Wednesday, September 23, 2009

Soapbox, links and taking stock

Anytime one puts significant time and effort into a project, the question arises: why am I really doing this? Are there not better ways to be spending my time?



There are a variety of reasons that one might have for deciding to work on home energy efficiency. I will detail some of them below, with some commentary of my own.
First and most important for me to this point in the narrative, is that I'm trained as an engineer, and good engineers cannot stand gross inefficiency in a system that they care to optimize. As I began looking into the apparently "standard" way things were done with my house, I quickly realized that efficiency was probably never a consideration; at least, not any more than the building codes required, which is apparently not much at all. This, plus my experiences in researching transportation efficiency (possibly a topic for another blog!) led me to understand the we have created a lot of the "built" world around us with little consideration of using energy efficiently. Another way of saying this is that we have embedded the assumption of incredibly cheap and plentiful energy into nearly everything we have built. To me, as this embedded assumption becomes less and less true, as it already has and as I predict it will over the next decades, more and more rapid disruptions will be forced upon us as our infrastructure becomes infeasible. I noticed a good bit of this during the oil price shocks of the last couple of years, and oil prices only affect the transportation part of the energy picture. I think it's self-evident that the hardships will be even more severe when the price of non-transportation energy, i.e. electricity, undergoes significant increase.
So how can we protect ourselves against the already noticeable increases in the cost and scarcity of energy? One way, friends, is energy efficiency in all things! There is a cost (monetary, environmental, and in land use) with any form of energy generation. It seems clear that the best thing we can do to help all of the above costs is to use the energy we generate as efficiently as possible, something we are patently not doing right now on a broad scale in this country.
The preceding paragraphs begin to touch on the second reason, a wide and oddly controversial topic called "environmentalism", which I won't explore in detail on this blog, in part because there are many great sources of information about it, including this blog that specifically touches on current environmental issues in America. While I like to think of myself as somewhat environmentally aware, my energy use alone probably disqualifies me from any great pretense of being "green". First and foremost, I live in a single-family home, the most energy inefficient way humans to protect themselves from the weather, and the creation of millions of which have forced the expansion of cities outwards far faster than if people lived more densely, causing billions more miles of vehicle trips every year. Second, I live in a city with poor mass transit options, death-defying bike lanes and/or lack thereof, so I drive a 2200 pound monster that spews CO2, NOx, and VOCs into the air anytime I have to get somewhere. Granted, I chose the cleanest, most efficient monster I could find, but that doesn't magically eliminate the fact that I'm burning the energy to take 2200 pounds for a ride every time I go somewhere; it just reduces its impact somewhat. Finally, at this point, my already energy-inefficient house (due to it having 4 walls and a roof leaking heat just to protect a very few occupants) is even more inefficient because it was built with minimal (if that) consideration for energy, and I'm not done retrofitting it yet :)
But fear not, adventurous reader. After a brief diversion into other energy-related matters, more improvements are afoot.

Sunday, September 20, 2009

Worth it...financially?

In my last post, I described some reasons why doing the work I'd done through 2007 was worth it. But I am aware that many readers want to know how different efficiency measures pay off from a purely financial point of view. This is certainly a reasonable question, although I would disagree that it is the only meaningful arena of consideration.
But to help answer the financial question, I will consider my first three improvements as a unit, since I performed them in a roughly overlapping span of time. Here are the numbers, as best my records have them:
Data:
Approximate capital cost of improvements: $1150.00
Approximate average reduction in monthly bills: $50.00

Calculations:
Payoff time: $1150 / ($50/month) = 23 months = about 2 years
Effective interest rate: (100% / 2) = about 50%

For comparison, the effective interest rate for a good bank account is maybe 6% these days. So, interested readers, peruse the following statement and marvel: my investment in energy efficiency is earning me over 8 times the effective rate of a savings or bank account.

One caveat in this is that I have discounted my own labor rate. For 2 of my 3 improvements, I paid for someone else's labor, so the calculation is correct. For the other improvement, I used my own (unpaid) labor to remove the old insulation blocking my soffits. This labor cost should ideally be included, which would reduce my effective interest rate. However, I did not track my hours of time on this. I would highly doubt that it would lower my interest rate to anywhere near the going bank rate.

One lesson from all this is that if you do these improvements yourself (i.e. you have more time than you do money to spend on energy efficiency), then you can reap incredible financial returns on your investment. In my case, over 50% of the money I spent was on paying for someone else's labor, not on materials. Had I done this work myself, spending more quality time in the attic, I would have more than doubled my effective interest rate, paying off the materials used (a ridge vent and baffles) in a single year.

