What is that radiant barrier thing?

The radiant barrier seems to be hardest attic improvement for the inexperienced efficiency seeker to understand. Most of us have an intuitive grasp of the other major improvements: additional insulation should work, if we have no other understanding of the physics, just on the basic principle that "if some is good, more is better." Additional ventilation should work just because we understand that breeze cools our bodies, and therefore it can cool our houses. Never mind that the principle is different; our houses don't sweat and use evaporation to cool (OK, some with swamp coolers do), but instead use ventilation to replace super-hot air with just hot air to reduce the temperature difference between the attic space and the conditioned space.

But with the radiant barrier, very few of us understand how something reflective could possibly work from inside the attic. Sure, we understand that if we put silvery reflective stuff on the roof or at the very least painted the roof white we would reflect a good bit of the sun's energy back out into space, and these things are quite true. But, as it turns out, installing reflective barrier properly inside the attic itself works and works dramatically well, as my own experience demonstrated. It turns out that the effect of covering the inside of a non-shaded attic with radiant barrier foil is about the same as covering the entire thing with shade from a shade tree. In effect, the sunlight's energy gets reflected back out. While this is different from tree leaves in that the tree absorbs the energy to make chemicals it needs, rather than reflecting the energy back, the upshot is the same: the energy does not get into your attic. It also turns out that this is only the case if the foil barrier is installed with an air gap of at least an inch (or so) facing a reflective side of the barrier, and whether that reflective side faces up or down is irrelevant. The barrier is ineffective if it is positioned between two other surfaces with no gaps. Hard to grasp intuitively? Yes. But impossible to deny in experiment after experiment.

Because of lack of intuitive understanding, a lot of folks lean towards additional insulation as the first improvement to make. But in hot climates such as ours in central Texas, the radiant barrier can be a good bit more effective, depending on the initial state of the house.

I have said it before, but it bears repeating: there are 3 physical ways that heat enters your home in the summer: radiation, convection, and conduction, and there is a solution for each of them. The absolute best way to keep that heat out of your house is probably to spend a little time and money on each of the 3 ways, rather than going all-in on a single solution. Thus, a radiant barrier to handle the radiation of heat, ventilation to utilize convection in your favor, and a little additional insulation to fight conduction might well do wonders for you. This approach actually tripled the efficiency of my own house; of course, your mileage may vary. Your house may be a lot less of a solar oven than mine was at the beginning.

So don't be afraid of that barrier, folks! It is affordable, it has no moving parts to break down, and it works!

The Key Principle of Energy Efficiency

I have talked to many people about energy efficiency. Almost invariably the discussion turns towards residential solar panels and high performance windows. Now, while these things are important, solar panels are _not_ an efficiency measure but instead an electrical generation system. High performance windows, while they are an efficiency measure, are probably the least cost-effective efficiency measure that one can undertake according to the vast majority of research I've read along with my own personal experience.
To folks at this level of knowledge, I would point out one major tenet of energy efficiency as I see it:

For a grid-connected house, saving energy is the same thing as generating it.

From the point of view of the electrical grid, a house that uses 1 kWh less per day looks exactly the same as a house with a solar panel system that generated 1 kWh that day. Both houses take 1 kWh less from the grid than their unimproved counterparts on any given day, and therefore both houses are reducing their energy bill by the same cost per day, and reducing the environmental impact of generating their required energy by the same amount.
In short, and it is worth repeating, those solar panels or wind turbines on the house are performing the exact same function as any energy efficiency improvements. Because of that fact, if you want to determine whether to improve efficiency or add generation to your home, it is logical to compare:

1. The up-front cost and effective interest rate of the improvement
2. The environmental impact of the improvement
3. The impact on the home's value of the improvement

These should be the major factors to consider when deciding whether to go with a generation option (typically solar these days) or efficiency. Bottom line: don't just assume you have to go with electrical generation to reduce your home's ecological footprint. The same amount of money will likely offset more energy usage if spent on efficiency than if spent on generation, depending on the starting efficiency of your home. If your house is anything like mine was when I started this whole adventure, you have a lot of low-hanging fruit to gather, for surprisingly little money and high rate of return, before it makes sense to consider generation.
That being said, the prices of solar panels have been dramatically reduced and ongoing efforts are being made to reduce installation costs. With appropriate subsidies a solar generation system may make good sense, at least for the homeowner. Whether it is worthwhile in the larger community, when considering the other things that the subsidy money might have been spent on in our current era of budget shortfalls, is perhaps a tougher question to answer.

So is Energy Efficiency Man bashing solar panels? Not in the least. The more the better, particularly in the Texas summer. Here in Austin, we had an all-time record electrical usage number a couple days ago. Solar panels will and do undoubtedly help reduce our peak summertime loads. However, EEMan would like to see every one of those solar panel-covered houses looked at for low-hanging efficiency fruit, so that we can get the maximum reduction in load on the grid. A net-zero (or energy positive) house is a great thing to aim for.

Until next time, be safe and be cool!

Reflections midway through the summer

We are now a good half of the way through the summer of 2010. Here in Central Texas, we've had a relatively cool June and July, with some clouds and even some rain, but August is already looking pretty rough. Our traditional summer high-pressure system has finally blanketed the state, capping any storms before they can form, and keeping high temperatures around 100 F.
It is too soon for another analysis of summertime energy performance (although my July usage was pretty darned good), but I am looking forward to the end of September when I'll have another good round of data in place for comparison. Since I haven't made any efficiency changes to the house since last summer, it might be nice to see if the "effectiveness" numbers that I've used to measure how well the house performs independently of the weather match up from last year to this year. If there's not a lot of change from the 2009 to the 2010 number, we can probably assume that "cooling effectiveness" is indeed a useful measure.
In the meantime, I am trying to think what I might do with this blog. My intention in starting it was to share some of my experiences so that other house-dwellers might learn how to, and perhaps be inspired to improve their own homes. Also, I wanted to get across a few major themes, including:

• Very low materials-cost improvements can provide significant savings
• Attacking heat on multiple fronts yields major synergy
  
• Return On Investment for efficiency can be better than most traditional investments
  

I think that I have done that, and hopefully amused and entertained a few people along the way.
But this begs the question: what now? I think I've grabbed the lowest-hanging efficiency fruit already. Although more can always be done, I find it unlikely that I'll improve the house further in the near term, due to the larger cost increments that will now be involved. So what will I write about?
I suppose I'll have to start writing about whatever ends up on my mind. There is much going on in the larger world of energy efficiency, energy future, grid planning, and all manner of related topics outside the microcosm of my now less-energy-inefficient house. I may need to add my voice to the many already talking about these larger topics. If nothing else, I now know from personal experience that there is much that can easily be done in this area.
In the meantime, if you, the intrepid reader, want to examine the journey that got me to this point, I encourage you to start from the beginning (which includes an Executive Summary with links to the various posts) and learn what you can about the lore of improving that enemy of efficiency, the single-family dwelling. Until then, adieu!