Saving Energy Through
Ecological Landscape Design

Donald Jacobson
1991 Woodrow Wilson Biology Institute

Objectives:

1. transcribe to scale the plant features of a common landscape.
2. determine true north and south.
3. collect and record data on a table.
4. calculate a rating for and describe a definition of insulation and insolation.
5. determine the 'ecological quality' of a landscape in a quantifiable manner.

Background:

Materials:

• graph paper
• magnetic compass
• measuring tape (optional)
• keys for identifying trees and shrubs (optional)
• protractor, string, tape or thumb tack, oak tag or cardboard
• trigonometry text with trig tables including tangent (or calculator with trig functions)

Procedure:

1. Using a standard piece of graph paper, draw a picture of your landscape to scale and include as much detail as possible. Include all the relative distances from each tree and shrub to the house. Step off the distances and record them on connecting lines. If no measuring tape is available, assume one step to be 3 feet.
2. Use a compass to determine magnetic north and south as accurately as possible. Mark these directions on your drawing. Note: True north and south need to be adjusted for according to your latitude. You may contact the U.S. Geological Survey for that information in your area.
3. Label all the trees and shrubs simply as leafy (deciduous) or evergreen (coniferous) and give each plant a number, eg. E1= Evergreen #1, L2= Leaf tree #2, etc. Then record the data on the table you will prepare in procedure 4.
4. Prepare a table for collecting data as follows:

   Tree	Distance	RSU	RSO	Extras
   Evergreen
   1
   2
   3
   Etc.
   Leafy
   1
   2
   3
   Shrubs
   Evergreen
   1
   2
   3
   Etc.
   Leafy
   1
   2
   3
   Etc.
   Total

5. Calculate the rating by giving each plant in the data table a value based on the information below. You may use tally marks in the table cells and then write the numerical value for each when you are through.

In addition, give any tree an extra point for being inside a 30 ft. radius of the house, and give any shrub an extra point for being within three ft. of the foundation. Similarly, give any leaf tree an extra point for being on the south or southwest side of the house. These values reflect high insulation for evergreens and high insolation for leaf trees with lesser values for small shrubs. To calculate the overall rating for this landscape, simply add the numbers as you see below.

Total Rsu=_____

Total Rso=_____

Extra pts.=_____

_________________

Sum =_____ (quality rating)

Analysis:

Going Further:

1. Determine the types of trees in your landscape to common name or species. This can be done by asking the homeowner or by using available tree and shrub identification keys. These may be procured from the local nurseryman, a library, or from the county extension agent for horticulture. Add 1 pt. for each tree that has a very dense growth pattern for insulation or insolation according to the information in the reference books or keys.
2. Estimate the level of maturity for your trees using these same references. For example, a silver maple tree will be noted to reach a maximum height of 60 ft. for your area. If you have a silver maple that is half that tall you would say it is 50% mature. (To be exact on the height, use the triangulation method described below). Add 1 pt. for a fully mature tree, 1/2 pt. for a 50% mature tree, etc.
3. Suggest a re-planting program for a poorly designed landscape. Do not cut any trees down. Plant only new trees that will not be shaded out or encroached upon by existing specimens.
4. Draw and design a new landscape that would achieve a rating of 80 or above.

Summing Up:

1. How would you define insulation and insolation without using scientific terms?
2. Why do you need to know true north and south for this activity?
3. Would you penalize a leaf tree in determining it's Rso if it was in a landscape in Puerto Rico? Montana? South Florida?
4. What change in Rsu would you suggest for 5 Blue Spruces growing in a tight row on the north side of a home in Minneapolis?
5. What incentives could the government institute to encourage both tree planting and ecological landscaping in the United States?

* Notes on using triangulation to determine the height of a tree:

1. Use a protractor to make a right angle on a piece of cardboard and mark the angles from 0 to 90.
2. Take a 12" piece of string and attach it to the origin of the angle with a tack or tape.
3. Hold the paper straight out from your eye so that the base of the paper is parallel to the ground.
4. Align the string so that it is pointing at the top of the tree you want to measure.
5. Record the angle created.
6. Step off or somehow measure the distance to the tree in feet.
7. Use the formula below to determine the height of the tree.

Tree Height= [(Base(ft.) x Tangent of the angle* )+ ht. of your eye above ground level]

*From trig tables in any trigonometry text or use the tangent function on an equipped calculator

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