Passive (and Active) Cooling
Passive cooling techniques (solar chimneys, thermal mass, ventilation, roof ponds, ...).And, efficient active cooling techniques
Passive Cooling:
- Passive Cooling Guides and Tools
- Shading
- Reflective Roofs (and Walls)
- Cooling Towers & Solar Chimneys
- Earth Tubes
- Reflectors
- Tips
- Efficient Active Cooling - Ventilation
- Efficient Active Cooling - Evaporative
- Efficient Active Cooling - More ways
Passive CoolingBasics
The Energy Source Builder newsletter
/ A very good article that provides a simple method to allow you to determine which passive cooling techniques are best for your climate.
This article is based on thebook "Sun, Wind and Light" (see below).
Be Cool -- Natural Systems to Beat the Heat,
Preethi Burkholder with Claire Anderson -- Home Power issue 108
Cooling Your Home Efficiently,
Claire Anderson -- Home Power issue 154.
How to get articles from Home Power ... / Home Power magazine article in issue 108 (Aug/Sept 2005)
Very good article on simple techniques to prevent heat gain and to provide passive cooling.
It includes a method to determine which cooling techniques will work best for your climate.
See also "Cooling Your Home Efficiently", Claire Anderson -- Home Power issue 154.
Design a Home That Keeps You Cool, Naturally,
William Hoffman, Fine Homebuilding August 2004
How to get articles from Fine Homebuilding ... / A home that illustrates how a number of simple cooling techniques that were combined in this house to avoid the need for air conditioning in this south Florida climate.
Passive Cooling -- Part 1 and 2
Cliff Mossberg
How to get articles from Home Power ... / Home Power magazine article, issue 82 and 83
Article on passive design cooling techniques for hot humid climates with examples. Many techniques covered.
Lakeland, Florida -- Side by Side Test,
Florida Solar Energy Center
Comparison of energy of a home designed with many energy efficiency features to a same size conventional construction home.
/ This is a very detailed and carefully done study of two houses of the same size in Lakeland Florida. One house was built conventionally, and the other was equipped with a wide array of features to reduce energy consumption, including: reflective roof, internal duct system, thermal mass inside insulation, high efficiency and properly sized AC, well designed overhangs, and optimal windows.
The measured energy consumption was 70% less on the house with low energy use features. A solar PV system offset and additional 22%, bringing the net energy use to near zero.
The reports provide quite a bit of detail on the saving achieved by each energy efficient design feature.
Passive Solar Cooled House in Tropical Areas
/ This is a fascinating house in Leyte Philippines that is passively cooled using a number of unique methods including a double roof, a strategy for shading south and north walls in low latitudes using the roof, and double walls on the east and west for shading.
The house also uses day to night temperature differences and basement cooled air as part of the cooling strategy.
This house is definitely worth taking a look at if you live in a low latitude hot climate.
Arizona Solar Center -- Passive Cooling
/ A good overview of passive cooling strategies.
Passive Cooling for Your North Carolina Home
North Carolina Solar Center
NC Passive Cooling Guide (pdf) / Good guide to passive cooling houses in the SE humid and warm climates.
From the NC Solar Center
Landscaping for Energy Efficiency
South Carolina Energy Office
Landscaping for Energy Efficiency (pdf) / Booklet on landscaping for energy efficiency. "Carefully positioned trees can save up to 25% of household's energy consumption".
Several other energy saving "briefs" also available here.
Window Overhang Sizing Tool
Sustainable By Design Solar Tools
/ Properly sized overhangs on south windows keep you cool in the summer and collect sun in the winter.
Designing Shading Overhangs with Google SketchUp
Be sure to pick a location near you, or enter your latitude/longitude -- otherwise, sun motions and shadows will not be correct. / SketchUp is a free 3D drawing tool from Google. In addition to be exceptionally easy to use as a general purpose drawing tool, it offers a shadows made by a built in sun. You can easily draw a wall with a window and overhang, and play the sun over it for various times of day and times of year.
It could also be used to layout your whole house (with trees and sunspaces), and see how the sun plays over it.
VERY easy to learn.
Sun, Wind and Light -- Architectural Design Strategies, 2nd Edition
G. Z. Brown and Mark DeKay / Details on a large number of specific design strategies for making effective use of the sun and wind, and natural lighting. It includes quantitative analysis techniques for each strategy. Intended for architects, but quite readable. Covers commercial buildings as well as residences.
2001 400 pages
Radiant Barriers,
SouthFace.org -- Energy Fact Sheet
Radiant Barrier Fact Sheet / A short but good Fact Sheet on radiant barriers from SouthFace.org.
