Insulation-best materials, thickness

Introduction: (Initial Observation)

Heat flows naturally from a warmer to a cooler space. In the winter, this heat flow moves directly from all heated living spaces to adjacent unheated attics, garages, and basements, or to the outdoors; or indirectly through interior ceilings, walls, and floors–wherever there is a difference in temperature. During summer, heat flows from outdoors to the house interior. To maintain comfort, the heat lost in winter must be replaced by your heating system and the heat gained in summer must be removed by your air conditioner.

Insulating ceilings, walls, and floors decreases this heat flow by providing an effective resistance to the flow of heat. currently fiberglass the most commonly used heat insulator for inside the walls and ceilings. Other widely used insulating material are cellulose, rigid polyurethane foam, Styrofoam and etc.

In this project we want to compare some of these material to see which one is the best insulating material. We also want to see what is the effect of thickness of these material on their insulation properties.

Information Gathering:

Thermal insulating materials are used to reduce the flow of heat between hot and cold regions. The sheathing often placed around steam and hot-water pipes, for instance, reduces heat loss to the surroundings, and insulation placed in the walls of a refrigerator reduces heat flow into the unit and permits it to stay cold.

Thermal insulation may have to fulfill one or more of three functions: to reduce thermal conduction in the material where heat is transferred by molecular or electronic action; to reduce thermal convection currents, which can be set up in air or liquid spaces; and to reduce radiation heat transfer where thermal energy is transported by electromagnetic waves. Conduction and convection can be suppressed in a vacuum, where radiation becomes the only method of transferring heat. If the surfaces are made highly reflective, radiation can also be reduced. Thus, thin aluminum foil can be used in building walls, and reflecting metal on roofs minimizes the heating effect of the sun. Thermos bottles or Dewar flasks (see Cryogenics) provide insulation through an evacuated double-wall arrangement in which the walls have reflective silver or aluminum coatings. See also Heat Transfer.

Air offers resistance to heat flow at a rate about 15,000 times higher than that of a good thermal conductor such as silver, and about 30 times higher than that of glass. Typical insulating materials, therefore, are usually made of nonmetallic materials and are filled with small air pockets. They include magnesium carbonate, cork, felt, cotton batting, rock or glass wool, and diatomaceous earth. Asbestos was once widely used for insulation, but it has been found to be a health hazard and has, therefore, been banned in new construction in the U.S.

In building materials, air pockets provide additional insulation in hollow glass bricks, insulating or thermopane glass (two or three sealed glass panes with a thin air space between them), and partially hollow concrete tile. Insulating properties are reduced if the air space becomes large enough to allow thermal convection, or if moisture seeps in and acts as a conductor. The insulating property of dry clothing, for example, is the result of air entrapped between the fibers; this ability to insulate can be significantly reduced by moisture.

Home-heating and air-conditioning costs can be reduced by proper building insulation. In cold climates about 8 cm (about 3 in) of wall insulation and about 15 to 23 cm (about 6 to 9 in) of ceiling insulation are recommended. The effective resistance to heat flow is conventionally expressed by its R-value (resistance value), which should be about 11 for wall and 19 to 31 for ceiling insulation.

Superinsulation has been recently developed, primarily for use in space, where protection is needed against external temperatures near absolute zero. Superinsulation fabric consists of multiple sheets of aluminized mylar, each about 0.005 cm (about 0.002 in) thick, and separated by thin spacers with about 20 to 40 layers per cm (about 50 to 100 layers per in).

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

Main question for this project:

Which home insulating material holds in the heat best?

An alternate question:

What will be the effect of thickness of insulating material in heat exchange?

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

Manipulated variables or independent variable is the type of insulating materials being tested.

Responding variable or dependent variable is the temperature drop (heat loss).

Controlled variables are:

If you are studying the effect of thickness of insulating materials on heat loss, then the manipulated variable will be defined like this:

Manipulated variables or independent variable is the thickness of the insulating material we test.

Hypothesis:

Based on your gathered information, make an educated guess about what types of materials are the best insulators.

Following is a sample hypothesis:

Among the five insulating materials (Styrofoam, Fiberglass, wool, cellulose, and polyurethane) that I am testing, wool is the best insulator.

My hypothesis is based on my personal experience with wool socks, jackets and blankets that can keep us warm better than similar products made of synthetic materials.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Experiment: Identify the best insulating materials

Preparation: Build a box that will keep heat in. Heat it with a 25-watt light bulb mounted somewhere in the box away from flammable material (A). Use a thermometer (B) to measure the drop in temperature.
Line the box (C) with the different materials we want to test.
Measure the temperature every 30 seconds.

