Category Archives: Design

Nauhaus Radio Interview

radioMike Figura and I did an interview about the Nauhaus prototype with Ned Doyle for his radio show, “Our Southern Community”. Okay, the interview was in February and I’m just getting around to listening to it. I’ve been busy, so sue me.

Anyway, this is still accurate and has good information about our work, though some things have changed. For example, Mike now wears a tie.

Here’s the interview divided into two parts:

Nauhaus Interview Part 1

Nauhaus Interview Part 2

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Nauhaus Primer: Talking Head About Carbon Neutrality and the Nauhaus Prototype

We recently recorded this video intended as a draft to help us work on our public spiel. It needs a lot of work, but I thought I’d post it anyway because it’s a fairly thorough introduction to what we’re doing generally and the prototype in particular.  Just pretend you’re in high school and lunch is next period…Go generic sports team with some sort of mammal as its mascot!


Carbon Neutrality and The Nauhaus Prototype from Clarke Snell on Vimeo.

Building Fundamentals: Thoughts on Picking a Place to Build

This article by Clarke Snell was originally published in the New Life Journal.

Unless you live under a rock on another planet whose sentient inhabitants have developed advanced anti-BS technology and the ability to block HGTV, you’re just about sick of the word “green” right now. With green oil companies, green Wal-Mart, and even green warfare (I shitake you not!), it’s enough to drive a rational person to pledge allegiance to another color. Alright, before we start the chartreuse revolution, let’s take a deep cleansing breath and get back to basics. Why green instead of blue or pink?

The answer is plants. You bring sun, soil, water, and air together and you get plants. Green plants. Underneath the hype, spin, and snake oil lies the simple profound concept that we live on a little magic rock that maintains a self-sustaining balance between a complex matrix of variables that together produce the color green…and LOTS of it. Any process or product purporting to be “green” is claiming to be conscious of and in some way in synch with this natural perpetual motion factory, this Green Machine.

A green building, then, is a building designed to work in concert with its natural surroundings. Admittedly, this is a complex undertaking that requires a lot of give and take, especially in the context of a “modern building” that is called upon to support a complex and demanding indoor lifestyle. Still, the most fundamental component of a green design is how the building interacts with the Green Machine manifested on the piece of land on which it sits. In fact, choosing the land and siting the building are more fundamental than the building itself because the building can be designed to fit the land, not vice versa.

Given this reality, what should you look for when buying a piece of land or choosing a building site for a green building project? Here’s my list of the top five things to consider:

  1. Sun. The sun’s path through the sky changes in a regular progression through the course of a year. For our region, the summary is that it hovers low in the southern sky during the winter and spends a lot of time high overhead in the summer. In our climate, a well chosen building site can provide considerable direct solar heat in the winter, solar generated electricity and hot water for much of the year, and protection from the sun’s heat in the summer. A poorly chosen site can produce the exact opposite results, changing the sun from your best friend into your worst enemy. In the mountains, this effect can be exacerbated. A northern ridge can create a situation where a section of land is completely (and frigidly) shaded for three months during the winter while a contiguous section enjoys full solar exposure. Luckily, it isn’t difficult for someone with simple equipment and a little training to create an accurate analysis of how the sun will interact with a given piece of land.
  2. Water. Water evaporates off bodies of water, falls to the ground as snow or rain, and then flows over or under the ground coming to rest in a body of water for the process to start all over again. This Ferris wheel called the hydrologic cycle is the ultimate recycling program and is a poignant manifestation of the old saying “what goes around comes around”. In green building, our goal is to redirect and use water as needed without affecting it adversely. Our first consideration is planning for the water that will fall on the land. Rainfall in our region varies widely. For example, the annual average for precipitation in downtown Asheville is 37 inches. Fifty miles away at Lake Toxaway, the yearly average is 92 inches!  Atlanta weighs in at about 50 inches. The amount of rainfall your building encounters can have an effect on a number of decisions from building materials, to water collection strategies, to garden and planting designs. For this reason, it’s important to research the rainfall profile for your specific location. Next, we need to consider how water flows over the land which means analyzing the existing contours and how they relate to potential building sites. Another consideration is finding a clean source of water for domestic use. The options are raincatchment, a spring, a well, or a municipal source. Where I live, for example, we were able to access a spring high enough above the house site that gravity creates sufficient water pressure. The result is a free, clean source of water that requires no pumps or external power source. Finally, we need to consider how to responsibly return the water we use to the hydrologic cycle.
  3. Wind. Wind can be used to generate electricity, though in our region residential projects rarely muster the requisite conditions (including enough cash) to make this practical. For the most part our concerns about wind will be focused on protecting the building from cold winter winds, exposing it to cooling summer breezes, and utilizing design and construction methods that will allow it to withstand the worst storms expected on the site. Unfortunately, air movement is the most site specific and unpredictable of the natural forces. Especially in the mountains, the only really accurate way to assess wind patterns is to chronicle the wind over an extended period of time, ideally at least a year. This can be done either by living on site or by installing a device called an anemometer. However, knowledge of regional patterns combined with common sense and some experience can go a long way toward understanding how wind on a given piece of land might interact with a planned building.
  4. Earth. So far we’ve looked at forces that operate on the land. Now, we turn to the land itself. We need to look at the shape, contour, and constitution of the earth to consider how a building might best nestle in to and be supported by it. We need to look for materials on site that might be useful, such as stone, timber, and clay. Perhaps most importantly we need to analyze the state of the existing natural balance, the Green Machine, and determine how best to partner with it. In urban settings, this process can be a lot more fun because the land has often been devastated by human intervention. The building project in this situation can be an act of repair. In a more pristine setting, construction will almost certainly be destructive to the natural order, so careful thought needs to be put into creating a long term positive out of an initial negative.
  5. Access. Roads are disruptive and expensive. If you’re building in the mountains, quadruple that sentiment. In the context of a green building project, the rule is simple: the shorter the road, the better. This can be counterintuitive because the first impulse is often to head for the ridge and that panoramic view. In many situations, there are simply better places to build…and by better I mean more pleasant and beautiful in addition to more practical.

