Crawl space encapsulation cost calculator

Closing the crawl space: the air rate R408.3 asks for

R408.3 starts with the ground. Item 1 asks for a continuous Class I vapor retarder over the exposed earth, its joints lapped 6 inches and sealed or taped, its edges carried at least 6 inches up the stem wall and attached to it or to the insulation. Item 2 then asks for one of four ways to deal with the air under the floor, and the quote you receive is shaped by the one the contractor picked.

Items 2.1 and 2.2 are air rates: continuous mechanical exhaust, or a conditioned air supply, at 1 cfm for each 50 sq ft of floor area, with a path back to the common area of the house and the perimeter walls insulated under section N1102.2.10.1. At the calculator’s default of 50 by 30 ft, that is 1,500 sq ft and 30 cfm. At 2,000 sq ft it is 40 cfm, at 1,000 sq ft 20 cfm. A quote built on either path should show a fan or a supply duct, a transfer grille or duct for the return, and a wall insulation line.

Item 2.3 covers an existing house whose crawl space already serves as a plenum under section M1601.5. Item 2.4 is the shortest of the four: dehumidification sized in accordance with the manufacturer’s specifications. It names no rate, no capacity and no efficiency. That is why the calculator does not size a dehumidifier for you; it asks for the capacity printed on the unit you are offered and works out what that unit can cost to run.

Where you live, the section may carry another number or amended text. Ask the building department which edition it enforces before you pay for a path it does not accept.

Keeping it vented: the opening area R408.2 asks for

Keep the vents and the code asks for opening area instead of air movement. R408.2 sets 1 sq ft of net ventilation area for every 150 sq ft of under-floor area. Exception 1 cuts that tenfold, to 1/1,500 of the floor, where the ground is covered with an approved Class I vapor retarder. On the default 1,500 sq ft the gap is plain: 1,440 sq in of net vent area over bare earth, 144 sq in with the cover. At 2,000 sq ft without a cover the figure is 1,920 sq in; with one it is 192 sq in.

The net free area of one vent is printed on its label or spec sheet. Enter it and the calculator divides and rounds up: at 50 sq in per vent, the 1,920 sq in of a 2,000 sq ft space without a cover take 39 vents. With the cover, the 1,000 sq ft example needs 96 sq in, which two vents of 60 sq in provide.

Placement is the second rule. The main text puts one opening within 3 ft of each external corner of the under-floor space. Exception 2 drops the corner rule where the ground carries an approved Class 1 vapor retarder, provided the openings are placed to give cross ventilation. The code writes Class I in the first exception and Class 1 in the second; the quotation above keeps both as printed. A crawl space that stays vented still takes the ground cover if you want the smaller opening area, so the barrier price below applies to both routes.

What a compliant dehumidifier costs to run

Electricity: U.S. Energy Information Administration, Electric Power Monthly, Table 5.6.A. Average Price of Electricity to Ultimate Customers by End-Use Sector, by State ↗, residential sector, 2026-08, read October 24, 2026; the calculator lists every state in its price field.

Federal rules do not set how many pints a crawl space dehumidifier must pull. They set how much water it must remove per kilowatt-hour. 10 CFR 430.32(v)(2) fixes a minimum integrated energy factor, in liters per kWh, for dehumidifiers manufactured on or after June 13, 2019: 1.30 to 2.80 for portable units by capacity, 1.77 or 2.41 for whole-home units by case volume. A unit that meets the floor exactly uses the most electricity the rule allows for a given amount of water, and that is the figure this calculator computes.

The arithmetic is short. Pints a day, times days a year, times 0.4731765, the liters in a U.S. liquid pint in NIST Special Publication 811, gives liters; liters divided by the minimum factor gives kWh; kWh times your price gives dollars. With the defaults, the AlorAir Helios MP55 at its printed 55 pints a day, on each of 365 days, removes 9,499.0 L. Its DOE class is not printed on the card read, so the calculator takes the lowest minimum that could apply: for a 55-pint unit, the whole-home row for a case of 8.0 cu ft or less, 1.77. The result is 5,366.7 kWh, or $974.59 a year and $81.22 a month at the U.S. residential price of 18.16¢ per kWh for August 2026.

