Passive solar design is the utilization of the sun's energy, the geographical climate, and the properties of different materials to heat and cool buildings. It includes a variety of methods that use no human-made energy to operate and can reduce the amount of energy needed for heating and cooling by considerable amounts. In years past, indigenous people who lived in harsh desert locations built partially-underground homes that kept them cool during the day and warm at night. They also built adobe homes in cliff-side caves that were chosen because the winter sun warmed them and the summer sun couldn't reach them.
Passive solar should not be confused with active solar design or photovoltaic solar cells. While active solar design is similar to passive, it uses small amounts of energy to help transport the heat created. For example, if a solar wall heats up air that then naturally rises, it is called passive solar; if a fan was used to help move the air, then it would be considered "active."
Below are examples of how some materials you provide your students might be used:
- Foam core board: for walls and roofing, absorbs thermal energy and releases it slowly, and is an insulator
- Thin clear plastic: to let light in as windows, to heat up the homes
- Aluminum foil: to imitate metal surfaces; reflects heat and light
- Thin rubber: absorbs thermal energy and releases it slowly\
- Black fabric: absorbs a lot of heat from light
- Glue: besides holding the house together, it serves as a final insulator to seal up any cracks and small air leaks in the passive solar homes
The “During the Day” test represents the presence of sunshine on a clear day, by shining the bright light on the model homes. If you have ever spent some time in the sun on a hot day, you know that the sun has an incredible ability to heat things up. Think of how hot the inside of a car gets after it has been in the sun for a while. Tapping the sun's power is useful in working towards becoming more energy efficient because its energy is free and in near endless supply. That's why we consider solar energy a "renewable" source of energy.
The simplest method of passive solar heating is sunlight shining through windows. Since we know that the sun rises higher in the sky during the summer than in the winter, engineers and architects design buildings that allow sunlight through the windows during the winter months when the building needs heating, but block the sunlight during the summer to help keep the building cool.
And the “During the Night” test simulates night-time conditions with a cooling breeze. This is done by removing the bright light and using a fan to blow a cool breeze to see how well the model homes retain their heat. After sunset, have you ever felt the warmth from a big rock or a concrete bench that has been in the sun all day? The rock and the bench absorbed and stored the heat, and released it slowly. Working in the same way, a key passive solar technique is for the radiant heat of sunlight that enters a building to be absorbed by a thermal mass inside the structure. A thermal mass might be a big wall or area of floor that is composed of a construction material that is able to absorb large amounts of heat, such as concrete, brick, tiles or even water. As the sun sets and the air temperature lowers, the thermal mass slowly releases the heat it gathered all day to help maintain a comfortable indoor temperature through the night. In the summer, the same thermal mass can draw warmth from the surrounding air to cool a space. In all seasons, the ability of thermal mass to store heat helps to maintain a uniform temperature.
Note on Instructional Sequence
Student should be familiar with the following DCIs before starting this lesson:
PS3.A: Definitions of Energy
- The term “heat” as used in everyday language refers both to thermal energy (the motion of atoms or molecules within a substance) and the transfer of that thermal energy from one object to another. In science, heat is used only for this second meaning; it refers to the energy transferred due to the temperature difference between two objects.
- The temperature of a system is proportional to the average internal kinetic energy and potential energy per atom or molecule (whichever is the appropriate building block for the system’s material). The details of that relationship depend on the type of atom or molecule and the interactions among the atoms in the material. Temperature is not a direct measure of a system's total thermal energy. The total thermal energy (sometimes called the total internal energy) of a system depends jointly on the temperature, the total number of atoms in the system, and the state of the material.
Per group of three students:
- 3 Thermometers (if possible use an infrared thermometer for the most accurate results)
- 1 watch or timer
- 1 clipboard
- 1 Passive Solar Design: Field Study Worksheet
Determine potential outdoor study sites that students will be testing to determine “How do different types of material affect the amount of solar energy that can enter a system and be transferred as thermal energy?” Find study sites that are similar to the materials students will use to design and construct their model passive solar houses later in this lesson.
Study Site Suggestions:
*Try to include materials that are used for building construction and materials that students can use to build their model houses.
