CASE STUDY: Carramorr
RESIDENTIAL - Design
Owner-builder milled locally sourced timber onsite
Construction of house powered by some solar energy
Designed to be comfortable in temperatures from +1ºC to 30ºC+
Location: Wondecla via Herberton, QLD, Australia
Year completed: 2005
The owners held a long term desire to build their own home and were at a stage of life where they had the skills, resources and the capacity to take time off work and funds to do the construction without raising a mortgage.
The basic objective was to build the home in an affordable manner, using recycled materials whenever possible and using methods with the least effect on surrounding vegetation and soil.
PLANNING AND MANAGEMENT
‘Carramorr’ was designed and built in open Eucalypt forest. The land slopes steeply and the site needed some trees removed but this was kept to minimum.
It was an objective to build the house using as much locally sourced materials as possible, so timber is the major component because of its availability. Some information on timber qualities was sourced from the Queensland Department of Primary Industries and Forestry and also from people with either building or timber experience.
The owner builders did most of the frame and roof construction before the wet arrived in force.
All building debris was immediately disposed of and never allowed to accumulate.
All of the construction was powered by solar energy and generators.
The soil is not good for trenches for septic systems so a dry composting toilet is installed to minimise pollution into a small creek eight metres from house.
A user guide for visitors was developed to assist them with battery storage management, composting toilet use and power management.
Wondelca is situated between Herberton and Ravenshoe on the southern part of the Atherton tablelands behind Cairns. It is about 915 metres above sea level and part of the highest area in Queensland. The home is subject to temperatures from +1º to 30º+ so it is a bit of a challenge to cover the extremes in this location.
The site was selected because it resulted in less disturbance to native forest as less trees needed to be removed. Neighbours were also considered and setbacks from existing developments for privacy and noise appropriately designed.
The water runoff and drainage was a big consideration as the site is at the bottom of a 300 metre long slope that is problematic in the wet season.
The house was also sited to be lower than rainwater collection and storage, allowing gravity feed supply.
The house was built on stumps that are 300mm to 5 metres above ground which minimised the effect on the slope and negated the need for a slab. Water runoff was purposefully directed well away from the house posts to minimise erosion.
The home is sited lower than surrounding forest and so has a buffer from cyclones as well as damage from tree debris. Having gone through the eye of Cyclone Larry in 2006 and having had Cyclone Yasi pass nearby in 2011, there has been no damage to the house. During these cyclones the solar PV system continued operating perfectly.
Because the hot humid wet season is the longest season the house has doors and windows situated to allow breezes from any direction. It has wide eaves and high ceilings so is comfortable on the hottest day without the need of fans or air conditioning.
The home is also 'closed plan'. Rooms can be closed off in winter to allow the wood fire to heat the living space or the kitchen stove to heat that space. Wood is sourced from the property, and natural attrition in the forest supplies more fuel than can be used in the three to four months of winter each year.
There are large areas of glass which facilitate views of the native forest just metres away from the house while allowing some loss of heat. Because of the wide eaves very little sunlight hits the windows or enters the house, resulting in very little fading of floors or furniture.
The home has 88m2 on the upper level and 24m2 of guest accommodation on the lower level.
This is a timber home sourced from local forest hardwood including the state forest and milled by a licensed miller. Second hand timber was also sourced from a variety of places including purchasing an old forestry barracks which was pulled down on site and transported to the house site. Material was also sourced from demolition yards, ‘dump shops’, and items mentioned on local radio/newspapers.
The windows and doors are timber casement windows and French doors.
Trees and logs already felled were also sourced and milled onsite.
There is very little if any PVC and no formaldehyde.
A lot of time went into protecting timber from the elements and only ten years later is some minor touch up of finishes necessary.
The home is well ventilated. Even summer evenings are usually cool and there is no need for fans or air conditioners.
The home is designed to allow natural daylight to penetrate all area’s so no artificial light is required in the day time. All artificial lights are 12 volt LED's and powered directly from a battery bank.
There is negligible outside lighting and what is there is solar powered.
A 1.3kw solar system and 6 x 12 volt deep cycle batteries services power needs. The inverter is a modified square wave 1500w. Most of the system is second hand though some new purchases included PV panels under the governments Green Loan system, which also allowed the purchase of a 12v fridge/freezer.
WATER AND WASTE
Rainwater is collected on site and gravity fed to avoid pump technology. A 3,500 litre water storage capacity is stored over 3 tanks. These tanks are all linked to a fire fighting pump to be used to fight a fire threatening the house.
Grey water is also collected and treated and pumped into an irrigation system for the native forest. Detergents and sanitisers are chosen for their ‘no pollution’ sulphate and salt levels.
The main sewerage waste is managed with a composting toilet. Much research and development has gone on with the composting toilet which doesn't achieve a satisfactory result (probably too cold for the process). Worms have been tried and enzymes with some success.
Kitchen waste is treated through a grease trap and then buried in a trench.
“We enjoy the quiet and privacy of our home and appreciate that we chose a position that also respects our neighbours. Sitting on our verandah we are 'communing with nature'.
We appreciate the predominant use of second hand materials, in particular the amount of different timbers used throughout the house. We also enjoy the flow of the rooms with the living space at the rear to get the breeze and the views. We especially appreciate the use of solar power so that we don't get electricity bills!”
Information and photos are supplied by the project owners and designers. The Tropical Green Building Network and James Cook University (the administrators) cannot guarantee the accuracy or authenticity of this content.