Additional Passive Cooling Strategies for Hot Climates

Windcatchers have been employed for thousands of years to cool buildings in hot climates. The windcatcher is able to chill indoor spaces in the middle of the day in a desert to frigid temperatures.

The following list includes dozens of low tech, low cost ways to cool buildings in hot climates passively without electricity or machinery, i.e., passive cooling or natural cooling. This list is in addition to the 11 or so simple passive cooling techniques that I talked about in my video the other day. Altogether there are over 50 practical methods for cooling your home sustainably. Despite all these wonderful methods, most people – at least in North America – live in poorly insulated boxy houses with costly, wasteful air conditioners. This is one example of “ignorance is not bliss”.
– night cooling: open the windows at night to let in cooler, fresher air.
– roof vents for improved ventilation. This could include a ridge vent and cupola.
– gable vents on gable end walls
– adequately shaded clerestory windows
– smaller windows on the east and west to prevent overheating (if the walls aren’t shaded)
– louvers and vents
– well located doors
– 50-100% more or larger windows on the leeward side than the windward side to help hot air to escape
– earth berming with moist vegetation such as grass
– keeping vegetation moist around the house to help cool the breezes (the yard)
– planting trees to funnel air toward your house
– plant trees that don’t block breezes
– wing wall to direct cool breezes into the home
– building on stilts
– stack effect: multi-story designs can be very effective at encouraging natural convection
– open plan living areas that encourage air circulation
– narrow floorplans
– orientation to catch breezes more effectively
– location: breezy locations near lakes, etc.
– outdoor living areas
– porches/verandas that shade the walls
– shaded, high thermal mass walls such as earthbags, adobe, etc.
– windscoop/windcatcher (with possible addition of a water element)
– evaporative cool wall such as double terra-cotta brick walls (low fired brick) filled with moist sand
– Venturi effect
– solar chimney: chimney designed to heat air and draw air from the house
– atrium or sunroom: can act like a solar chimney if properly designed
– basement: upper floors draw cool air upwards from the basement
– cool pantry and rootcellar
– well, open air cistern or underground water canal in the basement
– earth tubes in dry climates where mold is not a problem and digging is fairly easy
– roof insulation and reflective roof insulation
– fly roof (secondary roof over the main roof)
– green roof/living roof
– soffit vents and baffles between rafters to improve roof ventilation
– light roof color that reflects sunlight
– manmade water feature such as a lily pond on the windward side
– awnings (if you don’t have large roof overhangs)
– inner courtyard/open atrium
– pergolas and trellises to shade walls
– minimize sun reflection and re-radiation from surrounding environment: plants versus gravel or pavement
– blinds: close if sunlight is entering window
– avoid skylights unless openable and tinted
– smooth plaster reflects more light than textured plaster

Note: This is just a list of practical cooling strategies. There are plenty of ‘yeah, buts’ you should be aware of to prevent problems. There isn’t time or space here to cover everything. A fair amount of research is required to learn the details so you can optimize the passive cooling design for your home and building site.

Image source: Wiki – Windcatchers (good info on windcatchers)
Good reference with more details: Passive Cooling at House-Energy.com

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More on Timbrel Roofs

Timbrel roof by Guastavino

Readers really liked the previous post on Timbrel Roofs. This comment is from Paul, one of our readers.

“Your post a few days back about timbrel vaulting grabbed my interest, and I began to look into it. I found some interesting PDFs on Guastavino.net, in their resources page. Click on the Texts button. It contains several texts written in the 1895-1905 time period on fireproof building construction. I haven’t read them all yet, still working on the Prolegomenos on the Function of Masonry. Part II, 1904 text. I will read the earlier texts once I have finished this one.

It goes into some detail on why masonry is the ideal construction material, particularly for roofs, and why other materials (stone, wood and metal) are less than ideal. It also discusses the classical architectural advances of the Babylonians, Egyptians, Greeks and Romans at different stages of development.

I think you will find these texts of value.”
Paul

“Welcome to guastavino.net
The Guastavino Project at the Massachusetts Institute of Technology is dedicated to documenting and preserving the tile vaulted works of the Guastavino Company. In the late 19th and early 20th century, Rafael Guastavino Moreno and his son Rafael Guastavino Exposito were responsible for designing tile vaults in nearly a thousand buildings around the world, of which more than 600 survive to the present day. The remaining buildings are found in more than 30 U.S. states, and include major landmarks such as the Ellis Island Registry Hall, the Oyster Bar in Grand Central Terminal, and the Boston Public Library.”

Source: Guastavino.net

Follow-up email from Paul:
“Hi Owen,
It took some researching, but I found a clean (and free) copy of Rudolf Gustavino’s book on Cohesive Construction. This is the second edition and is complete, with all of the plates, etc. I printed a copy of this 167 page file for my research library. The new Adobe software has some tricks to it. It will automatically print double-sided (if your printer supports this) but can be disabled for printers that don’t have this feature.

When you read this file on your computer, it shows two pages at the same time, but when you go to print, it does a ‘flattening’, which I have never run into before, but what it does is to split the pages into one page per sheet. There is not a lot of print per page, this must have been a pocketbook, so that it could be taken to a job site and consulted.

