In the first of a two part series article, Jacob Deva Racusin explains the differences in monitors for your walls. This is “must know” information for every builder and owner.
Reviewed by Jeff Ruppert
Making Better Buildings: A Comparative Guide to Sustainable Construction for Homeowners and Contractors by Chris Magwood will be released this Spring and promises to be one of the most valuable tools for the designer and builder who wants to understand how their choices of systems rank in terms of environmental impact, cost and acceptability. No other compilation gives such an in-depth review of the most widely used natural building techniques. Not only will you find the tried and true methods of straw bale and rammed earth construction, you will find alternatives you never knew existed.
Being a guide, this is not a how-to manual. It does not have pictures showing how to build alternatives to concrete foundations, for example. What this book does is ensures you are not missing something, and if you are you will easily find it and be able to compare it quickly to what you think is the best choice. The information on each system is objective and easily referenced. What is so impressive about this book is the list of systems it covers:
- Walls and Insulation
- Floor and roof structure
- Sheathing and cladding materials
- Roof sheathing
- Surface finishing materials
- Mechanical systems
- Water systems
- Wastewater systems
- Heating and cooling systems
- Electrical generation
As a designer of natural buildings I found the tables used for comparison very easy to glance through. I was able to discern the most valuable information quickly once I became familiar with the format. Comparing choices is easy and finding the characteristics that may keep one system or another from fitting into a project simple. The format forces you to think about each system using the same set of parameters, such as code acceptance, embodied energy, waste generated, costs, durability, etc.
But let’s not mince words when talking about green building. This book is clear – the current mainstream methods of making buildings sucks from an environmental point of view and no matter how certified they are, they just aren’t that green. The systems reviewed in this book address the most fundamental issues facing our society and the construction trades. Systems such as steel and concrete construction are not included due to the simple fact that both materials cause huge harm to our environment. There is no need to waste paper (or bandwidth) on the higher end of impact and societal costs when you are focusing on real solutions. If you are reading this book it means you are serious about considering real alternatives in this day and age of high impact buildings and “greenwashing.”
Chris Magwood continues to bring us fresh ideas and perspectives with this publication. We recommend it not only to the professional designer and builder, but also to owners who are serious about making better choices on their next project.
Making Better Buildings will be available in March for $39.95 USD and CAD from New Society Publishers. It is approximately 460 pages and will be available in both paperback and as an eBook.
Paperback ISBN: 978-0-86571-706-0; eISBN: 978-1-55092-515-9
Disclaimer: Chris Magwood has appeared as guest editor in past issues and submits articles regularly to The Last Straw.
by Chris Magwood
The straw bale revival of the 1990s reintroduced builders to a pioneer building method that showed remarkable potential for building in a modern context. The nature of the basic components of a straw bale wall system – bales with plaster applied directly to bales – combined several obvious advantages over other wall systems while simultaneously raising some serious questions.
The advantages are familiar to TLS readers: low environmental impact, simplicity and well placed thermal mass. The serious questions and attempts to answer them were the lifeblood of TLS: What about moisture? Air tightness? Cold climates? Humid climates? Longevity of the straw in all these conditions?
There was a lot more going on in the construction world of the 1990s than the straw bale revival. The housing industry was recovering from multiple moisture-related disasters, many caused by overly airtight but under-ventilated homes and/or the use of un-vented “waterproof” exterior cladding systems. The research into these issues, among other factors, led to a rise in prominence of “building science” as a distinct engineering discipline. The straw bale revivalists were extremely lucky to have the attention of some of building science’s leading practitioners, in particular John Straube, who authored several key articles and studies about straw bale walls that were essential to answering the question of why bale walls were so resilient, despite some seemingly obvious moisture concerns.
Simply put, building science attempts to quantify the movement of heat and moisture through building assemblies and help designers and builders to make decisions that lead to structures that adequately deal with the moisture and temperature regimens of their particular climate and use.
This article appeared in TLS #57.
Loose Strings: Technical Discussions
by Jeff Ruppert – Colorado, USA
T e c h T i p s
A little known fact in the bale building realm is that a handful of people scattered across different continents have experimented with the idea of finishing their bale walls with wood or some type of manufactured siding. The technical term for siding over a bale wall assembly is a “rain screen.” The use of a rain screen (sometimes referred to a “multiple defense assembly”) on a bale wall plays the role of keeping rainwater off of the bale portion of the wall. This is in contrast to the standard way of finishing a bale wall with plaster and allowing moisture to come into contact with it on a regular basis (also referred to as “faceseal” walls). In fact, almost all of the literature to date on bale-wall construction makes the assumption that they are faceseal assemblies.
In this article, we are going to take a look at the pros and cons of in-stalling siding over a bale wall. To some people the idea of not having a plaster finish on a bale house would seem weird, mainly due to aesthetic reasons. However, for those who have chosen to use siding, aesthetics take a backseat to function due to high rates of rainfall throughout the year, as well as constant high humidity. The option of allowing bale walls to even get wet in the first place is not an option and therefore other systems must be considered.
