How did we get to this point? It seems to have taken so long…

• November 2016 – first started looking at existing houses around Hobart.
• February 2017 – heard about new house & land packages at The Brickworks, Garrington Park – a new development on 110 Ha of land made available after the K&D Brickworks closed down.
• March 2017 – made offer on a 1890’s cottage in New Town. So glad our offer wasn’t accepted. Sold for $50K more than we offered.
• September 2017 – visited some inspirational homes & owners as part of the Renew (Alternative Technology Association) Sustainable House Day.

• This biggest inspiration came from another Sustainable House Day home just over the hill in Lucaston. Our final floor plan with the central courtyard is very similar:

• October 2017 – 10 lots in stage 5 (of 9 stages) is open for offers. We make offers on two lots.
  • Our offer accepted on lot #66 Garrington Park. No more looking at existing old/ cold/ poor value-for-money houses.
  • Meeting at Hobart City Council Planning Dept.
  • Soil Test & Classification/ Geotechnical Assessment.
  • Meeting with larger off-the-plan home builder. Discussed options. Eventually decided they couldn’t offer us what we wanted from their range of designs.
  • Heather came up with her own floor plan. Lost? But the final plan has never strayed far from the original concept.
  • 1st Meeting with Jane, our wonderful “house designer” at the firm Designful.
  • Our new home is only 1.8km from the Intercity Cycleway, less than a km to local grocery shops, 3km to North Hobart, bus stop within short walking distance.

• November 2017 – site design by permaculture person.

• The concept was for a simple single floor layout, all on one level, no tripping hazards, low maintenance, thermally super efficient, close to services to minimize car use, enough outside space for a productive garden, a covered courtyard for relaxing, a shed for other stuff, his & hers “studies” that could be quickly repurposed as bedrooms for any overnight visitors, a simple Colorbond skillion roof, a carport rather than a garage.

• December 2017 – borrowed a builder friends laser level & did our own elevation measurements.

• February 2018 – concept drawings completed.

• March 2018 – checking sun angles for best house orientation with passive solar design.

• March 2018 – approaching potential builders.

• Had 1st meeting with who we now term “builder #1”. He thought he could start in June. We liked him & decided to go with him.
• Learnt how to use 3D Sketchup program & did 1st mockup of the combined kitchen/ living/ dining room.

• We sought out a well known architect who specializes in passive solar, condensation issues and PassivHaus design, Detlev, to get his thoughts & ideas of our current plans. He was keen for us to improve the thermal performance of the design by including an airtight membrane to reduce heat loss. For example our final wall design is similar to his sketch below in which there is (from left to right) outside wall cladding, cavity/ air gap, weather proof membrane A, insulation, airtight membrane B, cavity/ service duct, wall facing:

• Not wanting to increase the floor area, and after much passionate “discussion”, we compromise & go with a combined toilet/ bathroom rather than separate rooms.

• April 2018 – council planning application made. Accepted June.
• June 2018 – more shadow modeling – SketchUp is so handy for this sort of thing – just confirming how much sun we get into the rooms during winter & whether the windows are too big/ small etc.

• July 2018 – representation to council over privacy concerns with next door proposal for 3 two story units right up to our boundary. Concerns noted but nothing much we could do.

• August 2018 – design & building plans mostly complete.

• Builder #1 can no longer proceed due for family reasons. Scramble to find another builder… our “builder #2”.
• September 2018 – the big “engineering meeting” (Heather, me, 2 designers, builder, 2 engineers) – discuss concerns & possible options of the (likely cost of) concrete piers/ blockwork/ footings/ slab due to the terrible class P soil classification. Waiting for comparative quotes from builder #2.

• October 2018 – waiting, waiting for builder #2 but no word, no replies to phone calls or emails. Decide builder #2 is good at the talk but not good at the followup. Cut our losses and make contact with “builder #3”.
• December 2018 – finalize “selections” for builder #3 so he can provide a detailed quote.
• More modeling due to concerns about over-shadowing from adjoining two storey unit, and where best to place solar Photo Voltaic (PV) panels. On the house or the shed?

