A bag count only means something for the product it came from. If the spec allows either product, or the supplier substitutes, redo the count from the new chart.

Mistake 2: Bidding the Settled Depth

Cellulose settles. At R-49 this product goes in at 14.5 inches and settles to 13.1, about 10 percent. The fiber glass barely moves: 20.3 to 20.2 inches. The R-value on the chart is the settled R-value, so the crew has to blow to the installed depth, and the bag count in the chart already reflects that. If you measure an attic, see "R-49 = about 13 inches" somewhere, and price the depth yourself, you come up short on cellulose. Use the bags per 1,000 row, not your own depth math.

Mistake 3: Using the Wrong Area

The coverage in these charts is net: square feet of insulation. National Fiber's chart says it plainly: "Coverage per bag does not take in account framing." In an attic that barely matters. A 2x4 bottom chord at 24 inches on center takes 1-1/2 inches of every 24, about 6 percent of the area, but only for the first 3-1/2 inches of a 24 inch deep blanket. That displaces less than 1 percent of the total volume. So for attics, measure the attic floor area to the outside of the top plates and do not bother deducting framing. (Walls are a different story, as the dense-pack section shows.)

What does matter in an attic is where the area stops. Take the ceiling area of every flat ceiling under an attic, out to the outside face of the exterior wall top plates. Stop where a vaulted ceiling starts, because a vault is a different assembly. Knee wall attics, bonus rooms over garages and dropped soffits get measured separately.

Checking the Chart Against Itself

The minimum weight column lets you check the math. At R-60 on the fiber glass chart, 28 SF per bag x 0.904 lb/SF = 25.3 lb, which is the bag. At R-49, 35 x 0.710 = 24.9 lb. When your own arithmetic reproduces the bag weight, you are reading the right columns.

Retrofit Attics

On an existing attic you are topping up, not starting from zero. Measure the depth of what is there in several places, figure its rough R-value, and blow only the difference. ENERGY STAR's retrofit table, which it bases on the 2021 IECC, recommends adding up to R-60 in an uninsulated attic in zones 4A through 8, or R-49 on top of an attic that already has 3 to 4 inches. In zones 2 and 3 it recommends R-49, or R-38 on top of 3 to 4 inches.

The Paperwork Is a Line Item

The IECC (R303.1.1 and R303.1.1.1, repeated in the IRC as N1101.10.1) requires the installer to post a signed certificate. For blown fiber glass and cellulose it lists the initial installed thickness, settled thickness, settled R-value, installed density, coverage area and number of bags. The code also requires depth markers in the attic, at least one for every 300 square feet, fastened to the trusses or joists, facing the access opening, with numbers at least 1 inch tall. A 2,000 SF attic needs 7 markers. The bag count you bid ends up on the certificate, so the inspector will compare your bag count to the chart too.

Spray foam and dense-pack cellulose both fill a volume, so both have to be estimated in volume units. The difference is that foam is sold by the board foot and dense pack is sold by the bag.

Board Feet

A board foot of spray foam is 1 square foot at 1 inch thick, or 144 cubic inches.

Board feet = area (SF) x thickness (inches)

So 1,000 SF of wall at 3-1/2 inches is 3,500 board feet, and the same wall at 2 inches of closed cell is 2,000 board feet.

Drum-Set Yield: Label vs. Field

Foam comes in sets: one drum of A side and one drum of B side. Each set carries a theoretical yield in board feet at 1 inch. The ballpark numbers every foam contractor knows:

These are ballparks. The number you bid comes from the technical data sheet for the exact product and from your own yield records. The losses are real and they depend on the job. R-Value Associates lists overspray (worst on overhead work), porous substrates like bare block that soak up the first pass, cold substrates below about 60°F, and humidity. The contractor who started that forum thread was planning on about 25 percent waste for open cell and about 10 percent for closed cell.

Drum sets = board feet / (theoretical yield x (1 - expected loss))

Worked Numbers

A 1,200 SF metal-stud wall package gets 2 inches of closed cell.

• -Board feet: 1,200 x 2 = 2,400
• -At a 4,000 bd ft label yield with no loss: 0.60 sets
• -At a 20 percent loss (3,200 effective): 0.75 sets

That is a quarter-set difference on a small job. On a warehouse it is the difference between the job making money and not.

Do You Deduct the Studs?

