Job takeoff
Whole-house ventilation (MVHR or HRV) takeoff
Fit whole-house ventilation from one central unit, heat recovery (MVHR; an HRV or ERV in North America) or extract only: dust sheets under the ceilings cut for valves, supports along the ducts, vapour-tight insulation on the ducts to the outside and on any duct through cold space, mastic where the joints take it, and the waste, with the airflow design, the unit, the ducting itself, the valves and terminals, the condensate, the electrics, the door undercuts and the commissioning listed and never certified.
A takeoff is the trade word for the shopping list a job produces — every material, and how much of each, worked out by its own cited calculator.
- 9Measurements in
- 5Trades out
Choose the build-up
Each layer changes the materials below; the dimensions stay the same.
Compare one layer at these dimensions, with the rest of the build-up held as you have it:
Give the job once
Every figure on the right follows these, in the units you choose.
Been given a quote for this job?
Paste it into the whole-house ventilation quote check: each line is read against these same calculators — what it leaves out, what it adds, and what to ask.
Check the quoteEvery trade, from those dimensions
then change a dimension, and each line shows what moved.
| Trade | Quantity | |
|---|---|---|
Dust sheets under the ceilings being cutMasking and Protection Materials CalculatorDust sheets over the floors of the rooms you gave, at the calculator's opening sheet size: cutting a hole through a plasterboard (drywall) ceiling drops its dust straight down, and loft insulation and old ceiling debris come with it. The count is for floors; furniture that stays needs its own. None is taped.
Why this quantity?
Resting on
Change any other figure on the Masking and Protection Materials Calculator | 7 items | |
Duct supports (hangers, straps or clips) along the runsHVAC Duct Hanger Support Spacing CalculatorA support at each end of the duct you gave and along it at the calculator's opening maximum spacing, 2.44 m (8 ft), SMACNA's figure for sheet-metal duct: the room runs and both ducts to the outside, added together. Semi-rigid and flexible duct are clipped or strapped closer, at the maker's spacing, which replaces it; and each separate run needs a support at its own far end, so add one for every run after the first, as the calculator's own help says. A duct laid across loft (attic) joists rests on them, and its length can come off.
Why this quantity?
Resting on
Change any other figure on the HVAC Duct Hanger Support Spacing Calculator | 20 hangers | |
Vapour-tight insulation on the two outside ductsDuct Insulation Wrap Area CalculatorBoth ducts between the unit and its terminals, the fresh air in and the stale air out, wrapped along their whole length wherever they run, round a duct of the outside ducts' size measured over the wrap, with the calculator's waste allowance. Both carry air close to the outdoor temperature, so inside a warm house moisture condenses on them unless the insulation and its vapour-tight facing are unbroken, which the units' makers ask for. Where the two are bought already insulated (pre-insulated duct, or insulated flexible duct in its own jacket), the insulation comes with the duct: the row still shows this area, and none of it is bought separately.
Why this quantity?
Resting on
The waste allowance: the calculator's working figure, a trade convention. Change any other figure on the Duct Insulation Wrap Area Calculator | 46.08 ft² | |
Insulation on the room ducts in cold spacesDuct Insulation Wrap Area CalculatorThe length of room duct you gave through a loft (attic), floor void or garage outside the insulation, wrapped round a duct of the room ducts' size measured over the wrap, π × (diameter + twice the thickness), with the calculator's waste allowance: a warm duct in a cold space condenses the moisture it carries, and a supply duct there gives up the heat the unit recovered. Shown only where you give a length. Where the maker and the rules allow a duct buried deep in the loft insulation to stay bare, its length comes off.
Why this quantity?
Resting on
The waste allowance: the calculator's working figure, a trade convention. Change any other figure on the Duct Insulation Wrap Area Calculator | 67.39 ft² | |
Skip (dumpster) or a waste collectionSkip & Dumpster Size CalculatorThe loose waste over the rooms you gave, at the depth you gave, as light waste: the unit's and the ducts' boxes, duct offcuts, the cores cut from ceilings and walls, and the old extract fans. A load this size can go in the installer's van as readily as in a skip; the volume is the same either way.
Why this quantity?
Resting on
Change any other figure on the Skip & Dumpster Size Calculator | 0.5787 yd³ | |
Dust sheets under the ceilings being cutMasking and Protection Materials CalculatorDust sheets over the floors of the rooms you gave, at the calculator's opening sheet size: cutting a hole through a plasterboard (drywall) ceiling drops its dust straight down, and loft insulation and old ceiling debris come with it. The count is for floors; furniture that stays needs its own. None is taped.