Climate Consultant,
UCLA Energy Design Tools
Note: the psychrometric charts that this tool produces have an overlay indicating which type of cooling techniques will work well in your climate. A really nice tool. / Climate Consultant is one of the UCLA Energy Design Tools.
It provides a variety of ways to visualize weather for a specific location. Weather data files are available for hundreds of locations. This is a brand new version, and is very easy to use.
"It graphically displays climate data in either metric or imperial units in dozens of ways useful to architects including monthly bar charts, timetable charts, and psychrometric charts, sun shading charts, and sun dial charts."
One of the most interesting charts is the Psychrometric chart with overlays that show the design strategies (e.g. passive solar, evaporative cooling, .) will work for the location in question.
Radiant Barrier Pilot Project,
Florida Solar Energy Center,
D. Parker, J. Sherwin, and M. Anello
/ An FSEC evaluation of the energy saving for radiant barriers. Nine houses were monitored for attic temperatures and AC energy use before and after installing a radiant barrier.
Bottom line was an about 10% reduction in AC energy costs, and a somewhat improved comfort level.
Shading Structures
Window (and house) Shading
How to keep cooler, save money, and be green all at the same time
Window Shading Techniques
Gary / As much as half the heat gain to your house can come from unshaded windows. The sunny day heat gains from a hundred square feet of east or west facing window is the equivalent of running your furnace for several hours.
This is my 2 cents worth on several effective and (mostly) inexpensive ways to shade your windows and cut down on house overheating, high AC bills, and greenhouse gas emissions.
Sun Screens
The screen material from Phifer:
And another -- there are lots of them:
Exterior window shades -- search for shades:
A similar screening from Real goods / This seems like a pretty good idea for reducing summer heat gain on windows. The shades block up to 90% of sunlight, and mount in vinyl frames (like bug screens). It looks like they would work on a wide variety of windows, including ones that would be difficult to handle with other shading techniques. They do the shading on the outside, where its most effect.
It seems like a DIY version could be worked out. The PhiferSunTex material is said to be available at some home centers. Frames could probably be made from the same material that home centers sell for making insect screens.
Exterior Roll Up See Through Shades
Details... / These are exterior shades that roll down to to provide filtered shade, but still allow a view out.
We have these, and like them.
Details...
My Neighbor's Outstanding Trellis
All the details ... / My neighbor has a terrific trellis with vines shading structure. It makes for a great shady place to sit on hot sunny summer days. In the winter with the leaves gone, it provides filtered sun and some solar gain to the window area behind.
And, it provides beautiful fall color.
All the details ...
Alnet DIY Rollup Shade Cloth Shades
(no longer exists)
This site has bit the dust -- but, the Wayback Machine still has the project... / Plans for a simple rollup shade from shade cloth.
Trellis Cooling
Pictures of the trellis and other passive cooling features here:
/ ECO house in Rio de Janero uses an aluminum trellis to support plants that will shade the house wall from from sun.
Living Wall System
/ In addition to all the "green" benefits that these living walls provide, it seems like they could be very useful for reducing heat gain from walls that get a lot of sun.
Lots of example photos and some "hot to" information at this website.
Trellis Shading
DoItYourSelf.com Trellis Projects / Some sample projects/pictures that use an external trellis for shading. This approach works well on East and West facing windows where overhangs are not effective.
Shading Structures from 2007 Solar Decathlon
A little more on the German entry:
Quite a few Solar Decathlon pictures from Inhabitat:
/
German entry in the 2007 Solar Decathlon had a nice porch/shading structure. Note the roof of porch is PV modules. Note that this would even work on east and west exposures.
And, this nice overhang on the Urbana-Champaign entry.
Click pictures to enlarge.
Pictures from Inhabitat
Unique Bamboo Shading Structure Shades Full House
/ A home in France built to Passive House Standards uses a very unique shading structure that shades the full south wall of the house with movable bamboo shutters.
Some Trellis or Plant Screen Ideas ... / These are some shading trellis or plant screen ideas excerpted from a discussion on the HomeEnergySolutions Yahoo discussion group
Thanks to the folks at HomeEnergySolutions for the good ideas!!
The Green Shutter
/ A pretty neat design for a operable shutter with plants for sun control.
Schiavello Vertical Garden
From Inhabitat:
... / This design seems as though it might work well for blocking unwanted solar gain on windows (particularly on difficult to shade east and west facing windows).
For this purpose, it would best be installed outside the window on the ground or on a balcony.
Judging from the comments, it might be good to think about some type of watering system.
Alnet DIY Awning Plans
(no longer exists)
The above site is gone, but the Wayback Machine still has the project... / Plans for a simple wood framed, shade cloth awning to provide window shade and reduce heat gain.