For spray foam priced per square foot of wall, most applicators do not, for the reasons the forum veteran gave. What gets wasted in overspray and trimming makes up for the volume the framing takes. But know what you are giving away. At 25 percent framing, a full-fill open cell wall has about 25 percent less foam volume than net wall area x depth. If your yield records were built on jobs where you did not deduct, stay consistent. The deduction and your loss factor are the same allowance counted two ways, so never take both.

Dense-Pack Cellulose

Dense pack goes into closed cavities through holes in the sheathing or netting. The National Fiber chart gives coverage per 25 lb bag by cavity depth:

Check the chart with arithmetic. At 2x4, one bag covers 25.5 SF x 3.5/12 ft = 7.44 cubic feet, and 25 lb / 7.44 = 3.36 lb per cubic foot. That matches the density column. It also shows why the framing factor matters here. The chart assumes the bag fills 25.5 SF of cavity, and a 2x4 wall at 16 inches on center only has about 0.75 SF of cavity per SF of net wall. So:

• -1,000 SF of net 2x4 wall on the gross method: 1,000 / 25.5 = 40 bags
• -On cavity area: 750 / 25.5 = 30 bags

The real number sits nearer 30, plus whatever your crew loses at the hose and in hidden voids. The chart's density column also matters for the inspector. Several jurisdictions' insulation certificates ask for installed density, and the 2021 IECC certificate requires it for blown products.

Continuous insulation is the easy area to take off, because it covers the framing too. The DOE's REScheck documentation defines continuous insulation as insulation that runs continuously over structural members, and when it is specified REScheck assumes 100 percent of the wall is covered. So rigid board follows the net wall area, not the cavity area.

Sheets

Sheets = net area x (1 + waste) / sheet area

A 4 x 8 sheet is 32 SF. Waste on foam board depends on how chopped up the wall is. Roughly 5 percent on long plain walls and 10 to 15 percent on walls with many openings, corners and gables is a reasonable starting range to tune with your own records.

Seams, Tape and Fasteners

If the foam is also the water-resistive barrier or air barrier, the seams get taped, and that is a linear-foot line. A 4 x 8 sheet has a 24 LF perimeter, and every interior seam is shared by two sheets, so a field of sheets has about 12 LF of seam per sheet, or about 0.375 LF per SF. Add the perimeter of every rough opening, which gets taped or flashed separately. Fasteners (cap nails, screws with washers, or furring) come from the manufacturer's installation instructions and from the cladding attachment design. On thick foam, the siding attachment through the foam is often an engineering question, so flag it.

What the Code Asks For

The drawings should state R-values by assembly. When you have to check them, or bid a design-build job, here is the 2021 IECC prescriptive table (R402.1.3) for the lines an insulation takeoff touches, as compiled by the Pacific Northwest National Laboratory's Building America Solution Center:

"R-13 + 10ci" means R-13 in the cavity plus R-10 continuous insulation. Three things about this table change a takeoff:

• -The wall line is a menu, not a number. In zone 5, an R-30 cavity, R-20 + 5ci, R-13 + 10ci and R-0 + 20ci all comply. Those are four very different takeoffs: thick cavity fill with no foam, a 2x6 with thin foam, a 2x4 with thicker foam, or all foam outside. Price the one on the drawings.
• -R-49 can stand in for R-60, with a condition. In the 2021 IECC, R-49 can be used instead of R-60 in the ceiling when it covers 100 percent of the ceiling at full height, including over the wall top plates at the eaves. That usually means raised-heel trusses. On a standard truss where the depth pinches at the eave, it does not apply.
• -Adoption varies. Many jurisdictions are on the 2015 or 2018 IECC, with local amendments. Washington, for example, runs its own state energy code. Bid the code the permit is under, which the energy notes on the drawings should name.

Ignition and Thermal Barriers on Foam

Any foam plastic, board or spray, has to be separated from the interior by an approved 15-minute thermal barrier, such as 1/2 inch gypsum board. The IBC covers this in 2603.4 and the IRC in R316.4. In attics and crawlspaces entered only to service utilities, the IRC (R316.5.3) allows an ignition barrier instead. The listed options include 1-1/2 inches of mineral fiber insulation, 1/4 inch wood structural panel, 3/8 inch particleboard, 1/4 inch hardboard, 3/8 inch gypsum board, or 0.016 inch corrosion-resistant steel. Tested alternative assemblies, often an intumescent coating over the foam, can also qualify. The American Chemistry Council's spray foam industry group lays this out in its "Know the Code" document. For the takeoff, whoever owns the foam needs to know who owns the barrier. If it is you, it is a square-foot line with its own material and its own schedule.

