Mon Abri

1 11 2011

Mon Abri is now for sale.  After reading this page, you may want to also see this.

I’ve had numerous requests to explain or describe how our house works, and why it is so energy efficient.  So here is your very own post if you are one of those correspondents.

Mon Abri is French for “My Shelter”.  How it got to be called this is interesting in itself, because a very long time ago, when all this sustainable stuff wasn’t even a glimmer in my young eyes, I lived in a house in Toowong which had a brass plaque screwed to the front with those very words on it.  I was the only frenchman living there who understood its meaning, and I became rather attached to it.  One day, we were told we had to leave because the house was going to be demolished for redevelopment……  so I nicked it!  That was near forty years ago…. and the house is still there, they lied to us to get us out, serves’em right!  In any case, this name is highly appropriate under the circumstances, you couldn’t get a better shelter.  UPDATE: when I wrote this post, selling the house was not on my mind.  If/when we sell, I’m keeping the brass plaque….  just so any potential purchaser knows.  I’m too emotionally attached to it now, after 40 years of ownership…!

This is an older photo, and I’m using it because a lot of things are planted around the house now, and this gives a clearer view of the building.  The only external difference is the new 2kW solar array on the right section of the roof which is featured in an older post, and of course the AGA flue.

Our block falls from E to W, which, when you want to build a long narrow house facing N makes life difficult.  The reason for the E-W axis is that it gives you 100% control over how the sun interacts with the building, such that in Summer (when temperatures can go higher than 40°C) the sun almost never shines inside the house, and in Winter (when we saw -6ºC three years ago!) it does so all day long…. which is why there are so many windows on the N face of the building, even in the roof.  The house is 25m long, and only 3.6m wide along 10 of those metres.  You can see one of those narrow sections at the R of the picture, which is our formal living room.  You can see right through it in the pic, at the back we have a deck with fabulous views of two of the volcanic plugs which surround the area.  The other narrow section is our master bedroom, which has 3.6m high cathedral ceilings; you can just see the windows at the L end of the pic.  Both these rooms have fabulous ventilation because of their narrowness and glazing on the N and S walls.

The rest of the house is 7.2m deep.  It basically started as a 20m x 7.2m rectangle, but because of the lay of the land, I decided at the design stage to split the house in half lengthwise under the clerestory windows (in the roof), and slide the two halves 5m.  To this day I consider it to be one of my very best ideas!

To simplify the foundations and slabs, it is split exactly down the middle, the lower floor being 1200mm lower than the upper.  At the split, a filled concrete block wall retains the earth which is under the upper floor, giving us even more thermal mass.

The beauty of having a narrow house is that it no longer becomes necessary to have any windows facing E or W to light the rooms in daylight hours.  It’s a little known fact that Summer heat is not just a problem in the afternoon when the sun shines from the W, but every bit as much heat is gained from the E.  The Sun’s strength is exactly the same from either direction.  Nearly all the windows are recycled timber casement windows which swing out (rather than slide like modern ones) and are able to catch breezes from the NE on the the N side, and the SE at the back.  This is where our regular cooling breezes from the sea come from.  The clerestory windows are louvres, as are a few more on the S side, where the deck and back veranda exist.


The whole thing is well insulated, with R3.5 batts in the roof, and polystyrene slabs in the wall to an estimated R value of at least 1.5.  The long walls are clad in maintenance free colourbond corrugated iron.

To have a truly thermally stable house, you must have a lot of thermal mass, that is heavy material like concrete, inside the building. Thermal mass has the unique ability of soaking up heat, and storing it a long time. Just as black bitumen roads get very hot in the sun, and remain so, long after sunset. Therefore I had no choice but to build on a slab, and do so across the natural slope…. not easy.

Foundations like these didn’t come cheaply, but then just look at that gorgeous view… and then consider that when we have a frost outside we remain nice and cosy with no heating at all.  Now the AGA is going, it will be toasty warm even if it’s cloudy all day.  And last summer when the temperature hit 43° C, it just reached 30° inside, and cooled down overnight with the clerestory windows open to vent the house.  And I hasten to add the house is not yet finished, we still need to hang curtains and install pelmets to achieve total control.

In winter the sun shines into the house all day long and warms up the thermal mass which acts as a heater overnight keeping the temperature around 20 degrees or more until the sun comes up the next morning.

In summer the sun never enters the house, but any heat coming in through windows is soaked up by the concrete keeping the house cool.  At night the heat is vented out the clerestory windows.

Whilst it did cost a lot of energy to make all this concrete, unlike conventional houses this one will repay its debt for as long as it stands instead of adding to it.  I estimate that it will take just twenty years of habitation to do this, and we are already one third of the way into this period.

In 2007, Glenda and I won a Glossies Award for the house’s “Resource Saving” features.  It’s the very best house we’ve ever lived in bar none.

Pertinent links:



2 responses

12 11 2011

Well done! I looked at building a passively heated/cooled house in the 70s after the influence of Permaculture and the like. The initial plans looked quite similar but unfortunately due to the exigencies of life, it never came to fruition. I have bookmarked this spot and will refer to it for future inspiration. Best wishes.

11 03 2013

Love the design…exactly what I’d like to do with m y extension…problem is my house is east west orientation….I get the morning sun in the east and afternoon sun in the west

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