Tuesday, May 5, 2009

House Design Details

Once we had decided on a mudbrick house, the next stage was to sort out the nitty gritty of design. We drew up plans ourselves, taking care to integrate as many of our criteria as possible. The whole process was a matter of compromise and adjustment and aimed at reaching a final result which would best meet our needs, taking into account factors such as cost, personal preference and perceived significance, to reach what we considered the best acceptable outcome.

The house is basically rectangular in shape with kitchen, lounge and master bedroom to the north with large windows giving a view over our front yard, dam and down the drive. On the southern side are 2 other bedrooms, family room, laundry, bathroom and toilet. There are cathedral ceilings throughout, except for the utility areas which have a lower ceiling to allow for an attic space above. The kitchen, lounge and family room are open plan, which has proved very useful when we are hosting large groups (we’ve had up to 80 people inside).

Thermal mass provided by mudbrick walls, concrete slab and earth sheltered eastern wall heats and cools slowly, acting to moderate the internal temperature and making the home comfortable to live in all year round. The wood heater is only necessary on the coldest of days, but is used to create a ‘cosy’ atmosphere on other days.

Cross ventilation is obtained via windows to south and north in our open plan design. Vertical ventilation is created by low air intake from vents and windows and high air exit points in the clerestorey and high vents.

A Stanley Wood Stove is our main cooking appliance, heats all our water and provides some heating to the house. The flue passes through the wall into our HWS cupboard. This reduces the amount of heat coming from the stove in summer and makes the HWS area ideal for use as a drying cupboard. The hot water supply is gravity fed to taps using a 5m head from the header tank located within the ceiling space.

We’ve endeavoured to use natural materials to minimise chemical release from glues, plastics etc. Radial sawn timber is used extensively internally and externally as a wall cladding above windows and doors. The curves of the boards are perfect match for the flowing lines of the mudbrick. Radial sawn timber is a renewable resource, aesthetic and the milling process uses the whole log with little waste (unlike square cut boards).
Cypress macrocarpa is used for the frame. This is a plantation grown timber which is easy to work with, comparatively light, and contains oils that give it some resistance to insect attack.
These have been constructed to exclude summer sun but allow deep penetration into the house by the lower winter sun. They also protect the mudbrick walls from excessive rain.

Large built-in-robes provide storage space in each bedroom, a walk in pantry will have extensive specialised shelving and storage areas (for storing produce, home-made products etc.) and the roof space above wet areas has been built into an attic. We plan to build a cool cupboard in the pantry to negate the need for larger refrigerator.

The “A&A Wormfarm Waste System" processes our “grey and black” water. The water and solids flow into a below ground tank by gravity. A filter in the base holds back the solids which are broken down by aerobic microbes and worm activity. Liquids containing worm castings and minute particles of solids are pumped to absorption trenches. In the future, the liquids will be filtered through reed beds. The captured nutrients will be used to grow biomass as an additional source of composting material and the filtered water will irrigate fruit and nut trees.

After chatting to a qualified energy rater, we believe that our design would not reach the 5 star energy rating that has been in use for the past couple of years. If this is the case, it is proof that the current computer program used to rate houses is unsatisfactory as its calculations rely too much on insulation qualities and do not consider the full benefits of thermal mass.

The thermal mass in the house maintains comfortable temperatures year round. In winter, it rarely gets below 16⁰C, even when there are frosts outside (the Yarra Valley is known for heavy frosts). We generally start using the wood heater occasionally in May. It gets more use from June to late August (usually just in the evenings) and we only use it in spring if there happens to be an extra cold snap.

In summer, the temperature rarely gets above 30⁰C, and this should be improved once we install a vine covered pergola along the northern wall. Most of the time house temperatures hover around 20ยบ. In terms of function and pleasant living environment the house performs extremely well. Every room is well lit and “airy” and the aesthetic qualities of the building materials are pleasant to the eye. All living areas have good outlook over surrounding gardens and bush allowing us to enjoy the natural attributes of our environment.


Geoff said...

Fantastic! Sounds like a beautiful house to live in.

Did you have to go to a lot of trouble with the earth sheltered wall, with regard to sealing it etc?

I've read and heard from a number of people that suffered in the efficiency ratings due to inadequacies in the software. Hopefully as more "green" builders pop up and have something to say about it they will adjust it to more closely reflect reality.

Andrew and Heather said...

Thanks for your comments Geoff.

The earth sheltered wall was fairly straight forward. We sealed it with a waterproof render. To reduce the chance of water coming into contact with the wall we filled a 200mm cavity between the bricks and the soil with screenings. A drainage pipe at the base of this cavity should carry away any water. Our final precaution is to slope the ground level away from the house so surface water flows the other way. So far these steops have worked well.

Melissa Ellen said...

Loved reading the journey of your mudbrick build. Personally I don't think I could live in anything else now. Another mudbrick enthusiast!

Andrew and Heather said...

Thanks for the comments Melissa. You are right, there is something special about mudbrick apart from its qualities as a building material. I love the texture especially when it is highlighted by lighting at night time.

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