The Truth on Energy Efficiency and R-Value
Energy Efficiency is more than R-value. Superior walls are more than R-value. When people reference R-value in deciding on what types of building materials to use, ultimately what everyone is interested in is energy efficiency, and what impact certain materials will have on R-value.
Energy efficiency is determined by several factors such as the walls, windows and doors, roof or ceiling, mechanical systems; and internal loads such as lighting, appliance use, and number of people.
The first place to start when improving energy efficiency is the building envelope. The building envelope consists of the foundation, the walls, the doors and windows, and the roof. It’s difficult to have an efficiently conditioned building without controlling the enclosure. The overall performance of a well designed and energy efficient mechanical system is reduced, if the envelope is not efficient, thus costing you money.
WHY are insulating concrete form walls inherently energy efficient?
What is great about ICF walls is that they perform well in respect to the “Chosen Three” of energy efficiency- conduction, convection, and radiation. How so you may be asking?
Your Home Loses and Gains Heat in 3 ways:
–Conduction– def. The transfer of heat through two objects due to a temperature difference.
ICF walls have a consistent R-value that reduces thermal transfer through the wall assembly.
–Convection– def. the transfer of heat through circulation of heated part.
ICF’s are virtually airtight which reduces the “circulation” of heated air from one side to the other, which give a structure a consistent indoor climate
–Radiation– def energy that is transmitted through one side of an object and absorbed by the other side.
The thermal mass in ICF walls reduces the radiation of temperatures from one side of wall to the other.
There is not another wall system that can control all three of these elements of energy efficiency in one system. By the way did you notice R-value truly effects only one of the “Chosen Three”?
But why does everyone advertise and INFLATE the R-values of their product when that’s not truly what it is? We do not know. Our guess is that other ICF manufacturers or other wall systems or products in general use the highest number they can find, or create, to try to mislead customers into thinking their product may be superior. What they don’t tell you is that R-values are tested in a lab, so R-values may be different in different climate zones etc. Also, some folks use “Effective” R-value number instead of “Actual” R-value. Watch this couple minute video of Richard Rue, from NASA spinoff company EnergyWise Structures, truly explain the importance of the Chosen Three and the misleading R-values.
So, to try our best to break it down for you, and give honest values and representation of the R-value of ICFs, our Reward iForm has a steady state actual R-value of R-22 (Conduction!). This is the clear wall R-value, the whole wall assembly and all its materials from inside to the outside face of the wall (foam < concrete > foam). This is not like a framed (wood or metal) wall where insulation is placed into the cavities of the wall and they call it an R-18, when in reality its clear wall R-value is more like R-13 or lower. The wood or metal is not accounted for in the wall’s R-value, as a wood or metal stud by itself is an R-2 to R-6.
Secondly, the continuous EPS insulation and monolithic concrete wall provides an air tight envelope (Convection!). This is probably the biggest factor contributing to the excellent energy performance of an ICF building. Wood or steel framed structures need extra material and effort to even try to achieve this level of convection.
Finally, the thermal mass of the concrete in the ICF wall will moderate peak temperatures daily (Radiation!). The thermal mass performance is a function of the climate or region of where the building is located. A climate that has wider temperature fluctuations daily will get better benefits due to the thermal mass. Plus this will help to contribute to LEED v3: Indoor Environmental Quality points as well!
Once again R-value does not take into account Convection and Radiation.
So the ACTUAL R-values of Reward Insulating Concrete Forms is R-22, as are most ICFs. What is “Effective” R value? The effective R-value is the comparative R-value that a framed wall would need to be insulated in order to have the same energy performance as the same building built with ICF walls. It is not the R-value of the ICF wall. The effective R-value considers the actual R-value, the air infiltration rate and the thermal mass.
So you can see why some people will say “Effective R-value” of 32 all the way up to 60 for ICF walls. All of the other factors you cannot test in a lab, as it will vary on climate and other variables. It is a COMPARATIVE measurement, with everything else being equal in the comparisons. As an example we say an effective R-Value of 32+. That means in order for you to achieve that level on a non-ICF wall, you will need to insulate the framed wall to a level 32+ value.
Other areas of the envelope that will enhance the energy efficiency of the building would be to add energy efficient windows, to provide high quality design and construction of the openings, and to provide a well insulated roof and an energy efficient roof to wall connection.
Hopefully that gives you a better insight into R-values, green building and an overview of the building envelope.
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