A single-story slab-on-grade house, 40 by 50 feet outside dimensions, in climate zone 4A. Walls are 2x4 at 16 inches on center, 8 foot walls, with R-13 batts plus R-10 continuous foam outside (the "13 + 10ci" option). The ceiling is a flat ceiling under a vented attic with standard trusses at 24 inches on center, so the code number is R-60, blown fiber glass. Gable roof, eaves on the two 50 foot sides.

Step 1: Wall Areas

• -Perimeter: 2 x (40 + 50) = 180 LF
• -Gross wall: 180 x 8 = 1,440 SF
• -Openings: twelve 3 x 5 windows (180 SF), two 3 x 6'-8" doors (40 SF), one 6 x 6'-8" slider (40 SF), for 260 SF total
• -Net wall: 1,440 - 260 = 1,180 SF
• -Cavity area at 25 percent framing: 1,180 x 0.75 = 885 SF

Step 2: Batts

• -Cavity area plus a 7 percent cutting allowance (lots of windows): 885 x 1.07 = 947 SF
• -R-13, 15 x 93 in, bag labeled 106.56 SF: 947 / 106.56 = 8.9, so 9 bags

Compare what the other two areas would have bought:

Five bags of difference on one small house, and all of it comes from which area you used. Next, check the area answer with a piece count.

Step 3: Piece-Count Check

• -Stud bays at 16 inches on center: 180 x 12 / 16 = 135
• -Opening width: 12 windows x 3 ft = 36 LF, 2 doors x 3 ft = 6 LF, slider 6 LF, total 48 LF, which is 48 x 12 / 16 = 36 bays
• -Full-height bays: 135 - 36 = 99 full batts
• -Window bays keep about 3 feet of their 8 feet under the sill and over the head, so 27 window bays x 3/8 = about 10 batts' worth of short pieces. The 9 door and slider bays keep only the strip over the head, about 1-1/2 batts' worth.
• -Total: about 110 batts, or 110 / 11 = 10 bags

The piece count comes out about one bag higher than the area method, and that is useful information, not a problem. The piece count only removes the studs and plates. It does not remove the kings, jacks, headers, corners and partition backing, so it runs high. The 25 percent framing factor is an average across typical houses, and a simple rectangle like this one has less framing than average, so the area method runs a little low. The truth is between them. Order 10 bags. That is still 4 fewer than the gross-area number. If the two methods had disagreed by 30 percent, something in the measurement would be wrong and worth finding before bid day.

Step 4: Continuous Foam

• -R-10 continuous. Extruded polystyrene runs about R-5 per inch, so this is typically 2 inches, but confirm it against the product the spec names.
• -Net wall area: 1,180 SF
• -Sheets at 10 percent waste: 1,180 x 1.10 / 32 = 40.6, so 41 sheets of 4 x 8
• -Field seam tape at about 0.375 LF/SF: 1,180 x 0.375 = about 443 LF
• -Opening perimeters: windows 12 x (3 + 5 + 3 + 5) = 192 LF; doors 2 x (3 + 6.67 + 6.67) = 32.7 LF; slider 6 + 6.67 + 6.67 = 19.3 LF; total about 244 LF of opening perimeter to tape or flash

Gable ends above the ceiling are outside the thermal envelope in a vented attic, so they do not need continuous insulation to meet the energy code. Check the siding detail, though. If the cladding needs a flat plane all the way up, somebody is running foam or furring on the gables, and it may be you.

Step 5: Attic

• -Attic floor area to the outside of the plates: 40 x 50 = 2,000 SF
• -Johns Manville Attic Protector at R-60: 36.2 bags per 1,000 SF, so 2,000 / 1,000 x 36.2 = 72.4, 73 bags, blown to a minimum 24.3 inches
• -Minimum weight check: 2,000 x 0.904 = 1,808 lb, and 73 bags at about 25 lb each is about 1,825 lb. The numbers agree.
• -If the design used cellulose instead, at the National Fiber chart's 12.8 SF per bag: 2,000 / 12.8 = 156.25, 157 bags, blown to 17.7 inches

The R-49 substitute does not apply, because standard trusses pinch the depth at the eaves. If the drawings showed raised-heel trusses with full depth over the plates, the fiber glass count would drop to 28.4 x 2 = 56.8, 57 bags.

