Ventilation Cost Calculator

Every house should have some fresh air brought into it - in shoulder seasons houses get damp and often stinky. It's also good to dilute both the chemicals we bring into our homes and the chemicals we contribute ourselves from both ends...

How much does it cost to run? The answer may be less than you think, and you will probably see why I'm not a huge fan of ERVs and HRVs (energy recovery ventilators and heat recovery ventilators), they don't save as much as you might think.

Put in your zip/postal code and pick the city closest to you, or just select the closest city, and see what the numbers look like! You can adjust just about everything, so play with the settings to see what you learn! Click Download PNG to get the file to share with others. Have fun!

Annual Ventilation Cost Calculator

□ Location

Select from nearest cities with weather data:

or select city directly

□ Home Details

Floor Area iTotal conditioned floor area of your home.

1,500 ft²

Bedrooms iUsed in ASHRAE 62.2 formula: Qtot = 0.01×ft² + 7.5×(BR+1) CFM

Stories iNumber of floors — affects home volume and natural infiltration credit.

Enter floor area and bedrooms to see ASHRAE 62.2 required ventilation.

□️ Motorized Damper Cutoffs iMany systems use motorized dampers that close when outdoor temps are extreme, skipping ventilation (or relying on infiltration) at those times. This clips the heating and cooling load from bins outside this range.

□ Reduce your ventilation energy bill: Motorized dampers let you skip fresh-air intake during the coldest and hottest hours of the year — when conditioning outdoor air is most expensive. Use the sliders below to set your cutoff temperatures. The result cards will show your costs with cutoffs active alongside what you'd pay with no cutoffs at all, so you can see exactly how much the damper saves.

Low Temp Cutoff iDamper closes below this temperature — no ventilation (or infiltration only). Typical: 15–20°F. Set to minimum slider value to disable.

15°F

High Temp Cutoff iDamper closes above this temperature — no ventilation during hottest hours. Typical: 80–90°F. Set to maximum slider value to disable.

80°F

Set a city to see how many hours are clipped by damper cutoffs.

⚡ Energy Details

Heating Fuel iHow your home is heated. Affects cost to condition incoming fresh air in winter.

Heating COP iHeat pump seasonal average COP. Cold-climate HPs: 2.0–3.5. Seasonal average is typically higher than design-day COP.

2.5

Electricity iYour electricity rate in cents per kWh. US average ~13–16¢. Check your utility bill.

15 ¢/kWh

Cooling COP iSeasonal cooling efficiency. Central AC/HP: 3.0–5.0. Window AC: 2.0–3.0.

3.5

Heat Setpoint iIndoor heating setpoint. Fresh air is heated to this temperature when outdoor temps are below it.

70°F

Cool Setpoint iIndoor cooling setpoint. Fresh air adds cooling load when outdoor temps exceed this.

75°F

□️ Ventilation Systems to Compare

ERV / HRV — No Damper Balanced ventilation with heat recovery

Recovery Efficiency iSensible heat recovery. Good HRV: 70–85%. Premium units: 85–93%. ERV also recovers moisture, reducing cooling latent load.

75%

Fresh Air CFM iVentilation flow rate. Typical residential: 50–150 CFM continuous.

45 CFM

Default: ASHRAE 62.2-2010 rate — 0.01 × ft² + 7.5 × (bedrooms + 1). Update floor area or bedrooms above to recalculate.

Fan Wattage iTotal fan power (supply + exhaust). ECM fans: 15–40W. Standard motors: 40–80W+.

60 W

Fresh Air Intake Duct Passive duct — no fan, no damper, no heat recovery

Fresh Air CFM iPassive intakes: 10–80 CFM depending on duct size, stack effect, wind. All incoming air must be fully conditioned — no recovery.

40 CFM

Default: 10 CFM/person — Lstiburek's field-tested rate from 300,000 Canadian homes. Persons = bedrooms + 1 (assumes 2 in the master bedroom).

No fan electricity — fresh air enters passively and is conditioned by your HVAC system.

Fresh Air Intake + Damper & Fan AHU fan brings in a fraction of outdoor air

Effective Fresh Air CFM iTime-averaged fresh air rate. At 300 CFM handler with 10% OA = 30 CFM fresh. Use your actual average fresh air delivery rate.