If this all sounds complicated, it is. In fact, these basic parameters, along with others, come together to create an intricate matrix. What’s more, decisions made at this point have long reaching effects. For example, in a matter of minutes, a bulldozer will expose soil layers built up over millions, perhaps billions of years. The decision to move that soil is a decision to make a, for all practical purposes, permanent change to the make-up of that piece of land.

Don’t let that daunt you, though. The good news is that at this point in your project no decisions and therefore no mistakes have been made. Relax and enjoy the possibilities. I’m writing about this topic this month because this is the best time of year to be analyzing land for a green building project. It’s easier to get a picture of year round solar exposure when the leaves are off the trees and it’s easier to walk through the woods before the understory sharpens its thorns for the spring. If you’ve got land or are looking for land, now’s the time to put on the hiking boots. One word of advice: get some professional help. Our company offers land analysis services as do a number of other qualified professionals in our area. The stakes are simply too high to go it alone. Remember, the Green Machine is watching.

Building Fundamentals: Expanding the Concept of Health

This article by Clarke Snell was originally published in the New Life Journal.

My father-in-law just turned 80 and he shows no sign of slowing down. One of his favorite sayings is, “If you’ve got your health, the rest takes care of itself.” That about covers it, don’t you think? Like many truths, it’s easy to grasp and often difficult to do.

I’m sure that’s always been the case, but I wonder if it’s truer now more than ever. These days the discussion encompasses not only our own health, but the health of the planet itself. Wherever you come down in the spectrum of present environmental debates, I think that most would agree that we humans are adept at creating change, but inept at predicting the consequences of that change. Take the automobile, for example. Could anyone have imagined the effect that single invention would have on the entire planet? I’m sure it seemed like a great idea in those heady early days of its inception. No more cleaning up after your horse, and you got to wear those cool goggles and scarves, too. Now, in the heyday of the car, I’m just not sure that the convenience of sitting in traffic with everyone else twice a day to get to and from a windowless office that’s too far from your house is really worth all the pollution, expense, and shady political petroleum shenanigans. Honestly, I’d give a fortune in tree-shaped, Pina Colada air fresheners for a single decent bike lane.

I think one of our big problems is that we’ve come to confuse comfort and convenience with health. There’s no section of modern society where this malady is more prevalent than in our approach to buildings. For example, I grew up in Texas in the generation that transitioned from open windows and ceiling fans to “A/C 24-7, baby”. When the temperature was topping 100 degrees, that air conditioning sure felt great, until you walked outside and nearly fainted from the contrast. Not to mention that the net result was the adding of heat to the ambient air due to the realities of mechanical evaporative cooling. When you combine that fact with the effects of replacing plants that naturally bring air temperatures down with asphalt, concrete, and reflective skyscraper windows that have the opposite effect, what do you get?: Business men and women wearing wool suits in the summer to hazard frigid office buildings with questionable indoor air quality while the ambient temperature in the city climbs up to 10degF higher than in the surrounding countryside. (It’s called the “heat island effect” and is well documented.)

