The "Degree Hours" Calculation of Building Heating: Why Can Infrared Radiant Heating Lower Room Temperature from 22°C to 18°C and Still Be More Comfortable?

Author:

xiaolanjing

I. Understanding Building Heating Energy Consumption in One Chart: What Are "Degree Hours"?

The technical manual chart you uploaded reveals the core calculation logic of building heating energy consumption:

Heating demand depends on the indoor-outdoor temperature difference. Building heat loss is divided into two parts — transmission loss through roofs and walls, and ventilation loss through ventilation and door/window leakage.

The Duration Diagram in the chart is a standard tool for calculating annual heating energy consumption: the X-axis represents the 8,760 hours in a year, and the Y-axis represents outdoor temperature. The area under the outdoor temperature curve represents the annual temperature distribution, while the red area between the indoor target temperature line (e.g., 20°C) and the outdoor temperature curve is the Degree Hours — which is directly proportional to annual heating energy consumption.

Taking most regions of China as an example, the annual average temperature is approximately +8°C, and heating is required for about 6 months (4,380 hours) per year. This is the baseline of building heating energy consumption.

II. The Pain Point of Traditional Heating: Heating the Air, Not the People

The logic of traditional radiators and air conditioner heating is "heat the air first, then the air heats the people." This brings two problems:

High thermal inertia: It takes 10–30 minutes for an air conditioner or heater to reach the set temperature after being turned on; after shutdown, residual heat continues to dissipate, making precise control difficult.
High air temperature ≠ human comfort: Hot air accumulates upward, with high temperatures near the ceiling and low temperatures in the human activity zone, creating "hot head, cold feet." To keep feet warm, the room temperature has to be set to 22°C or even higher.

The logic of infrared radiant heating is completely different — it directly heats people and objects, like sunlight shining on the body, making people feel warm without heating the air.

III. Why Can Infrared Radiant Heating Save 30%–50% Energy?

Infrared radiation waves emitted by infrared heating lamps are absorbed by the human body, floors, and furniture and converted into heat energy. Without heating the air, heat loss is small and response is fast:

Thermal conversion efficiency: The average thermal conversion efficiency of mainstream infrared heating products reaches 92.4%, with top models reaching 94.8%–98%. (Source: aureumproducts.co.uk)
Energy saving rate: Infrared radiant heating is 30%–40% more energy-efficient than traditional resistance heaters; 20%–30% more energy-efficient than traditional convective heating (air conditioners, electric heaters); zoned heating in commercial scenarios can achieve 40%–50% energy savings. (Source: Dataintelo, Heater Guides)
Response speed: Instant heating with no warm-up needed; compared with optimally designed water underfloor heating, infrared systems still have a 5%–10% efficiency advantage due to low thermal inertia. (Source: Fraunhofer-Informationszentrum Raum und Bau IRB)
Smart control: Reducing nighttime temperature by 4°C for 8 hours can save 15%–20% energy; unoccupied period control saves 10%–20%; dynamic electricity price scheduling saves 8%–15%; combining all three can save 30%–45% energy. (Source: EnergieFluss24)

IV. The Most Counterintuitive Finding: Is 18°C Room Temperature More Comfortable Than 22°C?

A study by TU Dresden (Technical University of Dresden) in Germany yielded a surprising conclusion:

Reducing office room temperature from 22°C to 18°C while installing local infrared heating at workstations reduces total energy consumption by approximately 30%;
Each workstation requires only 120W of infrared heating power to achieve thermal comfort. (Source: ETHERMA)
Principle: Infrared radiation acts directly on the human body; even if the air temperature is 2–4°C lower, the human body's perceived temperature is actually higher — because the body directly absorbs radiant heat, rather than being "warmed up" by air.

This means: traditional heating sets room temperature to 22°C, but in fact a large amount of energy is wasted heating unoccupied air. Infrared local heating makes "heat wherever people are" possible.

V. Market Trend: From Industry to Buildings, Infrared Heating Accelerates Penetration

The global indoor infrared heating market size was approximately USD 2.24 billion in 2025, accounting for about 60% of the overall infrared heater market. (Source: PW Consulting)
The commercial near-medium infrared heating market is expected to grow from USD 1.56 billion in 2025 to USD 2.65 billion in 2032, with a CAGR of 7.8%. (Source: Simply Air Conditioning London)
The payback period for commercial infrared heating systems is typically 18–36 months. (Source: Dataintelo)
Driven by China's "coal-to-electricity" policy, a pilot village in Northeast China saw monthly electricity costs decrease by 15% after switching to infrared heating. (Source: Yancheng Ruihaojia Electric Heating Technology Co., Ltd.)

VI. Lanjing Optoelectronic: Providing Core Heating Lamps for Infrared Heating

Linyi Lanjing Optoelectronic Technology Co., Ltd. has deep expertise in the quartz infrared heating field. Its core products cover a full range of quartz infrared heating lamps, including carbon fiber lamps (medium wave, suitable for comfortable heating) and tungsten halogen lamps (short wave, suitable for rapid temperature rise), supporting full-parameter customization of dimensions, voltage, power, and gold reflective coatings.

For building and commercial heating scenarios, Lanjing Optoelectronic's heating lamps offer three major adaptation advantages:

Medium-wave comfort band: Carbon fiber lamps emit 2–5μm medium-wave infrared, matching the human body's absorption peak, providing a warm feeling without dryness;
Gold reflective coating: Minimizes backside radiation loss, concentrating energy toward human activity zones;
Long-life reliability: Quartz tube bodies are high-temperature resistant and thermal shock resistant; carbon fiber lamps have a design life of over 8,000 hours, suitable for long-term operation in commercial buildings.

Summary

The essence of building heating energy consumption is "Degree Hours" — indoor-outdoor temperature difference multiplied by hours. Traditional heating maintains comfort by heating the air in the entire room, consuming a large amount of energy on air in unoccupied areas; infrared radiant heating directly heats people and objects, making a room temperature reduction from 22°C to 18°C actually more comfortable while saving 30%–50% energy. Driven by global building decarbonization and "coal-to-electricity" policies, infrared heating is moving from industrial workshops to offices, commercial spaces, and residences. With wavelength matching and long-life design of quartz infrared heating lamps, Lanjing Optoelectronic provides core heating elements for the low-carbon transition of building heating.

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