Usually once a home is built, the builder hands the keys over to the new owner and unless there’s a problem, the builder moves on to the next project. However, in the case of a straw-bale built home in Peterborough, the home has been lived in for the past year and all water and energy consumed has been recorded. The goal was to see if, in fact, the home is Canada’s greenest home. You can read all about its features in the article I wrote last year. Chris Magwood, director of the Endeavour Centre, whose students built the home emphasizes that it’s not supposed to be a competition, it’s meant to demonstrate that building a green home is achievable using currently available technology that is locally available.
Archive for the ‘Construction Materials’ category
There are many ways green building materials can be defined, especially when it comes to taking account of their environmental impact and social results. There are quite a few materials being used today, such as engineered lumber, natural earthen materials, biomass building panels, paints with low or non-existent volatile organic compounds inside them, as well as a number of other products manufactured all around the world by companies who focus on protecting the environment and workers all around.
As the years have been going forward, a lot of manufacturers have been getting on the bandwagon concerning green building materials. There is hardly a product today that is not capable of being replaced by a type of environmentally safe and sound alternative, as well as a variety of green materials that only get better and better as time goes by.
Euroshield is a rubber roofing product that has been manufactured in Calgary, Alberta for the last 13 years. It is made from 75% recycled rubber tires and 20% other recycled material for a total of 95% recycled material. Each new roof contains between 250 and 1000 rubber tires, and any scraps produced during installation can be collected and recycled into new product (depending on location).
There are four product lines:
- EuroSlate, mimics the look of slate. Available in Brownstone, Greystone and Blackstone colours.
- EuroShake, mimics the look of cedar shakes — available in either the hand split or taper-sawn looks and three colours: weathered brown, grey and black.
Both the EuroSlate and EuroShake are the original products developed by EuroShield. They are about 3/4″ thick at the butt end and interlock using a tongue and groove system. They weigh approximately 3.3lbs/square foot and need no additional truss support.
Francis Ching is a well-known author and illustrator of books on design and construction, perhaps within the building sector his most well-known book is Building Construction Illustrated. Collaborating with Ian Shapiro on this latest book, the pair have developed a good introduction to green building for those just becoming familiar with the field, but it also serves as a good reference guide to green building for those of us with more experience.
“What is green building?”
The point of the question is to highlight the reality that it is really an evolving definition. Some buildings built to a high standard, have, upon evaluation, turned out to be less green than their standard counterparts because they use more energy than the comparative standard, whereas some net-zero or close to net zero buildings aren’t classified as green because the owner has decided not to go through the hoops necessary to become classified.
Further, the authors address why building greener buildings is important, referring to climate change effects as well as resource depletion. They also delve into the different green classification systems that are available.What I like about this book is that after reading it you gain a basic understanding of all the elements involved in building a better, more resilient, lower impact building.
Hosting a Design Charette
Shapiro and Ching emphasize that with the development, design and construction of any building, there are thousands of decisions that are made. One decision affects another, so it means that there are trade-offs for every decision. Getting the design done right at the beginning can save time and money down the road and one of the best ways to do that is to have a design charette. A charette is like a round table discussion where every involved party can have a say in how the design will affect their portion of the building from plumbing, electrical, HVAC concerns, material selection, and occupant use post construction. Ideally charettes include the architect, general contractor, sub-trades, building owner and manager, in other words, all stakeholders.
The book is clearly illustrated and dedicates a good section to design and design issues. Getting the design right is one of the best ways to have the most significant impact on constructing a lower impact building. Again the book is thought-provoking: the authors ask “green buildings are lower impact than what?” In fact Shapiro gently takes LEED to task because the system fails to give points for designing a building that has a smaller surface area (therefore less exposure to the elements), than its standard counterpart. In other words, no points are given for designing a more efficiently shaped building than might otherwise be built. The authors explain the differences between the different green building rating systems out there, including LEED, Passivhaus, Living Building Challenge, and Green Globes.
Another perspective of the book is that it teaches readers to design buildings from the outside in, in layers. So, it looks at landscaping, site and orientation and how those factors affect the design of the building. Further, Shapiro and Ching highlight with detailed drawings, the importance of surface area on the energy efficiency of a building. In general terms, the smaller the surface area, the greater the energy efficiency of the building.
It takes only one brief glance at the chapter on windows to confirm that all those glass condos going up all over Toronto and Montreal are an energy efficiency nightmare. Windows, in addition to having terrible insulation values, also pose potential leak problems between their frames and the building. If not sealed properly there is an extra source of potential drafts and water infiltration.
The chapter on building materials emphasizes the need to consider local, recycled and other materials with a low embodied energy. There is a handy table that shows the different embodied energy of different types of wall constructions.