One thing a lot of folks seem to assume is that after the payoff period (about 2 years for me), the improvements are "done" - that is, they are no longer making you money. This is the exact opposite of the truth. Every single month, from here until I sell my home, my investments in energy efficiency will keep my bank account $50.00 higher, which is the same as if I had a nice fat checking account sending me that amount in interest. In fact, these improvements give me the added benefit of "energy price insurance": should the cost of energy continue to rise, as it has in the recent past, the value of my investment goes up. My $50/month savings will be come $100/month savings if the cost of energy doubles.

So, according to my calculations, if you have any money to invest, investing it in your own energy efficiency makes a incredible amount of sense. "Should I put that $1000 in a savings account at 6% or into my attic at 50%?" For most of us, this question answers itself.

And not to put too fine a point on it, but I've still got another 2 years of improvements to tell you about. Be patient, energy efficiency enthusiasts, and read on!

Monday, September 7, 2009

Taking Stock: The Bottom Line



It was now the spring of 2007. I had successfully navigated the early waters of what amounted to the early low-hanging fruit of energy efficiency in my house:

1) Ductwork leaking conditioned air into the attic
2) Soffit vents blocked for many years by insulation
3) Insufficient and badly placed attic vents

Our electric utility company keeps online records of customers' electric usage by month. Using their numbers, I have been able to quantify my electric usage changes. Note that this is not a perfect analysis; for example, it does not take into account the fact that one summer does not have the exact same weather as the next. A fair disclaimer: the summer of 2007 was a cooler and cloudier one than 2006, the last summer before I made the improvements. Actually, the improvements started in 2006, so I will compare to 2005 readings. Nevertheless, the only data I have to compare are the utility readings, so here are the numbers:
Electric usage in 2005: 14,000 kWH
Electric usage in 2007: 8,000 kWH


In other words, the improvements had yielded at most a 44% improvement in my yearlong energy use, as best I can measure. The number may be somewhat less due to the unusually "cool" summer of 2007.

In addition to improving my energy efficiency quantified above, these few improvements had the following benefits:
A) Healthier air in the house. The leaky ductwork not only allowed inside air into the attic. By connecting the two airspaces, it must also have allowed attic air into the house. Attic air is chock full of dust, fiberglass fibers, mold spores (largely present due to #2 above) - this is why we wear masks when we work up there. Sealing those ducts has made the residents of the house healthier.
B) An attic less conducive to mold growth. The moldiest areas of the attic that I found were at the back of the house, where the soffit vents had been blocked since the house's construction. Increased airflow will keep moisture from being trapped and condensing in the attic, which will greatly slow the growth of mold.
C) The garage is noticeably cooler when I leave in the morning, and return in the afternoon. This just makes it a less unpleasant place to be when I have to be in there.

So was it worth it? I would have to say that I would not be Energy Efficiency Man if I felt that it were not. Although I started these projects from a standpoint of energy efficiency, as I learned more about the other benefits of my efforts, I becamse excited about them as well. Is there anything wrong with wanting to breathe air that isn't shared with fiberglass insulation? Is there something wrong with wanting to not reside under the world's largest urban mold colony, or not wanting to break a sweat when walking 8 feet to your car in the garage? No, indeed, gentle reader, but for the present, we will return to Energy Efficiency. (We will explore financial worthwhility in the next post).

For as great as progress was in 2007, I had whet my teeth on the gristly but chewable edge of making a single family dwelling energy efficient, and still I hungered. I had stuck my toes into the cool waters of a new way of thinking, and in my Web travels seen the obscure edges of such exotic concepts as reflective radiant barriers and R-values of materials. I longed to experiment with these concepts, with their efficient and (near and dear to my heart) low maintenance possibilities.

So follow me, gentle Reader, as I proceed into the next level of Energy Efficiency, for we have yet a ways to travel, more to learn, and Energy Efficiency to gain.

But was it too much?

