Short answer: one ton of refrigeration is 12,000 BTU/hr, and a Philippine room typically needs 500–800 BTU/hr per square metre of floor area before you add people and equipment — roughly one ton per 15–24 sq m. That range is wide on purpose. Sun exposure, glazing, ceiling height, headcount and equipment move the answer far more than floor area does, which is why sizing off a single per-square-metre number is how rooms end up cold, clammy and non-compliant at the same time.
1 TR = 12,000 BTU/hr = 3.517 kW · Code comfort condition: 20–24 °C, 50–60% RH, 4.60–7.60 m/min air movement in the living zone · Mechanical permit fee: ₱90.00/ton up to 100 tons packaged/centralized, ₱60.00/unit window type · Annual inspection: ₱25.00/ton first 100 tons, ₱40.00/unit window type
The Philippine National Building Code does not tell you how many tons to install. What it does do — in the Refrigeration and Air Conditioning provisions of the 2004 Revised IRR of PD 1096 — is fix the condition the installation has to deliver, and set physical requirements for the ductwork:
The Comfort Condition Is a Code Requirement
"The effective temperature and relative humidity of the air to be used for comfortable cooling shall be maintained at 20°Celsius to 24°Celsius and 50% to 60%, respectively, with 4.60 to 7.60 meters per minute air movement within the living zone." Read that humidity band carefully — it is the reason oversizing is a compliance problem, not just an efficiency one.
Ductwork Requirements Owners Rarely Check
Non-combustible ducts only — "steel, iron, aluminum or other approved materials," with only fire retardant lining permitted on the inside.
Access doors must be provided at all automatic dampers, fire dampers, thermostats and other apparatus requiring service and inspection.
Sealed penetrations — where ducts pass through walls, floors or partitions, the space around the duct must be sealed with fire-resistant material equivalent to that of the wall, floor or partition, to prevent the passage of flame or smoke.
Condensate must be drained — water from evaporators, condensers and other machinery must be properly collected into a suitable water or drainage system.
The duct-penetration rule is the one that quietly fails a fit-out inspection. A perfectly good split-type installation becomes a fire-code defect the moment a refrigerant and drain penetration through a rated wall is left unsealed.
A real cooling load calculation adds up where the heat actually comes from, rather than multiplying floor area by a single number. Three components dominate in a Philippine interior:
Estimates cooling load by the component method, converts it to tons of refrigeration and typical Philippine HP ratings, then applies the IRR of PD 1096 mechanical permit and annual inspection fee schedules.
Philippine suppliers quote horsepower, engineers quote tons, and nameplates quote BTU/hr. They are not interchangeable in the strict sense — horsepower originally described the compressor motor, not the cooling output — but the market has settled on conventional equivalents:
| Market rating | Approx. cooling capacity | Approx. tons | Typical use |
|---|---|---|---|
| 0.75 HP | ≈ 6,000–7,000 BTU/hr | ≈ 0.5 TR | Small bedroom, 8–12 sq m |
| 1.0 HP | ≈ 9,000–10,000 BTU/hr | ≈ 0.8 TR | Bedroom, 12–18 sq m |
| 1.5 HP | ≈ 12,000 BTU/hr | 1.0 TR | Large bedroom or small office |
| 2.0 HP | ≈ 18,000 BTU/hr | 1.5 TR | Living area, 25–35 sq m |
| 2.5 HP | ≈ 24,000 BTU/hr | 2.0 TR | Open office bay, 35–45 sq m |
Buy on the nameplate capacity in BTU/hr or kW, not on the horsepower badge. The HP figure is a marketing convention and varies between brands; the rated capacity does not.
The instinct to "add a bit extra for safety" is the most common sizing error, and the IRR's own comfort condition explains why it backfires. Air conditioning removes moisture only while the coil runs long enough to condense it. An oversized unit hits setpoint fast, shuts off early, and never completes that dehumidification cycle.
A room can sit comfortably at 22 °C — inside the Code's 20–24 °C band — while relative humidity climbs well past the required 50–60% because the unit short-cycles. The temperature reads compliant and the humidity is not. Occupants describe it as "cold but sticky," the fix gets misdiagnosed as insufficient capacity, and a second oversized unit makes it worse.
The other costs of oversizing are more familiar: higher equipment cost, higher starting current, more compressor wear from frequent cycling, and a larger electrical service than the building actually needs. That last one compounds — see how connected load drives service and transformer sizing.
