Study of efficient home insulation

Introduction: (Initial Observation)

Proper insulation is the most important factor in designing an energy efficient home. In cold winter days, insulation can keeps the heat inside. In summer days, insulation can keep the heat outside. Insulators are material that prevent heat exchange between inside and outside a house. Different material can be used to insulate walls, ceilings and pipes.

In this project, I want to see what material are being used as heat insulators and compare the effectiveness of different commercial heat insulators. I also want to see how does the thickness of insulation affect the rate of heat exchange.

Information Gathering:

Find out about different home insulation materials. Read books, magazines or ask professionals who might know in order to learn about the effect of insulators on preventing heat exchange. Keep track of where you got your information from. Following are some sample information:

What is insulation?

Insulation is any material mainly used to slow down heat flow. It may be mineral or organic, fibrous, cellular, or reflective (aluminum foil). It may be in rigid, semi rigid, flexible, or loose-fill form.

What are common insulators for homes?

Commercially available insulations are fiber glass, mineral wool, cellulose, foam and cotton. The two most common types of insulation for residential applications are fiber glass and cellulose. There are several things to consider before making an insulation decision:

Thermal Performance – Installed R-value
When insulating a home, it is important to get the R-value specified by the builder or the local building code. It’s also important that the product provide long-lasting thermal performance.

While R-value “per inch” is promoted by some manufacturers, the overall R-value installed is what counts. Fiber glass insulation products come in R-values ranging from R-11 to R-38 for fiber glass batts and rolls. Fiber glass and rock and slag wool insulation can be blown in an attic to nearly any R-value. More R-value alternatives provide greater flexibility in meeting code energy requirements in your area.

Lifetime Performance
In order to ensure the expected energy savings, it is important that the insulation does not deteriorate, or settle, over time.

Fire Safety
Fiber glass and cellulose perform very differently in terms of fire safety. Fiber glass insulation is naturally non-combustible because it is made from sand and recycled glass. Fiber glass insulation requires no additional fire-retardant chemical treatments.

Cellulose insulation is made primarily of ground-up or shredded newspaper, which is naturally combustible. To protect against fire, cellulose insulation is heavily treated with fire retardant chemicals. Though cellulose is treated with fire retardants, it is not fire proof.

Moisture
Insulation will lose its insulating efficiency or R-value when wet. Fiber glass and rock and slag wool insulation are not absorbent and, if exposed to moisture, will not wick up or hold water. They will dry out and retain their original R-value. Cellulose on the other hand will hold water, loosing its heat resistance.

Understanding Heat Transfer

Heat flows by three mechanisms: conduction, convection, and radiation. Conduction is the molecule-to-molecule transfer of kinetic energy (one molecule becomes energized and, in turn, energizes adjacent molecules). A cast-iron skillet handle heats up because of conduction through the metal. Convection is the transfer of heat by physically moving the molecules from one place to another. Hot air rises; heated water thermosiphons; a forced-air heating systems work by moving hot air from one place to another. Radiation is the transfer of heat through space via electromagnetic waves (radiant energy). A campfire can warm you even if there is wind between you and the fire, because radiation is not affected by air.

With buildings, we refer to heat flow in a number of different ways. The most common reference is “R-value,” or resistance to heat flow. The higher the R-value of a material, the better it is at resisting heat loss (or heat gain). U-factor (or “U-value,” as it is often called) is a measure of the flow of heat–thermal transmittance–through a material, given a difference in temperature on either side. In the inch-pound (I-P) system, the U-factor is the number of Btus (British Thermal Units) of energy passing through a square foot of the material in an hour for every degree Fahrenheit difference in temperature across the material (Btu/ft2hr°F). In metric, it’s usually given in watts per square meter per degree Celsius (w/m2°C).

R-values are measured by testing laboratories, usually in something called a guarded hot box. Heat flow through the layer of material can be calculated by keeping one side of the material at a constant temperature, say 90°F (32°C), and measuring how much supplemental energy is required to keep the other side of the material at a different constant temperature, say 50°F (10°.C)–all this is defined in great detail in ASTM (American Society of Testing and Materials) procedures. The result is a steady-state R-value (“steady-state” because the difference in temperature across the material is kept steady). R-value and U-factor are the inverse of one another: U = 1/R. Materials that are very good at resisting the flow of heat (high R-value, low U-factor) can serve as insulation materials. So far, so good.

R-value tests.

