The Little Hobart House 2023

House Notes – The Little Hobart House

Our little house has been inspired by visits to other sustainable houses, so we thank those home owners. It is certainly not a Tiny House. It works along passive solar design principles with a simple open plan layout on one level. The house footprint (110m2) on 700m2 of land leaves lots of space for outdoor living, and fruit & vegetable gardens. It has been designed for a older down-sizing couple that wanted minimal maintenance, ease of access, and to be warm in winter and cool in summer, while only needing minimal active heating or cooling, or even none. The solar electricity array & modest owner lifestyle almost certainly ensures the house is a Zero Energy Building. The great location means access to services by foot, bike or public transport is often faster, healthier and less polluting than using a car; the Intercity Cycleway is only a 5 minute ride away.

Key sustainable features of this home include:

  • Built using a well balanced combination of conventional solar passive and Passivehaus design principles to maintain a comfortable inside temperature all year round with good air quality. The design is biased towards surviving Hobart winters rather than hotter than average summers. Fortunately good design works for both seasons.

Key design principles include: 

  • The design aims to be Net Zero Energy Building (NZEB) (TBC).
  • A super efficient heat pump for hot water minimizes electricity. The timer is optimized to take advantage of midday solar power and the cheaper Time-of-Use tariff. Average energy usage is about 1.5kWh/day.
  • A super efficient 3kW split-system heat pump (the smallest in the models range) for heating the living room minimizes electricity. On its lowest fan setting the unit uses less than 250W and raises the living room by 2 degrees per hour on the small number of winter days when it’s desired. Other rooms are only indirectly heated via the ventilation system. This has worked out to be sufficient.
  • An appropriate proportion of north facing good quality windows to take advantage of solar access to heat the home – high Solar Heat Gain Coeffient (SHGC) to capture the radiant heat, and high U-value to then retain that heat.
  • Biased to a north-easterly rather than a strictly northern sun orientation for maximized morning heating & lighting.
  • High levels of draftproofing/ airtightness to minimize heat transfer.
  • High levels of wall and roof insulation to minimize heat transfer. 140mm studs (normally 90mm) with R4 fibreglass insulation, R7 ceiling insulation.
  • Medium level of well insulated floor thermal mass. Because of the poor soil classifcation (class P) we had little choice but accept the engineer’s design for huge amounts of concrete piering/ footings and thickened slab. Thermal bridging of (cold) ground temperature was minimized by a fully insulated slab-on-ground design – 100mm XPS underneath, and 43mm PIR around the edges.
  • Good levels of ventilation for air quality and to minimize condensation, carbon dioxide, VOC & other noxious gas levels. We use a heat exchanger instead of open windows, but fortunately it is exceptionally energy efficient.
  • Minimizing thermal bridging to reduce heat transfer.
  • Dark colored floor tiles in the living room to absorb the radiant heat.
  • Light colored roofing to reflect the radiant heat.
  • Current experience suggests additional shading to prevent summer sun will be unnecessary.

Other features of our home:

  • Livable Housing Australia design principles (tripping hazards, accessibility).
  • A north facing courtyard traps the morning winter sun for a lovely outside area.
  • 600mm wide eaves on three sides, and 1500mm on the back side provides a degree of protected outside cover even when raining.
  • 5 degree pitch skillion roof simplified construction, minimizes construction mistakes (poor sealing), allows safer access for cleaning the solar panels.
  • A mixture of Colorbond & cement sheet outside walls minimizes maintenance.
  • The relatively small amount of outside timber framing (under courtyard) is reasonably well hidden from the weather to minimize the need for painting/ maintenance.
  • 450×450 porcelain floor tiles throughout simplifies cleaning and reduces the tripping hazard.
  • Plain (boring) plasterboard inside walls. All walls are painted the same color to minimize # paint cans required for future touchups.
  • His & hers studies can be repurposed as guest bedrooms when needed.
  • All electrical circuits are individually monitored & logged for confirm building performance, identify unexpected power consumption.
  • A number of rooms are monitored & logged for temperature, humidity, CO2 & particulate matter. In particular the bathroom humidity is monitored to ensure adequate ventilation, living & bedrooms monitored for CO2.
  • Four wicking beds (1200L x 600W x 1000H) of own design.
  • Plastic house (5000L x 3000W x 2100H) of own design.
  • Well positioned windows minimize need for artificial lighting.

