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.

Workshop Update

cob workshopThings have been progressing slowly but steadily in the workshop since we finally got the roof finished in the winter.

Colin focused on getting the doors in right away, refining two old doors that came from his Dad’s work of deconstructing old houses on the island, and refitting a pair of salvaged french doors.  He also built a raised stone hearth from the pile of stones we have on the property, put in the stove pipe, and wired in the rough electrical circuits.  We got the insulation in the ceiling and the plastic vapour barrier secured over that and ready for the finished ceiling layer, which we think will be some kind of bamboo or sea grass mat.

rough sculptureI spent a couple of weeks on and off getting the rough coat of plaster on the inside and outside of the building.  This layer of clay plaster is the only rough coat needed on a cob wall, and is the same layer as the third layer that we put on the strawbale house.  (See my previous post called Natural Plaster for full details).  A mix of 4 parts sand, 2 parts clay, and 1 part straw with water to mix it to a troweling consistency kept me busy in the warmer days of late winter. rough plastered windows I cleaned up and shaped the sculptural aspects of the walls so they were ready for the final layer of plaster, which Tracy and I completed earlier in May, while the temperatures were still cool enough to give the plaster time to dry.  The final clay plaster took us 2 days to put on, a seemingly record pace for any one job to be completed in.  We mixed up the kaolin clay, sand, straw, paper pulp and whiting in the buckets the day before, and then added the rice flour paste, and borax and mixed multiple buckets together the morning we started plastering.  (See my older post Final Plastering for more exact details).  We got much of the simple walls done on the first day, then completed the wall with the windows and arched shelf the next day, cleaning up our tools by the afternoon.  I am always so amazed at how quickly the finishing layer goes, compared to the time it takes to get all the other layers beneath it built.final plaster

Last weekend, Colin and I built the one interior wall that separates the workshop from a small storage room.  It will also be the wall against which will be built Colin’s work bench.  It holds the majority of the electrical outlets and is a standard 2×4 construction filled with rock wool (Roxul) insulation and covered in plywood.  final plastered windows

There is not too much left to do in this simple building for Colin to finally move in and use the space for his wood working.  Right now he is coming to the end of a giant stone facing job and is looking forwards to working with the more forgiving medium of cedar wood.  I can turn my attention to finishing the outside of the building later this summer, playing with some creative designs for sculpture as well as getting the last coat of lime plaster done when the weather begins to cool off once again.     interior wall

Building A Small Cob Wall

While we have used the basic mixture for cob in many places of the house- in the floor, as rough plaster coats, and for sculpting – we have only one small wall that pays tribute to the building techniques of cob.  It is a short barrier that separates the back of the wood stove from an area that will one day be a staircase leading down to the rest of the house.  Only 8 inches wide, it does not have the usual girth of a supportive wall, and rests on a ledge of concrete that was poured with the rest of the foundation and connects to the back of the two foot tall stone hearth.  We embedded an air vent pipe that opens from the outside wall to behind the stove, allowing the stove to draw in fresh air as it burns.

We started the wall with a work party, inviting families, neighbors, and interested friends to lend a hand or foot in stomping, wheel barrowing, and shaping.  Children and cob are a perfect mix and add such a joyful presence to the job!  We used clay from our huge pile gathered for the previous plastering and floor sections, clay that originally came from a farm down the road that dug themselves a huge pond and discovered clear blue clay.  The sand is pit run sand from the island, (a silty and rough sand with lots of rocks – just fine for cobbing with) and straw leftover from the bales we got for the house.  Stomping includes mushing the mix together with your feet on a tarp, adding water as needed and rolling the mix in the tarp once in awhile to help move the bottom stuff to the top.  Inside the house, we took handfuls and pushed it into the growing ledge of the wall, using thumbs and sticks to really integrate each handful.  The work party got us up about 2 feet, at which point the weight of the cob began to cause the wall to slump out the bottom.  We let this part of the progress dry out for a day, then used a saw with large teeth cut into it to trim off the excess cob from the bottom until it measured the right width again.  We could then continue to add on to it until it began slumping again.  The lowest part of this wall reaches just over three feet, and then arches gracefully up another foot behind the hearth and the wood stove.  Then my mom got her hands in there to sculpt a draping vine along the top and dangling down the sides, smoothing out the top of the wall in a rounded curve.  After letting the wall completely dry out (about a month!)  I could finally mix up some green colour samples for the final plastering.  (See my previous post, Final Plastering, for details on mixing and applying natural clay plaster).  Working around the sculptured vine took lots of patience and forgiveness, but in the end the natural quality of the plaster reflects and brings out a beautiful ease and grace framing the hearth.

vine detail before being plastered

Indoor Stone Work

art at my feet

Colin has a natural talent for packing many things into a small space.  Fitting things into a closet, storing stuff in a shed, packing the car for a road trip, or loading a truck for moving have all been times when I have been so grateful for having Colin and his jigsaw puzzle skills.  So too, does this skill show up in his stone work, whether it is a dry stack landscape feature for clients, or a set of steps and a stone hearth for our house.  Our most local stone here is sandstone, which breaks naturally and easily in flat, rectangular shapes, while retaining a sound strength and many beautiful hues ranging from grey and black to orange and red.  The hearth is two feet high by three feet wide and three feet deep, holding the wood stove up at an easy loading height and providing a warm ledge on which to perch.  We used a variety of small stones to fill and decorate the spaces between the stones, and used a tile grout to seal and fill the cracks.

The three steps that lead from the mid-section of the house into the sunken living room have a nice curving fan shape sweeping on both the upper and lower steps.  Since the opening of the stairs was quite a bit wider than we really need in which to walk up and down, Colin took the time to build a seat into one side.  We have since discovered that the seat and the depth of each step are a great place to sit with our instruments and play music.  We also grouted the stairs and added many stones that we have collected from many beaches around the world.  Since the house is built on a slope of bedrock, bringing some of this stone into the interior of the house gives it the feeling that the land below us is emerging through.

Colin’s stone work tips:

Make sure to have lots of selection of rock.  Dry fit the layout of stones of the lowest step first, chipping and shaping any stones that need it.  Then remove them and place mortar underneath and begin settling the stones back in place.  As for the hearth, dry stack the lower levels first, making sure that joints do not fall above another joint.  When mortaring the cracks, we left the mortar recessed so we could cover the mortar with a dark tile grout.  Take your time.  Finding just the right rock for just the right space will give you a finished job that will be forever beautiful.

To see more of Colin’s stone work…http://thujawoodart.com

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