One day it is too hot and other days it is too cold. Do we need to replace the HVAC system?

This page is authored by Monika Kiss, Saint Leo University, based on work done during a week-long PREP workshop sponsored by the MAA, "Undergraduate Sustainability Experiences in Mathematics (USE Math) on Your Campus."

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Lewis Hall has had several problems with the air-conditioning and heating of its rooms. Should the university refit the building with new heating, ventilation and air-conditioning (HVAC) units or keep the ones that are in place?

Students will research the energy efficiency and cost of commercial HVAC units used by institutions. Students will perform a cost analysis of refitting Lewis Hall with new HVAC models verses staying with the units that are in the building already. They will create graphs, cost analysis reports, and they will propose a solution based on their findings. At the end of the project, students will present a formal proposal to the Board of Trustees and the President of the University.

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Learning Goals

Students will learn to
- Research the costs involved with purchasing HVAC units for large buildings,
- Build a model, spelling out assumptions and using spreadsheets with graphs for cost analysis,
- Understand the costs involved with maintenance/repairing HVAC units,
- Design a presentation at the appropriate level of detail for this particular audience.

Prepares students to build effective coalitions.

Engages students in civil discourse/ communications that lead to more effective decisions.

Catalyzes collective action.

Advances student literacy around sustainability issues.

Encourages self-reflection and personal development of their voice for solving societal challenges.

Students will gain deeper critical thinking skills, excellent data analysis skills, and the understanding of how models can assist in decision making.

Context for Use

Ideally used in an Intermediate Algebra or College Algebra class. This could be used as a group project over several classes or as a group project over a period of the term with guided worksheets.

Description and Teaching Materials

Faculty needs to provide data from the Facilities department describing:
- The energy costs involved in running the current HVAC units in the building over a year period,
- The depreciation value of the HVAC units (if available),
- The cost of repair/maintenance of the HVAC units.

Students must research:
- The cost of purchasing new HVAC units for the building using analysis of the machines energy efficiency and longevity,
- The cost of removing and disposing of the old HVAC units in the building,
- The cost of installation of the new HVAC units,
- The cost of maintenance and repair of the new HVAC units.

Teaching Notes and Tips

In order for the project to go smoothly, whether in class or as a group project out of class, some preliminary discussions would need to take place.

Discussion 1: Discuss the problem that we face.
Discussion 2: Brainstorming session designed to elicit all the variables that will affect the decision making which must be researched and the location of such information.
Discussion 3: Provide the information from the facilities department of the campus and going over the information.
Discussion 4: Review of Excel and how to use it.

Upon completion of the projects, there ought to be a formal discussion of all the projects for constructive criticism and review of presentations.


At the end of the project, students will have to
- Present in front of the class (e.g., power point presentation)
- Turn in a detailed, well-illustrated, typed proposal.

The assessment of each of the items will use rubrics. Faculty may use this Oral Presentation Rubric (Microsoft Word 2007 (.docx) 18kB Jul26 13).
The project combined grade will be 10% of the final grade for the class.

References and Resources

Reports provided by the facilities department.
Reports of costs of new HVAC products from sources such as Home Depot.
Reports of costs of installation of the new HVAC units by Air Conditioning companies in the event that the facilities department is not able to do this.