Intro Discussion and Field Investigation Preparation
- Ask students: How is the temperature in buildings normally maintained and controlled? (i.e. air conditioning and heat powered through electricity, gas, etc.) Approximately how much is an electric bill for a month? (If students do not know, provide them with a range appropriate for your area.) What contributes toward the electric bill? (Heat, air conditioning, light, powering electronics, etc.) Discuss with students how heat and air conditioning are big contributors to the electric bill and that the bills go up a lot in cold months when a lot of heat is needed for the house to stay warm or hot months when lot of air conditioning is needed for the house to cool down.
- Ask students to brainstorm with a partner: What would be the benefits and positive impacts of being able to heat houses without having to use electricity (or gas)? (people save money on their bills; if it is a cheaper alternative, then more people are able to heat their homes) Have students share their ideas with the class.
- Ask students to think about what happens to objects that are left in the sun for long periods of time. Have them share their experiences with a table partner before discussing as a class. If needed, you can prompt the conversations by asking them to think of how hot the inside of a car gets after it has been in the sun for a while, or how hot a parking lot, a basketball court, or playground equipment may get during the day under the sun. Ask them what is happening in terms of energy and temperature?
- Continue this discussion by asking the students if after sunset they have ever felt the warmth from a big rock or a concrete bench that has been in the sun all day? Why is the rock or bench warm? Why are they feeling the warmth? Have them think about the processes through which heat is transferred and what they already know about heat transfer. Why is energy being transferred? (It is transferred because of temperature differences.) Have the students share their ideas with a table partner before discussing as a class. (The rock and the bench absorbed solar energy, converted it to thermal energy, and are releasing heat slowly.)
- This conversation should be used as formative assessment because it elicits student prior understanding of heat transfer, temperature, and thermal energy and can surface misconceptions. Record all student ideas proposed during this discussion on chart paper and hang it up in the classroom so that it can be referred to as the students’ understanding of thermal energy deepens through this lesson.
- Ask students if, based off the discussion you just had, they think the sun influences a building’s temperature?
- Ask students to first discuss in pairs and then share with the class the following questions:
- When can the sun’s natural temperature influence on buildings be beneficial? Why? (In the winter, the sun can help keep the buildings warmer.)
- When can the sun’s natural temperature influence on buildings have negative impacts? Why? (In the summer, the sun can make it harder to cool a building.)
- Do buildings have to have solar panels or some sort of specialized technology to absorb the sun’s energy? (The answer is no. Building materials can naturally absorb the sun’s energy to varying degrees. If students are struggling with this question, ask them to think back to the bench example they discussed earlier. Did the bench have a solar panel? – No. Did it still absorb solar energy and did they feel the warmth from it? – Yes.)
- Ask students if based off the discussion so far, they can define what “passive solar heating” is. If necessary, break down the words for them, asking them what “passive” refers to and what “solar heating” refers to. Keep a working definition on the board.
- Discuss with students how passive solar heating can provide additional, free heating that can take the burden off of electricity or gas powered heating in buildings. Tell students that they will be challenged to design and build a solution for a one-bedroom passive solar model house that can maximize the absorption of solar energy into its system and minimize thermal energy transfer out of the system during the winter.
Before they start on their design, remind students that it is important to consider the type of materials they will use to design their house. Ask them, why is it important that engineers/architects consider the type of materials that are used when constructing houses? (If students need a prompt, ask them to think about this question in terms of energy absorption and transfer.) Will all materials absorb the same amount of solar energy? Why or why not? Tell students that they will watch a video about thermal energy and heat transfer to help them think about these questions.
- Have the students watch the Scholastic.com StudyJam video on heat. There might be a need to watch the video more than once, or to pause the video as it is playing to provide students with time to discuss new concepts.
- Video Summary is quoted from the end of the video.
- “Heat is different than temperature”
- “Heat is the amount of thermal energy that exists in matter”
- “Temperature is a measurements of the thermal energy within an object”
- “Little thermal energy equals low temperature”
- “High thermal energy equals high temperature”
- “There are three primary means of heat transfer: radiation, conduction, and convection”
- “Thermal energy, or heat, travels from warmer to cooler objects”
- After watching the video, discuss the following with students:
- How is heat different than temperature?