R-value measures resistance to heat flow. R-values given in labels, fact sheets, ads, or other promotional materials must be based on tests done under the methods listed below. They were designed by the American Society of Testing and Materials (ASTM). The test methods are:

a. All types of insulation except aluminum foil must be tested with
“Standard Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the Guarded-Hot-Plate Apparatus;”
_ “Standard Test Method for Steady-State Thermal Performance of Building Assemblies by Means of a Guarded Hot Box;”
_ “Standard Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus;”
_ “Standard Test Method for Thermal Performance of Building Assemblies by Means of a Calibrated Hot Box;”
_ “Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Thin-Heater Apparatus.”

R-Value

A material’s R-value is the measure of its resistance to heat flow. It is important to know the R-value because many states or regions require that a roof system have a minimum amount of thermal resistance on commercial, industrial, and/or institutional buildings. The way it works is simple: the higher the R-value, the more the material insulates.

Some common roofing materials and their corresponding values for Thermal Conductance (C) and Thermal Resistance (R) are shown in the following table.

The C-value (C) is a measure of the Thermal Conductance of the material and is the reciprocal of R, or

C is determined only when the Thermal Conductivity (k) of a material is known.

Thermal Conductivity is the measure of the amount heat that will be transmitted through a one inch (1″) thick piece of homogenous material, one square foot (1 ft.2) in size, in one (1) hour, when there is a one degree Fahrenheit (1?/font> F) temperature change. The equation for “k” is:

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.

How different heat insulators affect the rate of heat exchange between inside and outside a house. I want to measure the thermal conductivity of different insulators and see “which one has a lower thermal conductivity?”. (or Which one is a better insulator?)

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.

Independent variables for our experiment is the type of insulators that we choose to test and compare. Values are fiber glass, cork, wood, rock wool, slag wool. You can choose any other material for your study.

Dependent variable is thermal conductivity (Or the reverse of that which is thermal resistance).

Controlled variables are other environmental factors and experiment conditions that may affect the thermal conductivity. Controlled variables include weather temperature and humidity.

Hypothesis:

Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis. Following is a sample:

Among fiberglass, cork, wood, rock wool and slag wool, fiberglass has the lowest thermal conductivity (Or the reverse of that which is highest thermal resistance.)

Your hypothesis may be different.

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 1:

Introduction: We use a box as a model home and a light bulb as a heat source. We also use two thermometers to record the temperature of inside and outside of the model home. We can have two different methods of measuring the thermal resistance of our model home. One way is to warm it up using the light bulb and see how long does it take for the home to reach to a certain temperature. The other way is to warm it up and see what will be the highest temperature inside the house after an extended period of time.

Material:

1. Empty cardboard box about 1 cubic foot.
2. A light fixture with a 40 watt incandescent light bulb.
3. 2 thermometers
4. varieties if insulating material.

Procedure:

1. Place the light fixture inside the box. Make sure it is safe and the light bulb will not touch the box. Also make sure that the switch is on and the light will turn on as soon as you plug in the wire to an electric outlet. Close the box.
2. Inset a thermometer in the box. It is good if you use a thermometer that can show the temperature inside the box while it’s display is outside.
3. Prepare your data sheet, record the initial temperature inside and outside of the box and then plug in the light.
4. Record the temperature every minute until the temperature inside the box is 30º Fahrenheit more than the outside temperature.
5. Unplug the wire and wait about 15 minutes for the light to cool off. Open the box and wait another 15 minutes so the box and light get to the same temperature as outside.
6. Cover the box with one of the insulators that you want to test and repeat the above experiment.
7. Repeat these steps with every other insulating material that you want to test. You should finally have one data table for each insulator. Following is a sample of data table.

You can use each of the data tables to draw a graph. You may also combine multiple graphs with different colors in one sheet. In this way you can visually compare the speed of heat increase with different insulators.

Analyze your results table and graphs to determine which material are better insulators.

What we did

We set up two (single-glazed) houses: one with loft insulation only and one with loft and wall insulation.
We set up another two houses: one with double glazing and one with single glazing.
We switch on the heaters all at the same time and got the computer to record how fast they warmed.

Sample graph

These graphs of temperature against time show how quickly the houses warm up. Each color represents a different insulator.

Looking at the results

• Why are the temperatures of the houses increasing?
• Why do the graphs seem to level off instead of continuing to rise forever?
• How do the graphs tell you how wall insulation helps?

Extra

• Try to measure the temperatures at which the graphs level off. Do these help you to compare the usefulness of loft insulation.
• Try to measure the steepness (or average gradients) of the graphs. Do these help you to compare the usefulness of insulators.

