A North Shore Straw Bale Home

Straw bale may not be the norm in Cook County, but it is not a stranger. While people generally associate straw bale or earthen construction with the dry climate of the Southwest, straw bale is well suited to cold, snowy climates, as well. The key is the vapor management of the natural wall materials.

Our visit to this home in early February was incredibly comfortable.
This approximately 800 sqare foot one-story home was built by a couple with some supportive advice from a friend and an occasional helper in 2008-2009. It remains a cozy, well-functioning home that has stood the test of the years.

The home has approximately a 24x36 footprint.
It took two people just over 2 years to complete doing the work themselves. In the first year, they focused on the earthwork and did most of the building the second year, with some finishing work after that. 

Foundation:
The foundation is about 6 ft deep. It has a perimeter rubble trench which provides drainage. Over that, are insulated concrete forms (ICFs) set on the rubble trench that come up about a foot above grade. 
They said if would have done anything different, they might have added a bond beam around the perimeter over the rubble trench for the form to more easily set upon before concrete was poured in.

Inside the perimeter is a deep sand bed. This provides the passive heat battery that helps keep temperatures steady through the winter. Within that, are inlaid pvc piping connected to a hydronic/thermal solar panels (closed loop system) that brings heat to the sand and ‘charges' it with heat.. This system is typically turned on late summer to heat the sand below throughout the cold season, and turned off again in late winter so the home doesn’t overheat as the weather warms.

Planning must be carefully done before laying the foundation layers, so the pipes can be laid in the proper places before the groundwork is done. This includes things like the thermal system (above) as well as any drainage pipes. At the time of this build, it was appropriate to have drainage of grey water as long as water was being hand-carried in and was non-pressurized. (Building codes should always be referred to before building). The final floor is a slab on grade, and tile was chosen to finish most of the interior living area.

Roof -
Metal roof over purchased trusses with blown in 2 ft of cellulose over plywood for the ceiling, leaving a ‘cold’ roof that has performed really well.

Frame - 
There are many options for framing a straw bale, as well as using the straw bale walls as the support structure. For this project, the frame was post and beam with straw infill. Alone, this frame couldn't have stood as a structure on its own, but the straw bales and plaster coatings create a solid, sturdy structure.

Walls -
The straw bales were sourced at the time from Thunder Bay. 
The base coat of plaster utilized clay from the site, (approximately 6?str tons of it?)
The site clay required a fair amount of processing. It had to be screeted through wire mesh in order to get the rocks and larger elements out. That was one of the more difficult tasks.
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 - first coat was heavier straw and clay from site
 - second coat was chopped straw and clay soil from site
 - final exterior coat was lime plaster (and purchased sand?)
 - Windows were obtained from Builder Materials Outlet (BMO) installed flush to the exterior. A discussion we had was that there is some school of thought that windows installed in the middle of the wall might be more resistant to condensation. They like having the window to the exterior

Interior - 
- First coat was heavier straw and clay from the site
 - Second coat was chopped straw and clay soil from the site
 - Final exterior coat was specially purchased 70% light colored sand to 30% clay from Continental Clay, and they used mineral pigments to create an aquamarine and purplish blue wall colors.
 - The finish is smooth and satiny

Other 
Something to think about is planning where you want to hang heavy things on the wall like cabinets, and inlaying beams into the walls to support those structures.
They had air ventilation going into the home behind the firebox, as well as a small pvc pipe air outflow vent near the ceiling.
- There is a small wood cookstove for heat and cooking. They use about a cord of wood per year.
- Water is carried in, and they have an outhouse
- Connected to grid power - Electricity use is about $20/month
- They have a 'bucket shower' system that is lined with a water-resistant lime putty and marble dust over cement board and burnished just as it is drying to a fine finish.

 Performance - 
They can leave their house for weeks in the winter and it won’t freeze. The lowest the sand has gotten is 58 degrees in the coldest times over the years.
There has not been any cracking in the interior.
There has been some cracking on the exterior, especially at the corners of windows, which is easily repaired with mineral paint.
The small wood stove is enough to provide comfortable heat in the winter.