Village Science - Teacher Edition


Insulation & Vapor Barriers

Teacher Edition Contents

Skill, Tools, & Craftsmanship

Cutting & Drying Fish
Nails, Pegs, & Lashings
Falling Trees &
     Small-Scale Logging
Chainsaw Clutch & Chain
Ice Pick


Wood Stoves
Wall Tents
Insulation & Vapor Barriers
Gas Lamps & Gas Stoves


Piloting A Boat
Boat Design
Magnetos & Spark Plugs
Outboard Motor Lower Unit

Outboard Motor Cooling System
Snowmachine Tracks
Snowmachine Clutch
Winter Trails


  1. While in a warm house, close the cover on a jar. Bring the jar outside or put it in a freezer. Is there condensation inside the jar when it is cooled? Bring the jar into the warm house again. What happens?

    Condensation will form when the jar is cooled (if there was enough moisture in the air in the warm place before it was sealed.) When the cold jar is brought into a warm place, condensation will form on the outside of the jar for a while. Any condensation on the inside of the jar will evaporate when it is fully warmed.

  2. Breathe on a plate or piece of metal that has been cooled outside in sub zero temperatures. What happens. Bring it inside and watch what happens. Where does the frost go?

    It frosts on the cold plate, but evaporates in the warm building.

  3. The next time it gets –40° or –50°F, scuff your feet on a rug and touch a doorknob (or your brother’s ear). Is there a spark? Why do you think this doesn’t happen when it is warm?

    There is much static electricity during cold outside temperatures as there is very little moisture in the air. During warm outside temperatures, there is more moisture in the air, which “wicks off’ the static electricity buildup, so there is less evidence.

  4. The next time it gets very cold, put a blanket against the bottom of a cold window and leave it overnight. What happens? Why?

    The blanket freezes to the window. It insulates the cold widow from the inside temperatures, and moisture from the room freezes on the blanket.

  5. During cold weather, observe windows that are single, double, and triple pane. What difference do you see?

    Single pane frost terribly. Double pane frost a little. Triple pane seldom frost.

  6. How are winter shoe packs with felt liners like a wall without a vapor barrier? What happens in very cold weather when you try to take the liners out of the boots after wearing them all day? Why does this happen? Can you think of a way of preventing this?

    The moisture from the person’s foot goes to the outside of the felt liner and freezes against the inside of the rubber shoe pack. They are frozen in. if you put your foot in a plastic bag, and put that in the shoe pack, the moisture from your foot couldn’t reach the liner. Your foot would be warm, but wouldn’

  7. Compare shoe packs with felt liners to the white “bunny” boots or VB (vapor barrier) boots as they are called. What are the similarities and differences?

    They are similar in that they both have felt liners, and rubber on the outside. They are different in that the VB boots have the felt liner sealed off with a rubber vapor barrier on the inside. The felt liner in the VB boots never gets wet because the moisture of the foot cannot reach it. The felt liner in the shoe pack constantly gets damp from the individual’s feet.

  8. Check the houses in the village. Ask what kind of insulation is in the walls and ceiling. Is there a vapor barrier?

  9. Check the roof of an old abandoned cabin in your area. What kind of insulation was in the walls and ceiling?

  10. Try to find an old abandoned log cabin with a sod roof. Study the roofing materials.

  11. Test wet and dry insulation (wet & dry socks?) for their conductivity of heat.

    Damp socks transmit heat much faster than dry ones.

  12. Ask the oldtimers how they could detect a bear hole during winter months. Does one of these signs relate to condensation?

    The grass and branches around a bear hole will have condensation from the moisutre in the hybernating bear’s breath. This condensation is slight enough to be hard to detect.

  13. Put a glass tube or other piece of glass in a hot flame. Does it conduct heat well? Compare this with a metal coat hanger or other piece of long metal. Compare these with wood.

    Wood and glass do not conduct heat well at all. Metal is a good conductor.

