Sustainable House - Rammed Earth
Updated: Oct 6, 2018
By Steb Fisher & Wendy Wright
Victorian Residential Efficiency Scorecard – Star Rating 10
Salvaged from grandparents’ house in Melbourne.
Washing machine has both hot and cold inlets (hard to find, most have cold only)
allows hot/warm water from solar HW to be used for washing.
Clothes racks – from the UK - no drier.
Exhaust fan behind freezer draws warm air from living area through vent over clothes racks – not often needed
Clerestory windows provide extra solar heat.
Vestfrost Freezer – 0.75kWh/day. (full of home grown beef)
2nd freezer (in mud room) is a Westinghouse WCM3200WC and is less efficient 1.1kWh/day.
Stove top and oven both LP gas (grill electric)
Chosen because electric ovens use high wattage - not ideal for battery supply.
No dish washer
Bench top - salvaged Jarrah
5 Waste streams
Landfill / Recycling / Chooks / Worm Farm / Non-worm compost
We don’t have garbage collection and deliver to the Trafalgar transfer station
Fridge (not so efficient - more than 15 years old) 1.86kWh/day
5 main tanks (total 100,000+ litres.
shed roof to storage by shed – 22,000 litres, overflow to 24,000 litres, overflow to 5,000 litre stock water tank.
house roof to storage at the back of the house – 44,000 litres
hill/top tank as header tank gravity feed for the house supply- 11,000 litres
All tanks interconnected to allow transfers.
Pump up to hill/top tank 4,000 litres/hour, 0.75kW.
3 solar collectors – 3 x 2 m2 panels angled at 45º to horizontal. These thermo-syphon to HW tank on the roof.
HW tank is also connected by thermo-syphon to the wood stove. No electric or gas boost.
The wood heater has a small wet back – 1.8 litres – which generates about 5 kW for HW heating - the fire needs to burn fairly hot to get the full 5 kW.
When the weather is warm, but cloudy and there is no need for a fire, there is sometimes not enough solar HW. At such times we use the instant gas HW supply in the old part of the house for showers and washing up.
There is a HW line from the solar tank across to the old part of the house to save gas when there is abundant solar HW.
HW to taps pressure boosted by small in line pump
HW tank is open system as the wood stove aand the solar panels are unrestricted heat sources. Being open and at roof level with a relatively small head the water pressure requires a boost.
Shower 9 litres/min with flow restrictor removed as water pressure lower than mains
All internal water lines 18 mm/ 3/4 inch (normal is 12mm) to improve lower pressure flows
Fire system – 4 x 2 inch hydrants (N,S,E & W) with mobile (on large wheelbarrow) water pump/fire-hose
Planting around the house also planned to reduce fire risk
Gutter net to exclude leaves and embers
Bushfire Attack Level rating is 12.5 (Ember attack, radiant heat below 12.5 kW/m2 - lowest of the no zero ratings)
Conventional septic system with outflow pumped to septic lines in paddock due to council restrictions, landslip risk and difficulty of digging septic lines on steep slope. The septic lines are fenced because stock compress the soil above them. They are planted with 105 lavender plants for the bees.
3.6 kW photovoltaic system, angled at 28º to the horizontal.
5kW Selectronic inverter for both grid connect and stand alone battery operation. (low capacity batteries installed at present - about 4 hours worth)
Mains failure alarm to allow for powering down during outages
Lighting all 8W LED – total 376 W. Approx. 2.2 W/m2
The house is at the end of the SPAusnet line and has 2 phase supply. 1 phase connected to house/solar PV and 1 phase for shed supply and the grill.
LCD TVs 50W and 63W.
North 300 mm thick
South 400 mm think with a layer of urethane foam insulation in the wall
Stud walls – standard 90 mm with R2.5 insulation
External cladding - Radially sawn board and batten – silver top ash/ E. sieberi – from Radial Timbers in Yarram
Concrete waffle pod slab
concrete from Trafalgar Concrete
30-35% fly ash to reduce cement use. (this slows down curing so only poured in summer months)
Floors: dark ceramic tiles to absorb winter heat
Windows double glazed wood framed with 12 mm argon filled gap
Roof, pale colour to minimise heat gain and loss, R6 insulation
Retaining walls for veggie garden: Ecowood, non CCA treated pine. These have rotted, so are to be replaced with Mount Speed stone. New design in photobook.
PASSIVE DESIGN AND HEATING
Orientation - house faces almost exactly due North (true).
High thermal mass of rammed earth walls and slab
Verandah and eaves designed to exclude summer sun and allow winter sun.
Pergolas with grape vines to provide summer shade and allow winter sun
Entry and mudroom form airlock for the rest of the house.
Energy rating 10
Clerestory allows winter sun onto rear walls
Cooling – passive only
Cross ventilation to clerestory
Heating – Nectre wood stove rated up to 35kW
Wood box (insulated) with external door – wood loaded from outside
Vents above doors to allow flow of heat from the main room
Current wood supply from dead trees from 2009 fires and from timber fallen or felled on the property.
40 ninety-year-old large Radiata Pine were felled last year. The saw logs were sent to China for structural use. At the time there was no economic way to use the slash, which was burned. Subsequently a low price mulching option has been found.
Pines replaced with Blackwoods and Nut Orchard.
Local EVC planting on south boundary will be left to grow as a carbon sink.
Blackwoods cordoned off from stock in paddock also as future wood supply
Other plantings in orchard, nut orchard etc.
2 Narracan Peach
1 Stone Pine (pinenuts)
Also for bees
12 Ti Tree
24 Bottle brush
10 Paddock/Shade Trees
Bamboo windbreak – clumping (oldhamii)