Here are my thoughts on the subject. Gustavino used baked clay tiles, and even held a patent on how to make the edges staggered so that if a joint should fail, the tile would still be held in place by the shape of the tile alone. This is a really good idea, and this patent, which should be expired by now (the company shut down in 1965) so that this shape should be able to be used. Is it possible to use geopolymer to create these tiles, and possibly for use as the mortar? Some of Davidovits’ videos would indicate that this is indeed possible. Gustavino recommended tiles fired to a minimum of 2000 degrees F, so that if a fire should occur in the structure, the tiles would not expand significantly. This would prevent distruction of the structure, and seems to have worked, as the only Gustavino buildings that have been destroyed were done so deliberately, and not accidently by fire.

With earthbags for the walls, and geopolymer tiles used to create both floors and roofs, a building should last several generations. The only thing to ensure this would be aesthetics, for an ugly building is ugly forever, and is not likely to be kept around.

Gustavino used the arch in many different forms, but preferred the dome where possible, as it distributes the tension more evenly than a barrel vault will. He has a short discussion in his book how a barrel vault, built to his system, will stand up even if cracked diagonally from one corner to another. I found that point interesting. He liked to use arches (domes) even for ceilings that comprise the underside of floors, by putting up vertical ribs between the two surfaces of the appropriate height, generally 24 inches apart. To keep moisture from condensing between the two surfaces and to permit the running of pipes, wire, etc, he sometimes made them partially or completely hollow. This of course did not take into account insulation, but I suppose this could be installed before putting the floor down, as the arched ceiling is installed first.

I have seen some videos where modern test structures were tested to failure. However, every one of these were only one layer thick whereas Gustavino always built a minimum of two tile layers thick and up to 4 layers thick. As the tiles that he used were only 1 inch thick on the average, this makes for a very thin and light structure, yet one in which was of sufficient strength that after only a day or so, workers could walk across the structure and apply more layers of masonry.

All in all, I find the subject fascinating and full of promise.”
Paul

Image source: New York Daily Photo

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My Suggestions for Roofed Domes

An earthbag dome will likely have a longer lifespan and require less plaster maintenance if it’s protected by a durable roof. (click to enlarge)

Attach rafters to braces that are embedded between courses of earthbags. (click to enlarge)

Nailers help hold braces in position. (click to enlarge)

As discussed in a previous blog post the other day (see link below), dome roofs protect domes from moisture damage, shade the structure, reduce plaster work and capture rainwater. If you’re building in a rainy or snowy climate, your dome will likely have a longer lifespan and require less maintenance if you have a durable roof.

The drawings above show my recommended techniques using either wood poles or milled lumber. Wood poles are less expensive (or free), although they’re more tedious to work with. The basic ideas shown above can be altered to meet your needs. For instance, you could use purlins instead of roof sheathing. You could leave a gap between the roof and the dome for ventilation, add a skylight, gutters, etc.

Previous blog post on Roofed Domes

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Roofed Domes

Roofed dome by Superadobe Construccion Blogspot (click to enlarge)

Kentucky Dome Home roofed dome.

Rob Wainwright's roofed dome in Australia

Dome with embedded rafters at Blog Daum.net

Earthen domes evolved in deserts. Due in part to the beautiful and interesting shape, people started building earthen domes in rainier climates. But domes are more vulnerable to moisture damage than roofed structures. Without a roof, domes are exposed to the rain and snow. Plaster will eventually crack and when it does moisture can cause serious damage. One option is to build roofed domes as shown in the photos above.

Image source: Superadobe Construccion Blogspot
Image source: Kentucky Dome Home
Image source: Rob Wainwright dome in Australia
Image source: Dome with embedded rafters at Blog Daum.net

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ECHO Asia’s Earthbag Seed Bank

This small structure is the ECHO Asia Seed Bank’s earthbag house that is nearing completion.  ECHO promotes community-based seed sharing and saving. It is also part of their mission to recommend appropriate ways for communities and organizations in the developing world to better store seeds.

James (ECHO Asia intern) and Lue (Assistant Seed Bank Director) were trained in earthbag house construction by Engineering Ministries International (eMi).  To prevent the invasion of surrounding warmer air (the seed bank is located in a tropical/sub-tropical region), a small door with a foam interior and a thick but light ceiling composed of sacks filled with burnt rice husks were installed.  And to keep costs low, almost the entire structure was made from local, cheap materials, including a roof of fan palm thatch.

Data loggers will be installed to record the interior temperature and relative humidity.  These will be compared with outside readings over a period of one year. So we look forward to reporting on the long term results of the modification of temperature by the earthbag house and the potential of such structures for community-based seed storage in the tropics.

See sustainabilityquest.blogspot.com to read the entire article.

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The Easy Way to Make Ferrocement Roof Panels

Make ferrocement roof panels on the ground so you don’t have to plaster overhead.

I just found this great technique for making ferrocement roofs at Steve’s Flying Concrete site. Steve explains how to make roof panels on the ground so you don’t have to plaster overhead. This eliminates the most difficult and awkward step of making ferrocement roofs. The panels can be hoisted in place by crane or with a crew of strong workers.

