Sizing a cellar cooling unit comes down to one number: the volume the unit has to hold at 55°F, adjusted for how well the room is built and how hot the space behind it gets. Both WhisperKOOL and Breezaire rate their units in cubic feet, so that is the number to match.
What you need before starting
- Interior cellar dimensions in feet: length, width, ceiling height
- Which room the unit will vent into, and how hot that room gets on the worst summer afternoon
- Wall insulation R-value
- Whether the cellar has a glass wall, a missing vapor barrier, a standard interior door, or sits above grade
Step 1: Measure the room
Length times width times ceiling height, measured inside the finished room. A 5 by 7 closet with an 8 foot ceiling is 280 cubic feet.
Step 2: Find the exhaust temperature
A self-contained unit moves heat out of the cellar and into the room behind it. The hotter that room, the harder the unit works and the less it can hold. Leave a thermometer there on the hottest afternoon of the year and use that reading.
- Conditioned interior room: about 75°F
- Basement or utility room: 80 to 85°F
- Garage or attic: 85 to 95°F and sometimes higher
Manufacturers rate cellar cooling units against a room around 75°F. That is the baseline everything below adjusts from.
Step 3: Adjust for how the cellar is built
A poorly insulated cellar venting into a hot room behaves like a much larger room. Multiply your cubic feet by each factor that applies, and size against the result rather than the raw measurement.
| Condition | Multiplier |
|---|---|
| R-13 walls | 1.45 |
| R-19 walls (baseline) | 1.00 |
| R-30 walls | 0.64 |
| R-38 walls | 0.45 |
| Exhaust room hotter than 75°F | divide (exhaust temperature minus 55) by 20 |
| Glass wall or full glass door | 1.65 |
| No vapor barrier | 1.15 |
| Above grade or against an exterior wall | 1.20 |
Worked example. That 280 cubic foot closet, built with R-13 walls, venting into an 82°F basement: 280 times 1.45 for the insulation, times 1.35 for the exhaust temperature, gives 548. Size it as a 548 cubic foot room, not a 280 cubic foot one.
Step 4: Match to a rated unit
Pick the unit whose rated volume covers your adjusted number, with the least excess. Cheapest option we stock at each size, all of them self-contained and installable without a licensed technician:
| Adjusted volume | Unit | Price | Also fits |
|---|---|---|---|
| Up to 140 cu ft | Breezaire WKL 1060 | $2,148 | WKL 2200 at $2,437 |
| Up to 265 cu ft | Breezaire WKL 2200 | $2,437 | SC PRO 2000 at $3,165 |
| Up to 300 cu ft | WhisperKOOL SC PRO 2000 | $3,165 | Breezaire WKL 3000 at $3,055 |
| Up to 650 cu ft | Breezaire WKL 3000 | $3,055 | Slimline LS $3,415, SC PRO 3000 $3,425 |
| Up to 800 cu ft | WhisperKOOL Extreme 3500 Ti | $5,439 | Breezaire WKL 4000 at $3,521 covers 1,000 |
| Up to 1,000 cu ft | Breezaire WKL 4000 | $3,521 | SC PRO 4000 at $3,665 |
| Up to 1,500 cu ft | Breezaire WKL 6000 | $4,071 | WKL 8000 at $4,347 |
| Up to 2,000 cu ft | Breezaire WKL 8000 | $4,347 | SC PRO 8000 $5,165, Extreme 8000 Ti $6,559 |
Above 2,000 cubic feet no self-contained unit covers the room. You are into split and ceiling systems, which need a licensed HVAC-R technician and a signed startup checklist to keep the warranty. Those run from $6,119 to $14,669. See the WhisperKOOL buying guide for the full range.
Where sizing goes wrong
Undersizing. The unit never reaches setpoint, runs continuously, and the compressor fails years early instead of lasting its full service life.
Oversizing. The unit short-cycles, cooling fast and shutting off before it has pulled any moisture from the air. Humidity swings, corks dry, labels lift. Bigger is not safer.
Venting somewhere that cannot take the heat. A closet or a sealed garage fills with the heat the unit just removed, which raises its own intake temperature, which makes it work harder. WhisperKOOL does not recommend venting into either.
Ignoring the door. A standard interior door leaks more cooling than the rest of the envelope combined. Use an insulated door with a full perimeter seal.
Sizing to the empty room. A cellar filled with warm bottles pulls a much larger load for the first few days. Size with headroom for that first cooldown.
Let the calculator do it
The cellar cooling calculator applies every adjustment above, matches against the units we stock, and gives you the model with a cart link where the job is straightforward. Glass walls, exhaust spaces above 85°F, cellars over 2,000 cubic feet, and anything needing a split go to us instead, with your measurements attached so we are not starting from scratch.
Or send the numbers to (866) 430-2877. Authorized WhisperKOOL and Breezaire dealer since 2018.