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Adobe Homes for All Climates … Really?

Posted By admin On November 3, 2010 @ 12:00 pm In Green Building | Comments Disabled

Tristan Roberts at BuildingGreen.com recently posted a book review of Lisa Schroder and Vince Ogletree’s Adobe Homes for All Climates: Simple, Affordable, and Earthquake-Resistant Natural Building Techniques [1], in which he raised some legitimate questions about the book’s “all climates” claim.

Lisa Schroder was kind enough to respond to some of the questions that Tristan raised in his review. Is adobe really appropriate for all climates? Read on, and decide for yourself…

From the Building Green review:

Adobe Homes is filled with practical tips, gorgeous pictures, useful construction drawings, and step-by-step help for anyone looking to build adobe, whether a professional or a homeowner. There are tips on earthquake resistance for locations with seismic concerns. There is extensive guidance on the often-overlooked issue of setting up your site to mix, mold, dry, store, and build with adobe bricks. The book gets into finishes, integrating windows and doors, and a lot more.

Unfortunately for me, I wasn’t looking at the book with this lens. Before I could really contemplate setting up a site for adobe production, I had to be sold on adobe for this climate. I was looking for ideas on cozy earth building in a climate with 7,500 heating degree days (many of them cloudy, for days at a time), 500 cooling degree days, and a distribution of those heating degree days throughout 12 months. And an adobe structure in this climate will be an energy hog, because, as the authors note, adobe has a very low R-value.

In short, the “for all climates” tagline, which drew me in, is a stretch. Yes, there is a suggestion to add a layer of insulation in colder climates (mentioned in the inspiring foreword by Bruce King, and in a subsequent paragraph in the book). Yes, there are nice pictures of snow-covered Rocky Mountain adobe (which may be cold–at times–but gets a lot more sun, making adobe a better choice). But building an adobe wall and adding insulation to it for this climate requires at least a whole chapter (more than the paragraph currently devoted to it), and perhaps a whole book. Here are some questions that this “missing” chapter might help answer:

  • What kind of insulation works well with an adobe structure?
  • How much is needed?
  • Should the insulation be interior of the adobe, exterior of it, or both?
  • What are the benefits of building adobe and also a secondary insulation system? Why is it worth doing versus just using another construction system?
  • What construction and moisture details are necessary for adobe to be durable through a cold, wet, winter?
  • How does the addition of insulation affect the vapor profile of the adobe wall? Any issues to watch out for

I hope these will be considered in future editions or articles by the author. In the meantime, this looks like a great resource for natural builders in climates where adobe makes more sense–most classically, the Southwest U.S.

Read the full, original review at BuildingGreen.com [2].

Lisa Schroder responds:

Hello Everyone,

First of all, I want to thank you for an interesting discussion.  The topic of how to improve the insulation qualities of earthen walls has been in review for the past few years. My personal experience with adobe has been in areas where the sun does shine, even if just for an hour a day in the winter.  We often made bricks in the rain and covered them tightly with plastic to dry.  Adobe bricks don’t necessarily need the sun, but they do need to be protected from moisture and allowed to dry out.  However, when building an adobe home in colder, cloudy regions, insulation is often needed to make a comfortable home that uses the minimal amount of additional heating.

One great adobe mentor of mine is Quentin Wilson of the Adobe Association of the Southwest in New Mexico.  He states that “strange things will happen if you add insulation to the adobe.  The wall will perform better than the sum of the two R-values.”  He calls it phantom R’s.  This is because the adobe is not an insulator but a capacitor and conductor that mimics insulation in certain situations.  When you couple capacity with resistance you get more resistance than expected in a non-steady state situation.  Electrical engineers understand this as capacitive reactance or a band pass filter.

Considerable research has been done in many parts of the world on this topic and I am happy to share with you some of the conclusions.  Most importantly, the use of passive solar design is essential to utilize the sun’s energy to heat the home in the winter.  This may require reducing the eaves to allow the winter sun to enter the home.

Secondly, it is suggested that home owners insulate their adobe walls at least on the side facing away from the sun; this would be the north facing walls in the Northern Hemisphere or the south facing walls in the Southern Hemisphere.  One recommendation would be to attach 2″ battens, insulating with wool or another natural, breathable material, and cladding.  Many people also use 2″ of polystyrene with plaster over to increase insulation.  Dow Styrofoam Utilityfix xps is a closed cell foam and will not loose its R-value to moisture uptake.

Another good option would be to use conventional timber frame construction with insulation and cladding for the exterior walls and interior adobe brick walls for thermal mass.  These homes make use of all the good qualities of earth, such as regulating humidity levels and neutralizing airborne toxins.  The exterior walls do not require large overhangs, thus are suited for passive solar design.

Lastly, you can make adobe bricks with improved insulation values for exterior walls.  These bricks include light aggregates, such as untreated sawdust and paper pulp, and when combined with earth increase the insulation value.  The exterior side of these bricks walls require 3 coats of plaster for added protection against moisture.

Ultimately, what makes adobe homes suitable for colder climates is when they are designed for the sun.  The excellent thermal mass qualities allow the walls to slowly retain the heat and slowly release the heat into the home.  As for all green building products, some are more suitable to certain regions, and it may be difficult to acquire and produce the necessary adobe bricks in some places.  But studies show that adobe bricks made on site have the lowest carbon footprint of all building materials, and this should be considered with evaluating our building products.

I like the idea of including an additional chapter on insulating adobe where this topic can be discussed in depth with details and examples of the ideas mentioned above. Hopefully this information has shed some light on alternative ways to improve the insulation qualities of adobe brick homes.  I do believe that adobe brick homes can be suitable for all climates, when the appropriate design is applied.  Again, thank you for this lively and interesting discussion.

Lisa Schroder
Co-author of Adobe Homes for all Climates [1]


Article printed from Chelsea Green: http://www.chelseagreen.com/content

URL to article: http://www.chelseagreen.com/content/adobe-homes-for-all-climatesreally/

URLs in this post:

[1] Adobe Homes for All Climates: Simple, Affordable, and Earthquake-Resistant Natural Building Techniques: http://www.chelseagreen.com/bookstore/item/adobe_homes_for_all_climates:paperback

[2] BuildingGreen.com: http://www.buildinggreen.com/live/index.cfm/2010/10/26/Do-adobe-homes-really-work-in-all-climates--Book-review

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