  14. Visit a house under construction or talk to local carpenters. Do you see the vapor barrier? What do the carpenters say about vapor barriers?

  15. Ask oldtimers about sod roofs. Were they warm? Did they leak?

    Sod roofs were very warm and cozy. They didn’t leak if they were constructed properly. They had no vapor barrier, and the moisture from the house passed though the sod. The sod roof breathed the same way caribou mukluks breathe.

  16. Submerge a piece of closed cell foam (usually blue or pink) after weighing it. Leave it under water for a few days. Weigh it again. Did it absorb any water? What is the R factor of two inches of foam?

    Closed cell foam will not absorb water at all. It is excellent for underground insulating. 2’ of foam has an R factor of 10.

Student Response

  1. What four things do the bacteria require that cause wood to rot?

    Wood, heat, moisture, air

  2. What is vapor?

    Water in the air

  3. What would happen if there were no vapor in the air of our homes?

    We would have bloody noses and have a hard time breathing. Wood would crack. There would be a great deal of static electricity.

  4. Which can hold more water vapor: warm or cold air?

    Warm air

  5. What happens to the vapor in warm air when the air is cooled?

    It will release the moisture that is held as a vapor

  6. What happens when vapor gets into the walls of our homes?

    The air is cooled and it releases it’s moisture. This ruins the insulation’s ability to retain heat. The moisture also promotes rotting

  7. Draw a cross section of a wall that has insulation and a vapor barrier.

  8. What things in our homes naturally put water vapor into the air?

    People’s breath, boiling water, and cooking.

  9. If you tried to explain the use of a vapor barrier simply to someone who didn’t know, what simple rules would you give them?

    The vapor barrier must go between the living space and the insulation. There should be no holes in the vapor barrier. The vapor barrier and insulation work together. They should never be used apart from each other in the north.

  10. What two things make fiberglass good insulation?

    It doesn’t conduct heat and it traps dead air

  11. What are the three disadvantages of fiberglass insulation?

    It is unpleasant to install. It is destroyed by floods and little animals if they can remove it.

  12. What are two disadvantages of foam insulation?

    High cost and it emits poisonous gasses when it burns.

  13. Draw a cross section of a sod roof. Did the oldtimers use a vapor barrier?

    No. The oldtimers didn’t use a vapor barrier. The sod roof “breathed” allowing the vapor to pass through the sod.


  1. A roll of visquene is 8 x 100 feet. Assuming there are no overlaps (in reality there are). How many rolls of visquene are necessary to put a vapor barrier in a house 24’ x 36’, with walls 8’ high. The outside walls and ceiling need a vapor barrier. How many square feet will be left over for overlap and other purposes?

    Three rolls. 72 linear. ft. or 624 square feet left over.

  2. The above house needs _______ square feet of visquene. It comes in rolls of 12’ x 100 for $47.21 or rolls of 8’ x 100’ for $29.52. What is the best combination of rolls that can be purchased and what is the total cost?

    The best combination is 1 roll of 12’ wide and 1 roll of 8’ wide. Total cost is $76.73.

  3. Two inches of foam has an R factor of 10. Six inches of fiberglass has an R factor of 19 (round off to 20). A piece of foam is 2’ x 8’ and costs $14. Fiberglass costs $37 for a roll that contains 78 square feet. Which is the better insulation buy for a square foot?

    Foam is $.857 per square foot, giving an insulating value of R10 or $1.75 per square foot of R 20 (2’ thick). Fiberglass insulation is $.47 per square foot giving R 19. Fiberglass is by far the cheaper insulation.

  4. A building has 1276 square feet to insulate with six inches of fiberglass. The price of fiberglass landed on the jobsite is $.47 per square foot. What is the cost of insulating the house?


  5. Hank was building a 40’ x 56’ shop. He wanted to pour the concrete floor over 4” of foam. Each piece of foam is 2” x 2’ x 8’. How much would this cost if he could get the foam for $10.99 each? (Round off if you like.)


Questions or comments?
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