In other words, in our search for cool, we actually created heat and a questionable environment for health. If you’re not convinced, just stand in the middle of a busy city on a summer day and ask yourself if the forest that used to be there wasn’t a healthier environment. Though it’s seldom stated explicitly, I believe that the central tenet of the present green building groundswell is based on this idea. In fact, my one sentence definition of green building is “creating a healthy indoor environment without adversely affecting the outdoor environment.” If maintaining personal health is harder than it sounds, then this is even harder. I know that’s true because we, the pinnacle of evolution and the inventors of both spray cheese and the “virtual pet”, seem unable to get a handle on it. I’m here to help with some concepts that I find basic to creating buildings that support health both indoors and out.

Think Small

Here’s a riddle: how do you make the most efficient building in the world more efficient? Answer: make it smaller. That’s because though we may someday find a way to create resources or reduce pollution through our built environment, for now the simple fact is that our lives create pollution, waste, and natural resource depletion. Presently, we simply have to settle for a reduction in our adverse effects. On the physical plane, reduction means less, and less means smaller. Let’s not stop with buildings. Move closer to work to shorten your drive. Eat local to reduce transportation and packaging. Skip every other heartbeat…okay, I haven’t worked out the details on that one, but you get the idea.

Passive Then Active

In this context, passive and active represent two strategic approaches. Passive strategies interact directly with forces of nature to achieve a goal. Active strategies change a natural force into some other form to get a desired result. A sailboat is passive, setting a sail in the path of the wind to generate movement. A powerboat is active, burning organic fuels to run a motor to accomplish the same thing. Given any goal, we should always maximize passive possibilities first, then supplement that result with an active approach to reach the desired goal. In buildings, that means maximizing insulation and designing to let the sun in when we want it and keeping it out when we don’t to create the most advantageous interior temperatures first, then adding mechanical heating and cooling to tweak as needed. It means open windows before ceiling fans, and ceiling fans before air conditioners. It means water filters before chlorine and a paradigm shift to see the water leaving our buildings not as “waste water” but as “nutrient rich plant food” and all organic “waste” as useful compost. I could go on, but the point isn’t memorizing a list, but putting the concept into practice every day. Think of it as a mantra.

Do Not Poison Yourself, Your Family, or Your Friends

Let’s face it we’re awash in chemicals. The modern world is one big testing lab and we’re the mice. We mice need to band together and take over the lab. The first step is becoming aware of what’s in the things we put into our bodies and in our houses. As usual, that can be harder than it sounds and will require some level of compromise. The best strategy is to buy locally sourced stuff from local people because then we can verify quality, ingredients, and methods. If it’s not made locally, we should still buy it locally and give our merchants the following simple mandate: “We want the least toxic alternatives and we are willing to pay for them.”

Support Innovation

Let’s cut to the chase. There is no simple and no single way to create healthy indoor environments that support healthy outdoor environments. Modern life makes unique demands on buildings and every climate has its own idiosyncratic trials. In Florida, a big challenge is dealing with heat and humidity while creating good indoor air quality with minimal energy expenditure. In Michigan the analog is keeping warm with good indoor air quality and minimal energy expenditure. In our region, it’s a combination of both. There is no shortage of ideas and options, but each one represents an innovation from standard practice. The construction industry and government code system is by definition conservative and slow to change; therefore, there’s great inertial incentive to go with the flow or make minor incremental adjustments. As a result, a lot of what is labeled today as “green building” is basically rearranging deck chairs on the Titanic. The answer is for the consumer, i.e. you and me, to support innovation. To be a part of the solution, we all have to share responsibility and be willing to take a few chances, maybe make a few mistakes. My new bumper sticker: Ask For Innovation.

Live Outdoors

If all of this sounds complicated, don’t forget the old school approach, popular with plants and animals everywhere: be outside. Turn off the machines and go outside. I know that sounds simplistic, even preachy (especially since I’m sitting indoors typing on a computer right now), but once you get past that reaction it’s really a radical notion. Walk somewhere that you usually drive. Make outdoor cooking the default. Sleep outside. These and similar simple steps will not only improve our personal health (fresh air and exercise: duh) but, I believe, they are essential research toward understanding what ails the planet. For example, walking or riding a bike in an area colonized by cars is a transformative experience. It’s like being thrown into a tank full of sharks, only yesterday you were the shark. Your reptile brain will generate the following report: walking and bikes good, cars bad. In other words you can know something with your mind, but to understand it, you have to feel it with your body.