Air conditioning falls under the Mechanical Permit, one of the seven ancillary permits that must accompany a building permit — the IRR states plainly that "the Building Permit is null and void if not accompanied by the Ancillary Permits." Mechanical plans must be signed and sealed by a Professional Mechanical Engineer, not by the supplier installing the units.
| Mechanical permit fee (IRR of PD 1096) | Rate |
|---|---|
| Packaged/centralized air conditioning, up to 100 tons | ₱90.00 per ton |
| Every ton or fraction thereof above 100 tons | ₱40.00 per ton |
| Window type air conditioners | ₱60.00 per unit |
| Refrigeration (cold storage), per ton or fraction thereof | ₱40.00 per ton |
| Ice plants, per ton or fraction thereof | ₱60.00 per ton |
| Mechanical ventilation, per kW or fraction of blower or fan | ₱40.00 per kW |
The IRR closes that door in the schedule itself: "In a series of AC/REF systems located in one establishment, the total installed tons of refrigeration shall be used as the basis of computation for purposes of installation/inspection fees, and shall not be considered individually." Ten separate 5-ton systems in one building are assessed as 50 tons.
Neither gap is a reason to skip the permit — it is a reason to raise the question early, in writing, rather than accept a number at the counter.
A component estimate is a sanity check, and a good one. It is not a design. A full load calculation accounts for hourly solar gain by orientation, the thermal mass of the actual wall and roof construction, ventilation air quantities for the occupancy, duct and fan gains, and diversity between zones — and it produces the airflow and equipment schedule a Professional Mechanical Engineer will seal.
The comfort conditions, ductwork requirements, mechanical permit fees, annual inspection fees and kW-per-ton evaluation figures quoted above were read from the text of the 2004 Revised IRR of PD 1096 as published by the DPWH. The BTU/hr-per-square-metre base loads, occupant loads and the 10% design allowance used in the calculator are engineering rules of thumb calibrated for Philippine conditions — they are not code values and are not a substitute for a sealed mechanical design. Equipment HP equivalents are Philippine market convention, not an exact unit conversion.
How many tons of aircon do I need for a room in the Philippines?
For a typical Philippine room, a working range is 500 to 800 BTU per hour per square metre of floor area before adding people and equipment, which is roughly one ton of refrigeration for every 15 to 24 square metres. The spread is wide because sun exposure, glazing area, ceiling height, occupancy and equipment load move the answer more than floor area does. Use a component estimate rather than a flat per-square-metre figure, and have a Professional Mechanical Engineer run a full load calculation before you buy equipment for anything larger than a single room.
How many BTU is one ton of air conditioning?
One ton of refrigeration is 12,000 BTU per hour, or about 3.517 kilowatts of cooling. In the Philippine retail market units are usually sold in horsepower: 1.0 HP is roughly 9,000 BTU/hr, 1.5 HP roughly 12,000 BTU/hr, 2.0 HP roughly 18,000 BTU/hr and 2.5 HP roughly 24,000 BTU/hr. Those HP figures are market convention rather than an exact conversion, so always check the nameplate cooling capacity in BTU/hr or kW instead of buying by horsepower alone.
Do you need a permit to install air conditioning in the Philippines?
Air conditioning work falls under the Mechanical Permit, one of the seven ancillary permits under the IRR of PD 1096. The IRR's mechanical fee schedule charges packaged or centralized air conditioning systems at ₱90.00 per ton up to 100 tons and ₱40.00 per ton or fraction above 100 tons, and window type air conditioners at ₱60.00 per unit. Crucially, where a series of air conditioning or refrigeration systems sits in one establishment, the total installed tons of refrigeration is the basis of computation and the units are not considered individually.
What indoor temperature does the Philippine Building Code require?
The 2004 Revised IRR of PD 1096 states that the effective temperature and relative humidity of air used for comfortable cooling shall be maintained at 20 to 24 degrees Celsius and 50 to 60 percent respectively, with 4.60 to 7.60 metres per minute of air movement within the living zone. This is a design requirement, not a preference, and the humidity band is the reason an oversized unit can fail to comply even while the room feels cold.
Is a bigger aircon always better?
No. An oversized unit reaches the thermostat setpoint quickly and shuts off before it has run long enough to remove moisture, leaving a room that is cold and clammy at a relative humidity above the 50 to 60 percent band the IRR requires. Short cycling also increases wear on the compressor and raises energy use. Correct sizing is the goal, not maximum capacity.
Cooling load determines electrical service, ceiling void depth, and slab penetrations. Deciding it after the structural drawings are sealed is how projects end up with a service upgrade and a chased beam. AEDO delivers coordinated MEPFS design nationwide, with design-build in Negros Oriental.