Why this quantity? | 7 items | |
Duct supports (hangers, straps or clips) along the runsHVAC Duct Hanger Support Spacing CalculatorA support at each end of the duct you gave and along it at the calculator's opening maximum spacing, 2.44 m (8 ft), SMACNA's figure for sheet-metal duct: the room runs and both ducts to the outside, added together. Semi-rigid and flexible duct are clipped or strapped closer, at the maker's spacing, which replaces it; and each separate run needs a support at its own far end, so add one for every run after the first, as the calculator's own help says. A duct laid across loft (attic) joists rests on them, and its length can come off.
Why this quantity? | 20 hangers | |
Vapour-tight insulation on the two outside ductsDuct Insulation Wrap Area CalculatorBoth ducts between the unit and its terminals, the fresh air in and the stale air out, wrapped along their whole length wherever they run, round a duct of the outside ducts' size measured over the wrap, with the calculator's waste allowance. Both carry air close to the outdoor temperature, so inside a warm house moisture condenses on them unless the insulation and its vapour-tight facing are unbroken, which the units' makers ask for. Where the two are bought already insulated (pre-insulated duct, or insulated flexible duct in its own jacket), the insulation comes with the duct: the row still shows this area, and none of it is bought separately.
Why this quantity? | 4.15 m² | |
Insulation on the room ducts in cold spacesDuct Insulation Wrap Area CalculatorThe length of room duct you gave through a loft (attic), floor void or garage outside the insulation, wrapped round a duct of the room ducts' size measured over the wrap, π × (diameter + twice the thickness), with the calculator's waste allowance: a warm duct in a cold space condenses the moisture it carries, and a supply duct there gives up the heat the unit recovered. Shown only where you give a length. Where the maker and the rules allow a duct buried deep in the loft insulation to stay bare, its length comes off.
Why this quantity? | 6.22 m² | |
Skip (dumpster) or a waste collectionSkip & Dumpster Size CalculatorThe loose waste over the rooms you gave, at the depth you gave, as light waste: the unit's and the ducts' boxes, duct offcuts, the cores cut from ceilings and walls, and the old extract fans. A load this size can go in the installer's van as readily as in a skip; the volume is the same either way.
Why this quantity? | 0.42 m³ |
Also part of this job when you need it: Duct mastic round the joints — set joints sealed with mastic above 0.
Also part of this job when you need it: Duct mastic round the joints — set joints sealed with mastic above 0.
Estimates, not a quote. Each row gives its base, the allowance on top, the adjusted figure and what to order; change an allowance on the row, or open its reasoning to see every figure it rests on. A trade's own page carries what it does not cover — open the one you are about to order against.
Labour and programme
Person-hours for the rows going in, from trade rules of thumb: a range for each piece of work, never a price.
- Dust sheets under the ceilings being cut2.8 h (1.4–5.6)
- Skip (dumpster) or a waste collection0.4 h (0.2–1.3)
About 3.2 person-hours in the rows that carry them, between 1.6 and 6.9.
Trade by trade
- Labourer1 labourerhalf a day
About half a day, one trade after another at eight hours a day. Left out: drying and curing, deliveries, inspections, trades overlapping.
3 rows carry no hours of their own
- Duct supports (hangers, straps or clips) along the runs: Ductwork is not rated here: it is installed to a ventilation design by the installer who commissions it, and the design, not the length of duct alone, sets the time.
- Vapour-tight insulation on the two outside ducts: Ductwork is not rated here: it is installed to a ventilation design by the installer who commissions it, and the design, not the length of duct alone, sets the time.
- Insulation on the room ducts in cold spaces: Ductwork is not rated here: it is installed to a ventilation design by the installer who commissions it, and the design, not the length of duct alone, sets the time.
Labour and programme
Person-hours for the rows going in, from trade rules of thumb: a range for each piece of work, never a price.
- Dust sheets under the ceilings being cut2.8 h (1.4–5.6)
- Skip (dumpster) or a waste collection0.4 h (0.2–1.3)
About 3.2 person-hours in the rows that carry them, between 1.6 and 6.9.
Trade by trade
- Labourer1 labourerhalf a day
About half a day, one trade after another at eight hours a day. Left out: drying and curing, deliveries, inspections, trades overlapping.
3 rows carry no hours of their own
- Duct supports (hangers, straps or clips) along the runs: Ductwork is not rated here: it is installed to a ventilation design by the installer who commissions it, and the design, not the length of duct alone, sets the time.
- Vapour-tight insulation on the two outside ducts: Ductwork is not rated here: it is installed to a ventilation design by the installer who commissions it, and the design, not the length of duct alone, sets the time.
- Insulation on the room ducts in cold spaces: Ductwork is not rated here: it is installed to a ventilation design by the installer who commissions it, and the design, not the length of duct alone, sets the time.
Setups you have saved
The build-up, the dimensions and any allowance you changed — kept on this device, and reusable on any job. Your prices are not copied in: they stay in your price book, so a setup never holds a stale one.
