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 Earthen Floor

burnishing the floor at the "leathery" stage

The south room floor is the one spot in the house where we continued with our plan for laying out an earthen floor, in hopes of capturing the heat of the southern sun that streams in during the winter months.  The rest of the house, which was originally intended to be an earthen floor, became cork flooring due to some time pressures and uncertainties regarding the success of the earthen floor process. (See my previous post titled The Layers Beneath Our Feet for a total description of the floor.)  We found lots of information, tips, recipes, ideas, things that didn’t work, and things that did from a variety of resources, some of which contradicted each other, or were from climates very different from ours, or which used materials that were unavailable or too expensive for us.

lots of considerations and discussions

Figuring out what to do was challenging.  Tracy joined us again for the experience of mixing and laying our earthen floor, and we are grateful to her for sharing her observations and experiences of working with natural plasters.  (Tracy is our natural plaster and straw bale teacher.)  We wanted to use what we had and we felt most comfortable with techniques that were familiar to us from the wall plastering that we had just completed.  Cracking seemed to be the biggest common result, and one that is difficult to fix without a very messy look.  We heard of filling the cracks with different coloured plaster to create a marbled look, but we never found a source of a good example of this method.  A certain amount of experimentation, intuition, applied knowledge and trust was going to be needed.  This was the point at which we were grateful that it was now only a small 200 square feet that we had to do.

clay slip

We decided to follow (loosely) a set of well laid out steps and recipe ideas from Anne and Gord Bailey, of Eco-Sense on Vancouver Island, ecosenseliving.wordpress.com.  We adapted the recipe to what we had available, which was screened clay mixed into a slurry, red clay mixed into a slurry, stucco sand, horse manure, straw, and some red pigment.  We started by laying down a cob sub floor at a depth of 3/4 inch using a mix that resembled our second coat of wall plaster.  When that was dry we mixed up the top layer in 5 gallon buckets, then tried a technique we saw on the internet of laying burlap all over the floor area, wetting it and slopping clay slip as a binder then troweling on the 1/4 inch thick top layer.  I am breezing through the details here because it didn’t work.  We thought that the burlap would help reduce the shrinkage factor of the clay that leads to cracking, but it didn’t at all, and it also prevented the top layer from bonding well to the layer below the burlap.  We think it dried too fast, the layer was not wet enough, the burlap wasn’t soaked well enough, or there was just too much clay content in the mix to begin with.

troweling on the top layer

So we ripped it up!  Just chipped through to the burlap and pulled, and it lifted too easily.  We crumbled it back into the buckets, then worked out a few new ratios of higher sand and straw contents.  We laid out some sample areas and let them dry to see how the cracking went, and decided to make the mix with 4 parts sand, and one part clay slip.  Because of the remixing, it is hard to say what the quantities were for the various other ingredients.

sifted manure

Fibers (manure and straw) were around 1 1/2 parts, and water content was based entirely on feel and how the mixer spun.  Not too wet, not too runny.

This time we left out the burlap.  We also poured buckets of water all over the floor the night before to keep the cob subfloor cool and to prevent it from sucking moisture out of the layer we troweled on top.  We hung blankets over the windows to try to keep the summer sun from hitting it right away.  It took a whole day of two people troweling on hands and knees to get our 200 square feet covered once again, then while it slowly dried we lay planks across the floor so we could burnish it, giving it a polished look while compressing it more, and hoping to prevent too many cracks.  The outcome was 90% better than the first try.  We had a few thin cracks, mostly where it dried the fastest, and no lifting.

The recommended method for fixing the cracks was to use some left over plaster.

the worst of the cracking after the second try

We dried it out, crushed it, screened it through window screen, then sprinkled it into the cracks while wetting the area with a mister and troweling it smooth as best as we could.  There was a bit of texture difference for sure, but we decided that it was a natural floor overall and a bit of texture was fine!  Then we began with the oiling and waxing.  This was another reason we were glad to have done only a small portion of our floor- we brushed on 3 coats of boiled linseed oil, and two coats of Land Ark oil, which contains beeswax, tong oil, linseed oil, citrus extract, and pine rosin.  Land Ark is made with only natural, non-altered ingredients from sustainable resources, without chemical processing, bleaching, or harmful additives.

oiling with linseed oil

We have also used it on the timber frame,door and window trims, the baseboards, and the ceiling boards.  It actually feels great to get on my skin, and I love the smell of it as I have done much of the staining.  For more info on a great product- www.landarkwoodfinish.com.  The cost of this oil runs at about $85 a gallon, so we were hesitant about what it may have cost in oil to finish a larger area of floor, since we didn’t know how many coats the floor would take.  We read that it could be anywhere between 3 and 10, with at least 2 being the straight linseed oil.  Then we waxed the floor, using another natural wax from Land Ark, and then buffing it hard with a buffer.  The golden flecks of straw suddenly jumped out, and the places of various texture and colour deepened and settled in.

The best part of the finishing of the floor was not anything that we read or heard about in all of our earthen floor research, and so here I would like to add it in as a recommended part of laying an earthen floor.  Don’t move in any furniture, but set up the stereo.  Lite some candles, build an altar, and invite as many people as can dance on your floor.  Put on a rocking playlist, strip off the socks and stomp, swirl, boogie, laugh, and send all that energy of celebration, gratitude, and joy through the soles of your feet  into the hard work and beauty of the earth.  That’s what we did, quite unexpectedly.  We felt warmly supported by our friends, and happy to finally be able to open our space for gathering together and sharing what we have.

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.

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