What you can do

• Try a similar experiment yourself, but this time warm your houses until they reach a steady temperature. Then measure how fast they cool. Is this a better way of studying insulation?
• There are other ways to heat the houses. You might instead place a hot block of metal in each house and see how well the house keeps it warm. Do you think this is worth trying?
• Find out about the cost of insulation and how much heat energy you can save by using it. Then calculate how long it would take to pay for its installation.

Experiment 2:

Introduction: Since we are using a light bulb to warm up the model house, it is very easy to calculate the amount of energy used for heat. We simply multiply the watts by time (hour). For example a 40 watts light bulb in 2 hours consumes 80 watt hours energy. Watt house also can be converted to calories or BTUs.

With this in mind, why not calculate the R-Value of different insulators. Following are some information that we may need to convert different units of energy to each other.

Procedure:

Start by measuring the R-Value of an empty carton box as follows:

1. Place a 40 watt desk lamp or portable lamp inside a carton box. Make sure that the hot light bulb will not touch the box and cause fire.

2. Test the lamp and make sure that the switch is on, so the light will turn on if you plug the cord to an electric outlet. Unplug the cord for now.
3. Close the box and seal any holes with tape.
4. Record the starting temperature inside and outside of the box. Temperature inside and outside must be the same at this time.

5. Place the box on some kind of stand. You must make sure that heat exchange will happen from all sides of the box.
I inserted four wood dowels in a piece of board and used them as stand.
6. Turn on the light and record the temperature of inside the box every minute until you see no temperature increase for 3 minutes.
7. Use the room temperature and the maximum temperature inside the box along with the box dimensions to calculate the R-value of the carton box. See the calculations in Calculations section.

Cover the box with different insulators such as fiber glass or Styrofoam (one at a time) and perform the above experiments again. The results that you will get is the R-value of the box plus the R-value of the insulator that you are testing. Do not touch fiberglass. Sharp fibers can hurt your skin. Wear gloves and goggles and apron.

Materials and Equipment:

List of material can be extracted from the experiment section.

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.

For experiment 1, in addition to the data tables and graphs that you make, you will need to create another data table and record the time it took for the house to warm up with different insulators. You will then use this table to make a bar chart. Each bar represents a different insulator.

Calculations:

To calculate R-Value to the following:

1. Calculate the BTU of your heating device by multiplying the watt hours by 3.412. I used a 40 watt light bulb, so the BTU in one hour is 40 x 3.412 = 136.48
2. Measure the thickness of the insulator in inches. Cardboard was 1/8″ and fiberglass was 1.5″.
3. Measure the difference between the room temperature and the maximum temperature inside the box. In a sample test the temperature difference was 27ºF.
4. Measure the surface area of the box. In my test it was 4.1 square feet.
5. Calculate the C-value = (BTUs * inches of thickness)/(hour * ft2 * Fº)
   In my empty box example:
   C-Value = (136.48 * (1/8)) / (1 * 4.1 * 27) = 0.154
6. R-Value = 1 / C-Value = 1 / 0.154 = 6.4

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.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.

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.

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.

References:

List of References

Project Advisor notes:

With the increasing price of energy, energy efficient home can save us thousands of dollars in energy cost each year. In hot summer days, insulation must prevent the heat from entering the home. In winters the heat must enter and remain inside the home. All these are possible by an efficient design and insulation.

In this project you focus on studying insulation material and perform experiments to compare the efficiency of different material. You may also compare the efficiency of one specific insulator in different temperatures, different thickness, different densities or any other possible variable that may affect the efficiency of an insulator.

Comparing Insulative Properties of various natural and commercial insulators.

http://nvl.nist.gov/pub/nistpubs/sp958-lide/010-013.pdf

http://www.hukseflux.com/application details/building_detail.htm

R-VALUE — A unit of thermal resistance used for comparing insulating values of different material. It is basically a measure of the effectiveness of insulation in stopping heat flow. The higher the R-value number, a material, the greater its insulating properties and the slower the heat flow through it. The specific value needed to insulate a home depends on climate, type of heating system and other factors

R value = the number 1 divided by the U value.

Its units of measurement for R-value are: (square feet x hour x degree F)/BTU in the English system and. (square meters x degrees C)/watts in the metric system. …

http://hem.dis.anl.gov/eehem/99/991110.html

http://hem.dis.anl.gov/eehem/feat_cats.html – R-VALUE%20MEASUREMENT

http://hem.dis.anl.gov/eehem/feat_cats.html – WATER%20CONSERVATION

http://www.geoscienceltd.com/lab.html