Lighting Rules Of Thumb (HVAC)

Offices, Commercial

  • General 1.5–3.0 Watts/ ft²
  • Private 2.0–5.0 Watts/ ft²
  • Conference, Meeting Rooms 2.0–6.0 Watts/ ft²

Banks, Court Houses, Municipal Buildings, Town Halls

2.0–5.0 Watts/ ft²

Police Stations, Fire Stations, Post Offices

2.0–3.0 Watts/ ft²

Precision Manufacturing

3.0–10.0 Watts/ ft²

Computer Rooms

1.5–5.0 Watts/ ft²


1.5–3.0 Watts/ ft²


1.5–2.5 Watts/ ft²

Cocktail Lounges, Bars, Taverns, Clubhouses, Nightclubs

1.5–2.0 Watts/ ft²

Hospital Patient Rooms, Nursing Home Patient Rooms

1.0–2.0 Watts/ ft²

Hospital General Areas

1.5–2.5 Watts/ ft²

Lighting Rules of Thumb 103

Medical/Dental Centers, Clinics, and Offices

1.5–2.5 Watts/ ft²


1.0–4.0 Watts/ ft²

Apartments (Eff., 1 Room, 2 Room)

1.0–4.0 Watts/ ft²

Motel and Hotel Public Spaces

1.0–3.0 Watts/ ft²

Motel and Hotel Guest Rooms, Dormitories

1.0–3.0 Watts/ ft²

School Classrooms

2.0–6.0 Watts/ ft²

Dining Halls, Lunch Rooms, Cafeterias, Luncheonettes

1.5–2.5 Watts/ ft²

Libraries, Museums

1.0–3.0 Watts/ ft²

Retail, Department Stores

2.0–6.0 Watts/ ft²

Drug, Shoe, Dress, Jewelry, Beauty, Barber, and Other Shops

Watts/ ft²


1.0–3.0 Watts/ ft²

Malls, Shopping Centers

1.0–2.5 Watts/ ft²


1.0–2.5 Watts/ ft²

Auditoriums, Theaters

1.0–3.0 Watts/ ft² (3)


1.0–3.0 Watts/ ft²

Bowling Alleys

1.0–2.5 Watts/ ft²


What is the purpose of lighting rules of thumb in HVAC design?
The purpose of lighting rules of thumb is to provide a rough estimate of the lighting load in a building, which is then used to size the HVAC system. This is important because lighting can account for a significant portion of the total heat gain in a building, and accurate estimation of this load is crucial for designing an efficient and effective HVAC system.
How do I apply lighting rules of thumb to different types of spaces?

Lighting rules of thumb vary depending on the type of space. For example, offices typically require 1.5-3.0 Watts/ft², while precision manufacturing spaces require 3.0-10.0 Watts/ft². By using the appropriate rule of thumb for the specific space type, designers can estimate the lighting load and design the HVAC system accordingly. It’s essential to consider the specific requirements of each space, including the type of lighting, occupancy, and activities taking place.

What factors can affect the accuracy of lighting rules of thumb?

Several factors can affect the accuracy of lighting rules of thumb, including the type and efficiency of lighting fixtures, the reflectance of surfaces, and the occupancy patterns of the space. Additionally, the use of natural light, task lighting, and other lighting strategies can also impact the overall lighting load. Designers should consider these factors when applying lighting rules of thumb to ensure a more accurate estimate of the lighting load.

Can lighting rules of thumb be used for energy-efficient design?

Yes, lighting rules of thumb can be used to design energy-efficient HVAC systems. By using energy-efficient lighting fixtures and designing the system to meet the actual lighting needs of the space, designers can reduce the overall energy consumption of the building. Additionally, strategies such as using natural light, occupancy sensors, and dimming controls can further reduce energy consumption and improve the overall efficiency of the HVAC system.

How do lighting rules of thumb impact HVAC system sizing?

Lighting rules of thumb directly impact HVAC system sizing, as the estimated lighting load is used to determine the required cooling capacity of the system. If the lighting load is underestimated, the HVAC system may be undersized, leading to inadequate cooling and discomfort for occupants. Conversely, if the lighting load is overestimated, the HVAC system may be oversized, leading to wasted energy and increased costs.

Are there any limitations to using lighting rules of thumb in HVAC design?

Yes, there are limitations to using lighting rules of thumb in HVAC design. These rules are general guidelines and may not accurately reflect the specific conditions of a particular building or space. Additionally, they do not take into account other factors that can impact the HVAC system, such as equipment heat gain, ventilation requirements, and outdoor air temperatures. Designers should use lighting rules of thumb as a starting point and consider other factors to ensure a comprehensive and accurate HVAC design.