Retractable version
Alnet DIY Pergola Plans
(no l onger exists)
The above site is gone, but the Wayback Machine still has the project... / Plans for a simple wood framed, shade cloth pergola from Alnet.
Alnet DIY Trellis
(no longer exists)
The above site is gone, but the Wayback Machine still has the project... / Plans for a simple wood framed, shade cloth trellis from Alnet
Elegant Shade Structure
Popular Mechanics
(Pop Mech has dropped this article
but, its still available on the Wayback Machine... / Plans for a very elegant shade structure. This could be used as a standalone shade structure or adapted to shade a house window.
Very detailed plans.
Windsor Shade shelter
California Redwood Association plans... / Detailed plans for a free standing shading structure.
Could be used for yard/deck shade, or to shade a window.
Rollup shade plans
From Charlie's Green House
The Plans (pdf) / Plans for a simple rollup shade from Charlie's Greenhouse in Seattle.
Solar Deck Canopy -- How Well Does It Let Light Through During Winter?
Amy Heidner, PE, 2012 / This is a very interesting paper demonstrating the use of PV panels as part of a shade canopy that provides shade for living space that was overheating and generates solar electricity as well.
The aim of the project was to provide sufficient shading to keep the living area behind the canopy from overheating, while at the same time not providing so much shade that the deck and living area would be too dark.
The authors found that by selecting a PV module design that lets some light through and adding some glazed areas above and below the PV modules that they could get just the right light levels under the canopy.
Shade Sails ,,, / Shade Sails (or Solar Sails) are fabric membranes supported by fixed anchors, and positioned to provide shade. They are laid outand tensioned in such a way as to be very resistant to winds.
They can be used to shade decks, porches, play areas, windows, ...
They canbe very nice looking indeed, and can handle some difficult shading problems.
Example photos, and design information here ...
Reflective Roofs
Comparative Summer Attic Thermal Performance of Six Roof Constructions,
Danny Parker and John Sherwin,
Florida Solar Energy Center, 1998
The full paper ... / This is an excellent paper that compares the attic temperatures for 6 different roof constructions.
Following the findings of this study can havea major impact on your cooling costs.
If you don't have time to read the full paper, here is my quick summary of the findings...
Cool Metal Roofing
/ Reflective metal roofing can keep your house cooler and save on cooling bills.
Measured Cooling Energy Savings From
Reflective Roofing Systems In Florida:
Field And Laboratory Research Results,
Parker, Barkaszi, Chandra, and Beal
Florida Solar Energy Center
Measured and Simulated Performance of Reflective Roofing Systems in Residential Buildings,
Parker, Huang, Konopacki, Gartland, Sherwin, and Gu.
A sampling of commercial sources ... / Actual measurements of reduction in cooling energy for 8 homes in Florida before and after coating the roof with a reflective (white) coating.
Cooling energy savings averaged 20% just by going to a more reflective roof.
The papers cover both roofing materials that are reflective as well as coatings that can be applied on existing roofs.
The paper on Roofing Material Reflectivity is good and surprising.
"CoolWall" Paint
ORNL Report... (pdf)
The flip side of this is that if you live in a cold climate, painting your home with a dark shade will result in a saving in heating energy. / "CoolWall" paint reduces cooling costs by formulating the paint to be reflective in the IR, but any color you like in the visible spectrum. In other words, you can get the same sort of cooling benefit that comes from painting your house white without having to have a white house.
While many of the "save energy with paint" schemes are scams, this one has been tested extensively by the ORNL (see links), and does result in a 4 to 21% reduction in cooling energy.
It should not be used in cold climates in that the same high reflectance in the IR that reduces cooling energy use increases heating energy use. For example, in Richmond VA, the reduction in summer cooling energy is more than offset by the increase in winter heating energy.
In the ORNL testing, white paint outperforms the IR reflective cool wall colors -- so, white paint is good for hot climates.
David's White Roof Experiment ... / David painted his roof white to measure the amount of cooling that the reflective roof brought to his attic and living area.
White roof paint experiment ...
From one of the comments on this David's roof:
"...all houses in traditional villages on Greek islands have white roofs. And they use lime, just like you."
Wolfgang's Cool White Roof... / This is another roof made highly reflective using hydrated lime to coat an existing roof.
The coating is very reflective, and while it does not last forever, it does last longer than you might think.
Wolfgang has kept track of attic temperature and AC use and reports significant savings.
Applying a White Coating to a Rubber Roof... / A nice diy package of instructions for applying a reflective white coating to a black tar roof.
A great passive way to provide significant building cooling.
They have some advice on what paint to use here...
Monitored Summer Peak Attic Air Temperatures in Florida Residences,