Step 6: Attic Accessories

• -Baffles (rafter vents) at every truss bay along both eaves: 50 x 12 / 24 = 25 bays per side, about 50 baffles
• -Depth markers: 2,000 / 300 = 6.7, 7 markers
• -Attic hatch: one insulated, weatherstripped hatch cover, plus a dam around the opening tall enough to hold back 24 inches of loose fill
• -Installer certificate, filled out with the thickness, settled R, density, coverage area and the 73 bags

The Takeoff Summary

Nothing on that list is exotic. The wall batts and the attic bags are the lines that swing, and they swing on area definition and on the chart row, which are the two things this guide is about.

Most insulation money is lost on scope, not arithmetic. Run this list against the drawings before the number goes out.

Envelope Surfaces That Hide

• -Rim and band joists. On every floor level over a basement or crawlspace, and between floors on multistory work. It is a linear-foot measurement times the joist depth, and it often gets spray foam or cut-and-cobbled board rather than batts.
• -Walls between the house and an attached garage. These are exterior walls for energy purposes and get the same R-value.
• -Ceilings and floors over garages. A bonus room over a garage has an insulated floor, and those batts need supports.
• -Knee walls and the attic floor behind them in finished attics and bonus rooms. Knee walls also usually need an air barrier on the attic side.
• -Cantilevered floors and bay window bottoms.
• -Slab edge and under-slab insulation. The 2021 IECC calls for R-10 continuous to 4 feet in zones 4 and up, and R-5 under the full slab when the slab is heated. It is often in the concrete scope and often in nobody's scope.
• -Basement and crawlspace walls, when the design makes them part of the envelope instead of insulating the floor above.
• -Vaulted and cathedral ceilings, where the cavity depth limits what fits and compression rules apply.
• -Sound batts in interior walls, floors between units, bathrooms and bedrooms. These are not energy code items, so they live in the spec and the partition schedule, not the energy notes.

Accessories and Code Items

• -Baffles at every rafter or truss bay at a vented eave.
• -Attic hatch and pull-down stair covers, insulated and weatherstripped, plus a dam to hold back the loose fill.
• -Depth markers, one per 300 SF of attic.
• -Installer certificate, filled out and posted.
• -Air sealing: top plates, penetrations, the drywall-to-framing joint, around windows and doors. It is sometimes in the insulation scope and sometimes a separate line. The 2021 IECC's blower door limits (3.0 ACH50 in zones 3 through 8) mean someone owns it.
• -Fire blocking and draftstopping that the insulator is expected to install or protect.
• -Thermal or ignition barrier over foam in occupied space, attics and crawlspaces.
• -Vapor retarder: kraft facing, poly or a smart membrane, as the wall section shows.
• -Batt supports in floors: wire, strapping or netting.
• -Tape, cap nails and sealant for continuous foam, per the manufacturer's instructions.

Job Conditions

• -Two trips instead of one. Walls are insulated before drywall, attics after drywall and ceiling finish, so a new-construction job usually needs at least two mobilizations. Price the trips, not just the product.
• -Inspection timing. An insulation inspection before drywall is common. A failed inspection or a missing certificate is a return trip.
• -Retrofit conditions. Old insulation to remove or top up, vermiculite that stops the job until it is tested, knob-and-tube wiring that cannot be buried, and recessed lights that need IC-rated covers or boxes.
• -Foam job conditions. Substrate temperature, humidity, masking, and ventilation and re-occupancy times. All of it affects yield, and some of it affects the schedule.

Two Habits Worth Building

First, keep area and product separate in the takeoff. Record gross, net and cavity area for every wall type even when the product only needs one of them. When a spec change swaps batts for foam, or cellulose for fiber glass, you change the conversion and leave the measurement alone.

Second, keep your own yields. Bags per 1,000 SF you actually blew, board feet per set you actually got, batts left over per house. The manufacturer charts are good. They are also lab numbers from ideal installations, and the foam forums are full of applicators who learned that the hard way. Your own numbers are what make your bid tighter than the next one.