Oops, I see that I’ve well exceeded my monthly word ration, so it’s time to close. The point, in summary, is that a holistic concept of health has to encompass our bodies, our buildings, and our planet. As with our personal health, the key is in learning the basics and then acting responsibly. When it comes down to it, your health is my heath, our health is their health, and everyone’s health is built on the health of the planet itself. Of course, that brings us back to the same old conclusion that bears repeating until we finally get it: we’re all in this together.

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  • Passive House Institute:  www.passivehouse.us
  • The Living Building Standard (No credits, just prerequisites.  It’s about what you did good, rather than being about what you did less bad.):  http://www.cascadiagbc.org/lbc

Notes from the Green Building Trenches: Should You Build Your Own House?

This article by Clarke Snell was originally published in the New Life Journal.


Just let me vent for a minute. I’ve been having a little trouble with my brain, nothing serious or anything… just been forgetting things, blacking out, and feeling a strange compulsion to listen to ‘N Sync. Okay, so I don’t need to be a rocket scientist to know I need brain surgery, right? Anywho, I’m a handy guy, so I’m thinking I’ll do it myself. I figure I can do a better job for less money and get the personal satisfaction to boot. I’m a careful dude, though, and after reading the pamphlets I’m not sure if I want to do it all myself, just assist in the operation, or simply run the hospital during the procedure. I decide to call a neurosurgeon for some pointers, right? I left four messages with different “doctors” explaining my situation clearly: I don’t have much money, I want to do as much of the brain surgery as possible myself, and I need it done immediately.  Would you believe it? Not ONE of them returned my calls. I guess they were too busy playing golf.
[Insert dream sequence music here.]

Insane, right? Out of touch with reality, eh? Interestingly, though, if we change the topic from brain surgery to house remodeling or other construction (and “playing golf” to “drinking beer at Hooters”), then this “rant” becomes a story I’ve heard repeated with a straight face by a number of people. But are the two really that different? How realistic is it for the average person to consider having a considerable role in the construction or remodeling of their own home? Where does this idea come from that we can do our own brain surgery…I mean house building?

The phenomenon is even more pronounced in my specific neck of the construction woods: “green” and “natural” building. I completely understand the impulse. In fact that’s how I first got involved in construction. I didn’t know a kerf from a smurf when I decided to build my own house. All I knew was that I wanted a house and I didn’t have to be a brain surgeon to see that modern houses were expensive energy hogs. They also often seemed like soulless, black-holes of emptiness…and then there was that bathroom wallpaper with seashells. It was all very confusing.

I set out to find a better way. I eventually built a house that is substantially heated by the sun for a fraction of the going square foot cost. Though my wife and I live and work there, our electric bill is usually less than $20 per month. We use less than 100 gallons of propane per year and have free water. By most standards, that’s very efficient. It’s also a beautiful place (though, like most owner-builts it’s not completely finished) and I have the personal satisfaction of having done it myself. This isn’t personal back scratching, just a testament to my credentials for making the following statement: Owner-builder beware. The road is potentially fraught with danger, stress, spousal unrest, and cramps in your check writing hand. I’m not saying you can’t do it, just be careful. The first step is to get real. Here’s a list of a few, from my point of view, popular myths that you should be aware of:

Myth #1: There are simple materials and techniques that can make house building accessible to everyone.

At some point in history regardless of your lineage, your ancestors built their own houses. People grew up involved in house building and repair and thus it wasn’t something to learn or study, it was a part of life. For most of us, those days are long gone. What’s more, a modern house is considerably more complicated than most of its forebears. I’m not talking fiber optics and heated towel racks here. Energy efficient construction, the hallmark of all environmentally conscious building, is a distinctly modern concept that requires careful design and attention to detail in construction. Even operable windows and doors are a complicated technology requiring a fair amount of skill to implement. The “simple” materials and techniques that people talk about (cob, cordwood, straw bale, etc.) are almost exclusively relegated to filling wall volume and as such just scratch the surface of the complex matrix that is a house.

Myth #2: “Natural” or “green” building is easier because it works with nature, using less complicated systems.

The evil genius of modern construction is the combination of mass-produced components with forced air HVAC (heating, ventilation, and air conditioning). This allows you to replicate a design anywhere using the exact same quality-controlled components. The floor plan can be of basically any shape and size and the building situated unconsciously because the indoor air is “conditioned” and moved around mechanically. This is the lazy way, and we pay for it collectively with the pollution and resource depletion caused by its resulting profligate energy consumption. The better approach is to create a building that works with natural forces on the site (sun, water, and wind) to create a comfortable base interior environment. This approach is more subtle, takes more thought, and is less forgiving of mistakes. For example, you can replace a too small boiler with a bigger one, but you can’t move your house to take proper advantage of winter solar heat gain.

