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Solar Home: Design Philosophy

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House 1-13

I began thinking about building a new house shortly after I read “The Long Emergency” in 2005. I had become uncomfortable living in a house much larger than our needs before then, and even though the house was energy efficient, reading this book caused me to become much more critical of the excess energy we were using.

We also considered buying a house and dramatically upgrading the insulation, air sealing, and windows in what is now called a “deep retrofit.” However, I didn’t feel I could accomplish my emerging goal of being 100% Solar with an existing house, though I now know it is very possible, especially with PV prices declining. But also since so few houses built in the last 50 years considered the sun, finding one that would work for us, in our school district, would have been difficult. 

Then, in early 2008, my wife said, “If you build another house it has to be more comfortable!” It was this statement and the fact that as a home energy advisor I had met many people who were more concerned with comfort than cost that our second primary goal emerged – it had to be comfortable!

It took a little while to define what “100% Solar” meant to me – grid tied but not dependent for “long emergencies”; minimal use of the wood stove to, “make thermal ends meet”; and minimum high tech materials or critical systems. Each of aspects requires further explanation and I hope to provide it someday, but for now you can see my challenge shaping up.

Also, “comfort” required, at least some quantification. I had thought our existing house was quite comfortable but evidently Judy hadn’t. The main problem was that when the sun set the main area cooled off a bit, enough to make her uncomfortable while she worked with the kids homework and prepared dinner. Later when I arrived, I would start a wood fire and all was well again. So after a bit of discussion, we decided that we would be comfortable, if the air temperature was at least 68 degrees (we had always kept the thermostat at 67 degrees). So, just a little bit more would do the trick, as long as we didn’t have any drafts or cold spots.

In March 2008, I began working on the details. “God is in the details” is a simplification, I quickly learned. There were thousands of decisions to be made and many more options to discard. I could only focus on so many options and quickly adopted a short list of philosophies that helped me think differently about what our house was to be. Some of these might help you, whether you are building new, undergoing a major or deep retrofit, or even if you are making an improvement or adding a room.

I built as “small” as I could. I coined the term, “The Just Big Enough House©” as my motto; this is an extension of what Sarah Susanka introduces in her very excellent book, The Not so Big House. Remember, it costs money, time, maintenance, taxes, energy, etc. for every square foot you build, so question deeply and be sure you need it before you build it.

I used “Zero Based Justification” to help think about size. This is an extension of the accounting approach of Zero Based Budgeting. Zero Based Budgeting is the approach that you don’t start from last years budget and add X%, as is done in many businesses and often in government; rather you have to justify every dollar needed in your next budget, starting from the first dollar. This makes budgets much more reflective of what needs to be done and an opportunity for critical discussion. I applied this philosophy to space and in every iteration tried to limit space to area we needed, not include space we used to have.

Still it is important to look ahead. Hopefully you and your family will live in this home for many years. Build it with flexibility to adapt and accommodate your evolving life styles and physical needs as this often saves more money and energy in the long run.

Demand that “Form follows Function.” This does not deny beauty; it just questions beauty for beauty’s sake. You won’t always win this battle, not even with yourself - I didn’t. For example, our house needs south overhangs to reduce summer heat gain. I very neatly designed them into the form. It doesn’t need east or west or north overhangs, but I built them anyway. I just felt the house looked unfinished (ugly) without a level of consistency in this detail. You win some, you lose some. As solace, keep in mind that better looking houses are more apt to be cared for and purchased, so in the long-term they will have less embodied energy per unit of use!

Form did follow function in hundreds of detailed decisions, but I started within the context of wanting a fairly traditional looking home. I didn’t want people to think that to be energy efficient a house had to look extreme or odd. I wanted to build a house that others might want to live in, and I felt a traditional appearance would help and give me some general guidance in the design.

Conserve First. It costs several times as much to create a watt or BTU as it costs to save one. It was with this understanding that I “assumed” a very energy efficient envelope that needed to be very air tight.

Still there were many decisions to make on how to build that envelope and ultimately I used a variety of techniques, depending on the function.

Conservation doesn’t mean doing without. It means, at least in our case, living better with much less energy. But also, if you want to build at lower cost, building a very energy efficient envelope allows smaller heating and air conditioning systems.

Think Inside the Box. While energy was cheap, most everyone changed the way things were done, what was expected, and what was acceptable. With cheap energy: huge houses could be warm in every corner; cars could go 80 MPH carrying one person to work; food could be imported from the far reaches of the world; and a lot of energy was wasted. Now we must think differently; we must make some concessions; and we must live within our means (IMHO).

We want and need to be comfortable (my wife’s main requirement in allowing me to build a new home). But, we don’t need the whole house to be comfortable, especially when we are not in an area. We don’t always need to have 120 degree water to shower. We don’t need to wash clothes in hot water; we can line dry. And, we can sleep very well at a cooler temperature. Our examination of what we “need” resulted in the Active Area concept and the Heat Management System, two concepts that let us be comfortable and better utilize energy. Thinking inside the box or house is critical in understanding how you can build what you need.

Look to building science and computer science. We can do what we have always done; but if we do, we will get what we always got – energy inefficient homes. We need a new approach to building a home. We need to think about the energy that the home will use over its entire life.

Building Scientists say, “Build it tight, ventilate it right” – be sure your builder understands this. Be sure everyone understands the importance of high integrity in the thermal barrier, air barrier and vapor barrier. And then you will be in a position to take advantage of the sun! While it is not as consistent as you and I might like, it is a reliable energy source, and there is science to estimate exactly what it can do.

Joseph Lstiburek’s, “Builder’s Guide to Cold Climates” will go a long way toward keeping you out of trouble. And home energy modeling software, such as Performance Systems Development’s home energy modeling software TREAT (Targeted Retrofit Energy Analysis Tool) is a great place to start when evaluating construction alternatives relative to energy use.

Minimize technology. If it was possible, I’d build a passive 100% Solar Home; but it isn’t if you want daily, predictable comfort in our climate. Geothermal heat pumps are the best alternative for existing homes that can’t maximize their use of the sun and an overwhelming cost advantage for homeowners who only have access to propane or oil; however, for new homes the sun is a better way.

But for our house, I wanted simpler. The most complex components in my 100% Solar Home will be an inverter and circulator pumps – both fairly easy and economical to swap out in an emergency.

Not Far Out! I wanted to build a house with standard building materials and skills. It isn’t that I’m uncomfortable experimenting with new stuff, but I understand that to be acceptable to more people the fewer experimental aspects the better. This doesn’t mean this house won’t be different; there will be many aspects that people/builders will need to adjust to (high insulation focus & cost; very low infiltration; no central heating system; an Active Area; sleeping in lower temperatures; showering when the sun permits; etc.).

Some think such thinking is strange - that what I’m proposing is a series of sacrifices. I look at these changes as challenges my family and I are willing to accept, adjustments necessary to live within our resources. Hopefully, the inconveniences will be minimized. We already know for example that room temperature variances will not be nearly as large as we were willing to accept. Still, we won't know exaxtly how this house will perform until we finish the solar thermal system and live here a year. But that was part of the excitement in building this house - to see exactly how comfortable and how little energy it would use.

Next, I will review the solar concepts we utilized and how we applied them in our climate.

Dan Gibson is the Reporter and Chief Coordinator of Our Energy Independence Community (http://www.OEIC.us). Previously he performed home energy audits for five years in NYSERDA’s Home Performance program and new home ratings in the New York ENERGY STAR Home program. He is currently building a 100% Solar Home. He can be reached at DanG@OEIC.us


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