Why does efficiency matter? Americans will have varying priorities, but there are some common factors.
Americans care about their health, spending a $$/year. and given the amount of time we spend inside
our homes, they can have a significant impact on our health. Mold, viruses, bacteria, Volatile Organic
Compounds (VOC’s), temperature swings, dust, pollen, CO2 level, Oxygen level, and so much more are
markedly improved in our Efficient homes.
The primary reason so many people are giving Insulated Concrete Form (ICF) construction a close look is
the energy savings, or efficiency of these homes. While most building “experts” are more reserved, the
folks who have owned ICF homes are true believers, and spread the word.
But what makes our homes so efficient? Is it just the ICF’s? And why do ICF’s perform so well?
The short answer is that our standard ICF wall has an R-value of 23. Not too impressive you say? At first
glance, I agree. Very easily we can upgrade to r-35 and beyond, but R-value is not the entire picture. Our
homes perform well because EVERY piece of the home has been tuned to work as a system to deliver
exceptional energy performance. In other words, it isn’t ICF construction alone. ICF’s do however, have a
very significant role to play.
ICF efficiency is due to these three properties: Better insulation, Continuous insulation, and Thermal
Mass. Let’s briefly look at each in turn:
Better insulation. While every type of insulation has its purpose, some insulations are better for your
walls. Loose fill insulations are particularly prone to convective looping.
Here’s what I mean: Even if an insulated wall cavity were perfectly air-sealed (and air leaks only
exacerbate the problem), cold air on one side and hot air on the other introduces a convective force: the
one side heats air within the insulation while the other side cools it. Air moves within the insulation,
from one side to the other; and this convective current only increases in speed as the temperature
outside drops. Thus, the colder it gets, the more rapidly your walls lose heat. The thermal performance
declines just when you need it the most!
Solid insulations, such as Expanded Polystyrene (EPS) do not have this problem, as they prohibit the
movement of air. But not all solid insulations are equal either. There are some whose performance
degrades quite dramatically as the mercury drops. So to recap, solid insulation is better, except when its
not. Got that? If you’re taking notes, just specify EPS insulation, and all will be well.
Continuous insulation refers to the way the concrete core of the wall is sandwiched between
uninterrupted layers of EPS insulation. It isn’t difficult to understand why uninterrupted insulation is far
superior to conventionally framing and insulating a wall. Just try downhill skiing in West Michigan with
an exposed midriff!
The picture above shows just how much of a wall cannot be insulated when stick framing; in most cases
the framing displaces over 20% of the insulation. This is making Swiss cheese out of our insulation
“coat”! Thus, the actual thermal performance of a stick framed wall is pretty dismal when compared to
the rating on the insulation. This may be small potatoes in Honolulu, but in Grand Rapids we need to pay
attention to such matters. Shocking, I know; misleading product data.
Thermal Mass is one that is a bit harder to quantify. We’ll expound it further in a future blog post, but
for now think of the concrete mass in the center of that insulation as a giant battery that takes a long
time to charge and discharge. The difference is that this battery stores heat, not electricity. This long
time period evens out the highs and lows of the day, and even week. The thermal mass of an ICF home
means you will never be too cold one night and too hot the next day.
Taken together, these three factors contribute to a standard r-23 ICF wall outperforming any other r-23
wall. And that is without mentioning the airtight performance of an ICF wall.