You may use different methods for mounting your light bulb. In either case make sure that the light bulb is not very hot or very close to the sides of the box. Some insulating material are flammable and will catch fire if getting hot.

If you are using solid insulating material such as fiberglass boards, you may cut them to size and then use them to cover the inside of your box. For all other material you need to use glue or place them in bags to form a quilt. Make your bags from paper or cloth.

Do not use a very hot light bulb. Depending on the size of your box, you may use a 5 watt up to 40 watt bulb.

Procedure:

The box is heated for 15 minutes using the light bulb, before every test.
The first step is to record the temperature drop for the box without any lining material. This provides a set of data against which we can compare various lining materials.

Now line the box with one of the materials; close the box; turn on the light bulb for 15 minutes; Start recording the temperature drop every one minute as soon as you turn off the light bulb.

Repeat this twice for each insulating material and average the results. Keep the box open between your trials for about 15 minutes or until the temperature inside the box equals the room temperature.

Do this over again for each of the materials being tested.

Insulation test result for one inch (thickness) insulating material.

The numbers in the above table are unreliable test results. Especially there are high temperature drops (shown by ??) that do not conform with the rest of data. You need to perform the test and come up with your test results.

Insulating materials listed above are just an example. You need to test at least three different materials for your project.

Repeat the experiments with two inch insulating materials and record the results in a new table.

Insulation test result for two inch (thickness) insulating material.

Note: Instead of heating the box for 15 minutes before every test, you may heat it until the temperature gets to 75º Celsius (167º F) and then start recording temperature drop.

This is described in the following procedure:

New Procedure:

The box is heated to 75ºC (167ºF) using the light bulb, before every test.
The first step is to record the temperature drop for the box without any lining material. This provides a set of data against which we can compare various lining materials.

Now line the box with one of the materials; close the box; turn on the light until the box gets to the 75ºC temperature and then turn it off; Start recording the temperature drop every one minute as soon as you turn off the light bulb.

Repeat this twice for each insulating material and average the results.

Do this over again for each of the materials being tested.

Insulation test result for one inch (thickness) insulating material.

The numbers in the above table are just examples. You need to perform the test and come up with your own test results.

Insulating materials listed above are just for example. You need to test at least three different materials for your project.

Repeat the experiments with two inch insulating materials and record the results in a new table.

Insulation test result for two inch (thickness) insulating material.

Materials and Equipment:

Material and equipment used for this experiment are:

• A metal or cardboard box (Metal is preferred because it is not a good insulator)
• A light bulb with wire and plug assembled on the box (adult supervision required). If the open space inside your insulated box is about 1 cubic foot, a 15-watt light bulb may be used.
• Samples of insulating material (Styrofoam, Fiberglass, Cellulose, Wool, Polyurethane foam).
• Thermometer for about 0 to 90 centigrade.

Results of Experiment (Observation):

After all the data has been collected, the results are recorded in a chart, and displayed in a graph. Following is just a sample:

Calculations:

The only calculation that you need is calculating the average for your repeated experiments.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

Your completed tables or chart also may appear hear.

Conclusion:

Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

This is a sample by another student:

The pink insulation retained heat best.
Cotton was hardly better than no insulation.

Discussion:

Pink insulation is the standard insulating material for house construction. It is no surprise that it kept heat in better than the other materials.
Styrofoam would probably perform better in thicker sheets; the thickness used here was much less than the pink insulation.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.

Visit your local library and find a few books related to insulation, architecture and energy saving. There are millions of books and other publications related to insulation. Some of those may be found in your local library.

Following are 3 web links and two books.

Kipping food hot

A Good Sample Project

Investigating Insulation

Living Homes
Thomas J. Elpel’s Field Guide to Integrated Design and Construction
4th Edition, May 2001

The Superinsulated House:
A Working Guide for Owner-Builders, Architects, Carpenters and Contractors
By Ed McGrath

Profusely illustrated with 100 charts, tables, drawings, photos, plus bibliography and index
ISBN 0-918270-12-X paperback, 8 ½ x 11, 103 pages, $19.00

Journal of Thermal Envelope and Building Science

Published in Association with:

International Council for Research and Innovation in Building and Construction
Editor:Mark Bomberg
Concordia University, Canada

For more books and journals, search the Internet with keywords such as “Insulation book” and “Insulation Journal”