What R You Doing?
A four part series looking at insulation, R-value, and value.
What is the value of good? No, this isn’t a Zen and the Art of Motorcycle Maintenance moment, but we all want to know how much is really worth it. So you’re building a new home or updating your existing home and you have the same questions we all do. When it comes to insulation, how much is enough? What are my options? And at what point, as the phrase goes, “are we putting lipstick on a pig?”
There are a lot of companies out there to tell you what you need and why their product is best. Do I really need a tank of premium gas? (Probably not.) What is the difference between name-brand bottled water and the store brand? (Very little.) Can I buy generic mayonnaise? (Never, I’m picky about mayo.)
So the first question, “What’s in my wall?”
If you’re building a home and using wood or steel framed construction, you will need to use insulation inside the wall cavity. This is usually cellulose or fiberglass batt or blown insulation. It’s cheap, code compliant, and has been used for decades. But it’s not so great.
Drawbacks of blown-in insulation
- Not extremely efficient (cost per inch of material, design, and labor continues to rise)
- For added insulation, walls must be made deeper/thicker (sure we can just build thicker walls)
- Risk of making home too tight and creating dew points in the wall (musty basement or stale air)
- Highly susceptible to leaks and thermal bridging due to wall studs (ever feel when the weather changes suddenly outside…)
- Low saturation rate (just like cotton, when it’s wet it doesn’t keep you warm)
Current building codes may also require that continuous insulation is added to the outside of the wall so that every seam in the wall is sealed. This greatly adds to the time, labor, materials, and overall cost of construction. While additional external insulation may increase the R-Value, it does little to improve disaster resistance to high winds, fire, flood, or other challenges from Mother Nature.
Okay, I’ll buy that, but what else can I do?
Well currently you can insulate in the following ways:
- Batt or blanket fiberglass, mineral wool, plastic or natural fiber insulation.
- SIPS – Structural Insulated Panel Systems. These are essentially an OSB ice cream sandwich with solid foam insulation as the ice cream.
- Continuous rigid foam board insulation (Polystyrene, Polyisocyanurate, Polyurethane)
- Spray foam and foamed in place (Cementitious, Phenolic, Polyisocyanurate, Polyurethane)
- ICFs (Insulating Concrete Forms)
- And a few variations on the same theme. Visit this page for more information.
So most of those are well known, but let’s talk about Insulating Concrete Form construction. What is it? If you’re familiar with SIPS, you know that they are like an ice cream sandwich (wood is the cookie, dense insulation is the ice cream). ICFs create the same flavor of wall but put the insulation on both sides of a concrete core. So foam insulation is the cookie and reinforced concrete is the ice-cream. Okay, that sounds hard … Ha, well it is and that’s good. Good and simple.
When building with ICFs you only do things once:
- Stack the wall
- Reinforce the wall as you go
- Create openings as you go
- Fill the foam forms with concrete keeping them plumb and level as you go
- Finish the wall
Compare that to building a cavity wall which can be complex and tedious to do correctly. So many pieces to keep straight and plumb, so much cutting, and so many seams to seal. Cavity walls of all types also suffer from thermal bridging or a thermal shortcut because the studs aren’t insulated. Studs connect the interior to the exterior and act like a straw sharing heat or cold between the inside and outside of a structure.
And that leaves us…
ICFs deliver a wide range of benefits over cavity wall construction (strong, soundproof, vapor barrier, pre-furred) just to name a few, but let’s focus on insulation. The 5” of EPS foam on many ICFs provide R-11 on both sides of a solid concrete wall (R-22 total). Why is that important? The concrete core, while being very strong, is also very slow to change temperature. Insulating both sides keeps the wall temperature incredibly stable. There’s not enough heating during the day or cooling at night to affect the concrete wall. This means the buildings heating or air conditioning doesn’t have to work as hard (or at all in many climates).
Okay, but so what?
Well, not using your HVAC much means that you can buy smaller units to match the need. Purchasing smaller units saves you money upfront, but the ICFs keep the interior temperature so stable that you’ll save money every month (forever) because your HVAC system doesn’t have to work as hard as in traditional cavity wall construction. You also get significant resistance to natural disasters such as fire (4-hour rating), wind protection (200mph), noise (STC 50+), flood (EPS doesn’t rot or host mold or mildew) and decay (protected EPS foam doesn’t decay or lose its insulation value like most other insulation).
So the long and the short of it… [Cue dramatic music, “dunh dunh, duunhhh”]
ICFs just makes sense. They deliver superior results, are safer, greener, and quickly pay for themselves through HVAC equipment savings and reduced monthly utility costs. Okay, now you’re interested, but not all ICFs are alike. How do I know what to buy?
Part two will discuss how we know that ICFs are a better way to build in terms of insulation and R-value. That’s right, we’re gonna hit you with some science baby! Click here for Part 2.