How far does a budget go?
At your own prices, with this build-up unchanged.
About this job
A whole-house system replaces a scatter of bathroom and kitchen fans, each run when somebody remembers it, with one unit that runs all the time. A heat recovery unit (MVHR in Britain; an HRV in North America, or an ERV, which passes moisture across as well as heat) draws stale, moist air out of the kitchen, the bathrooms and the utility room, passes it through a heat exchanger beside the fresh air it draws in from outside, and supplies that fresh air, warmed, to the living rooms and bedrooms. The air crosses the house under the doors, from the rooms it is supplied to towards the rooms it is drawn from, which is why every internal door is trimmed to leave a gap. A central extract unit (mechanical extract ventilation, or central exhaust) does the drawing out alone, and fresh air comes in through trickle vents in the windows. How much air each room needs, which unit moves it at which fan speeds and what size each duct is are the ventilation designer's, under Approved Document F in England or ASHRAE 62.2 in the US: that design is the first item listed, and none of it is sized here.
The ducts decide whether the system works as it was designed. British rooms are commonly fed by semi-rigid radial duct, one unbroken run from a distribution box to each valve, pushed onto its spigots with the maker's clips and seals; North American rooms by rigid metal or flexible duct branching off trunks, its joints brushed with mastic. Every tight bend and crushed length costs airflow, so runs are kept short and gently curved. A duct through a joist is held to the rules on notching and boring, which leave room for a small hole near the middle of a joist's depth and none at all for a 150 mm (6 in) duct in most house joists; so ducts run between the joists, over them in the loft (attic) or in a boxed-in route, and whether a joist is weakened by a hole is a question raised here and left to the rules and the designer. Where a duct crosses a cold loft or floor void it is wrapped, or the moisture it carries condenses inside it. The two ducts between a heat recovery unit and the outside are different again: one brings air in from outside and the other carries air the heat exchanger has already cooled, both close to the outdoor temperature, so inside a warm house moisture condenses on their outer faces, and each is wrapped along its whole length in a vapour-tight insulation.
The rows are what a page can measure: the dust sheets in the rooms whose plasterboard (drywall) ceilings are cut for valves, the supports along the ducts, the insulation on the outside ducts and on any room duct through cold space, the mastic where the joints are sealed with it, and the skip. The duct itself, its bends and distribution boxes, the valves and the terminals follow the design and the unit's own system, so they are listed and not counted. An MVHR or HRV unit makes water in its heat exchanger in cold weather, which runs through a dry trap to a drain, kept from freezing where it crosses the loft; an ERV passes that moisture back into the house and needs a drain only where its maker asks for one. The unit's fused supply and any boost switches in the wet rooms are electrical work. Commissioning is the part that proves the rest: each valve's airflow measured and set to the design with the doors shut, and written down, a record that comes from the installer or a tester and that, in England, building control asks to see. The insulation answers in square metres or square feet; the mastic only in US quarts, the tub it is sold in across North America, and its row appears only once joints are given.
How each line reads
- Base
- What the calculator gives for these dimensions, before anything is added.
- Allowance
- Cutting waste, a lap or spare stock — named, with where it comes from, and changeable on the row.
- Adjusted
- The base with its allowance on top.
- Order
- What to buy: the adjusted figure in whole boards, bags, rolls or lengths.
The order this happens in
Quantities do not tell you the sequence, and on this job the sequence is where the money goes wrong.
- Have the ventilation designed before anything is bought: the airflow each room needs, where the unit goes with room to change its filters, each duct's route and size, where the valves go, and where the fresh-air and exhaust terminals go, apart from each other and from flues and drains.
- Sheet the rooms, have textured ceilings or old boards checked for asbestos before they are cut, and take out the old extract fans, isolating their circuits and keeping any hole a terminal can reuse.
- Core the walls or the roof for the terminals, cut the ceiling holes for the valves, and lift boards where a duct runs in a floor void, boring or notching a joist only where the rules allow.
- Hang the unit on its anti-vibration brackets, level, on a boarded platform where it stands over loft joists; run the ducts from it to each valve position and out through the wall or roof, fitting each outside terminal as its duct reaches it so no cored hole stands open, supporting the ducts as they go, sealing every joint, and wrapping the ducts to the outside and every duct that crosses cold space.
- Fire-stop round each duct that passes a fire-separating wall or ceiling, weather a roof terminal into the covering as it goes in, run the unit's condensate through a dry trap to a drain, and have the electrician run the unit's supply and any boost switches.
- Make good round the valve holes and the cores, fit the room valves once the ceilings are made good, trim each internal door so air can pass under it, and connect the unit.
- Have the installer or a tester measure each valve's airflow with the doors shut and set it to the design, and record it with the unit's settings, and the electrician tests the unit's supply.