Myth #3: If you do it yourself, you’ll save money and get a better product.

This statement is part of the great CON-tractor vs. c-LIE-nt culture wars. The owner-builder variation is to make cost comparisons between owner-built and contractor-built houses without factoring in the cost of the owner’s labor. That’s just bad math. Every hour you spend on your house is an hour that you aren’t spending at a job that you know how to do. Unfortunately, beginning construction workers with your skill level earn low wages, don’t get paid vacations or holidays, and often don’t even have insurance. Moving from spending time at your job to grunting and groaning at your construction site is most likely a financial loss. In other words, it would be cheaper to pay someone with more skills to do the work while you earn cash to pay them. As for the quality of the product, when did you ever do a good job on anything the first time you tried it? Fundamentally, you have to ask yourself this question: do you really want to trust some clueless novice, i.e. you, with something as precious and practically fundamental as your own house.

In the end, the real question is about your goals. If you are looking for a vision quest, building your own house is a great one. Just realize that you’ll spend so much time (measured in years, not months) amassing knowledge and practical experience that the most practical outcome is that you’ll find a profession in the process. On the other hand, if you’re looking for the most cost-effective way to build the most environmentally conscious house that fits your needs, I strongly suggest making yourself part of a design and construction team that is dominated by experienced professionals. We’re not all CON-tractors, just like you’re not all c-LIE-nts.

Planning a Great Neighborhood

This article by Michael Figura was first published in the New Life Journal.

While people make a place great, a neighborhood’s pattern of development has a large impact on how people within a neighborhood interact and socialize.  An important characteristic of a well planned neighborhood is that people have many chances to unexpectedly run into each other.  People who see each other on a frequent basis tend to have deeper relationships, which creates a stronger sense of community.

One pattern of development that fosters frequent interaction among neighbors is Traditional Neighborhood Development.  Traditional Neighborhood Development (TND) is a new term that describes an older pattern of city development.  TND development is seeing a comeback today.  With TND development, homes are close to each other, are close to the street and are close to commercial areas.  Homes are close to each other to create enough density to support transit and pedestrian modes of transportation, both of which do not work well at low densities.  Homes are close to the street so that people who are on their front porches see their neighbors as they are walking by.  Homes are close to commercial areas so that people can walk places instead of having to drive.  Streets are designed to make walking safe, enjoyable, and easy.  Residents enjoy quality parks that are within close walking distance to homes and businesses.  In such a neighborhood, the built environment structures people’s daily patterns in such a way to foster frequent interaction among neighbors.

Juxtaposed to the Traditional Neighborhood Development is the typical American subdivision.  In the typical American subdivision, people usually have to drive every time they want to go somewhere.  Because driving isolates motorists from their environment, neighbors do not interact as much as they go to and from their destinations.  If you do not believe this, ask yourself how many people you know slowly drive through their neighborhood with their windows down telling everyone who is outside “good morning” while they are on their way to work?  If you do that, your neighbors probably think that you are a little bit strange.  On the other hand, if you walk to work and you pass your neighbors on the way, they would probably think that you were a little bit strange if you did not say hello… at least in the South.

Great neighborhoods usually do not just happen, but rather take careful planning by municipal planners.  Zoning codes can help create the type of development that fosters frequent interaction among neighbors.  Ironically, until recently, most cities and towns did not only discourage this type of development, but actually made it illegal.  For the last 60 years, zoning codes across America have by-and-large mandated automobile oriented development, where houses must be on large lots and must be set back far from the street.  But things are changing in many progressive cities and towns across the States, with a shift towards Traditional Neighborhood Development.

If you do not currently live in a neighborhood where the pattern of development fosters community, the good news is that you can work with municipal planners to help to transform your neighborhood by creating a Neighborhood Plan.  In a Neighborhood Plan, planners work with the community to identify residents’ goals and objectives for their neighborhood.  The planners then create strategies for how the neighborhood can achieve their goals.  The governing body (e.g. City Council), officially adopts the Neighborhood Plan and works with the residents to implement the strategies that were outlined in the Plan.  If creating a Neighborhood Plan for your community is something that interests you, a good way to get the process started is to get together with your neighbors and write a letter to the Planning Director of your municipality asking for a Neighborhood Plan to be performed in your area.

Programming Your Next Home Purchase to Help Create Sustainable Communities

This article by Michael Figura was first published in the New Life Journal.