One of the best features of this book is that it is an all in one reference guide for looking at how to build better buildings from design through to commissioning (evaluating a building’s systems to make sure they are all functioning properly). Once read cover to cover, it can be used as a reference guide to greener building and the different factors that need to be taken into account. While the book does not delve deep into any one area, it does provide a readable and approachable overview that’s easily understood by laypersons as well as professionals familiarizing themselves with green building practices. If I have one complaint, it is that for old people like myself, the spidery, handwritten style font is difficult to read.
About a month ago I posted an article written by Terrell Wong, an architect specializing in sustainable building and design, about a straw bale addition to a home she had designed. She was frustrated because the city of Toronto denied it even though the city had built a straw bale building in High Park. One of the reasons the structure was denied was because the design doesn’t use a vapour barrier. The theory regarding a vapour barrier is that it is necessary to prevent water vapour from permeating walls and getting stuck there leading to mould and mildew problems which could eventually cause significant structural deterioration — not to mention indoor health problems. But straw bale building has been around for a lot longer than vapour barriers and homes built from straw have been around for hundreds of years in Europe and still stand today. What that indicates is that as long as you know what you are doing, straw bale homes are perfectly safe, healthy and durable, contrary to what someone unfamiliar with straw bale building might think.
After I posted the article, I was contacted by Mick Paterson, a project manager with The Fourth Pig, a co-operative sustainable building not-for-profit group based in Baysville, Ontario. He is currently overseeing a straw bale addition to a house in Toronto. They received approval from the city just as he contacted me, so his project was good to go.
I took the opportunity to visit when I was briefly in Toronto in June, to get a feel for a straw bale home and to ask questions that tend to come to mind when thinking about straw bale building. After the tour, I sent the team my questions and concerns — which I think are fairly representative of straw bale novices like myself. So, below are my questions and concerns, followed by Mick’s and his team’s answers.
1. The straw goes moldy after a while and can lead to such problems as black mould and wall collapse.
Fourth Pig: Moisture is the enemy of any type of construction. The straw bales would only become moldy once prolonged heavy exposure to moisture is seen. A straw bale home must have a breathable protective coat. Lime and clay based plasters provide protection from bulk moisture while allowing any absorbed humidity to escape from the wall.
2. Straw can’t act as an insulation material.
Fourth Pig: Straw can be classed as one of the oldest insulation types on the planet. Straw has been used in Europe for centuries for insulation in different forms but straw bales as a wall construction and insulation really took off in the US in the mid-19th century. Its r value is dependent on the bales compaction, orientation and construction detailing. The most agreed upon r value is 30 for 2 string bales or 1.4 to 2.6 per inch.
3. Its fire rating is low and therefore unsafe to use as a building material.
Fourth Pig: Both ATSM in the US and CSIRO in Australia show testing on straw bale walls to have a high resistance to fires with a 2 hour fire rating on plastered walls and 30 minute rating on an exposed strawbale. There are several examples of commercial straw bale buildings word wide. In Australia there is a veterinary hospital and in Colorado a Waldorf school chose straw bale as the only wall material for all 22,000 sq. ft. of its classrooms.
4. You need a vapor barrier to protect the straw from moisture.
Fourth Pig: Vapor barriers are not necessary for a straw bale wall as the plaster skin provides a similar function. As an added benefit lime and clay plasters allow the straw to absorb and release water vapor on both sides of the wall, preventing damage from accumulation. This happens in cold to hot climates, and dry to humid ones.
5. What is the best material to use for covering up the straw bale and why?
Fourth Pig: Natural plasters like lime and clay provide the most benefits for straw bale walls for their breathability qualities. Various factors such as design, cost, performance and historic longevity have shown the benefits of using lime and clay and avoiding cement and acrylic based plasters or covering the straw bales with drywall.
6. Can straw bale be used for houses that are more than one story high?
Fourth Pig: The limits to how high you may build a SB wall are the same limits all buildings face. With intelligent design a skyscraper could be constructed with a façade of strawbales. (We would like to retrofit a multiple storey building with strawbales!)
7. How long does a house made with straw bale generally last?
Strawbale walls and all buildings will last as long as the buildings inhabitants make them last. All buildings require regular maintenance and upkeep as do strawbale walls. With proper design and upkeep SB walls can last for centuries or more. There are strawbale homes in the US that are still standing and in great condition from the mid to late 1800s.
8. Is it more or less expensive than building a stick built house?
Straw bale walls can be cheaper than regular insulated wall construction but there is so much variation of wall finishes and detailing that that need to be taken into account when trying to compare apples to apples. You will not get an R30 insulation value out of a traditional stick framed wall.
For more information on building a straw bale home, or have more questions about the material’s durability, visit the Fourth Pig’s website, or contact them directly.