For those of us who live in drier climates, the consideration of moisture is not as dire, therefore giving us more choices. However, doesn’t the siding option make sense if you are concerned about moisture at all? If you would like to design a building with mixed finishes, such as a combination of plaster, masonry and siding, this would open up the opportunity to include bale walls as an option on those projects. In fact, by installing a rain screen over bale walls are we not greatly reducing the potential for moisture damage, as David Eisenberg puts it, by “designing problems out of the project” from the start? We will explore these issues and hopefully offer you another choice in your search for solutions.
In the old days, a rain screen was simply an exo-barrier that was attached to a building to catch rainwater and shed it before it could hit the structure behind it. The Norwegians titled this approach the “open-jointed barn technique,” since originally it was used in conjunction with the construction of barns1.
With tighter construction and newer forms of finishes, the technology of rain screens has evolved into a science. One of the advantages of using a rain screen on a bale wall is that, no matter
how you do it, it will probably add a significant layer of protection that would otherwise not exist. This assumes that you do not install the siding to accidentally direct water into the wall. The potential exists for this to happen, so just like any other type of finish, pay attention to the details!
No matter what type of wall you build, the driving forces of moisture will be:
- Air pressure difference (gradient)
- Surface tension
- Capillary action
- Rain drop momentum.
The dominant force acting on your walls will be the difference in air pressure across the siding itself. As the wind blusters around your house, there are pockets of less and more pressure ever changing within and around your wall assemblies. The main goal is to minimize any pressure differences so water is not accidentally driven into the wall assembly. By minimizing pressure differences, the main force acting on nearby moisture will then be gravity, drawing water down to the ground where it belongs, before it reaches your bales.
In order to equalize pressure, an air gap behind the cladding (siding) needs to be well ventilated to the atmosphere. This can be achieved through different methods, but whatever you do, make sure not to create a gap for wind to blow rain behind the cladding. This means providing ventilation behind the siding so air can pass through easily, but including a barrier at the points of ventilation to keep wind-driven rain from entering.
The advantages of using a rain screen are:
- Adds another option for finishing bale walls (aesthetic),
- Keeps moisture completely off the bale portion of the wall assembly,
- Provides replaceable/changeable finish,
- Has low or no maintenance (depending on material),
- Uses local materials in northern climates near forested areas.
The disadvantages of using a rain screen are:
- Plaster finish is not an option on a bale wall,
- May not be as durable as some types of plaster,
- Materials may not be sustainable or even available in your area,
- Aesthetic of siding may not match your project.
Rain Screen Concept on Bale Walls
It is important to remember that no matter how we finish bale walls, they must be sealed with plaster. This means that even if we choose to use a rain screen, we must apply at least one coat of plaster. One way to install siding on bale walls is to first install nailers for the siding. These can be in the form of 2-in.x2-in. wood strips attached to the sill plate and beam at the top of your bale wall.
We recommend attaching the nailers before stacking the bales, but you can do it afterwards if you like. Once the nailers and bales are in place, one coat of plaster is applied between the nailers. A rough coat of plaster over the bales is all that is necessary. Little or no troweling is required because no one will ever see the results. After plastering, building paper is stapled to the nailers and the siding is then installed, leaving a gap behind the paper for ventilation and drainage.
One issue of concern with this method is the gaps that can occur between the plaster and nailers as the nailer wood shrinks over time. These gaps can allow air to ?ow in and out of the bale wall, creating a loss of insulating value, as well as a path for insects and/or rodents. Extra care and/or the application of caulk can take care of these gaps. Also, these gaps can be eliminated if the nailers are installed after plaster is applied. Whatever you do, be sure that a gap remains between the back of the siding and the plaster.
This is but one way to install siding on to a bale wall. There are variations to this concept, but the goals remain the same – keeping rainwater and back-splash off your bale walls. Pay attention to the details and remember the forces that are acting on water that comes into contact with your walls. Holding these basic concepts in mind will help you design your wall system. And most important, do your homework first!
Happy wall building!
1. Rainscreen Cladding: A Guide to Design Principles and Practice.Anderson, J.M. & Gill, J.R. Butterworth-Heinemann, 1988.
Ed.Note: Jeff encourages TLS readers to send in questions and comments to The Last Straw. There may be outstanding issues that builders are dealing with that most laypeople may not aware of. There are always many questions from people new to straw-bale construction. With this in mind, this column is offered and intended to encourage everyone to educate themselves to the fullest extent regarding building construction, and we are here to help in any way we can. This forum endeavors to offer the best of our knowledge, with no claim to its completeness, but to the spirit of bale building as a continuing evolution of one form of habitat within the larger realm of natural building. We offer this forum for dialogue, with no implication of being right or wrong. This forum is for you, the learner, artisan and teacher.
