While the formula "square feet / wattage of the fixture" is a very rough guideline, it's not accurate enough to rely on when converting a school into a church. There are many factors to consider to ensure proper lighting for your new worship space. Here's why this formula falls short and a better approach

Why the Simple Formula is Inadequate:
Desired Light Levels (Footcandles)

Different spaces require different light levels. Classrooms need more light for reading and writing than a sanctuary for prayer. Churches often need varied light levels for different activities, such as services, fellowship, and meetings. That formula doesn't account for needed light levels.

Fixture Efficiency (Lumens per Watt)

LEDs vary greatly in their efficiency. A higher-quality LED fixture will produce more light (lumens) per watt than a cheaper one. The formula just looks at watts, not lumens.

Room Reflectance

Light bounces off surfaces. A room with white walls and a light-colored ceiling will require less light than a room with dark walls and a dark ceiling. This is not taken into account with the formula.

Ceiling Height

Higher ceilings require more powerful fixtures or more fixtures to get the light down to the floor.

Fixture Distribution

How the light is spread out from the fixture affects how evenly the room is lit.

Purpose of the Room

A sanctuary will need different lighting than a classroom used for Sunday school.

Local Codes and Regulations

There may be specific lighting requirements for churches or public spaces in your area.

A Better Approach to Lighting Your Church


Determine Required Footcandles

Research recommended footcandle levels for the different spaces in your church.

Sanctuary/Worship Area

Consider different scenarios: general lighting for services, brighter lighting for performances, and softer lighting for prayer.

Fellowship Hall

Lighting for dining, social activities, and possibly performances.

Classrooms

Lighting for reading, writing, and other activities.

Offices

General office lighting.

Hallways and Entryways

General illumination for safety and wayfinding.A good starting point is to use IES (Illuminating Engineering Society) recommendations. You can often find general guidelines online.2.

Calculate Lumens Needed

Use the following formula (more accurate than just square feet/wattage):

Lumens Needed = (Footcandles x Area in Square Feet) / Light Loss Factor Footcandles

The desired light level for the space.

Area in Square Feet

The area of the room.

Light Loss Factor (LLF)

This accounts for dirt accumulation on the fixtures over time and depreciation of the light source. A typical LLF is between 0.6 and 0.
8. Use a lower LLF for dirtier environments or when you expect less frequent cleaning.3.

Choose LED Fixtures Based on Lumens

Select LED fixtures that provide the total lumens calculated for each area. Look for the "lumens" rating on the fixture packaging.4.

Consider Color Temperature

The color temperature of the light affects the mood.

Warm White (2700K-3000K)

Creates a cozy, inviting atmosphere, suitable for fellowship halls and relaxation areas.

Neutral White (3500K-4100K)

A good general-purpose color, suitable for offices and classrooms.

Cool White (5000K-6500K)

Provides a bright, energetic light, suitable for task lighting or areas where high visibility is needed.5.

Consider CRI (Color Rendering Index)

CRI measures how accurately a light source renders colors compared to natural sunlight. A higher CRI (80 or above) is generally preferred, especially in areas where color accuracy is important.6.

Layout and Distribution

Arrange the fixtures to provide even light distribution across the space. This might involve using more fixtures in some areas than others.7.

Dimming

Consider using dimming systems, especially in the sanctuary, to create different moods for different services and events.8.

Professional Consultation



The best approach is to consult with a lighting professional or electrical engineer. They can perform a lighting analysis, taking into account all the factors mentioned above, and recommend the most appropriate fixtures and layout for your specific needs. This is especially important for a project of this scale.

Example (Simplified)

Let's say you have a classroom that is 20ft x 30ft (600 sq ft). You want 50 footcandles of light in the classroom.

Lumens Needed = (50 footcandles x 600 sq ft) / 0.7 (LLF) Lumens Needed = 42,857 Lumens

You're using 2x2 LED fixtures that produce 3500 lumens each. Fixtures Needed = 42,857 Lumens / 3500 Lumens per Fixture Fixtures Needed = Approximately 12.3 fixtures

Therefore, you would need approximately 12-13 of these fixtures in that classroom. This is a simplified example and DOES NOT take into consideration the actual layout of the room and the distribution of the light coming from the fixtures.

Key Takeaways

The simple formula is too simplistic for a project like converting a school into a church. Focus on lumens, footcandles, and light distribution. Consider the color temperature and CRI of the light.*

Consult with a lighting professional for the best results and to ensure code compliance.

By taking a more comprehensive approach to lighting design, you can create a beautiful and functional space for your church. Flag for review