E. Earth and Space Systems · Heat in the Environment

Keeping Heat Where We Want It: Technologies That Reduce Heat Loss

E1.1 A1.3 A1.4 A2.1 A2.2 A3.1 A3.3About 55 minutes

Learning goals

I can explain how homes lose heat by conduction, convection and radiation.
I can describe technologies that reduce heat loss or heat transfer, and explain how each one works.
I can assess the social and environmental benefits (and some costs) of these technologies.
I can describe Inuit knowledge of keeping warm, such as building igluit.
I can design, build and test an insulated container.

Words to know

insulation
Material that slows the transfer of heat, usually by trapping air in tiny pockets.

R-value
A number that shows how well a material resists heat flow. A higher R-value means better insulation.

weatherstripping
Strips of foam, rubber or felt around doors and windows that stop drafts.

heat pump
A machine that moves heat from one place to another (for example, from outdoor air into a house in winter) instead of making heat by burning fuel.

heat recovery ventilator (HRV)
A machine that brings fresh air into a house and uses the warmth of the stale air going out to warm it.

iglu (plural: igluit)
An Inuit snow house, built from blocks of snow.

passive solar design
Designing a building to collect, store and spread the Sun's heat without machines, for example with large south-facing windows.

A drafty house

Put your hand near the bottom of an outside door on a windy January day. Can you feel cold air sneaking in? Every bit of heat that escapes in winter has to be replaced by the furnace or heater, which costs money and often burns fuel. Keeping heat where we want it is one of the simplest ways to save energy.

Close-up of a rubber door sweep sealing the gap under a wooden front door, with snow outside. — A door sweep like this blocks cold drafts, cutting heat loss by convection. Small fixes like this lower heating costs and emissions. AI-generated image

How a house loses heat

All three kinds of heat transfer are at work:

Conduction through walls, roofs, floors, window glass and door frames.
Convection when warm air leaks out through cracks and cold air leaks in (drafts), and when air moves next to cold windows.
Radiation of infrared energy out through windows.

In summer it works the other way: heat gets into the house, and air conditioners use energy to remove it.

A house in winter loses heat in all three ways: conduction through walls and roof, convection as warm air leaks out, and radiation out through the windows.

Technology	How it works	Which heat transfer it reduces
Insulation in walls and attics (fibreglass, mineral wool, cellulose, foam)	traps air in tiny pockets so heat flows slowly; higher R-value = better	conduction (and convection inside the walls)
Double- or triple-pane windows	two or three layers of glass with air or argon gas sealed between them	conduction and convection
Low-e coating on window glass	an invisible, very thin metal-oxide layer that reflects infrared back into the room	radiation
Weatherstripping and caulking	seals gaps around doors, windows and pipes	convection (drafts)
Heat recovery ventilator (HRV)	outgoing warm, stale air warms incoming fresh air without mixing them	heat lost through ventilation
Smart or programmable thermostat	lowers the temperature when people are asleep or away	reduces the temperature difference, so less heat is lost
Vacuum flask (thermos)	a vacuum between two walls (no particles) and shiny surfaces	conduction, convection and radiation
Light-coloured or "cool" roof	reflects sunlight in summer	radiation (heat getting in)

Technologies that reduce heat loss or unwanted heat transfer.

Heat pumps and passive solar design

A heat pump works like a refrigerator running backwards: it moves heat from the outdoor air (or from the ground) into the house in winter, and from the house to outside in summer. Because it moves heat rather than making it by burning fuel, it can deliver more heat energy than the electrical energy it uses. Modern cold-climate heat pumps work even in many Canadian winters.

Passive solar design uses the Sun directly. In Canada, large windows facing south let in low winter sunlight. Thick floors of tile or concrete absorb the heat during the day and release it at night. Roof overhangs shade the windows from the high summer Sun.

Inuit knowledge: keeping warm in the Arctic (A3.3)

Inuit have developed and passed down knowledge of keeping warm in one of the coldest places on Earth for thousands of years. This knowledge uses the same science you are learning:

Igluit (snow houses): snow is full of trapped air, so snow blocks are an excellent insulator. The dome shape is strong and has a small surface for its size. The entrance is often built lower than the living area, so cold, dense air settles there and does not flow into the living space (convection). Sleeping platforms are raised, where the warmest air collects. A traditional qulliq (a stone lamp that burns seal oil) gave light and heat; the qulliq is still lit today at gatherings and celebrations. An iglu can be much warmer than the outside air.
Caribou-skin clothing: caribou hairs are hollow and trap air, making very warm clothing. Layers with fur facing in and out trap even more air.

Inuit continue to build igluit today, mainly as shelters while travelling or hunting on the land, and experienced builders teach these skills to young people. Engineers and architects designing for the North also learn from this knowledge.

A simple cross-section of an iglu (not to scale). The entrance sits lower than the living space, so cold, dense air settles there, while the raised sleeping platform is where the warmest air collects.

Benefits and costs (assessing the technology)

Social benefits:

Lower energy bills, which especially helps families who struggle to pay for heating.
Comfort and health: fewer drafts and cold spots; homes stay safer during winter power outages and summer heat waves.
Jobs, including skilled trades: insulation installers, carpenters, window installers, HVAC technicians and home energy advisors (A3.1).

Environmental benefits:

Less fuel burned → fewer greenhouse gas emissions and less air pollution.
Less demand for electricity, so fewer new power plants are needed.

Costs and trade-offs:

Upgrades can cost a lot up front, even if they save money over many years. Government rebates sometimes help.
Making some materials uses energy and resources.
A very airtight home needs good ventilation (such as an HRV) so moisture and stale air do not build up.

