Kirrawee Hempcrete Duplex 2020

About Kirrawee Hempcrete Duplex

The aim for building this home was to incorporate social and environmental sustainability features to provide accommodation for a seniors couple and for their adult daughter, who has a disability.

Social sustainability aspects include being a single storey duplex, thus providing accessible accommodation for us as we age as well as our daughter.

We included features such as flush thresholds throughout, including at the external sliding glass doors (which required a special order); a wider entrance and hallway; heights of door handles, power points and light switches meet accessibility requirements; wider doorways; turning circles in the kitchen and main bathroom that would accommodate a wheelchair, if needed; a built-in shower seat in the main bathroom; and provision for mounting grab rails beside the toilets, bath and in the showers. We were also aiming for low maintenance, which affected the choice of external cladding and the use of native gardens to the street front.

Environmental sustainability aspects are featured by the use of hempcrete in all external walls, providing exceptional thermal and acoustic insulation; double-glazing to all glazing; kitchen benches of recycled hardwood; a design that ensures exclusion of sun in summer yet allows full sun during winter onto the thermal mass of a tiled concrete floor; waste heat from the (heat pump) hot water storage tank, located in the laundry, is used to dry clothes on lines suspended from the raked ceiling, thus avoiding the use of a clothes dryer; maximising PV panel capacity on both rooftops; use of structural insulated panels for the roofing, with no penetrations, thus maximising the roofing insulation; installation of DC ceiling fans for cooling in summer and distribution of warmth from the north-facing living areas to the southern bedrooms in winter, via central hallway (which can be shut off); use of Envirocrete 40% in the floor slab; and using a pod floor slab construction, thus reducing the amount of Envirocrete needed and increasing the R-value of the slab.

Prior to demolition, we secured fittings, for re-use, such as the kitchen sink and tapware, the built-in vacuum cleaning system, the main bathroom vanity cabinet, wardrobe hanging rails and drawers, and doorknobs and locks. During demolition and construction, our builder separated waste materials and sent to appropriate recycling facilities. We are still working on the landscaping, but a major feature in the backyard is our gabion retaining wall, which we and several generous friends constructed, and the permeable paving that allows rainwater to go through to the sub-soil where it is ultimately used by plants as it trickles through the garden.

In the 18 months since we moved into our new home, we have used the RC air conditioner on fewer than half a dozen occasions. We are in nett credit from our PV solar credits.