When you are looking for a home, office or commercial space to purchase or rent, you usually go through a process called Programming.  Programming is the process of determining your needs and deciding how a building should be designed to suit those needs.  Most people list their desires for a building, rank those desires, and then try to find a building that matches those needs.

Urban planners think about city design in much the same way, although their “building” is a town or region and the needs are that of the public at-large.  However, city and regional planning in America is hindered because of strong private property rights sentiments and because planners have to design around the automobile (see Dominance of the Automobile, September, 2007).  In order to do our part to help create sustainable communities, we need to think about whether or not the buildings that we are contemplating purchasing or renting are helping to strengthen our communities and foster a more sustainable society.

How to do this with your next real estate transaction?

Fortunately there is a guidepost.  The American Institute of Architects (AIA) has published Ten Principles for Livable Communities.

Next time you are looking at buying or renting a building, or even constructing one, consider taking these principles and ranking the buildings that you are evaluating on a 1-10 scale to see how they stack up.

The AIA’s Ten Principles for Livable Communities (abridged)*

  1. 1. Buildings on a Human Scale

Buildings that are in compact, pedestrian-friendly communities give residents the ability to walk to shops, services, cultural resources, and jobs.
2. Community with Choices
Buildings that are in communities with a variety of housing, shopping, recreation, transportation, and employment create lively neighborhoods, mix socio-economic classes and accommodate residents in various stages of their lives.

3. Mixed Use Development
Buildings that are in communities with a mix of different land uses and varied building types create vibrant, pedestrian-friendly, and diverse communities.

4. Existing Urban Centers
Buildings that are in existing urban centers take advantage of existing streets and services, which reduces the need for new infrastructure, helps to curb sprawl and promotes stability for city neighborhoods.

5. Transportation Options
Buildings that are in communities where residents can walk, bike and/or use public transit, in addition to driving, help reduce traffic congestion, protect the environment and encourage physical activity.

6. Vibrant Public Spaces
Buildings that are in communities with vibrant public spaces enable residents to have welcoming, well-defined public areas for personal interaction, celebration and reflection, art and cultural appreciation, civic participation and public events.

7. Neighborhood Identity
Buildings that help create a “sense of place” gives neighborhoods a unique character, enhance the walking environment and help create pride in the community.

8. Environmental Resources Protection
Buildings that are in the countryside and are on substantial amounts of undisturbed land help to create a balance of nature in conjunction with development to preserve natural systems, protect waterways from pollution, reduce air pollution, and benefit property values.

9. Landscapes Conservation
Homes and farms that are in the countryside and are on substantial amounts of land help protect contiguous open space, local farms and wildlife habitat, which are essential for environmental protection, local food production and recreational needs.

10. Design Matters
Buildings that have excellent urban and rural design are the foundation of successful and healthy communities.

* The AIA’s Ten Principles for Livable Communities have been adapted to fit the context of buying, renting or building real estate.  The unabridged version of the Ten Principles for Livable Communities can be found at http://www.aia.org/liv_principles.

Passive Solar Design


This is the second article in a series originally written for New Life Journal.


By: Clarke Snell


Let’s not beat around the bush. In this day and age, heating and cooling our houses amounts to spending a lot of money to create a lot of pollution. That’s because most of the energy we use for this purpose comes from burning fossil fuels. What’s worse, as a society our response to skyrocketing oil and gas prices has been to keep making the skies dirtier. The weird thing about this whole scenario is that everything we’re burning is just stored solar energy.

Here’s the process: Plants turn sunlight into energy which is turned into living tissue. Animals eat the plants. Plants and animals die. Wait several hundred million years. Drill deep wells and dig big holes to access resultant oil, gas, and coal. Transport all over the planet and burn copiously until supply begins to get scarce. Fight wars and panic until lights go out and heat goes off.

I don’t know, wouldn’t it make better business sense to skip the “middle man” and go directly to the source, i.e. the sun? Duh. The technique is called passive solar design: the conscious manipulation of the sun’s direct energy to affect the temperature inside a building. It is clean burning, runs for free after installation, has no moving parts, comes with a lifetime guarantee, isn’t susceptible to power outages or unexpected supply shortages, requires no special maintenance, and can be accomplished by simply rearranging the materials used in a conventional modern house at little or no extra expense.

Though its most effective real world implementation is a beautiful dance between science and art, the concept behind passive solar design is elegantly simple: if you want heat, let the sun in; if you want cool, don’t let the sun in.

