Facts about Insulation R Value
R value is the measure of the resistance of a material to heat transfer. Specifically, the R value measures the time for heat to transfer from one side of a material to the other side. You can think of R value as a way to calculate the number of hours a square foot surface of material must be heated to change the temperature by one degree on the other side of the surface.
Example of R Value
Take for example, a piece of fiberglass insulation board which has an R value of 10. The fiberglass board must be heated for roughly 10 hours in order for the other side of the surface to change its temperature by one degree. You can say that the fiberglass board has a very good insulation. That explains the reason fiberglass board is a popular insulation material used in a lot of houses.
Additive R Value
One of the greatest things about R value is that it can be added when there are several insulation materials that are appended together. For example, if you have a wall or a roof that is composed of fiberglass boards, foam sheets and polyurethane boards that are stacked together, you will have a material with R value that is the total sum of all the R values of each individual material.
Take note that if in between these insulation materials is an air gap, you need to take into account the R value of the air gap. Air is an excellent insulator and the approximate R value for air is one per one inch of air gap thickness.
R Values for Building Materials
The building industry usually utilizes a standard R value per inch of thickness for every insulation material. However, there are cases in which some insulation materials’ R values are taken for the materials as a whole instead of based on the thickness. As a result, you need to take note of these R values when you are summing up the R values of several materials.
The best practice is to carefully check the manufacturers’ specification in terms of R values for the building materials. The R values for certain materials can be much higher or lower if they are taken based on the materials as a whole.
R Values and Energy Saving
You can say that the higher the R value of a material, the more energy efficient the material is. Material with high R value means it’s more difficult for heat transfer to occur across the material. The material will be an excellent insulator to heat.
As a result, when choosing materials for house renovation or a building project, always use materials with high R values. An R value of five to six for a material is considered a good value. In general, a completed wall or roofs will have an R value of between 20 and 25.
You will save quite an amount of heating cost if the building is constructed with high quality materials that have high R-values. Besides, the equipment used to heat the house will also work less if the amount of heat less is greatly reduced and that will translate to significant of dollars saved in the long run.
R Value Alternative
An alternative to R value is the U value. The U value is the inverse of the R value. Some building materials such as windows use a U-value instead of R value. As a result, the higher the U value for a material, the less energy efficient the material is. A material with high U value means heat can easily transfer across it and the material is a poor insulator.
Some building elements such as the double glazed windows have U value of between 0.40 and 0.30. When translated to R value, that is the equivalent to an R value of 2 ½ and 31/3 respectively.
Future R Values
Rising energy cost has pushed manufactures to create building materials with higher R values. In recent years, the building industry has invested a lot of money into the research and development of more energy efficient building materials. As a result, sophisticated buildings materials with extremely high R values and yet durable as well as light weight are invented.
One such material is the silica aerogel insulation material with an R value of 10. The silica aerogel is not only light weight but also durable and is extremely cost effective. Other improved materials are the polyurethane foams which can provide an R value of 10.
In short, future building materials will push towards having higher R value of at least 30 to 40 per inch per thickness. When these individual materials are assembled together, the total R value achievable will be over 60 or more.