40 CFM

Default: 10 CFM/person — Lstiburek's field-tested rate from 300,000 Canadian homes. Persons = bedrooms + 1 (assumes 2 in the master bedroom).

Fan Wattage (effective) iAverage fan power. ECM at low speed: 50–150W. PSC: 200–400W. If fan runs 25% of time at 150W, enter ~37W.

35 W

□ Select a city or enter a ZIP / postal code to calculate annual ventilation costs.

□ Methodology & ASHRAE 62.2 Formulas

▾

Required Ventilation Rate

This calculator uses the ventilation rate formula from ASHRAE 62.2-2010 (which was also in effect for earlier editions back to the standard's introduction in 2003):

Q_tot = 0.01 × A_floor + 7.5 × (N_br + 1) Where: Q_tot = total required ventilation (CFM) A_floor = conditioned floor area (ft²) N_br = number of bedrooms +1 = accounts for occupants beyond the bedroom count

Example — 1,500 ft², 3 bedrooms: Q = 0.01 × 1,500 + 7.5 × 4 = 15 + 30 = 45 CFM

Note on ASHRAE 62.2-2013 and later: The 2013 edition raised the floor-area coefficient to 0.03, producing meaningfully higher required rates that add both heating and dehumidification energy load (especially in humid climates). Joe Lstiburek argued this increase was not scientifically justified and introduced BSC-01 as a competing standard using the lower 0.01 rate. The 2018 IRC also adopted the 0.01 rate. At the 2014 ACI Great Ventilation Debate in Detroit — a lively 5-on-1 panel — Lstiburek cited 300,000 Canadian homes ventilated at roughly 10 CFM/person with no documented ill health effects, lending real-world support to lower rates. Nate Adams (author of this calculator) was there in the front row and wrote up the event for Green Building Advisor. Use the CFM sliders in this calculator to model any of these rate approaches.

Note on dehumidification: This calculator estimates heating and cooling sensible load only. It does not include dehumidification energy, which can be significant at higher ventilation rates in humid climates — another reason the 0.03 rate adds real cost that this tool does not fully capture.

Reference standards & further reading:
• ASHRAE 62.2 — Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings (purchase from ASHRAE)
• BSC Standard 01-2015 — Lstiburek / Building Science Corporation ventilation standard (free PDF)
• Nate Adams — "Another Report on the Great Ventilation Rate Debate" (Green Building Advisor, April 2014)
• Nate Adams — "Finally! We Can Control the Air Quality in a Home" — one approach to dampers and duct design

Infiltration Credit

ASHRAE 62.2 allows naturally leaky homes to subtract a calculated infiltration credit from the required mechanical ventilation. The credit depends on how airtight the house is (measured in ACH₅₀):

Q_inf = (ACH₅₀ / 17) × (V_home / 60) Where: ACH₅₀ = air changes per hour at 50 Pa (from blower door test) V_home = home volume = floor area × 8 ft × stories (ft³) /17 = terrain/shielding factor (ASHRAE default for suburbs) /60 = converts CFM to "per minute" to match units Net required mechanical ventilation = max(0, Q_tot − Q_inf)

This calculator uses ACH₅₀ = 13 for the "low" (leaky home) estimate and ACH₅₀ = 3 for the "high" (tight home) estimate. A tight modern home provides little infiltration credit and puts almost the full load on the mechanical system.

Heating Energy per Bin

BTU_heat = CFM_net × 1.1 × (T_heat − T_bin) × hours Cost depends on fuel: Heat pump: BTU / 3,412 / COP × ¢/kWh Electric resist.: BTU / 3,412 × ¢/kWh Natural gas: BTU / 100,000 / AFUE × $/therm Propane: BTU / 91,600 / AFUE × $/gallon Oil: BTU / 138,000 / AFUE × $/gallon 1.1 = sensible heat factor for air (BTU/hr per CFM per °F)

Cooling Energy per Bin

BTU_cool = CFM_net × 1.1 × (T_bin − T_cool) × hours × 1.3 Cost: BTU / 3,412 / COP_cooling × ¢/kWh 1.3 = latent load multiplier (outdoor air is often humid in summer, adding moisture removal load on top of sensible cooling)

ERV / HRV Recovery Credit

CFM_conditioned = CFM_net × (1 − η_recovery) Where η_recovery = sensible heat recovery efficiency (0–1). An 80% HRV only requires conditioning 20% of the incoming air volume. ERVs also recover latent heat (moisture), reducing the 1.3× cooling multiplier in practice — this calculator applies recovery to sensible loads only (conservative).