Our loving star has made the process so much easier by methodically changing its path through the sky throughout the year. In our region, the winter sun rises to the southeast, stays low in the sky to the south, and sets to the southwest. The summer sun rises to northeast, stays high in the sky most of the day, and sets to the northwest. This is an amazing stroke of luck because it means the sun is low in the sky when it’s cold outside and high in the sky when it’s hot outside. Low sun is easy to let into a building, while high sun tends to be blocked by the roof and other protrusions of the building itself. Perfect!

With this basic observation under our belts, we’re ready to realize a passive solar masterpiece. First, we need to find the right place to build. In our region, that means a site that will give us unobstructed access to the low southern winter sun. Some trees or other obstructions to the east and especially the west would be great to block the hot rising and setting summer sun. (A ridge or evergreens to the north might block some winter winds, but wind is very site specific so we’d have to spend some time on site to make that call.)

Next, we’ll design our building to let in a lot of winter sun and block a lot of summer sun. Building shape is the most basic parameter. In our area, the best shape is longer on the east-west axis, creating more wall surface on the south and less on the east and west.

The main avenue for sun to enter the building will be through glass. From a heating point of view, only south-facing glass will create a net solar heat gain, so other glass should be minimized. However, north, east, and west glass are an important part of our natural ventilation cooling and daylighting strategies. This is where the delicate interplay of science and art comes in, in other words we’ll find beautiful compromises.

The heating equation, in any case, is straightforward, we simply have to carefully match the square footage of our southern glass windows and doors to the amount of “thermal mass” we place in the building. Thermal mass simply means something that stores heat, so technically everything is a thermal mass. Dense heavy materials usually store heat well. Water, concrete, stone, and earth are good examples. A great place to put mass in a building is in a concrete or earthen floor. Sun flows in through glass covered openings and is stored in the mass of the floor. The mass sucks up heat, thus preventing the house from overheating during the day, then slowly releases the heat after the sun goes down keeping the house warm at night. The trick is creating the right balance. Science to the rescue! We have everything from rule of thumb glass to mass ratios to computer assisted thermal modeling at our disposal.

Next, we’ll need to design our roof overhangs and other protuberances so that they follow our mantra: block sun when it’s hot, let in sun when its cold. The poster child for this is the southern trellis covered with deciduous vines (grapes and hops are two options for you vintners and brewers out there). Thick leaf cover that blocks the sun in spring and summer dies back in fall and winter to let the sun through. Since we know where the cooperative sun will be in the sky at any time of year, roof and window overhangs can be sized to interact with the sun exactly as we like.  We’ll add covered patios on the east and west, again to block low hot sun, and one on the north to create an outdoor room that will be shaded all summer long.

Finally, we’ll work with the surrounding landscape to heighten our design. In tandem with our patios, we’ll add shade trees, especially to the west and north. Plants not only create shade, but evaporative cooling which is the natural technology mimicked by your refrigerator and clanking, polluting window A/C or HVAC unit. We’ll also create a focus to the south, perhaps placing an outdoor kitchen under the trellis with a kitchen garden in front of it. We’ll place doors and windows that encourage cross-ventilation and allow effortless transitions to outdoor rooms. Don’t forget that in our climate a little tweaking back and forth between sun and shade makes the outside comfortable for most of the year. Outdoor rooms are inexpensive access to the mansion of nature. Of course, we’ll also design a unified insulation strategy that includes measures to slow convective, conductive, and radiant heat loss through the building, but that’s another story.

Ta-da! A passive solar masterpiece that will supply a baseline of heat and cool at the right time of year which can then be enhanced to create the specific indoor environment of your choosing. Though you may not get the picture from this frantic overview, none of these design features need to control the look or feel of the building. Passive solar is flexible if you are. It’s a pivotal design concept, not an architectural gestalt.

Disagreement abounds even on some of the basics. For example, some people feel that our climate is too wet to allow for natural ventilation as a cooling strategy because open windows plus humidity can result in mold. In the end (here’s where you refer back to that lovingly pawed copy of my column from last month that’s taped to the fridge), the right approach to passive solar is going to have to match the specifics of who you are with the specifics of the place your house will sit.

I will however be unequivocal about one thing: you are going to heat and cool your house with solar energy one way or another. The only question is if you want it free and clean or expensive and dirty. This may sound like a laughably obvious choice, but a cursory glance at any cityscape or subdivision will show that the sun is presently laughing at us, not with us.

