# Outdoor Lighting Design Calculations – Part Four

In the previous Article "
Outdoor Lighting Design Calculations – Part One ", I indicated that The outdoor lighting can be classified according to application as follows:

1. General lighting,
2. Accent lighting,
3. Orientation lighting,
4. Floodlighting,
6. Sports lighting.
And I explained the facade lighting in this previous article.

Also, In the previous article "
Outdoor Lighting Design Calculations – Part Two ",I indicated that the Floodlighting is generally used in (5) types of lighting design which are:

2. Wall washing lighting,
3. Signage lighting,
4. Area lighting,
5. Vegetation.
And I explained the facade lighting in this previous article. I explained also the wall washing, signage and Area lighting in the previous article " Outdoor Lighting Design Calculations – Part Three ".

Today, I will continue explaining the last type of flood lighting;Vegetation lighting as follows.

Vegetation Lighting

In the field of landscaping, trees are the most important elements for forming areas. The shape and size of the trunk and tree crown (upper part) vary depending on the type of tree. So, lot of Vegetation lighting criteria for the trees can be found based on number and distribution of these trees as follows:

1. Single tree,
2. Lined trees,
3. Group of trees.

First: Vegetation lighting for single tree

Vegetation lighting criteria for single tree differ based on the following factors:

1. Tree size,
2. Form of tree,
3. Season.

1- Vegetation lighting according to tree size

Size of the trunk and tree crown (upper part) divide the tress into two types as follows:
1. Large tree,
2. Small tree.

A- Large trees

We have (7) scenarios for Vegetation lighting of large trees as follows:

1- Floodlight in front: Floodlights aimed upwards make the tree crown (upper part) appear three-dimensional.

2- Floodlight on the right: Floodlights aimed upwards make the tree crown (upper part) appear three-dimensional.

3- Floodlights right and left: Two floodlights from the front, yet to the side, illuminate the crown (upper part) evenly as a voluminous mass, while floodlights mounted at the side add greater emphasis to the three-dimensionality.

4- Floodlights on three sides: Floodlights arranged around three sides illuminate the crown (upper part) evenly from all sides and reduce the three-dimensionality of the tree form.

5- Floodlight behind: Floodlights in the background create back-lighting and make the tree crown (upper part) into a silhouette

6- Uplight: Uplights at the trunk accentuate the trunk as a linear feature and visually connect the crown (upper part) to the ground.

7- Spotlight from above: Depending on the season, light from above will either emphasize the contour of the crown (upper part) or accentuate the shadows of the branch structure on the ground.

Recommendation for Vegetation lighting of large trees:
• On large trees, several luminaires may be necessary to achieve an even illumination and to avoid a distorted perception of light and dark parts.
• Luminaires arranged on several sides give an even illumination of the tree, while one or two luminaires create a greater three-dimensional effect.
• Narrow-beamed uplights are suitable for highlighting any striking, tall tree trunks.
• The texture of the bark is brought out stronger when lighting from the front.
• Positioning the luminaires to the side gives rise to a narrow line of light on the trunk.
• When illuminating a wall behind a tree, the silhouette of the crown (upper part) and trunk becomes apparent.
• Spotlights mounted in atria or on facades can cast the contour of the tree and/or branches as a shadow on the ground.

B- Small trees

If we make a Comparison between Vegetation lighting of large and small trees, we will find that one or two luminaires accentuate trees of small dimensions while several floodlights produce an even illumination of large, fully grown trees to avoid a distorted perception of light and dark parts.

Recommendation for Vegetation lighting of large trees:

• Flexible, directable luminaires with ground spikes can be repositioned and re-aimed as the tree grows.
• Luminaires recessed into the ground blend into the area of landscape better but require more work to reposition however.
• Tree growth and avoiding glare are two points that must be considered when arranging and aiming the luminaires.

2- Vegetation lighting according form of tree

The most well-known tree forms are as follows:
1. Rounded,
2. Weeping,
3. Columnar,
4. Conical,
5. Palm.

1- Rounded
Tree:

2- Weeping
Tree:

3- Columnar
Tree:

4- Conical
Tree:

5- Palm Tree:

Recommendation for Vegetation lighting for different tree forms:
• Floodlight illumination emphasizes the shape of the tree crown (upper part) as a solid volume.
• Positioning the luminaires close to the tree underlines with grazing light the texture of the crown (upper part) and of the trunk.
• The illumination from below brings out the three-dimensionality of the crown (upper part) when the foliage is quite open.
• Rounded, weeping trees with dense, low hanging foliage that cannot be seen through, lend themselves to floodlight illumination and the luminaires are best positioned outside the area under the tree.
• On spreading trees with thin, see-through foliage, illuminating from within the area under the tree, using uplights allows the whole tree crown (upper part) to appear aglitter.
• Illuminating a tree with grazing light requires a flat incident beam at approximately 15 degrees.
• Spherical trees require a greater distance between luminaire and crown (upper part) than columnar trees do here.
• Narrow-beamed uplights are particularly suitable for lighting high palms.
• The desired illuminance must be selected to suit the reflectance of the leaves.