# Smart thermostat plan

set day_temp to 20

set night_temp to 17

set away_temp to 16

forever:

if time is between 22:00 and 6:00:

target = night_temp

else if motion_sensor says nobody is home for 30 minutes:

target = away_temp

else:

target = day_temp

if room_temp < target - 0.5:

turn heat on

else if room_temp > target + 0.5:

turn heat off

wait 1 minute

A plan for a smart thermostat program (A2.1). It uses the clock and a motion sensor to choose a target temperature (it checks the time first, because sleeping people do not move around much), then turns the heat on or off to stay within half a degree of the target. Some new smart thermostats use artificial intelligence to learn a family's routine and adjust on their own (A2.2).

Worked example

Let's assess a technology: weatherstripping

Assess weatherstripping a drafty old door. What does it do, and what are its social and environmental benefits and its costs?

How it works: it seals the gaps around the door, so warm air cannot leak out and cold air cannot leak in. It reduces heat loss by convection (drafts).
Social benefits: the house feels warmer and less drafty; the family pays less for heating.
Environmental benefits: the furnace runs less, so less fuel is burned and fewer greenhouse gases are released.
Costs: the weatherstripping costs money and time to install, and it wears out after some years and must be replaced.

Weatherstripping is a low-cost, high-benefit technology: it reduces drafts, saves money and cuts emissions, with only small costs.

Just for fun

Riddle: What do you call a house with no insulation in January?

A very expensive way to heat the outdoors.

Hands-on activity

Design challenge: the ice cube keeper (A1.3)

Challenge: design and build a container that keeps an ice cube from melting for as long as possible.

You need: identical ice cubes, a small resealable plastic bag for each ice cube, small boxes or plastic containers (all about the same size), and insulating materials from home such as newspaper, cotton balls, wool socks, bubble wrap, aluminum foil, felt, scrap fabric or packing foam, plus tape, scissors and a clock.

Plan: decide which materials to use and how to layer them. Think about all three heat transfers: what will slow conduction? Convection? Radiation? Sketch your design and label it.
Build: put an ice cube in a sealed bag and place it in the centre of your container.
Control: put an identical bagged ice cube in an empty, uncovered container.
Test: leave both in the same place. Check every 15 minutes (opening your container quickly) until the control cube has melted, then keep checking yours.
Measure: record the time until each cube has completely melted. Or, after a set time such as 1 hour, pour the meltwater from each bag into a measuring cup and compare.
Improve: change one thing in your design and test again. Did it work better?

What to look for: the best designs trap lots of air (cotton, wool, bubble wrap), seal out drafts, and may use a shiny layer to reflect radiation. The insulated cube should last much longer than the control.

Communicate: share your results in a table and explain which design features worked best and why.

Safety (A1.4): use scissors carefully, cutting away from your body; a grown-up helps with any hard cutting. Keep plastic bags away from young children. This challenge uses ice only, with no hot water.

Your turn

Name the three ways a house loses heat and give an example of each.

How does insulation slow heat transfer?

What does a higher R-value mean?

How do double-pane windows reduce heat loss?

Why does a heat pump use less energy than an electric baseboard heater for the same amount of heat?

Give two features of an iglu that help keep it warm.

Give one social and one environmental benefit of insulating a house.

More practice: warm-up

What stops drafts around a door?

What is the plural of iglu?

Which direction should large windows face for passive solar heating in Canada?

Why are caribou-skin clothes so warm?

Name one skilled trade that helps make homes more energy efficient.

More practice: on your own

A thermos has a vacuum between two walls and shiny surfaces. Explain how it reduces all three kinds of heat transfer.

In the smart thermostat plan, what temperature does the program aim for at 2:00 a.m. if someone is home?

Why does a very airtight new house need a heat recovery ventilator?

Why is the entrance tunnel of an iglu often lower than the living area?

A family says insulation is too expensive. Give one argument for doing it anyway and one way to make it more affordable.

Challenge

In the ice cube design challenge, two students' results are: design A, 145 minutes; design B, 210 minutes; control, 40 minutes. How many times longer did design B last than the control? Which features might explain it?

Explain why reducing heat transfer can also help in summer, and give one technology example.

Assess this technology: replacing old single-pane windows with triple-pane windows. Include how it works, one social benefit, one environmental benefit and one cost.

Check your understanding

Quiz

How does most home insulation work?

Weatherstripping mainly reduces heat loss by...

A material with a higher R-value is...

Why is the entrance of an iglu often lower than the living area?

A heat pump heats a house by...

Which is an environmental benefit of reducing heat loss?

A vacuum flask keeps drinks hot because the vacuum...

For parents and teachers

Big idea (E1.1): technologies such as insulation, better windows, weatherstripping, HRVs, heat pumps, thermostats and passive solar design reduce heat loss or unwanted heat transfer. Students assess their social benefits (lower bills, comfort, jobs) and environmental benefits (fewer emissions), and their costs. Inuit knowledge of igluit and caribou-skin clothing shows the same science (A3.3). The design challenge uses an engineering design process (A1.3) with safety (A1.4); the thermostat plan practises coding (A2.1) and links to emerging technology (A2.2); trades are named (A3.1).

How to help: go on a "draft hunt" together on a windy day, holding a strip of tissue near doors, windows and outlets on outside walls to see where it flutters. Look at the attic insulation (from the hatch only) or the windows together.

Common difficulties:

Thinking insulation makes heat. It only slows heat transfer.
Thinking a sweater "is warm". It traps your body's heat.
Presenting igluit as only historical. Inuit build igluit today, especially when travelling on the land.

Safety: scissors with care; plastic bags away from young children. Do not enter attics; look from the hatch only, as insulation fibres can irritate skin and lungs.