PURPOSE: To determine thee thermal conductivity of some commonly used building materials.

DESCRIPTION: A slab of material 1/2 inch thick is placed between two 1-liter plastic bags, each containing 2.2 lbs of water. The thin plastic bag allows good conductivity between the water and the surface area of the insulating slab. One bag contains water at room temperature and the other contains water initially at a temperature of 180-190 degrees Fahrenheit. The outer sides of the water bags and the insulating slab are surrounded by a styrofoam box at least three inches thick. Measurements of the temperature of the water on each side are made at regular time intervals and the average temperature difference is determined over some total time. The conductivity is then calculated in units of BTU/inch second degree Fahrenheit.

SUGGESTIONS: This measurement is not very precise. Comparisons between different materials can, however, be easily made. Check bags for leaks, particularly if very hot water is used.

REFERENCES: (PIRA unavailable.)

EQUIPMENT: Conductivity of Building Materials gizmo with two digital thermometers, room temperature water, hot water, Ziploc storage bags, samples of wood (pine), styrofoam, and glass/air/glass double-pane window.

SETUP TIME: 15 min.

Go back to Lecture-Demonstration Home Page.