Read that figure as a ceiling under a stated assumption, not as a bill. The default assumes the unit removes its full rated capacity every day you enter, which means running all day, every one of those days, at the conditions it was rated under. A crawl space that dries out lets the unit cycle off, and a model rated above the federal minimum uses less for the same water. Put the pints you expect it to remove in “Water removed” and the season in “Days running a year”, and the estimate follows. A portable 55-pint unit removing 20 pints a day at California’s 29.75¢ comes to 1,233.6 kWh and $367.01 a year. Set the class to unknown and the same water is divided by 1.77 instead of the portable row’s 2.80, so the label is worth reading before you trust either number.

Electricity prices come from EIA’s Electric Power Monthly, Table 5.6.A, residential sector, August 2026, published on October 23, 2026; EIA marks its 2026 values as preliminary. The price field lists every state. If your bill shows a different rate, type it in the field below it and it replaces the EIA price.

The ground cover minimum, priced at listed rolls

Item 1 of R408.3 says what the ground cover must do, and that turns into an area you can price. The sheet covers the floor, climbs 6 in up every stem wall and overlaps 6 in at each joint. On the default 50 by 30 ft space that is 1,500 sq ft of floor plus 6 in along 160 ft of wall: 1,580 sq ft before laps. The calculator lays the strips along the length, adds a 6 in lap for each extra strip, and prices the result at each listed roll’s price per sq ft.

Twelve rolls from three sellers fit that space with no thickness filter. The lowest material cost is $162.99, the median $342.50, the highest $706.32. Those are material only: no tape, no sealant, no fasteners, no labor. The sheet is also sold by the roll, not by the square foot, so an order rounds up to whole rolls and the leftover is yours.

Thickness is not a figure in R408.3. The section asks for a Class I vapor retarder and names no mil count; the rolls listed run from 6 to 20 mil. Choosing a minimum thickness narrows the list. At 12 mil and up on a 1,000 sq ft space, six rolls from two sellers remain, from $213.25 to $478.82. Asking for 20 mil leaves the single Crawl Space DIY roll; above that, nothing listed matches and the calculator says so instead of guessing.

Crawl Space DIY also sells kits that bundle barrier, tape, sealant and fasteners: $469.99 and $599.99 for 1,200 sq ft in 12 and 20 mil, $1,079.99 for 2,000 sq ft. A kit is another product, so it stays out of the roll prices. Set its coverage against the 1,580 sq ft the cover needs once it climbs the walls, not against the floor area alone.

Dehumidifier prices from three sellers

Thirty dehumidifier listings were read on October 24, 2026: most from AlorAir’s crawl space and basement category, three from Crawlspace Depot and two from Crawl Space DIY. The lowest price printed is $359.73, the median $611.12, the highest $2,064.99. Each is the price the seller showed that day, with its kind in the last column: AlorAir cards print two prices and the first is kept, Crawlspace Depot prints an MSRP and a “Now” price, Crawl Space DIY strikes through an original price and shows the current one.

Capacity is where the cards differ most. Only two AlorAir cards print a capacity under AHAM conditions: the Helios MP35 at 35 pints a day and the Helios MP55 at 55. The same two cards print 70 and 120 pints “at saturation”, a different test point that gives a larger number. Several other AlorAir cards print only the saturation figure, Crawlspace Depot’s cards print no capacity, and Crawl Space DIY’s carry 80 and 100 pints in the product title with no test condition stated. Enter the AHAM capacity when the label gives it: a saturation figure fed into the capacity field would raise the water removed, and the kWh with it.

None of the cards read prints the DOE product class or the case volume, so the price list cannot tell you which efficiency floor a unit falls under. The quote section only compares your dehumidifier line with the lowest and the highest listing.