We were so happy & fortunate to use a local passionate designer that belives in small, sustainable, cost effective housing. And small local builder (team of 3) that were honest, hard working, generous, and built to a high standard of quality. Based on the experiences & horror stories of neighbors we would never recommend any of the larger well known building companies. We learnt a lot from the owner-built mud brick house we built 30 years ago – things we could do differently or better. We let the experts build it this time although the layout, floor plan and most of the detailing is ours. We each obtained an OH&S “white card” and our generous builder allowed us to be onsite, which towards the end was almost every day for what seemed like months, making decisions and doing the jobs we had decided to do ourselves.

Jobs we did ourselves:

  • All painting.
  • Install of low voltage wiring – alarm, sound system, data.
  • Install of HRV.
  • Install of eave sofitt vents.
  • Install of all joinery.

There will be further information on the topics below by the time of the event:

All the nice photos (C) Threshold Constructions & Suzie Elizabeth Photography.

Please get in contact if you’d like any further info.

Sustainability Features

Years Open
    • Energy efficiency:
    • Draught proofing
      Efficient lighting
      Efficient appliances
      Energy monitoring
    • Passive heating cooling:
    • Cross ventilation
      Heat recovery ventilation system
      Passive solar designed home
      Thermal mass
    • Active heating cooling:
    • Split system airconditioner
    • Water heating:
    • Hot water heat pump
    • Water harvesting and saving features:
    • Stormwater management
      Low flow shower heads
      Drip irrigation

    • Average water consumption per day:
    • 53kL
    • Water harvesting and saving
    • All hard surface runoff is collected into detention tanks & flow limited before exit to mains
    • Energy Efficient Lighting
    • LED lights throughout
      Natural daylight
    • Window Protection:
    • Blinds

    • Window Protection:
    • Fly screens
    • Sustainable materials:
    • builder used all left over timber as fire wood
    • Insulation Type:
    • Ceiling
      External walls

    • Ceiling Type:
    • Bulk – glass wool
    • Ceiling Rating:
    • R7.0
    • Floor Type:
    • 100mm high density extruded foam under (XPS) & 43mm PIR edge insulation
    • Floor Rating:
    • R3.0
    • External Walls Rating:
    • R4.0
    • All-Electric Home?
    • Yes
    • Renewable energy used:
    • Solar PV grid connect
    • Size of PV system:
    • 5.8kW
    • Average Daily Energy Consumption:
    • 3kWh
    • Total cost of home when constructed:
    • $450,000 in 2019 (not including cost of land)
    • Cost estimate of sustainable home/features:
    • $28,500 (incl. slab insulation, 2nd wall membrane, wider studs, thicker wall/ ceiling insulation)
    • Estimate of annual savings:
    • $1500 (based on $0 electricity compared to 2-person avg. 7 MWh/year 50/50% time split tariff 93)
    • House Size
    • 110m2 (not incl. courtyard 22m2 & shed 36m2)
    • BAL Rating
    • No BAL rating requirements at time of construction
    • Roof
    • Metal (Colorbond)
    • Wall Materials
    • Lightweight construction (timber frame)
      Metal (Colorbond)
    • Window and Door Types
    • Low-e, films
      Sliding windows/doors
      Tilt and turn
      Triple glazing
    • Universal design accessability
    • Adaptive design
      Universal access
      Wheelchair accessible
    • Universal Design Features
    • 100cm minimum door opening width
      Hobless showers
      Kitchen bench/table for wheelchairs to access (75-85cm high)
      Lever handles for doors (no knobs)
      Minimum 110cm wide hallways
      No stairs/steps
      No Corner cupboards
      Rocker style light switches
      Shower head on rail for various heights
      Slip resistant flooring
      Space around toilets for ease of access in wheelchairs
      Strong fittings like towel rails that can be used as hand rails
      Tapware to be easily accessed from outside the shower
      Washing machine/dryer on plynth for easy access
      Window openings easily accessible
    • Number of bedrooms
    • 1
    • Number of bathrooms
    • 1
    • Garden / Outdoors
    • Composting
      Drip irrigation
      Edible garden
      Native plants
      Wicking beds
    • Waste Reduction Practices:
    • Compost all food scraps
      Make jams/conserves
      Pickle and preserve food
      Take own containers to the supermarket and for take away food
      Waste free/reduced construction site
    • Healthy home features
    • Airtight house design
      Automated ventilation system
      Carpet free - tiles/concrete/timber flooring throughout
      Cross flow ventilation
      Heat recovery ventilation (HRV)
      Indoor plants for air filtration
      Natural light and ventilation
New Town TAS 7008
    • Housing Type:
    • Standalone House
    • Project Type:
    • New Build
    • Builder
    • Threshold Construction
    • Designer
    • Designful

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