Fair Conditioning Carbon Offset from AC’s – Fair Conditioning

Carbon Offset from AC’s


Architectural Design


Building Services



Academic Year

2'nd Year


3'rd Year

Complexity Level




Content tags

Air Conditioning


Carbon Footprinting


Climate Justice

Activity Type

Numerical Exercise

Activity duration

< 1 hour


To estimate the number of trees required to offset GHG emissions of refrigerants from ACs installed in college buildings.


Students will realise that offsetting carbon emissions from AC’s by planting trees is an impractical solution.


Details of AC’s installed in their own college campus.


A conceptual knowledge of 

  1. Carbon Footprinting.
  2. Global Warming Potential (GWP).
Given Data
  1. 1 tree absorbs approximately 0.25 ton of CO2 in its lifetime.
  2. Life-cycle refrigerant charge (C) 1.5 kg of refrigerant/TR
  3. 1 ton ~ 1000 kg

Step 1: Students find out the total air conditioning load (TR) of the campus.

Step 2: Students find out the refrigerants used in the AC’s installed in college campus.

Step 3: Estimate the total amount of refrigerants used in AC’s in the college campus (kg of refrigerant).

Step 4: Estimate the carbon emissions from the refrigerants used in AC’s in the college building in CO2 equivalent (t CO2e).

Step 5: Estimate the number of trees to be planted to offset the emissions from refrigerant usage in the college building.

Sample Calculation

Step 1: Air conditioning load in college campus (TR) = 40 TR

Step 2-3-4: 

Refrigerant NameR22R134aTotal
Cooling Load in the Building (L) (TR)202040
Total Refrigerant used in building (CxL) (T) (kg of refrigerant)303060
GWP (kg of CO2 /kg of refrigerant)18101430
Carbon Emissions from refrigerants (E) = T x GWP (kg of CO2 e)54,30042,90097,200
Carbon Emissions from refrigerants (t CO2 e) = E/100054.342.997.2

Hence, Emissions from refrigerants used for AC’s in entire college building in t CO2e = 97.2 t CO2

Step 5: No. of Trees to be planted to offset GHG Emissions of refrigerants used in college building = $$\frac{\:\text{Carbon Emissions from refrigerants }}{\:\text{Lifetime Carbon Absorption Capacity of one tree }}$$

= $$\frac{\:\text{97.2}}{\:\text{0.25}}$$

~ 390 trees


To learn more about carbon footprint, refer Supplementary Notes Section

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