Thermal Mass

In our climate, even on the hottest days of summer, the outdoor nighttime temperature drops below the indoor temperature. Using massive materials inside the insulated envelope, we can take advantage of that diurnal temperature swing to reduce the amplitude of the indoor temperature swings. The mass absorbs heat during the day and radiates it back at night.  If we do a good job of keeping that mass shaded during the summer there’s no need for mechanical cooling and the dog has a nice cool floor to lie on.

Thermal Inertia
Talking about thermal mass in more detail gets a little more complicated. I’m afraid we’re going to need a few definitions:

  • Heat capacity is the ability of a material to absorb heat.
  • Diffusivity is a measure of the speed heat moves thru a material.
  • Effusivity describes the ability of a material to exchange heat with it’s surroundings. It is similar to emissivity (as in low-e or low emissivity windows).

Good materials for thermal storage have high thermal inertia.  They have a high heat capacity, but low diffusivity and effusivity.  Metals don’t work well for thermal storage.  They can take on a lot of heat because they have a high heat capacity, but they can’t store it very long because they also have high diffusivity and effusivity.  Metal heats up quickly, but it gives it right back. Clay is much better for storing heat in a timeframe that’s useful for conditioning houses.  It has a high heat capacity, but low diffusivity and effusivity. It’ll take all day to heat up a cold earthen floor sitting in a room with a warm air temperature, but it will take all night for it to radiate that heat back. That’s what we’re looking for.

mathis

Even when the two items are identical in temperature, the metal feels colder. Why? Wood is not a good conductor of heat, so it is slow to absorb the heat from your hand. Metal has higher thermal effusivity, so the heat from your hand flows into the metal quickly – creating the sensation of it feeling cold.

Mathis Instruments

In our climate massive construction is awesome in the summer. The downside is that dense materials like tile, concrete, and compressed earth block also feel cool to the touch during the winter. That’s why European stone castle walls are covered with tapestries.

Mean Radiant Temperature
To derive your Mean Radiant Temperature, look around you and take the temperature of every surface you see. You are exchanging heat with all of those surfaces. Surfaces warmer than you radiate heat to you and all the other colder surfaces. You’re just another room surface exchanging heat with all the others. To be comfortable all the surfaces around you need to be within a few degrees of each other (and you), and in a well insulated house with good windows they will be. However, believe it or not, our skin does not have good temperature sensors. Instead, we have excellent heat flux sensors. All of the surfaces in a room can be exactly the same temperature, and some will still feel colder than others when we touch them. The surfaces that feel colder are the ones with higher effusivity. The castle tapestries have low effusivity so they feel warmer than high effusivity stone.

Radiant Heating
In a typical (minimally insulated and drafty) house, radiant floor heating feels great because the mass is heated up to about 80 deg F. The floor radiates heat up to other surfaces, and brings the mean radiant temperature up so we’re nice and toasty. The problems are:

  1. radiating 80 deg F from the entire floor is a lot of heat.  A house that needs that much heat is wasting a lot of energy, and it should be insulated better.
  2. you lose a lot of ability for a slab to absorb free heat coming in the windows from the sun if the mass has already been heated by radiant tubing.

In an efficient well sealed house, a conventional concrete radiant floor heating slab won’t have to rise above about 73 deg F to meet the heating load (assuming the entire floor is heated). You will wonder if the heat is really on because it won’t feel warm. Even though the floor slab is adding heat to the house and the mean radiant temperature is high enough that we aren’t radiating much heat to the other surfaces, concrete has a relatively high effusivity. It exchanges heat with us pretty easily and feels cool even with a slight temperature difference. In a passive solar house, high effusivity materials located in areas that get direct solar gain will feel tactically warm on sunny days, but those same materials in northern rooms without solar exposure or in southern rooms on cloudy days won’t.

Recommendations
If you use radiant heat, insulate the house well enough that a small area of radiant will heat the entire house. Locate it in northern rooms (especially bathrooms) that can’t be heated by the sun.

Concentrate high heat capacity materials in the south rooms where they will do the most good. Use low-medium effusivity materials to store heat. Assuming no radiant heat, a north bath or kitchen would be better off with low effusivity wood or cork floors and wood countertops, but the same room located on the south would benefit from medium effusivity concrete countertops and tile floors.  Likewise, soft earthen plasters will feel warmer than hard venetian lime plasters, and soft lime and gypsum plasters will feel warmer than harder cement based plasters.

This spreadsheet shows the effusivity and interface temperature (how warm the surface feels when you touch it) for a few typical materials. I assumed an 85 degree hand surface temperature and all other surfaces at 70 degrees, but you can go to the spreadsheet and change those values as you see fit: Google Docs | Thermal Effusivity.