3- Vegetation lighting according to season

The appearance of trees is characterized by blossom (flowers) and foliage (tree leaves) in the course of the seasons as follows:

1. Spring: Floodlit illumination of the tree crown (upper part) particularly brings out the beauty of the outermost blossom.
2. Summer: the dense foliage makes the crown (upper part) appear as a solid mass.
3. Autumn: Colored leaves are characteristic for the autumn.
4. Winter: the lighting effect is reduced to the filigree branch work.

Recommendation for Vegetation lighting in different seasons:

• Lamp selection is a factor that influences the color of light and the color rendition of the leaves and blossom.
• Daylight white colors of light emphasize blue-green foliage colors, whereas warm white colors of light accentuate brownish-red leaves.

Second: Vegetation lighting for lined trees

The most well-known lined shapes of trees are as follows:
1. One row,
2. Two opposite rows (Tree-Lined Avenue),
3. Group of rows.

1- Vegetation lighting for one Row of trees

The effectiveness of rows of trees to delineate space depends to a very large extent on the type of tree. Thus, depending on the type of tree, a closely planted row of trees can appear as a wall or a “colonnade”.
We have (3) scenarios for Vegetation lighting for Rows of trees as follows:

1. Floodlight: Floodlights with asymmetric light distribution give homogenous light from base to canopy even on tall and broad rows of trees
2. Uplight: Narrow-beamed uplights highlight the tree trunk as a vertical, linear feature.
3. Spotlight: Upwardly directed spotlights emphasize the tree canopy.

Recommendation for Vegetation lighting for Clusters of Rows of trees:
• Narrow-beamed and well-aimed luminaires reduce the glare and the spill light into the surroundings.
• The tree growth must be considered when positioning and aiming the luminaires.

2- Vegetation lighting for Two opposite Rows (Tree-lined avenue)

The spatial profile of tree-lined avenues depends to a very large extent on the type of tree. Thus, depending on the type of trees, an avenue of narrowly spaced trees can act as a wall and segregate a definite area or can appear as a colonnade.

We have (3) scenarios for Vegetation lighting for Tree-lined avenue as follows:

1. Floodlight: Floodlights with asymmetric light distribution give homogenous lighting from base to canopy even on extensive avenues of tall trees.
2. Uplight: Narrow-beamed uplights highlight the tree trunk as a vertical, linear feature.
3. Spotlight: Upwardly directed spotlights emphasize the tree crowns.

Recommendation for Vegetation lighting for Tree-lined avenue:
• Narrow-beamed and well-aimed luminaires reduce the glare and spill light into the surroundings.
• The tree growth must be considered when positioning and aiming the luminaires.

3- Vegetation lighting for group of tree rows:

Its Vegetation lighting criteria is a multiple of that for one row.

Third: Vegetation lighting for Group of trees

The groups of trees can be classified into tow shapes as follows:
1. Clusters of trees: very near trees to each other act as one unit, so luimaires are used for the whole group not for each tree.
2. Group of scattered trees: trees spaced from each other, so each tree can have its own luminaries.

1- Vegetation lighting for Clusters of trees

We have (3) scenarios for Vegetation lighting for Clusters of trees as follows:

1. Floodlight at front: Floodlights located in front illuminate the tree crowns evenly.
2. Floodlights at sides: Floodlights positioned at the sides produce a hard contrast of light and shadow. Luminaires on two sides avoid hard shadows.
3. Uplights: Uplights at the trunk emphasize the trunk as a vertical linear feature.
Recommendation for Vegetation lighting for Clusters of trees:

• The cluster of trees can be visually differentiated by using different luminaires and differently aimed.
• The decentralized illumination of trees allows a differentiated lighting of a cluster of trees.
• Spatial depth is created by adding lighting emphasis in the foreground, middle ground and background. Stronger brightness contrasts support this effect.
• Narrow- beamed luminaires provide highlighting, while broad-beamed floodlights take on the task of general lighting.
• Having several luminaires with high cut-off angles reduces the glare compared to a few broad-beamed luminaires.
• Narrow-beamed and well-aimed luminaires reduce the superfluous emission of light into the surroundings.
• Spotlights are suitable for additional highlights.
• Tree growth and the avoidance of glare are to be considered when positioning and aiming the luminaires.

2- Vegetation lighting for group of scattered trees

The tree crowns of narrowly spaced trees combine to take on the effect of a canopy.
We have (2) scenarios for Vegetation lighting for group of scattered trees as follows:

1. Spotlights: Broad, upwardly directed beams of light emphasize the underside of the tree canopy.
2. Uplights: Narrow-beamed uplights highlight the tree trunk as a vertical, linear feature.

Recommendation for Vegetation lighting for Tree-lined avenue:
• Having several narrow-beamed luminaires reduces the glare compared to a few broad-beamed luminaires.
• On pathways and traffic routes, it must be ensured that the luminaires are well shielded to prevent glare.

Preferred luminaries for Vegetation lighting:
1. Spotlights
2. Floodlights
3. Uprights
Applications for Vegetation lighting:
1. Park and garden complexes
2. Entrance areas
3. Atria

In the next topic, I will explain the Outdoor Lighting design calculations methods. Please, keep following.