Support

Does LoadSizer need an internet connection?

No. The app is 100% offline — every calculation runs on your device, instantly, anywhere on a job site with no signal.

What's the difference between Quick and Detailed mode?

Quick mode asks for just floor area, ceiling height, room type, main sun-facing side, insulation level, occupants, and whether it's the top floor — enough for an instant estimate. Detailed mode lets you describe the room's actual construction: exterior walls and windows by orientation (area, U-value, SHGC, shading), roof, ground-floor slab, occupants and activity level, lighting, equipment, and outdoor-air ventilation (ACH), for a more precise result.

What do I get as a result?

Sensible, latent, and total cooling load (in W, Btu/h, kW, or ton — your choice) plus the sensible heat ratio (SHR), a heating load for the coldest design day, a bar-chart breakdown by component (walls, windows, roof, people, lighting, equipment, outdoor air), and a recommended commercial AC size rounded up to a size you can actually buy, shown in Btu/h, ton, and the common HP label.

Where does the climate data come from?

Outdoor design temperatures for the 35 built-in cities come from ASHRAE Climatic Design Conditions, not a single number applied to an entire country. If your city isn't listed, you can enter your own design climate (outdoor design dry-bulb, coincident wet-bulb, latitude, elevation) under Settings.

What calculation method does LoadSizer use?

A simplified version of the ASHRAE 1997 Fundamentals CLTD/SCL/CLF (Cooling Load Temperature Difference / Solar Cooling Load / Cooling Load Factor) method — a well-established approach for estimating room cooling loads from wall, roof, and glass construction, solar orientation, and internal/ventilation gains. It uses each component's peak value rather than a full hour-by-hour simulation, which is intentionally on the conservative (slightly oversized) side for a quick sizing tool.

Is this the same as a full Manual J calculation?

No. LoadSizer is meant for fast sizing guidance — a room-by-room estimate you can get in under a minute. It is not a substitute for a full Manual J or ASHRAE RTS (Radiant Time Series) load calculation performed by a qualified professional, and it is not certified or endorsed by ASHRAE or ACCA. Always verify against a full calculation for a final design or permit submission.

How is the recommended AC size chosen?

LoadSizer takes your calculated cooling load, adds your chosen safety factor (10% by default, adjustable in Settings), and rounds up to the nearest commercial split-AC size (5,000 to 60,000 Btu/h). If the chosen size is more than 30% above your calculated load, or the load per floor area looks unusually low or high, the app flags it so you can double-check your inputs.

Can I change units?

Yes — Settings lets you pick temperature (°C/°F), area (m²/ft²), length (m/ft), and power (W, Btu/h, kW, ton, or HP) independently. Changing display units never changes the underlying calculation, which always runs in SI internally.

Can I work with multiple rooms and buildings?

Yes — each project holds any number of rooms, and you can create multiple projects (e.g. for different houses or job sites). Free accounts can add one room to one project; LoadSizer Pro (a one-time purchase, not a subscription) unlocks unlimited rooms and projects.

How does PDF export work?

LoadSizer Pro can generate a PDF summary of a project — every room's cooling/heating load and recommended size, plus the building total — and hands it to your device's native share sheet so you can save it, print it, or send it however you like.

Is LoadSizer available in other languages?

Yes — English, Español, 中文（简体）, Português (Brasil), 日本語, 한국어, Tiếng Việt, and ไทย are all supported. Switch under Settings → Language.

Is this a subscription?

No. LoadSizer Pro is a one-time purchase. There are no subscriptions and no ads.

Does the app collect any of my data?

No — see the Privacy Policy for details.