- How are thermal energy and temperature related?
- What are the three ways that heat transfer occurs?
- Think back to the bench example at the beginning of the lesson. In what process was the energy from the sun transferred to the Earth and to the bench? (Radiation) Why do you feel the warmth when you touch the bench (or the materials at the study site)? (Energy will go from hot to cold regions through conduction in this example. Since you are colder in temperature than the bench, there will be heat transfer from the bench to you.)
- What are other examples you see in your life every day that involve conduction? Convection? Radiation?
- What are the differences between insulators and conductors?
- What are everyday objects that use conductors? Why?
- What are everyday objects that use insulators? Why? (i.e. travel coffee mugs have insulating materials to keep the coffee warm inside for a longer time)
- The video stated that it is difficult for heat to pass through insulators. Why is it important to include insulators when building houses? What role do insulators play in a passive solar house design?
- Have students think back to the examples they discussed for conduction, convection, and radiation. Have them draw a diagram that shows an example for each. Tell students to identify the hot and cold regions of their systems and to illustrate the flow of energy (input, internal transfer, and output) for each of their diagrams. With a partner, they should discuss the transfer of energy in their diagrams and how it is connected to temperature differences. The discussion should involve students coming up with their own questions to ask their partners.
Field Investigation Protocol
- *Note – The following steps may differ depending on how much your students are involved with planning the protocol (and what steps they decided to include). Whether the students collaboratively plan the protocol or are given the step by step instructions, it is important for students to understand what data they are collecting, why they are collecting that specific data (how will it help them answer the question), and why they are doing certain steps in the protocol.
- Ask students to help plan a field investigation that can answer the following question: How does the material type affect the amount of energy that can be absorbed?
- In order to help students brainstorm, you can ask them to think about the following questions: What happens to different objects when they sit in the sun for long periods of time? In the shade? Why does this happen? What factors affect how this happens? (You are looking for answers in terms of temperature, heat, etc.) What data can you collect (that can indicate whether the materials are absorbing solar energy)?
- This planning process should determine potential study sites around school property that have different materials, the type of data that students will be collecting, how the data will be collected, any tools needed for the investigation, and potential protocols. Record the final information on chart paper for students. The field investigation worksheets can be changed according to the ideas that your students come up with.
- Divide the class into groups of three students, and assign each group a study site around school property.
- Pass out the thermometers, stopwatches, clipboards and worksheets. (Review how to use a thermometer if needed.)
- Instruct students to read through the worksheet so they understand the data they will be responsible for collecting and why they are collecting it: date, time, site, weather conditions and three temperature readings for their study site. Ask students why they are recording three temperature readings, and why they need to wait three minutes before recording the temperature. Why is it important to record the date and time of the investigation? Before going outside they should record their study site on the worksheet.
- Have the students locate their study site and place 3 thermometers flat on the ground. To keep the sun from interfering with the thermometer readings, shade the bulbs of the thermometers from direct sunlight. You can do this by standing between the sun and the thermometer.
- To ensure an accurate reading wait 3 minutes. Record temperatures on the worksheet without picking up the thermometers. This measurement is a moment in time, and does not represent a change in temperature, but it should allow for students to compare results between different sites and note patterns in their data.
- To record the energy coming from the sun during the time they are conducting this field study, students should hold their thermometers in the sun without touching the bulb for 3 minutes.
Field Study Analysis
- Calculate average temperatures in Celsius (oC) for each location. (Average = (trial 1 + trial 2 + trial 3)/ 3)
- Create a classroom chart with all of the study sites and temperature averages. Have the students compare and discuss all of the results and comment on trends they notice in the data about the different material types. Ask them the following questions:
- How do the temperature readings indicate how much energy a particular material was able to absorb?
- What patterns do you see in your data in regards to temperature?
- Based on your temperature readings, did the materials absorb the same amount of solar energy in reference to each other? Support your answer with evidence and reasoning.
- Think about the type of materials that had higher temperatures. Are there any similarities in the characteristics of those materials?
- Think about the type of materials that had lower temperatures. Are there any similarities in the characteristics of those materials?
- What are the differences between the materials that had lower temperatures and materials that had higher temperatures? Why do you think these differences contribute to the temperature differences?