Jeff Ruppert, P.E., Principal, Odisea LLC, Ecological Building, Engineering and Consulting, P.O. Box 1505, Paonia CO 81428, 970.948.5744 <[email protected]> www.odiseanet.com
Jeff has been in the construction trades for over 25 years, beginning as a laborer and draftsman on his father’s construction projects. He has spent many years working on construction projects he designs, and is a licensed engineer in Colorado.
This article appears in issue #57 of TLS. There have been other articles about moisture sensors in recent years.
by Habib John Gonzalez – British Columbia, Canada
This article appeared in a slightly longer version in TLS#22/Spring 1998.
Here are the simple steps and materials needed to build your own bale wall moisture sensor:
1. Determine what depth of the bale you want to monitor and cut the 3/4-inch PVC pipe to that length.
2. Make the white pine sensor disk 1/8-in. thick to fit snugly into one end of the pipe.
3. Solder two lengths of telephone wire to two pairs of small bolts. One end of the pair of wires is bolted to a PVC pipe cap so the tips will protrude from the finished interior wall. The other end of the wires will be bolted to the sensor disk.
4. Use epoxy to glue the disk to one end of the pipe; run the wires through the pipe and fasten the other pair of bolts to the interior wall end cap. Glue the cap to the pipe.
5. Glue a perforated pipe cap over the sensor end of the pipe.
6. The sensor is ready for installation in the bale wall.
7.The TimberCheck moisture meter is available from www.leevalley.com
8. A number of bale wall moisture studies were sponsored by the Canadian Mortgage and Housing Corporation (CMHC). You can get a summary of all of the CMHC moisture work on their web site www.cmhc-schl.gc.ca/publications/en/rh-pr/tech/dblist.cfm?mode=year. Scroll down to the bottom of the list for 00-103 (year 2000, document 103) on straw-bale moisture monitoring.
1. Outer end-cap
2. Perforated PVC pipe
3. Wood disk with screws
5. PVC pipe
6. Inner end-cap
7. Screw contacts
This article originally appeared in TLS #58.
by Rene Kilian – Denmark
Save money on your black and grey water while protecting the environment!
All properties without sewage facilities in rural areas of Europe must meet minimum standards for wastewater treatment. It can be expensive joining on to the main sewage lines. A planted filter’ – a modern kind of reed-bed system with vertical waterflow – has low operating costs and is an inexpensive alternative.
Approximately 30 of these filters have been built in Denmark. The systems are planted with wetland plants, and occupy around 16m2 per dwelling.
The system complies with the latest Danish standards, which are stricter than the European standard.
Along with this, environmental impact is reduced and the homeowner can save money on sewage connection and payments. The investment can be paid for through savings in less than five years, when compared to a standard sewage connection. Here is an example.
Reuse of treated wastewater
Søren Raffnsøe built his own straw-bale house, went about it in a way that was as environmentally and economically friendly as possible. The way that water comes in and out of the house has
been considered in a holistic manner, and is the first of its kind in Denmark.
The house has its own planted filter to treat wastewater. The system is only 8m2 because the house has a composting toilet.
The planted filter is a biological-cleaning system. The system, designed by René Kilian, is an effective alternative to a sewage connection. The system can even be integrated into a garden where it could resemble a garden bed growing with thatching reeds, iris and bullrushes.
The recycled water becomes so clean that you can reuse it to flush the toilet, wash clothes and water the garden. As compost toilets don’t use water, Søren uses the water only in his washing machine and garden. See Figure 1.
Along with this, he saves 50 percent in his usage of drinking-quality water. To collect the excess recycled water, he has made a little pond in the garden, where there is an extra cleaning process that created a habitat for plants and animals. The drinking water itself is also special. He has installed a ’vitalizer’ in his drinking water pipes. This revitalizes the water so it attains the same quality as spring water.
Payback in less than five years
A planted filter of 16m2 suitable for a normal household, will cost around 60,000 Danish kroner/$11,083.80 USD. Connection to public sewage costs one household around 40,000 kroner/$7,389.21 USD. The investment can be paid back in less than five years, as you can save on annual wastewater bill payments. Ongoing costs for a planted filter are 0 kroner /m3; there is just a government tax of 1.60 kroner /m3. Costs for sewage are approximately 35 kroner /m3. This means a dífference of nearly 33.50 kroner / m3. With an average consumption of 170m3 per year, a household would save around 5,700 kroner/$1,052.96 USD per year, or 140,000 kroner/$25,862.20 USD after 25 years.
If you chose a reuse system in addition to this, and saved 50 percent on water consumption, you save 7,000 kroner/$1,293.11 USD per year. After 25 years, you will have saved 175,000 kroner /$32,327.80 USD. With the correct wastewater solution, you can really save money and protect the environment.