Enter your square footage to find a CentricAir model that fits your home, the attic vent area to go with it, and how many windows to open.
Size a whole house fan by your home’s square footage and number of stories. CentricAir’s sizing guide lists the home size each model is built for, from a single room up to two story homes of 4,400 square feet. Then check your attic: you need about 1 square foot of net free attic vent area for every 750 CFM of fan airflow.
Whole house fan size calculator
Enter your home’s details below. Everything updates as you type.
The suggestion is the smallest CentricAir fan listed for your home size and number of stories, from CentricAir's sizing guide. CentricAir recommends the largest fan your existing attic ventilation can support, so a bigger model may suit you better. This is a starting point, not a replacement for a site visit.
How do you pick the right size whole house fan?
Start with your square footage, then check your attic and windows.
- Know your home.Note your living area in square feet and whether the home is one story or two.
- Find your model.Look up your home size in the CentricAir sizing table below. Each model lists the largest one story and two story home it is built for.
- Check your attic vents.Divide the fan's CFM by 750 to get the net free attic vent area you need. CentricAir rounds this to the nearest quarter square foot and lists it on every model page.
- Plan your windows.Open about 4 square feet of window for every 1,000 CFM.
What size whole house fan for a 2,000 square foot house?
For a one story home, a CentricAir 3.4, 4.0 or 4.0 ECM.
That is one of the most common sizing questions on Google. For a two story 2,000 square foot home, the CentricAir 2.7 tops out at 1,800 square feet, so the CentricAir 3.4 is again the smallest fit.
In the CentricAir lineup, a CentricAir 3.4 (3,242 CFM) is listed for single story homes up to 2,500 square feet and two story homes up to 3,400. CentricAir's own advice is to buy the largest fan your existing attic ventilation can support, and not to add roof vents just to go bigger.
| Model | Airflow (CFM) | Net free attic vent | One story, up to | Two story, up to |
|---|---|---|---|---|
| CentricAir 1.5 | 1,263 | about 1.75 sq ft | 700 sq ft (single room) | n/a |
| CentricAir 2.0 | 1,918 | about 2.5 sq ft | 900 sq ft | 1,400 sq ft |
| CentricAir 2.7 | 2,709 | about 3.25 sq ft | 1,350 sq ft | 1,800 sq ft |
| CentricAir 3.4 | 3,242 | about 4.0 sq ft | 2,500 sq ft | 3,400 sq ft |
| CentricAir 4.0 | 3,921 | about 5.25 sq ft | 3,000 sq ft | 4,400 sq ft |
| CentricAir 4.0 ECM | 4,146 | about 5.5 sq ft | 3,000 sq ft | 4,400 sq ft |
From each model's page at centricair.com, September 2026. Airflow is the California Title 24 rating.
Why does attic ventilation limit fan size?
All the air the fan moves has to leave through your attic vents.
If the vents are too small, the attic pressurizes and the fan cannot move its rated airflow. Building America recommends at least 1 square foot of net free vent area for every 750 CFM. Net free means the open area left after screens and louvers, which is smaller than the vent's outside size. That is why every CentricAir product page lists the vent area each model needs.
How many windows do I need to open?
About 4 square feet of open window for every 1,000 CFM.
That is Building America's guideline. For a 3,242 CFM fan, plan on about 13 square feet of open, screened window, or three to four ordinary windows opened partway. Open the windows in the rooms you want cooled first.
Compare CentricAir and QA-Deluxe models side by side.
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Frequently asked questions
What size whole house fan do I need for a 2,000 square foot house?
In CentricAir's sizing guide, the CentricAir 3.4 (3,242 CFM) covers single story homes up to 2,500 square feet and two story homes up to 3,400. The CentricAir 4.0 and 4.0 ECM also fit. Check your attic vent area before you choose.
How do you calculate whole house fan size?
Start with your square footage and number of stories, and find the CentricAir model listed for that home size. Then divide the fan's CFM by 750 to get the net free attic vent area it needs.
Can a whole house fan be too big?
A fan can be too big for your attic vents. Building America recommends 1 square foot of net free attic vent area per 750 CFM. Without enough vent area, the fan cannot move its rated airflow.
How many windows do I need to open?
About 4 square feet of open, screened window for every 1,000 CFM of airflow, according to Building America.
Keep reading
Sources
- U.S. Department of Energy, Building America Solution Center (PNNL), Whole-House Fans, updated Sept. 29, 2022.
- California Energy Commission, 2025 CF1R-NCB-01-E Prescriptive Newly Constructed Building form, and 2022 Energy Code Section 150.1(c)12, Whole House Fans (Energy Code Ace).
- CentricAir product specifications and prices, centricair.com, accessed Sept. 2026.
- CentricAir, What size house fan do I need?, accessed Sept. 2026.