In the last episode, we attacked the second part of our attic airflow problem by installing a ridge vent to let the hottest air out of the top of the attic. So now I had a fairly complete intake system of open soffit vents and extra grille vents, as well as a real outflow system. But, as the careful reader will recall, the "net free area", or airflow capability, of the intake and outflow systems should match as closely as possible.
The ridge vent manufacturer helpfully supplied the net free area per linear foot of vent, and given that I knew the length of my ridge, I could calculate my total outflow. In addition to the ridge vent, I retained the two original "turtle vents" (holes with an inverted pan over them to keep the rain off), since they still seemed to operate properly - which we checked with a simple piece of paper held below the vent on a hot day - the paper was sucked up against the turtle vent, showing that the airflow was still out. This mattered - if I had changed the dynamics of the attic too much, the turtle vents might have become intakes, bringing very hot air off the shingle surface into the attic: definitely an Energy Inefficient situation.
So, by adding up the ridge vent area and estimating the turtle vent area, I got a rough number of the net free area of my outflow system. The hope was that my inflow system would roughly match, or slightly exceed (according to some sources) that number.
I didn't have specifications for my soffit vents, but some back-of-the-envelope estimates multiplied by the measured length of the perimeter of my house yielded a good estimate. I added to that the net free area of the grille vents I had added. The result: I still was short of intakes, by a pretty good amount.
In the meantime, I had noticed another possible Efficiency Issue with the house: the garage in the summertime tended to get very hot during the day, and tended to hold that hot air, right against the house, for the entire night. In most people's books, holding a large reservoir of hot air against a surface who's other side is being cooled is a no-no for efficiency. In fact, this problem yielded another chance to kill two birds with one stone.
How to cool the garage and add more intake area to the attic at the same time? Well, as good luck would have it, my attic access hatch was located in the garage. This was cause for another Eureka moment: I could leave the attic access hatch slightly open, leave the garage door open slightly to allow air in (but not so open as to allow the neighbors curious cats in), and voila! The outside air would flow into the garage all night long, up the attic access, through the attic, and out through the ridge vent. Instant no-moving-parts, no-electricity-required cooling for the garage and supplying of air for the attic. As readers of this blog might well imagine, words alone cannot express the excitement I felt when I realized this commonsense answer to my dilemmas.

Problem: Inflow area into the attic insufficient to match ridge vent
Problem: Garage holds heat all summer long
Solution: Slightly open garage door, slightly open attic access in garage, instant cooling!
Lesson: I don't always have to buy or install something to solve an Energy Efficiency issue

Ridge Vent to the Rescue!

Problem: Not enough outflow area for hot air to leave the attic
Problem: Existing outflow vents on the roof are not even near the peak

Searching the web for solutions to these problems yielded a growing consensus: the best way to ventilate a modern attic is a combination of soffit vents for air intake into the attic, which I had recently cleared, and something called a ridge vent for outflow of the hottest air from the attic. The ridge vent is nothing more than a couple of long but narrow slits cut through the roof beside the longest peak at the top of the roof. For my house, the longest peak doesn't run the full length of the house, but it does run about 2/3 of the length. The ridge vent also includes a covering made by a ridge vent supplier that gets installed over the top of the slits so that rain does not fall right into the attic. There is some art and value added by the different vendors in this component - different designs allow better or worse airflow, are better or worse with wind-driven rain, etc.
The thing that Energy Efficiency Man likes about ridge vents is that they are simple, have no moving parts to wear out, and will require very little maintenance. For some ridge vent systems, there is a filter over the slits that will require changing every few years, but that is about the extent of ongoing maintenance. Finally, in my particular case, the fact that this solution is placed at the peak of the roof means that it solves both of my problems in one fell swoop.
Before we proceed to my particular experience with ridge vents, I should note that there are some vocal detractors of the technology out there. I have seen claims (mostly from one person who sells a competing system) that ridge vents won't work well because the covering forces hot air to flow down momentarily, which it doesn't want to do, to work its way out of the attic. While this is true, I would challenge folks to design a roof vent that doesn't require something like this and still blocks rain from entering the attic. Most existing vents have this problem. Furthermore, and this is yet another area where aspiring Efficiency Men and Women out there should consider their own local weather patterns, my area has pretty consistent winds through the summer months, and in my case, those winds flow across the roof perpendicular to the wind. Due to the Bernoulli effect that we all know and love, that familiar physics principle that makes sailboats move and airplanes fly, the prevailing summer winds create a low pressure area on the downwind side of my ridge, and a higher pressure area on the upwind side, creating a "pump" that helps move the air out even faster than hot-air convection normally would. At least this is true in theory; I have no easy means to test it.
But back to my own experience. In short: I decided on the ridge vent, and I had the good fortune to find a workman who would buy and install a ridge vent for me for a very good price. In one afternoon he had cut the requisite long strips out of the roof, and unrolled and installed the ridge vent rain baffle/air filtration system over the long cuts.
However, one question remained foremost on my mind: would the new outflow area be enough to balance the intakes? The answer to that question will have to wait...

Solution: Ridge vent installed at the very top of the roof