• Issues with building surveyor over our choice of polycarbonate roofing over the courtyard – height, durability issues. Need for safety mesh? Need for mainland Spotted Gum framing instead of local hardwood. Need for oiling/ painting.
• January 2019 – received quote from builder #3 – yikes/ wince – we were really really hoping it would be substantially less cost, and there’s little options for saving $ – can’t do anything much ourselves – not allowed onsite.
• February 2019 – scramble to find another builder… our “builder #4”.
• March 2019 – building plans submitted to engineering for 2nd time – stamped. Then building plans submitted to the (private) building surveyor – stamped – Certificate of Likely Compliance issues. Then building plans submitted to the council for building approval. Then building plans submitted to the council for plumbing approval.
• Final technical specifications:
  • General
    • 110m^2 internal floor area
    • main bedroom, two studies, combined kitchen/ dining/ living room
    • light colored Colorbond skillion roof, 5 degree pitch
    • horizontally orientated Colorbond wall cladding except for the courtyard and carport walls where we have used Cemintal cement sheeting with a vertically orientated weatherboard look
    • wide north facing hallway with floor to ceiling glass wall to capture maximum winter sun
    • assembled on-site timber stud wall framing, assembled off-site timber roof trusses
    • plasterboard internal walls & ceiling
    • high efficiency split system heat pump for living room only; no other space heating
    • high efficiency heat pump hot water (after months of calculations decided that evacuated tube solar hot water was no longer cost competitive); this investigation & design is worthy of a blog post in itself
    • glazed porcelain tiles throughout
    • four of the internal doors are cavity sliders to maximize usable floor space
    • prefabricated 6 x 6m shed – 36m^2 is the maximum area of shed that an owner can self erect without needing approval
    • roller blinds only for windows where privacy is an issue, considered insulating honeycomb blinds but not cost effective compared to double or triple glazing
    • 5 kW solar PV system to be situated on the house roof; originally was to be on the north facing shed roof; this investigation & design is worthy of a blog post in itself
  • Foundations (class P uncontrolled fill with pockets of groundwater, bedrock @ 2m)
    
    • 450 dia. concrete piers to 2m, with N16 tie rods into footings
    • 450 x 450 strip perimeter footing with top & bottom 4-L12 trench mesh
    • From zero to three extra core filled concrete blocks between footing & slab – needed on northern fill side of house.
    • 150 thick 25 MPa concrete slab with top & bottom SL92 mesh
  • Thermal aspects
    • construction to “near-PassivHaus standard”, but with thermal bridging weak points not fully analyzed, certification not sought
      • the slab is compromised by thermal bridging of 31
        uninsulated piers
      • 90mm noggings in 140mm stud wall to reduce bridging
    • all windows & external doors are triple glazed, U-value ~0.8, SHGC ~0.56; tilt-turn openings for natural ventilation
    • 100mm R4 XPS under-slab insulation
    • 50mm R2 PIR slab edge insulation
    • 140mm thick timber stud with R4 bulk glasswool insulation
    • 45mm internal cavity between plasterboard & stud wall for services, and locating airtight inner membrane (ProClima Intello)
    • 45mm external cavity between stud wall & outside cladding, and locating weatherproof outer membrane (ProClima Exstasana)
    • roof weatherproof outer membrane (ProClima Mento 3000)
    • 280mm R7 ceiling bulk glasswool insulation (two layers of R3.5)
    • mechanical heating & ventilation recovery via a Zehnder Q350 HRV unit, provides 92% heat recovery with an operating power of ~20W
    • thermal modeling using open source USA Dept. Energy EnergyPlus simulation software suggests the minimum floor temperature at 8am after week of coldest winter temperatures will be 21C – here’s hoping…
    • 600mm eaves all-round but otherwise the extent of external summer shading devices will be decided after some lived-experience
    • recirculating oven rangehood to avoid airtightness issues

Will 2019 be the year we move from Longley back to Hobart?

With any luck we’ll sign a contract this Friday 15th March, and building will commence in June…