What is Passive Solar Architecture? Part One

I’ve been threatening, um, I mean promising you this posting for a long time. And here it is, finally. Keep in mind I am not a designer or a meteorologist. If you have any questions, ask them in the comments and I’ll pass them on to Steve Belardo, the designer and mastermind of my dream house project, for answers. I just read a book on the subject. Well, of course I did, being a librarian…but I know this only makes me dangerous and NOT an expert!

I’ve added some pictures to illustrate the concepts because that is also what I do, as you know…

Here we go, then!

The goal of this house is to NOT use the HVAC system.

Oh really? Yes, really. The house has been designed to maintain a comfort level throughout the interior structure for around 330 days out of the year. There will be heat and cold spikes that might make me run to the heating/cooling system, but generally-speaking, the hum of the air conditioner or the whoosh of the heat turning on will be a rare occurrence.

So, how does this work?

Solar heating systems, whether active [solar panels] or passive [the building structure itself] act in much the same way [as a conventional heating system]. The sun’s heat is gathered by solar collectors or the structure, transmitted to the heat storage mass, held until needed, and then distributed to spaces for warmth, where sooner or later it passes through the weatherskin (building exterior) as heat loss.

Solar space heating is less polluting, more economical, and healthier for our environment and economy than any other energy source. –David Wright: Natural Solar Architecture: A Passive Primer

By using solar-friendly building materials like adobe blocks and wood, situating the house to catch the sunlight properly, and installing appropriate doors, windows, and roofing materials, the house can heat and cool itself most of the time.

How cool (or hot) is that?!

The goal of passive solar design is to create structures that respond to the patterns of nature. –David Wright: Natural Solar Architecture: A Passive Primer

So, what are “patterns of nature”?  Generally speaking, the patterns that affect building design are landscape and weather. Once the site of the building is identified, then you are dealing with a “micro-climate” (landscape and weather taken together) specific to that very particular spot.

Landscape means land and the type of land can range from desert to hills, mountains to forests, and the seashore to the tropics. In the case of this house, we have a combination of land types: prairie (dry grasses, windy, winter blizzards, summer drought); desert (dry, hot, sunny, dusty, flash floods); and mountains (trees, thunderstorms, cold winters, snow, deep freezing). This complicates things a bit. A bit!? Well, yes, it’s pretty hectic around here sometimes…

Landscape includes soil. Here I know we have a lot of gravel and rock, which both have good thermal capacity, but I’m not sure about the rest of it.

Vegetation is part of the landscape, too, of course. All vegetation–grasses, low and high shrubs, deciduous and evergreen trees–have a role to play. In the landscaping for this new house, I plan to use only native plants because I know they will probably succeed and the water use to maintain them will be low. Which plants to choose and where to place them are definitely questions to ask because these decisions affect the passive solar process.

Water is part of the landscape. Or sometimes it is not! Where is it? How much of it is there? How can it be accessed? What kind of processing (filters, etc.) does it need? How much will be used? I’ve talked about the water situation here and why a water reclamation plan is so important.

Latitude and an understanding of where the house is physically situated is a critical part of the design.

The first day I met Steve, he and I stood at the building site and he explained where the sun would be in the winter and the summer and how he would organize the placement of the building structure to take advantage of this. NOW I am beginning to understand what he told me so many months ago. The angle of the sun based on the distance we are from the equator combined with the different seasons has definitely had an impact on Steve’s decisions regarding the physical placement of this house. I’ve watched him calculate these measurements and he actually shifted the angle of the house a few degrees towards the north just prior to breaking ground. Why? He had been on site for many weeks and he realized that the sun was not quite where he had expected it to be. So, he adapted. And that is part of this design process, too–adapting to “the patterns of nature.”

Krevit-house-planThe original plan for the house showing physical orientation and initial water storage ideas

Interestingly, “view” is a component of the micro-climate and plays a role in the design of the house:

“It is the task of the designer to respect and harmonize with the surroundings. Mother Nature seldom makes mistakes with view. Man often does.” –David Wright: Natural Solar Architecture: A Passive Primer

Steve took this into consideration, as you know! The view from every window and door is stunning.

All of the features above fit into the landscape part of the “micro-climate.” What about the weather? Weather is obviously a big factor in passive solar design.

Weather includes temperature, sunlight, weather cycles (storms, winds, rains), precipitation, humidity, air motion and wind, and the weather record.

I know the following from living here for almost an entire year:

  • temperature range is much wider than I expected: 100 degrees down to 15 degrees
  • sunlight is brighter and lasts longer, but there are many cloudy days
  • not too sure about weather cycles, but I experienced four definite seasons, with several hail storms and two snowfalls, and the rainy season returned this year
  • it does not rain much of the year but the rainy season seems to make up for it–annual precipitation is usually less than 20 inches, though
  • humidity? what is that?
  • the winds blow A LOT in the winter and spring, but not so much in the summer
  • must look up a record of the weather here, although the last 2-3 years, with sustained drought and wildfires, seem like an aberration

Obviously all of these weather elements play a part in planning the house and preparing the house and its occupants to withstand the worst and enjoy the best of the weather.

Now you have a picture of the “micro-climate”–the landscape and the weather–of which this new house is a part. Aesthetically-speaking, Steve has ensured that this hand-made house “feels” like a part of the micro-climate as well, by making appropriate choices regarding colors and textures, both inside and outside. His vision is this: the house should appear to have grown up out of the ground; it should seem organic and it should be at one with its surroundings.

I think we are almost there!

Much more information is presented in the book, of course, but these are the basic elements that need to be considered when planning a passive solar structure. And you find yourself asking: Yes, but HOW does passive solar architecture really work?

This is how David Wright describes it:

A building that passively utilizes the energy of the sun for year-round space conditioning involves three basis principles:

1. It must be designed to accept or reject solar heat when called for.

2. It must have the thermal integrity to maintain internal comfort despite the range of climatic forces acting on its weatherskin [building exterior].

3. It must incorporate the ability to retain the presence or absence of heat within.” — from Natural Solar Architecture: A Passive Primer

More on this in Part Two, where we will discuss conduction, convection, radiation, and other fun stuff. Hey, I’m only one chapter ahead of you, so hang in there!

One thought on “What is Passive Solar Architecture? Part One

  1. Not TOO painful! And the illustrations were lovely. What a worthy part of the landscape your home will be. I think it’s fair to say Tony would be impressed though not surprised – even if he didn’t want to live in West Texas.

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