A Better Building Envelope

by GBGC Expert: Gordon McKnight, Dow Building Solutions

When you think of “green building” you probably fall into one of three categories:

  1. You love it and will do anything to support it;
  2. You do it because your customers are asking for it; or
  3. You don’t really get what all of the hype is about…buildings are still being lived in today that are hundreds of years old and no one has died right?!

Regardless of your category, be a good sport and play along for a moment.

When you hear the word “green,” what comes to your mind? I envision grass, clovers, my little brother’s face after getting off his first roller coaster ride, and everyone’s favorite — money!

When someone says “building,” what pops into your head? It could be a construction site, a framing crew, a skyscraper, or perhaps your kid’s half-built Lego castle you’ve tripped over three times today.

Now turn to someone nearby and ask what they think of after hearing those words. Were their thoughts different than yours? Probably! And even if the first image was the same, I’d be willing to bet you some of that green money the next two were different! It’s no wonder that many of us get frustrated and give up on green building. “Good riddance…not even the experts can agree,” you might think. Trust me, I know the perception. What I’d like to do today is provide you with a few key takeaways for green building that we should all be able to agree on, and give you an important place to begin. For you green building experts, this will be old news. But for those of you on the cusp of believing in building green, this is be a great starting point. 

Let’s begin with the facts. There are a few key elements to green building that the experts will point out:

  • Energy Savings
  • Resource Efficiency
  • Water Efficiency
  • Indoor Environmental Quality

Those seem pretty obvious after they’re in front of us, right? Here’s the hard part…where do you start on the journey to building green? When you think about energy efficient products, it’s very typical to think of all of the things inside one’s home: an energy efficient HVAC system, energy star washer and dryer, ducts insulated so heavily and effectively that your five-year-old tells his teacher that daddy build a spaceship in his attic, and a stellar refrigerator with matching kitchen appliances. The list goes on and on. But what’s the point of having all of that great stuff on the inside for us to enjoy and our kids to destroy if we don’t have an effective, state-of-the-art, energy saving, moisture rejecting, cavity warming, mold deterring (should I continue!?) way of protecting our amazing home? If we don’t start with the outside, what’s the point of sensationalizing the inside?

So where should you start? The envelope! The outside of a home shields us from Mother Nature’s elements. Maslow’s Hierarchy of Needs has told us for years that people must have shelter before they can move on to the next level of needs — not a memory foam mattress, not crown molding or cathedral ceilings — just plain ole shelter!

If we don’t put our efforts into the outside of the house, we might as well wave the white flag and say green building just doesn’t give us the results we want… because it won’t. How great does your energy efficient washer/dryer look if you have a mold epidemic inside your wall cavities? I for one wouldn’t be too worried about washing my clothes. In the words of your five-year-old son who loves the attic spaceship, “We need to create this cool, superhero strength force field to keep the bad stuff outside from getting inside to hurt us!” Okay, that might be a bit of a stretch. I would’ve added, “…and do it in a way that actually reduces the home’s energy waste and carbon footprint.” Much better. I don’t think anyone has ever said, “Protecting your home from the elements isn’t important.” But you may not know that we can actually build a more comfortable, durable, efficient home by building a green envelope! How?

On a cold and rainy day in Houston this December you’ll probably put on a thicker, water resistant jacket, right? Just a raincoat wouldn’t suffice, because you’d still be cold. And if it’s a hot, humid summer day next June and you’re headed to the beach, you’ll probably put your soda in a cooler. Duh, no one likes a warm Coke! Think about both of those examples. What are you doing to protect what’s important from the elements? INSULATING! DING DING DING! (You knew this was coming from the Dow girl didn’t you? I promise you’ll see I’m unbiased).

But anyone can insulate their home — fill the cavities with a high R-value building material and we’re good to go right? Wrong! If we’re building green (or a better, more durable home for that matter), we need to insulate the entire exterior. Experts like CertainTeed’s building science applications manager Lucas Hamilton (see, I play fair) would agree that, “If you only insulate between the studs, you’re only insulating 75% of your building.” That doesn’t seem very energy efficient, does it? That’s like buying a new refrigerator without the door! Certainly not green.

So what’s one very cost effective way of starting your green building adventure without having to sacrifice too much of your green money that you’d like to spend on the inside? Three words: Continuous Rigid Insulation. Energy loss (the anti green building!) comes from five main sources:

  • 5% ceilings
  • 17% doors and windows
  • 17% above grade walls
  • 38% air infiltration
  • 23% basements (thank goodness we’re in Texas though!)

Continuous insulation can help mitigate the two largest sources for energy loss in Texas — above grade walls and air infiltration, which account for more than half of our home’s energy loss. By building green with continuous insulation, you take the battle against wasting energy head-on. With taped seams and a half-inch of continuous insulation like Dow Styrofoam Residential Sheathing on the outside, you can decrease your home’s potential mold problems and indoor air quality issues, make your homes feel more comfortable, while putting less stress on your HVAC system, reduce the number of air changes per hour in your home, reduce your HERS score (a big win for green building!), keep your mother-in-law  from complaining that your guest room is damp (Oh, and the bed wasn’t made right!), and also allow you to reduce some costs on other elements that you’ll encounter on your green building journey.

In some cases, adding R3 continuous insulation on the outside of one’s home can reduce the HVAC tonnage, allowing you to spend less money. In others you’ll be able to use a less expensive cavity insulation while maintaining a higher effective R-value! Dow’s testing has shown that the effective R-value of a 2×4 wall with an R-13 batt is actually about R-9.3. If we were to add a half-inch of continuous insulation (R-3) to that wall and reduce the batt to an R-11, we would actually have an effective R-value of 10.6! A cheaper wall that performs better? Hey, maybe green building isn’t so bad!

Now don’t even get me started on the return on investment (ROI) for using continuous insulation. I actually dislike the term, but customers love it don’t they? I’ll save that soap-box for another blog.  However, if you like the “ROI” term when discussing green building with customers, it will be hard to find another product (other than rigid foam) that will do more to protect their home’s integrity while also producing a relatively quick return on their investment. If adding rigid foam costs an average home between $500 and $1,200, and home owners can say it saves them at least $30 a month on their energy costs then you can quickly see green building is good for our environment and our wallets!

Now I’m sure I haven’t persuaded all of you yet that green building is a great idea, or that starting with the envelope is where the journey needs to begin. So I’ll leave you with this last comment that many proud Americans can hang their hats on: Reducing the five sources of energy loss in homes would mean using less fuel to heat and cool our homes right? Where does most of our fuel come from? I have a feeling even your five-year-old could tell you, “Not America.” So what happens if every home started reducing their fuel intake? We would become less dependent on the woes of other countries and more in control of our prices, and future. A bit of a spin, but nonetheless, very true. 

Those of you who aren’t firm believers in green building will have a few things to churn over after reading this. My hope is that some of you scratch your heads and perhaps do some further research. Please. There are benefits to Continuous Rigid Insulation and other air and moisture retarders that I didn’t even touch upon.

For questions on this particular green building element and any others, feel free to reach out to me and my awesome green team, the Green Built Gulf Coast Committee. The GBGC committee members make my green building knowledge look elementary. They’re good! We can help you, your customers, or even that five-year-old (don’t quote me on that) better understand easy ways to achieve green building and create a better environment for your family or your customers.