- Take the waste away, and hand over the commissioning record, the unit's manual and its filter schedule.
What this takeoff does not cover
- The design and its figures: how much air each space needs, the unit and its fan speeds, the duct sizes and the valve positions, set by Approved Document F in England or ASHRAE 62.2 in the US. It is one listed item, the designer's; the site's pages for air change and duct size answer sizes, and none is reached here.
- An airtightness test (a blower door test), which a designer may ask for before the unit is chosen or after it is in.
- Combustion air for an open-flued boiler, fire or stove. A balanced unit in a tighter home can starve one of air, which is a question for a gas or solid fuel engineer, not for this job.
- Fire dampers and fire-rated duct where a duct passes a fire-separating wall or floor: the fire-stopping round the duct is listed, and which damper, if any, is the fire strategy's.
- Fans room by room instead of this job's one unit, each with its own duct and grille: a job of its own, one fan at a time, with its own takeoff on this site. Positive input (a PIV unit), blowing air in from the loft, is another thing again.
- Heating or cooling the air in the ducts: a post-heater, a cooling coil, a ducted heat pump or an air conditioner, and a summer bypass sold as a separate module.
- Measuring the ducting by length with its bends, branches and distribution boxes, and counting the valves and the grilles or cowls where the ducts leave the house: each follows the designer's layout and the maker's range, so each is listed as work, not a row.
- Redecorating beyond making good: the plaster round each valve, the cores and any boxing are made good as listed work, and repainting whole rooms is not in this job.
- Servicing once the job is done, and filters after the first set; the unit's filter schedule is among the papers the owner is given.
Quote check
Been given a quote for this job?
Paste it into the whole-house ventilation quote check. Every line of it is read against these same calculators and your measurements. Quantities only, never prices.
What it leaves out
Every line this takeoff has that nothing on the quote reads as.
What it adds
Labour, removal, hire, fees — each named for what it is.
What to ask
One list of questions, ready to copy. Never a verdict.
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Frequently asked questions
- What does the whole-house ventilation takeoff give for a typical job?
- Opened at Floor of the rooms with a valve 70 m² · Duct from the unit to the rooms, every run added 40 m · From the unit to each outside terminal 3 m · Room duct through a cold loft (attic) or void 12 m · Room duct diameter 0.1 m · Outside duct diameter 0.15 m · Duct insulation thickness 0.03 m · Joints sealed with mastic 0 · Loose waste, as a depth over those rooms 0.01 m, it orders: Dust sheets under the ceilings being cut, 7 items; Duct supports (hangers, straps or clips) along the runs, 20 hangers; Vapour-tight insulation on the two outside ducts, 4.15 m²; Insulation on the room ducts in cold spaces, 6.22 m²; Skip (dumpster) or a waste collection, 0.42 m³. Opened at Floor of the rooms with a valve 750 sq ft · Duct from the unit to the rooms, every run added 130 ft · From the unit to each outside terminal 10 ft · Room duct through a cold loft (attic) or void 39 ft · Room duct diameter 4 in · Outside duct diameter 6 in · Duct insulation thickness 1 in · Joints sealed with mastic 0 · Loose waste, as a depth over those rooms 0.25 in: Dust sheets under the ceilings being cut, 7 items; Duct supports (hangers, straps or clips) along the runs, 20 hangers; Vapour-tight insulation on the two outside ducts, 46.1 ft²; Insulation on the room ducts in cold spaces, 67.4 ft²; Skip (dumpster) or a waste collection, 0.58 yd³. Every figure follows the dimensions you give it.
- Which calculators does the whole-house ventilation takeoff run?
- 4 calculators, for 5 lines: Masking and Protection Materials Calculator, HVAC Duct Hanger Support Spacing Calculator, Duct Insulation Wrap Area Calculator, Skip & Dumpster Size Calculator. Each has a page of its own with its formula and its sources; the takeoff runs them all on one set of dimensions.
- What does the whole-house ventilation takeoff leave out?
- 9 things, each named on this page: The design and its figures; An airtightness test (a blower door test), which a designer may ask for before the unit is chosen or after it is in; Combustion air for an open-flued boiler, fire or stove; Fire dampers and fire-rated duct where a duct passes a fire-separating wall or floor; Fans room by room instead of this job's one unit, each with its own duct and grille; Heating or cooling the air in the ducts; Measuring the ducting by length with its bends, branches and distribution boxes, and counting the valves and the grilles or cowls where the ducts leave the house; Redecorating beyond making good; Servicing once the job is done, and filters after the first set; the unit's filter schedule is among the papers the owner is given.
- Can I check a quote for this job against the takeoff?
- Yes. The whole-house ventilation quote check reads a quote's lines against these same calculators and your measurements, and reports what it leaves out, what it adds and what to ask. It reads quantities, never prices.