Bales of Insulation- A Full Report

exterior bamboo piningWe are heading into our third season of winter in our straw bale house.  Hard to believe really – I so clearly remember the feeling that the house would just never be done – but there you have it, two years later we are really beginning to see the way the design and materials of the house perform through the seasons.  Last winter was a relatively mild winter in an already mild climate zone, and the winter before we didn’t really move in fully until January, so getting a sense of how much wood we might burn and how much our heating/electrical costs would be throughout the winter months has only just begun to be obvious.

winter sun bouncing off the pond

winter sun bouncing off the pond

Our three forms of heat are the wood stove, hydronic in-floor heating, and passive solar orientation.  The winter sun arches across the sky, sending it’s light and heat into our east and south windows (when it is out!) staying entirely above the top of the trees of the ridge across the valley of which we face.  At certain times of the spring and fall, the light of the sun bounces off the pond below us which lights up our ceiling with ripply light- an unplanned bonus!  We have an earthen floor in the front room, which noticeably absorbs the warmth and retains it into the evening.  The wood stove sits on a two foot tall stone hearth and is backed by a short cob wall, both of which absorb sun heat as well as stove heat.

In floor heating tubes covered by 3 inches of cob sub floor

In floor heating tubes covered by 3 inches of cob sub floor mass

Our in-floor heating is divided into two zones, one for the bathroom and north side of the house, and one which circulates the front south room.  They are set to come on if the temperatures of the rooms drop below 19 degrees celsius.  The front room heating has never come on, and the backroom zone clicks on early in the mornings of the coldest days of winter.  The tubes are embedded under 3 inches of cob, which then also retains heat for longer.

We primarily rely on the wood stove for immediate heat.  This year we lit our first fire on November 20th, and mostly because we were nostalgic for that first cozy fire.  We kept the fire going for about an hour, and then we were too hot.  We have found that we really only need to light a fire around four or five o’clock, depending on the temperature outside, and let it die down around nine, otherwise it gets up to 25 degrees!  upraised wood stoveWe have been having a cold spell right now, where temperatures fall towards -2 or -3 degrees at night (oh my!), and then we might light a fire at three in the afternoon.  Our evening fires keep the house sitting at 20 until late the next day.  Last year, this translated into our using less than half a cord of fire wood in the whole season.  We have an older style stove that doesn’t have any of the newer reburning/efficient innovations, and our space is 920 interior square feet.

The southerly exposed room of the house is lowered by two steps, (which is where the wood stove is) and so the heat tends to naturally move towards the north side of the house as it attempts to travel upwards.  If we leave one window open in the loft of the back room, the heat is pulled even more into that space.  Another design feature of the walls themselves are the wrap- around construction – meaning that the bales are continuously wrapped around the outside of the timber frame, leaving no thermal breaks except where there are doors and windows.  We used double pane thermal glass with argon gas and a low-E squared coating.

west side, south side

south and west side- wrapping bales, sun exposure, and roof overhang

I love the heat that a wood stove gives, but I am not excited about the amount of wood and trees that need to be burned.  It is not entirely a “clean” way of heating.  Eventually we will have three wood stoves on our property – this one, one in the work shop, and one in our addition to this house.  Luckily, Colin’s business of crafting furniture from salvaged red cedar means that we have a lot of  great kindling and fire wood just from his waste.  I am comforted to know that we can potentially heat our spaces for years on just a few dead or cleared trees.  We took out a few trees when building the house, and haven’t even started using them.  This fall, I chopped almost two cords of wood from those trees, which will potentially be three years of wood.  The less wood we go through the better – we even find that turning on the stove to make dinner warms the space efficiently some nights.  Certainly, if we have friends over in the evening, lighting a fire usually leads to opening some windows.

Straw bales reportedly  have an R value of 30-60.  The building code requires that insulation needs to have an R value of 20 in walls.  We have experienced this amazingly efficient quality of insulation, in the winter and in the summer, when the inside of the house is cool and refreshing on hot days.  With a 3 foot overhang of the roof blocking out the sun’s light in summer and the rain in the winter, I am ever more convinced that straw bales are a fantastic way of providing natural temperature control in any climate.

