Here are the types of natural building that we do and some common questions concerning them:
Straw Bale Walls have a superb R value (not to mention it is a natural and local material) which is why we encourage their use as insulation in buildings. They stack between a less dense wood frame, either on their side (18″) or flat (24″) and then are plastered on either side. The plaster seals the wall while allowing it to breathe and securing lateral loads. After the plaster has dried, you can put any other finishes you like over top.
Straw can be mixed with clay to be used as a thermal mass in between wooden form work. This type of wall is known as Straw Clay and creates a very high R value and with a 12” thick wall that takes 12 weeks to dry.
Straw is sustainable because it is a local material that saves on transportation pollution, as well as a naturally biodegradable material. This means that straw does not off-gas as other manufactured insulation products do, and keeps the carbon footprint and embodied energy very low to create the healthiest indoor environment possible.
Straw bales provide a thicker wall that is sealed in with plaster, which gives an R value in a range of 25-35+ compared to the typical stick frame home that has an 18-20 R value. This range is dependent on whether the straw bale is stacked on edge or flat and the type of plaster coating that is applied to the surface. For more detailed technical information, CLICK HERE.
Once the straw bales have been coated on either side with plaster, it seals up and does not let moisture in, but allows vapour to pass through the walls. This way the walls “breathe” and dries out any moisture (and mold) while keeping a healthier indoor air quality. A straw bale or straw clay wall is hygrophilic, which means it is vapour permeable and allows the moisture to wick in and then wick right back out again.
Straw Bale walls provide a very low sound transmission, and varies in STC from 50-70, which is still way beyond the standard wall type with a ~40 STC rating. Once you experience a straw bale or straw clay building, you will find it remarkable at how quiet it is to live in one.
Building with straw only affects the cost of the exterior walls, as everything else is built like a typical house, although we encourage sustainable and recycled building materials for all components. There is a wide range of choices for the other sustainable systems, materials and finishes that you could select – which can be tailored to your budget. A straw bale house is a high performance system which costs roughly the same price as building any quality home, yet because of its energy efficiency, it can return the investment much sooner in operating costs. Straw bales costs only ~ $5 per bale and the cost of earth or cement lime plasters are very inexpensive. The labour to apply the plaster may take longer than perhaps laying a brick & mortar wall due to it requiring a minimum of two coats on both the inside & the outside of the wall.
Another cost consideration is what does it cost the earth in terms of long term embodied energy or as a waste product. Straw & clay have an incredibly low emobdied energy due to the wall system as being composed of primary sourced, non-processed, ingredients and is completely biodegradeable. By choosing to build with straw, you can make an individual choice that is reflected in the cost that is also ultimately better for the long term health of the earth as well as for several generations of human beings living on the earth!
Straw in a field or in a loose pile could be flammable. Once it is compressed into a dense block it starts to slow down and smolder & smoke more due to the lack of airflow in the centre. And as soon as it get’s sealed in a plastered wall system, it reduces the risk of fire significantly. When the straw compressed into a dense block bale it dramatically decreases the ability of oxygen to feed the fire into the straw. Straw Bale walls are generally given from a 1 to 2 hour fire rating. For more detailed technical information, CLICK HERE.
The straw that is used to build with consists of the dry stems of cereal grains after the seeds have been removed, called cellulose. As opposed to Hay, cellulose straw fibres have no nutritional value and therefore do not attract any mice or rodents. Even if they did want to venture inside the walls, they would have a very hard time digging through more than an inch of hardened surface plaster!
Each story of a straw bale home is divided by the flooring structure, so that each floor carries the load and distributes it to columns instead of the walls. The main concern with height is lateral stability, not strength. Straw Bale houses are better if they are one story, more because of the need to protect the top edge with a good +2′ overhang. However, two story straw bale houses are often built with certain details to enhance the wall protection. Three story’s are possible, but it starts to get awkward and difficult with scaffolding to supply the straw and plastering that high and is generally not recommended.
Earth is the fundamental natural material, that is always accessible. Rammed-earth walls are simple to construct, noncombustible, thermally massive, strong, and durable. They are created from an external support or mold and then filled and compacted with a mixture of earth, sand, gravel and clay.
Earth Bag buildings offer the similar qualities but are made up of manageable sized bags of earth stacked on top of one another, usually in dome formations and secured on each level by barbed wire. These can be as simple or as extensive as you can imagine and be finished in either plaster or piled with more earth and there are lots of variations of combining them with other building methods.
To read more about the building techniques, this website has answers to all sorts of questions.
Since wood is a common building material, there are many ways to build with it, including the most common, cheap and unsustainable ways. However there are also ways to ensure you are getting your lumber from sustainable sources and designing in a way to think about future re-use.
Make sure it is FSC certified, which means it has been harvested from a renewable source and managed using sustainable practices. The wood will have a black stamped label on each member attesting to this certification. Ask to confirm availability before you order or buy at any lumber supplier – sometimes they may take a few weeks to confirm delivery.
In all construction methods, choosing re-used wood is best. Craigslist or Kijiji often has listings of people demolishing some building that you can pick up for next to nothing. It takes more time to work with to cut, remove nails, etc. Pallets can sometimes be utlized as well. There are also wonderful reclaimed wood store suppliers (Like Timeless Materials in Kitchener or Habitat for Humanity ReStore’s) that source unique reclaimed wood flooring, timber, windows, doors, etc. Next priority would be to use only FSC certified wood. Another option is if you have a rural property with a woodlot is to cut your own trees and get them milled on site.
Cord Wood Construction, sometimes called ‘stackwood’ or ‘stackwall’ construction is a natural building method in which short logs of pieces of debarked trees are laid horizontally within a mortar and insulation mixture. It can also incorporate old/colourful glass bottles for aesthetic and light. The advantages to this natural building type is that it can be done using natural and sustainable materials – hopefully from close to the building site – and builds a thick wall (12″ – 24″) which has a higher R value and thermal mass than standard stick frame homes.
Timber Frames use larger amounts of wood from larger and older trees, which take longer to grow back, but compared to the process and manufacturing that typical lumber goes through, it is not a great difference. Usually when you are building a timber frame, it is a better quality home and therefore has more attention to efficiency and other sustainable materials.