Radiant Barriers: How Easy Physics Could Save You Tons of Money
Of all the cool and interesting things I've learned in my adventure in conservation that began with reading Lester Brown's Plan B 2.0, the one that has really popped my eyeballs out the most so far is radiant barriers. Once you learn about what radiant barriers are and what they can do, I promise you that you will never look at a house the same way again.
Without putting too fine a point on it, after what I've read on this incredible application of basic physics, NO home should be built without incorporating this technology. Why? Simple: it's a huge energy saver that can also save you tons of money in heating and cooling your home!
Okay, first off, what is a radiant barrier? At its most basic, it's a highly reflective material, usually bonded to a flexible backing. Imagine the shiny side of aluminum foil on a material that doesn't tear so easily. And you've seen radiant barriers before: think about those shiny sunshades for your car, or those little emergency blankets that look like aluminum foil, or even an old-style thermos bottle that had a really shiny surface on the inside.
All of these radiant barriers operate on the same basic principle: they reflect heat back toward its source. So, take the car sunshade, sitting inside your windshield: it helps keep your car cool because it's not just shading the interior of the car (you could just do that with some cardboard), it's reflecting the sun's heat back out.
Those little shiny emergency blankets work because, if you're out in the cold and you wrap one of them around you, it reflects the radiated heat from your body back toward you, rather than letting it escape into the cold air; but in a hot climate it can also help keep you cool by radiating the sun's heat away from you. And ditto with the thermos bottle: cold liquids stay cold because the heat from outside the bottle is reflected back away from the cold liquid, while hot liquids stay hot because the heat is reflected from the inside of the bottle back into the liquid. You got it?
If you think about it in terms of infrared light - which is essentially radiant heat, like the heat from the sun on your face - just bouncing off of a reflecting surface, it's just basic physics. There isn't any real rocket science here, this is stuff we all had in high school (even if we weren't really paying attention!).
Now, let's compare a radiant barrier with insulation for a moment. As I've explained, radiant barriers essentially reflect heat energy back toward its source. Insulation, on the other hand, absorbs heat: insulation basically just tries to slow down the passage of heat from the "hot" side of the insulation to the "cold" side. It doesn't stop or reflect it, it just soaks up as much as it can. It's a heat resistor, and in fact the "R" in insulation ratings - like R-11, R-19, and so on - means "resistance" to heat transferred through conduction (where the heat is transferred through a medium, like when hot soupt transfers heat into the spoon you left sitting in the soup).
Sure, if you have enough insulation you can absorb and slow down enough of the heat passing through a substance or structure to keep it warm or cool for some length of time. But if you keep applying the heat long enough, eventually it will get through.
And there's something else you probably didn't realize: now that your insulation has stored up all that heat, when the heat source disappears (like the sun goes down), do you think the heat in that insulation just disappears - "Poof"? Nope: all that stored heat gets radiated back out again. That's why in summer, even after it's cooled off in the evenings, your walls will still feel warm, even hot, and your air conditioner has to keep running to get rid of it (and the same with the cold leaching out in the winter). All that stored heat has to go somewhere!
So, here's the question: After reading the above on radiant barriers compared to insulation, which sounds like the best way to control heat that wants to get into (summer) or get out of (winter) your house? Reflect the heat back toward its source, or store it up and then have to deal with it?
I don't know about you, but my vote goes for a radiant barrier! I mean, honestly, this is such a huge "Duh!" after I researched it that I really was mad that I didn't know this a few years ago when our house was built. If I had things to do over again, I would have had our builder install a radiant barrier on the exterior of the house, as well as the attic.
And I'd also go so far as to say that, from what I've read, radiant barriers should be a mandatory code item for any new construction. According to what I've researched, just adding a radiant barrier to the exterior walls and attic could cut your heating and cooling costs by as much as 50%!
But while it's too late to do anything about most of the walls in our home, I can still make some major improvements to the attic and the garage. As a matter of fact, I recently bought some radiant barrier material that I'll be installing soon on the garage doors, which are basic aluminum doors without even any insulation: talk about massive heat gain in summer and loss in winter! If your garage is like ours, it's like an oven in summer and an icebox in winter, and the heat/cold not only gets transferred into the rest of the house through the interior walls, the master bedroom is above it. So keeping that room warm or cool is a lot harder!
Now, if this has gotten your attention, I'd like you to refer you to what I believe is the best web site out there for information and radiant barrier products: Horizon Energy Systems. These folks don't pay me a penny, I'm not an affiliate with them (and if I was I'd tell you): but they have done tons of applied research and developed a line of products that I believe are the best available, and I want to toot their horn because what they have to say is extremely important (and they have a very good overview of what radiant barriers are).
For example, for my garage radiant barrier project (which I hope to turn into a video podcast), I purchased 500 sq ft of their basic Radiant Barrier Wrap for $74, including shipping. That should be enough to do both our garage doors, the exposed outside wall of the garage, and the ceiling that is a big heat sink for our master bedroom. They have other products - in particular, RBS Chips and Thermal Control Membrane, or TCM - that are tailored for attic and other applications and are more expensive, but the long-term energy savings more than outweigh the short-term costs. Plus, most of this stuff is really easy to install, even for an unhandy guy like me!
So, if you're having a home built or extensively remodeled, do yourself a huge favor and talk to your builder about having radiant barriers installed! Wrap the exterior walls, garage doors, and have it installed in your attic (but make sure they do it the right way - most builders aren't familiar with radiant barriers). You won't believe this, but the folks at Horizon Energy Systems say that you'll need to significantly downsize your heating and cooling system for it to run properly (which means you'll save lots of money, not only on installation, but on operating costs!).
For the rest of us who can't do much about the basic structure, wrap your garage doors and interior walls where you can, and put radiant barrier material in your attic.
You can also wrap your water heater and ducts in radiant barrier material to help keep heat where it's supposed to be and reflect it back from where it's not. Heck, Horizon Energy Systems says you can even put this stuff in the headliner of your car to help keep your car's interior cooler!
Bottom line: radiant barriers can save you a ton of money and energy, and every home (and cars and who knows what all else!) can probably benefit in some way from applying this basic principle of physics!