The Layers Beneath Our Feet

We built our house on the top section of a bedrock slope – a perfect place for anchoring the house to a solid mass.  The concrete stem walls are pinned directly to the rock in a way that reaches around and flows over the various natural undulations that existed, allowing us to avoid any blasting.  At the south side, where the slope falls downwards, the cavity in which we back filled with shale was about 8 feet deep, and on the north wall side, it was only 2 feet.  An earth berm set back from the over hang of the roof lifts another 2 feet the length of the north wall, providing a small shawl of soil around the chilly side.  We had learned from Michael Reynolds and his design features that the planet Earth is a thermally stabilizing mass that delivers temperature without wire or pipes, and we wanted intuitively to be connected to that constantly warm, grounding energy.  “The outer few feet of the earth heats up and cools off in response to surface weather. However, deeper in the earth, about four feet and beyond, the temperature is more constant (around 58 degrees). Here, the earth can be used to both cool and stabilize temperature if the home is appropriately designed.”  earthship.com/comfort-in-any-climate.   So the fill of local shale went in, packing solid down to the bedrock below.  While it is not a true tapping in to the mass temperature of the earth, (instead of digging down, we filled the ground in below us) it felt better than an awkward crawl space and manufactured insulation.  On top of the shale went our vapour barrier of plastic, on to which we needed (by code)  a layer of insulation. Most common here is the pink foam board, but we looked around and found that mixing agriculture grade perlite with a modest amount of concrete (6 shovels perlite to 1 shovel concrete) and laying it 4 inches thick gave us the same value to code as the pink stuff.  We could also neatly pack it in around all the water pipes that we put down on the plastic layer.  We were able to easily anchor the hydronic in-floor heating pipes to the perlite layer before we continued up with a 3 inch thick cob slab as a sub floor.  We had a bobcat mix all that up for us and we hauled it in and trowelled it in place as level as we could get it.  Our original plan at that point was to finish it off with an earthen floor everywhere except in the kitchen, bathroom, mudroom and utility room, where we would tile instead.  Our search for cheap tile however, was fairly unsuccessful, as was our search for a trusted earthen floor recipe and method description.  Our time was being pushed as was our wallets, and at some intersections of journeys, there come times when priorities begin to change places.  Our three years in the trailer was wearing us thin, and with Colin back at work to uplift our bank account, time became scarce as well.  Accomplishing 800 square feet of earthen floor became daunting and expensive as we waded through the estimates of finishing oil and wax, kaolin clay and stucco sand.  Then I stumbled upon a place in Vancouver that was selling ecologically certified cork flooring at a ridiculous cheap price compared to other prices we had collected, so we put in an order that would cover all but the very front south facing room.  Colin was determined to make an attempt at an earthen floor in the room that receives all the passive solar sun, so as to keep the principle of mass heating intact without too much expense and time.  The cork flooring was beautiful to install- an interlocking system that floats above the subfloor, allowing for expansion with the temperature fluctuations of the in-floor heating.  Of course, because the cork was not as thick as we had planned for with the earthen floor, and the sub floor not at all level enough for cork tiles, we had to trowel an inch of concrete on to the whole area.  The cork floor is durable and flexible, warm and soft on the feet.  The earthen floor section was indeed another journey of experiment, a journey which I will write about in another post dedicated entirely to the process of the art of earthen floors.  We are glad to have only done the one small section, but we are also excited about repeating the process in the second half of the house.  It is wonderful to have the opportunity to test the methods that we are choosing on this half of the house, so we can learn from our experiences and navigate with more knowledge for the second half of the house.

Our Strawbale Home

My husband, Colin, and I spent a few years previous to when we bought our land, checking out a variety of natural building projects- cob, stawbale, rammed earth, cordwood, houses, garden sheds, playhouses- in various states of construction, doing workshops and reading books about land development theories and off-grid possibilities.  I remember walking into peoples’ homes, finished or not, and wondering when I would be the one answering questions in clay dusted work clothes, passing on the vision of a beautiful and healthy living space.  A few weeks ago we hosted our house on the Pender Island Eco-Homes tour, and I was able to see myself in just that light as I greeted over a hundred people throughout the day.  It’s been 2 and a half years since we began the foundation, and 2 and a half years of living in a 23 foot trailer as a family of four in the mean time.  We have worked beside a huge array of friends and community neighbors of all ages, with many of our materials being locally sourced.

Buying into the land with us (and making the reality of the price affordable for us all!) is my mother Margaret, otherwise known as Nana.  Colin and I have always welcomed the idea of shared land buying and building- we researched and looked into the prospect of larger, intentional community style projects here on Pender before this piece of land presented itself in such a way that we could not ignore.  We asked around for anyone else who wanted to join in, but it seems to have worked out for us to get going with Nana and keep our doors open for future co-creators.  The whole design of the house involves two more small levels descending down the rock slope in front of the part we are currently building, which will be a level of bedrooms and a level with an open kitchen and living room for our growing family.  The section we started with is a 590 square foot suite for Nana with a 290 square foot shared art studio.  This strawbale house opens into a nice size mud room, with a door leading south to Nana’s kitchen, bedroom, and living room space all in an open format (the front section with the curved, living roof).  A door leading north from the mudroom goes into the art studio and utility room (back section of house with sloping metal roof).  There is a small storage loft above the mudroom that will serve as a bedroom for the kids while we are building the other half of the house in the future.  We chose to build the house in sections due to the fact that we are living in a 23 foot trailer, and Nana is paying rent down the street, and getting one section done faster so that we can move into it together is much more appealing than waiting even longer and stretching our finances further before getting something comfortable to live in.  Nana has been a great help with taking time with Taeven and Cedar, baking us bread and treats, making meals when we are working late, and adding her artistic touches when she can, as well as taking on any jobs she can help with.  She also manages to help plant, weed, or harvest in the garden.

Colin designed the floor plan himself with considerations of the passive solar capacities available through the south facing slope that we are building on.  He hired our friend Garrett (McLoed Timber Framing) to design and work with Colin on the traditional wood jointed frame.  We used beams salvaged from old bridge timbers by a company on Vancouver Island.  The bales were bought from a family owned farm in Saanich, and we are covering them with natural plaster- a foot mixed combination of clay, sand and straw which is then spread over the bales by hand, and then covered with another layer smoothed by a trowel.  A final coat of lime plaster will seal in the  whole wall system, keeping it breathable, dry and super insulating (Straw bales are reported to have an R value between 35 and 60!)  We have a hydronic in-floor heating system laid beneath an earthen floor, the final layer being yet to happen.  This past summer we had a fabulous work party to get all the soil up onto our living roof, and it is now planted with native succulents and other sedums that I have been propagating over the last 2 years.  I hope to be able to post our continuing developments as we work this winter, as well as describing in more detail of any of the steps we have already completed.

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