- If the data had been collected during the evening or during the night, what differences would you see in the data? Why? What about during different days of the year?
- What are the limitations of your data collection?
- Return to the chart about energy that was generated at the beginning of this lesson. Using what they now know from the field study and video, have the students revise the chart by adding, removing and modifying the information as a class. This information will be part of their scientific reasoning when then complete their performance task at the end of this lesson.
Part 2: Design and Construct Passive Solar Houses
foam core board
thin clear plastic
Popsicle sticks and/or craft sticks
thin rubber (any kind
black fabric (any kind)
pencils, erasers and white or graph paper for designing
Design Challenge Handout
**Note – This article has some terminology and concepts that are more advanced and that students do not need to know. Depending on your students, you can edit the article to include only the relevant parts (thermal mass, insulation, and different angles of sunlight during the summer vs. winter) or you can choose another source that address those three concepts.
- Have students brainstorm about the following in groups and then discuss with the entire class. Have students write down their ideas/answers, and they should leave space to come back to add on to their ideas later. You can also write down their ideas on the board during the class discussion and can leave space to come back to add to/modify their ideas later.
- When designing homes, why do engineers/architects need to consider how the temperature inside buildings is affected naturally by the sun? (They need to consider where to place the windows and how much sun will come through.)
- What aspects of designing and building a house will be affected when considering a passive solar house design?
- Geographic location; orientation; insulation; placement, amount, and size of windows; size of house; use of overhangs; colors; ventilation/circulation; etc.
- Encourage students to ask each other questions about how each of these elements affects energy transfer
- How do engineers/architects use the understanding of how materials absorb energy when designing homes? (Heating and cooling homes; what materials to use as insulators, etc.)
- They need to think about all of the seasons in the building’s location. Why? (The direction/intensity of the sun in the winter is different than the summer. You don’t want the house getting as hot in the summer as in the winter.)
- ● Divide the class into groups of two or three students.
- ● Pass out the Passive Solar Home Design articles. Have students read the article and then think about the questions they answered before. Is there anything they can modify/add to their answers? Have students discuss these modifications/additions with their group and record them on their papers.
- ● Ask students and discuss: How does a thermal mass affect thermal energy transfer in a system? How does insulation affect thermal energy transfer in a system?
- ● Discuss with students that they need to design and build a solution for a one-bedroom passive solar model house that can maximize the absorption of solar energy into and transfer of thermal energy in its system and minimize thermal energy transfer out of the system during the winter. They will test their designs by tracking and recording the temperature inside their house during a winter day and night simulation. Their goal is to be able to heat up the house during the day, and retain most of the heat during the night.
- Tell students they need to think about the angle of the sunlight during a winter day. Based off of the diagram in the article what do they estimate the angle of the sunlight to be? (Around 45 degrees). They need to keep this in mind when designing their house since it will be tested in winter sunlight conditions.
- ● Have the teams brainstorm ideas and discuss possible passive solar heating materials and techniques based on all the discussions and their results from their field investigation. Encourage them to think about how they can include thermal mass and insulation in their designs.
- ● Hand each group a Design Challenge Handout. Have them look over the handout; answer any questions they may have. Be sure that they understand the design constraints and materials they will be able to use during construction.
- Design Challenge: To design and build a one-bedroom model passive solar house within the design constraints, utilizing passive solar heating techniques to warm up the house as much as possible (maximizing absorption of solar energy into the system) and sustain that temperature as long as possible (minimizing thermal energy loss out of the system) during the winter.
- Troubleshooting Tip: Before students begin to design and build, tell them the size of the testing thermometer, because in order to make good readings during the testing phase, it must fit through the door of the passive solar house and entirely inside, and be able to be read through a window.
- Design Constraints: Floor size ≥ 70 square inches; Roof height ≥ 4 inches; Door size must be able to accommodate a thermometer that can be placed entirely inside the middle of the passive solar house with the door closed, and be able to be read through a window.
- ● Encourage students to design unique houses. For example, they do not necessarily have to have the traditional four walls.
- ● Once teams have come up with several ideas, have them choose one and sketch it on paper. Double-check their designs to make sure they meet the requirements before they can get their materials.