“My latest idea is pre-fabricated, arched triangle, roof panels. 12 -18 ft wide–On the ground you build arched triangles in a dish shape. Finish the inside of the dish, flip the dish over, set with a crane and this becomes the ceiling of the dwelling.–No overhead plastering. A row of tiles inside, finishes interior ceiling.

The panels can either be set in a circular pattern to form a “dome” or alternating in a line to roof a rectangular shaped room. Building triangular dishes– start with insulation then structural layer and then polish the inside of the dish. THE HARD PART–Turn the dish over and stack it in vertical pile until the crane comes to set 8 dishes. Crane –reality check– for these dishes on the first floor I’d say 4 hrs at $150/ hr is $600– or $75 X 8 panels. Set the dishes and stick them together in the valleys– form work very simple using plaster lath– mix this pour on site, (pour out of a 5 gal bucket) and vibrate from above. 1/2 yd should go a long way.”

More details at Flying Concrete

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Loft or Attic Trusses

Loft or attic trusses create efficient extra space in the attic that can be used as a loft or for storage. (click to enlarge)

We have previously discussed a number of low cost, do-it-yourself trusses and roof systems. Use the search engine above with keywords such as ‘truss’ or ‘roof’ to find older blog posts.

Today’s post is about a special type of truss called loft trusses. Also called attic trusses, room-in-attic trusses and attic storage trusses, they create cost efficient extra space in the attic that can be used as a loft or for storage. This method is one of the most practical ways to gain space, often because attics are not fully utilized. It’s almost free space. Many times attic trusses have steeper roofs to create additional space, and can be used in place of conventional trusses. You don’t have to build the loft right away. The loft can be built at a later date when you can afford to finish it. Standard truss spacing is usually 24” apart. Truss manufacturers typically give free quotes and engineer the truss to meet local codes.

Trusses are one of the best options for building roofs. They are popular because they are very strong, efficient and relatively lightweight. They also create ample space for roof insulation. Trusses can be built before the walls are finished, and installed quickly. Trusses are made of multiple short pieces of light-weight wood. Because trusses span longer distances, fewer center walls or supports are needed. If you live where building codes are enforced, then using trusses will make code compliance much easier.

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The Sustainable Urban Dwelling Unit: Timbrel Vaults

The 'Sustainable Urban Dwelling Unit' (SUDU) uses timbrel vaults, and is constructed with only soil and stone.

Timbrel vaults offer another low cost, sustainable roof building method. This method is suitable for do-it-yourself owner builders if you do the research. Suggestions include: use a simple design with a reinforced concrete bond beam and modest spans. Look into using low-fired, lightweight brick like the type used in Mexico and SE Asia.

“The ‘Sustainable Urban Dwelling Unit’ (SUDU) in Ethiopia demonstrates that it is possible to construct multi-story buildings using only soil and stone. By combining timbrel vaults and compressed earth blocks, there is no need for steel, reinforced concrete or even wood to support floors, ceilings and roofs. The SUDU could be a game-changer for African cities, where population grows fast and building materials are scarce.”

Source: No Tech Magazine (This site has hundreds of great articles on low cost living and building!)

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Basic Earthbag Building DVD Finally Available!

I am pleased to announce that Owen Geiger’s Basic Earthbag Building DVD is finally available for purchase. It has taken more time than expected to complete the production, but it is well worth the wait I think.

Owen is a natural teacher who understands how to present information in a clear and understandable way and this DVD is excellent for introducing folks to the basic essentials of sound building practice using earthbags. Much of the DVD is derived from actual instruction at workshops, so you witness the whole process from the ground up.

After an introduction to the tools and supplies that are necessary for building, they construct a small sample wall with a rubble trench foundation. Every step is fully explained and demonstrated as the wall proceeds.

The second portion of the DVD takes you through the process of building a functional cool pantry that is attached to a house. Here you can see how doors can be framed and roofs attached. There are many tips and tricks that emerge from watching that could be invaluable in constructing most any project.

At the end there are some bonus scenes that include tips for building a dome, an animated fly-through of Owen’s Enviro Dome, and a tour of Owen’s completed Earthbag Roundhouse.

With over three hours of solid instruction, this DVD would be a valuable addition to anybody’s building library. You can review portions of this DVD by exploring the short clips that are shown on Owen’s YouTube Channel. And you can purchase the DVD directly from the manufacturer for $28.

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La Casa Vergara

La Casa Vergara was designed by José Andrés Vallejo and built in Bogotá, Colombia in just 5 months, early in 2011.

I am delighted to see that professional architects are beginning to accept earthbag technology as a viable approach to building. La Casa Vergara is a fine example of  an upscale home that is built by a professional crew, with solid engineering and with all of the amenities and refinements that you would expect in this class. The attention to finishes, flooring, light, and form make it an aesthetic journey just to browse the photo gallery.

I have assembled an extensive project page that reveals much about how it was actually constructed. There is very little descriptive text, so you have to study the images to follow the proceedures, but there is much to be learned from this project.

From the architect’s website.

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