Energy Savings
three main ways ICF walls outperform regular wood-framed walls
Insulated Concrete Form (ICF) walls are know to typically save homeowners up to 50% on their energy bills. Yet, the R-values ratings of ICF walls are, on average, R-23 versus the R-20 rated conventional stud walls. So how are these tremendous savings possible? It’s “The “ICF Effect” – a combination of continuous insulation, airtightness, and thermal lag, which together give ICF walls their stellar energy performance.
1. Continuous Insulation
Regular stick-built walls can lose a tremendous amount of heat due to thermal bridging while ICF walls, their two layers of thick continuous foam insulation, don’t lose any heat due to thermal bridging.
A picture is worth a thousand words and these two thermal images were taken over 20 years ago, on a cold November morning in Alberta, Canada, of two homes side by side. The thermal image on the left of a regular wood-frame home and the thermal image of the right was of a home built with Logix ICF.
The drastically different amount of heat loss through the walls is striking!
Thermal Image of a Wood-Frame House
Thermal Image of a Logix ICF Home
2. Airtightness
Thermal bridging is not the only means by which heat can leave a building. Convection, or heat transfer through airflow, is a another common way for heat, and cold wintry air, to find their way through the envelope cracks.
As building science shifts its attention from insulation to airtightness, uncontrolled air movement has become the focal point in newer codes. Quite simply, structures that are more air tight are far more energy efficient.
Even with high-performance insulation products, wood-frame builds can do a poor job of controlling airflow. Based on a study by the RDH Building Science Laboratories, light wood frame structures dating between 2002 and 2012 have an average airflow of 4.8 Air Changes per Hour (ACH) (excluding mechanical ventilation).
In contrast, according to the same study, ICF structures see about 1.26 ACH, which is a very high level of airtightness.
That’s not to say that a stud wall can’t be made airtight. It can. But the labor hours needed to seal and tape every single crack and crevice can significantly extend a project. On the other hand, ICF walls are monolithic and don’t require extensive sealing to be airtight.
3. Thermal Lag
Thermal lag is the delay of heat transfer through a wall. Materials with a higher thermal mass – the ability to absorb heat – prolong this delay.
Why does thermal lag matter? Because it helps preserve the indoor air temperature even as the outdoor air cools. This lets heating systems stay inactive longer, thus giving homeowners extra savings on their energy bills.
A study done by Cleb Laboratory Inc reveals the colossal effect thermal lag has on a wall’s energy performance. In Cleb’s guarded hot box test, a conventional low-mass stud assembly was matched against a high-mass ICF wall.
The two walls showed vastly different results when subjected to the same plummeting temperatures in the “cold” chamber. While the stud wall chamber saw its heater come online as soon as the outdoor temperatures fell, the ICF chamber maintained its indoor temperature for more than 50 hours before the heating unit switched on.
With the wood-framed wall, the heater turned on almost immediately.
In total, the ICF wall was projected to create an energy savings of 149% over the stud wall over the course of the test.