- ● Give the teams time to build. The amount of time you can dedicate to this project is up to you. Keep them on task by setting interim deadlines.
- Design Review: Midway through the building phase, have groups give brief presentations to the class (or just the teacher) discussing their designs. Make sure they discuss the passive solar heating techniques they are using, how those techniques are best suited for a house built for winter conditions, and how their knowledge of energy transfer is influencing their design decisions. Allow time for questions from their peers.
Part 3: Test and Assess the Passive Solar Houses
Passive Solar Houses (built during Investigation 2)
Passive Solar Design: Data Recording Worksheet
Graph Paper (or Excel software)
For one “During the Day/ During Night” testing station (you may want more than one station):
- 300-watt light bulb
- desk or clamp lamp (that can safely accommodate a 300-watt light bulb)
- floor or box fan
- bucket or plastic container (for the ice)
- watch or timer to determine 30-second intervals
“During the Day” and “During the Night’ testing stations. Refer to the Teacher Testing Steps Handout for more information.
- "During the Day": Set up the bulb at a 45-degree angle so that is will be about 8 inches away from the structure’s roof. Setting it up any closer might burn the foam board; setting it up too far away reduces the difference in results between designs.
- "During the Night": Set up the fan a few feet away from the model home with a bucket of ice in front of it. Immediately after the “During the Day” testing you will need to shut off the light and start the fan so make sure everything is close enough to ensure consistent temperature readings.
- Additional Suggestions: The testing takes a while and groups may lose interest when you can only test one group at a time. Have students use the time to complete other assignments. Or, shorten the time by making available more than one testing station if you have the supplies.
Make sure the lamp you use can safely accommodate a 300-watt incandescent light bulb. A 300-watt bulb can cause burns or melt some materials, so be sure to monitor.
- Once the groups are done building their passive solar houses and the testing area has been set up give each team the Data Recording Worksheet. Then, start conducting the tests as described below, having the teams record their data on their worksheets.
Setting up Testing Area
- Tell students they will now be testing their designs in a winter day and night simulation by setting up their house in a small scale version of the house and sun. Ask them to discuss the following questions in their groups.
- What can represent the sun in the scale version?
- How can the sun representation change to simulate the day vs. the night?
- How can the sun representation simulate winter sunlight?
- Temperatures drop during the winter night – how can that be represented? Then, tell students they are limited to using a fan and ice cubes. How can they use those materials to represent the winter night?
- How can they measure the absorption of solar energy? How can they figure out whether the house is maintaining or losing the thermal energy overall?
- Discuss students’ answers with the class and make sure they understand all the components that are needed in the small scale system, especially what each component represents in the real world. Discuss the testing stations that have been set up for them. Make sure students understand what data they are collecting, what it represents, and why they are collecting it. Review the data worksheet with them before they start the testing.
Testing Part 1: "During the Day"
- Have the students insert the thermometer through the door and entirely inside the passive solar house, positioned so it can be read through a window. Record the baseline room temperature.
- Positions the light bulb at a 45-degree angle about 8 inches away from the roof. (Setting it up any closer might burn the foam board; setting it up too far away reduces the difference in results between passive solar house.)
- Have students take and record temperature measurements every 30 seconds so they have enough data to graph their results in the table on the Data Recording Worksheet. Do this for a minimum of 8 minutes so enough data is gathered to be able to compare with other teams.
Testing Part 2: "During the Night"
- Set up the fan a few feet away from the model home with a bucket of ice in front of it. As soon as the first part of testing is over, turn the bright light off and the fan on.
- For a minimum of 8 minutes, have students take temperature readings at the same time intervals as the "during the day" testing and record on their worksheet.
Analysis & Results
- In their groups, have students generate a line graph of their results on graph paper (or using Excel software) with time on the x-axis and temperature on the y-axis. Have students calculate the largest positive slope and the largest negative slope and record the calculations on their data sheet. Have students discuss the answers to the questions in the Analyzing and Interpreting Data section and then record their answers in their data sheet. The questions are:
- What trends do you notice?
- What does a positive slope indicate? What does a negative slope indicate?
- At what time was there the largest positive slope? At what time was there the largest negative slope? Talk about this relationship in terms of thermal energy transfer.