Fan Electricity

Fan electricity cost = Watts × 8,760 hrs/yr / 1,000 × ¢/kWh Fans run continuously year-round regardless of outdoor temperature. Passive fresh air intakes have no fan — $0 fan cost.

Fan motor heat is not modeled bin-by-bin in this calculator. In reality, all fan electrical energy becomes heat inside the conditioned space (1W = 3.412 BTU/hr), which offsets heating load in winter and slightly adds to cooling load in summer. For a 35W fan this is roughly ~119 BTU/hr — meaningful relative to a small net ventilation load, but complex to attribute accurately. The fan electricity line shows the gross electricity cost; treat it as a slight overestimate of net cost in heating-dominated climates.

Temperature Bin Data

Weather data is ERA5 reanalysis (European Centre for Medium-Range Weather Forecasts), averaged over 1991–2020. Bins are 5°F wide. The midpoint of each bin is used for cost calculations. All 185 cities are embedded directly in this file — no internet connection is required for calculations.

Damper Cutoffs

When a motorized damper is set to close at extreme temperatures, any bin whose midpoint falls outside the range [Low Cutoff, High Cutoff] contributes $0 heating/cooling cost — that ventilation simply doesn't happen. Fan electricity is still counted for always-on systems. The "no cutoffs" charts and cost row on each card show what costs would be if the damper never closed, so you can see the energy penalty of skipping those extreme hours.

ERV/HRV and passive fresh air intakes are modeled without damper cutoffs — ERVs have built-in defrost modes and are typically run continuously, while passive intakes have no mechanical shutoff. Only the "Fresh Air Intake + Damper & Fan" system applies damper cutoffs.

Why does "Fresh Air Intake + Damper & Fan" often cost less than "Fresh Air Intake — No Damper"?

Three factors combine to make this comparison nuanced:

1. Damper cutoffs: The motorized damper skips ventilation during the coldest (and hottest) hours, reducing conditioning load. The "Damper saves approx. $X/yr" line on each card shows this effect in isolation — often small in mild climates.

2. Different default CFM: The two systems have independent CFM sliders. If the passive intake is set higher than the dampered system, it will condition more total air volume and cost more regardless of the damper. Set them to the same CFM to isolate the damper effect alone.

3. Fan electricity: The passive intake has zero fan cost. The dampered system adds fan electricity (typically $30–60/yr for a small AHU fan). This partially offsets the heating savings from the damper.

Bottom line: the dampered system trades fan electricity cost for savings on extreme-temperature bins. The net benefit depends heavily on your climate, CFM settings, and how cold your winters get.

Important: the infiltration credit creates a nonlinear effect at low CFM. If your required ventilation rate (say 30 CFM) is close to the infiltration credit (e.g. ~23 CFM for a leaky home), then the net conditioned CFM is very small — only 7 CFM. Raising the slider from 30 to 40 CFM increases net conditioned air from 7 to 17 CFM — a 2.4× jump in heating load — even though the slider only moved 33%. This is why costs can look surprisingly different between systems set to similar but not identical CFM values. Set all three CFM sliders to the same value to make a clean apples-to-apples comparison.

Parameter	Default	Notes
ACH₅₀ (leaky)	13	Typical older home, low estimate scenario
ACH₅₀ (tight)	3	Well-sealed modern home, high estimate scenario
Ceiling height	8 ft	Used to estimate volume for infiltration credit
Sensible factor	1.1	BTU/hr per CFM per °F for air at standard conditions
Latent multiplier	1.3×	Applied to cooling loads to account for moisture
Terrain factor	17	ASHRAE 62.2 default suburban/rural shielding class

Consider a Fresh Air Intake

While I like the idea of ERVs and HRVs, they are fairly expensive ($3-6K installed), require extra maintenance (filters need to be changed), and don't save that much money, even in cold climates like Minneapolis. At least if you run lower flows like 10 cubic feet per minute per person that I have found work well in most homes.

A simple fresh air intake is much less expensive so you can use the budget upgrading other parts of the system (might I suggest fully communicating equipment?) The intake does require the fan being on 24/7 to work.

Take a look at this blog about how I handle fresh air in our own short term rentals.