Published contractor bands, kept apart from the listings

Four cost guides publish bands for the whole job. HomeGuide prints $3 to $10 per sq ft, or $3,000 to $15,000 in total. Palm Build prints $1,500 to $15,000 and writes that most homeowners pay $3 to $7 per sq ft, rising to roughly $10 where severe moisture, mold or structural repairs are involved. Polyguard prints $1,500 to $15,000 for professional encapsulation, American Dry $5,000 to $16,000. None of them shows the jobs behind its band, so they are summaries to hold a quote against, not prices.

The calculator applies each per-sq-ft band to your floor area and leaves each total band as printed. At 1,500 sq ft, HomeGuide’s per-foot band becomes $4,500 to $15,000 and Palm Build’s $4,500 to $10,500; at 2,000 sq ft, $6,000 to $20,000 and $6,000 to $14,000. No band is averaged with another, nor with the seller listings above: a roll of barrier and a contractor’s installed job are different things, and folding them into one figure would describe neither.

The two kinds of band do not always agree. HomeGuide’s per-foot band at 2,000 sq ft tops out at $20,000, above the $15,000 ceiling of its own total band. The page shows both rows and lets your quote fall where it falls.

The cost of waterproofing a crawl space

Search for the cost of waterproofing a crawl space and most of the result titles are encapsulation cost pages, because the work quoted is the same: a ground cover, vents sealed or the space closed, often a drainage or sump line, and a dehumidifier. This page prices that job with the same tool. The barrier, vent sealing, dehumidifier and drainage or sump fields take the lines of a waterproofing quote as written, and the total is placed against the same four publishers.

What the page does not price is the drainage itself. R408.2 and R408.3, the sections quoted here, size neither a drain nor a sump, and no listing for either was read, so that line stays a number from a contractor who has seen the site. The model code also splits the two spaces: R408 governs the under-floor space and its ground, while a basement wall that holds back soil falls under R406, the waterproofing and dampproofing section. If your foundation has basement walls rather than a crawl space, the foundation wall waterproofing check measures that wall area and checks a quoted membrane against the R406 material list.

Read an encapsulation quote line by line

The quote section has eight lines: vapor barrier installed, vent sealing, dehumidifier, drainage or sump, wall insulation, mold treatment, permit fee and one other line. Type each line the way the contractor wrote it. Leave a field blank when the work is not part of the job, and enter 0 when the contractor says it is included in another line; the line-by-line table then shows the difference between “not entered” and a zero.

The calculator adds the lines you entered, divides by the floor area, and sets the total against each publisher’s band at your size, one row per band. A 1,000 sq ft space quoted $4,000 for the barrier, $200 for vents and $1,500 for a dehumidifier totals $5,700, or $5.70 per sq ft: within all six bands. A 600 sq ft space quoted $9,000 for the barrier and $3,000 for mold treatment totals $12,000, or $20.00 per sq ft. That lands within the four total bands but above both per-sq-ft bands, which at 600 sq ft reach only $6,000 at HomeGuide and $4,200 at Palm Build. A small space with a large mold line is where the two kinds of band part company; ask for the mold work to be described in writing.

The dehumidifier line is read against the listings: below the lowest, between, or above the highest. A line above $2,064.99 is not wrong, but it buys more than the unit, so ask what it covers: the drain line, a condensate pump, ducting, the installation. Wall insulation is priced only as the line on your quote; this page computes no insulation quantity.

Crawl space encapsulation cost questions

Read the result with its boundaries

• R408.2 and R408.3 are read as the model text of the 2021 IRC in the Hawaii adoption on UpCodes, checked against the Colorado and New Hampshire adoptions the same day. Your local adoption and its amendments decide.
• The dehumidifier figure is the energy a unit at the federal minimum integrated energy factor would use for the water and the days you enter. It is a ceiling under that assumption, not a measured value of any model and not a bill.
• The DOE product class comes from the unit’s label. When it is unknown, the lowest minimum that could apply is used, which gives the highest energy.
• Seller prices are what three sellers printed for each kind of product on October 24, 2026. Rolls, kits and dehumidifiers stay in separate lists and are never averaged with a published band.
• The bands are summaries published by four cost guides, without the jobs behind them.
• No insulation quantity, structural check or drainage design is computed. Wall insulation and drainage are quote lines.