- Are there any anomalies? Why?
- Have each group discuss the concepts in their original design, and share their final results with the class. Create a large classroom chart with three columns (“Design Materials”, “Daytime Slope”, and “Nighttime Slope”) and record each group’s results while they are sharing.
- As a class, compare and discuss the results, looking for patterns and anomalies in the results. A larger slope during the daytime means great temperature gains, while a larger (less negative) slope during the nighttime means better heat sustainability.
- Ask the students to begin making statements about how the energy flowed through their designs during both the daytime and night time scenarios in preparation for the performance task. Have them go back to their design sketch and add in arrows that show energy input, transfer, and output. Have them discuss the energy processes (that the arrows symbolize) in their groups.
- Have students discuss (in their groups) and answer the questions in the Results section of their data sheet. The questions are:
- Compare your results with other groups.
- How did your group’s passive solar design model results compare to the other model homes?
- What worked well in your design? What seemed to work well in other groups?
- What were the constraints of the design? How did you address them?
- What part of your design worked well? Why?
- What did not work well in your design? What are the limitations of your models? How would you modify your design to achieve a more optimal design?
- What potential impacts (positive and negative) can your houses have in the real world? (Examples: The houses use passive solar energy, so they use less fuel-driven energy; the insulation materials may have negative impacts on the surrounding environment; the design of the house may result in higher building/maintaining costs for people)
- Have the groups share with the class (or with just you) what parts of their design worked well and why, what part of their design did not work so well (what were the limitations) and why, and what modifications they came up with. They should explain why they decided upon those modifications and how the modifications will affect the absorption and retention of energy in their house’s system.
Part 4: Writing Performance Task
Copies of Writing Performance Task Rubric
- Present students with the following Writing Performance Task.
Writing Performance Task: Construct a scientific explanation for how the use of certain materials provided the best passive solar system for your house, maximizing the solar energy that entered the system and minimizing the energy that was lost from the system. *Note – This assumes that students have had experience with scientific explanations and know the parts: claim, evidence, and reasoning. If students have not, then they will need more support with this practice.
In their scientific explanations students should include the following:
- Describe the flow of energy through your passive solar house.
- Support your proposed flow of energy (claim) with data (evidence) that you collected when you tested your design.
- Apply appropriate scientific ideas around thermal energy and conservation of energy to link you claim and evidence (scientific reasoning).
- Propose a new passive solar design based on what you have learned, and draw a sketch of your new and improved design!
Be prepared to present your argument to the class.
- Before students begin working on their scientific explanations, ask students to share what they think constitutes a strong scientific explanation. After a few responses, review the Scientific Explanation Rubric.
Performance Task Scaffolds:
- Provide sentence starters.
- Have the students discuss their thoughts as a group before they have to write their response.
- Have students peer review the performance tasks and offer suggestions to their classmates.
- Allow students to complete the performance task through writing, drawing or presentation.
Passive Solar Design:
Lesson Extensions and Suggested Scaffolds
Additional Resources on Passive Solar Design
- Explore current events related to solar energy and climate change with grade level appropriate readings.
- Watch a video on a library in Queens, NY that utilizes both passive and active green designs.
- Watch the video, “A Home That Heats Itself.”
“Michael Sykes, a builder from North Carolina, has created a home that can heat and cool itself using only solar energy. The principle at work is "phase change." Sykes has engineered the resin in the wood he builds with to change phase at 70 degrees F. The resin goes from liquid to solid and back to liquid again at room temperature. The phase change allows the walls to soak up and trap vast amounts of heat during the day--cooling the room. At night, the wood releases the heat and warms the home. In this video, Ira talks with Sykes about how it works. Sykes won first prize for his Enertia Building System at the 2007 Modern Marvels Invent Now Challenge, sponsored by The History Channel and the National Inventors Hall of Fame Foundation.”
Extended Design Iterations
- Students can build the new passive solar design they suggested in their performance task to determine if they improved their design.
- Suggested changes to materials; supply new materials; limit materials; apply a ‘cost’ to materials; change design parameters.
- Conduct research on local and national “green” buildings that utilize passive solar designs to regulate internal building temperatures. Compare and contrast these buildings to structures that rely on geothermal heating and cooling.