Retrofit Detroit: Insulation Design Challenge
Heat transfer and cost-vs-performance trade-offs for aging Detroit housing stock.
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Standards
HS-ETS1-3 — Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints.
Why Does This Matter?
Many Detroit homes are a century old and were built before modern insulation standards existed. Retrofitting them to cut heating costs is one of the most common real engineering decisions homeowners across the city face every winter.
Objective
Test how different insulation materials affect heat loss from a model "house," then recommend a retrofit package balancing cost and performance.
Materials
- 4 identical small boxes or cups (the "houses")
- Insulation materials to test: cotton batting, bubble wrap, foam sheet, crumpled newspaper (or teacher-provided options)
- Hot water (teacher-poured, moderate temperature)
- Thermometer (1 per box, or shared with careful timing)
- Stopwatch
- Provided price-per-square-foot data for each material
Safety: Use warm, not boiling, water. Handle thermometers carefully. Wipe up spills immediately.
Procedure
- Wrap three of your four boxes with a different insulation material; leave the fourth uninsulated as a control.
- Have your teacher add the same volume of warm water to each box at the same starting temperature.
- Record the starting temperature in each box.
- Record the temperature again every 3 minutes for 15 minutes total.
- Calculate total temperature drop for each box over the 15 minutes.
- Using the provided cost data, calculate a "performance per dollar" score for each material (temperature retained ÷ cost).
Data Table
| Material | Start temp (°C) | Temp at 15 min (°C) | Total drop (°C) | Cost/sq ft |
|---|---|---|---|---|
| Control (none) | — | |||
Analysis Questions
- Which material retained heat best? Which had the best performance-per-dollar score? Are they the same material?
- How much better did the best insulated box perform compared to the uninsulated control?
- If a homeowner has a limited budget, would you recommend the best-performing material or the best value material? Justify your answer using your data.
- Real wall insulation also has to resist moisture and fit within existing wall cavities. How might those added constraints change your recommendation?