While once something of a novelty, prefab homes marketed as being “net-zero energy capable” are de rigueur these days — if not part and parcel along with a tight building envelope and high-efficiency appliances, consumers have come to expect rooftop solar as a standard add-on with the purchase of high-performance, precision-built homes.
More rare, however, are modular dwellings billed as “carbon-positive” — that is, prefab homes that go well beyond “zero” by producing more energy than they require while also taking into consideration factors that impact the home’s overall carbon footprint beyond run-of-the-mill energy usage.
Based in the Melbourne suburbs, Aussie prefab firm ArchiBlox recently unveiled a snazzy little one-bedroom abode that's being heralded as the world’s very first carbon-positive prefab residence.
Dubbed Carbon Positive House, the high-efficiency prototype dwelling made its debut earlier this month (hat tip to Dwell) on Swanston Street in Melbourne’s City Square as part of the 2015 Sustainable Living Festival. Smart and stylish with a focus on both comfort and innovation, the boxy modular digs aren’t, looks-wise, too dissimilar from a photovoltaic panel-clad creation you might see on display at the U.S. Solar Decathlon with one key difference: this home isn't a one-off show home but a commercially available residence.
And while the 77 square meter (a little over 800 square feet) home doesn't easily fall under the "tiny house" banner, it's positively peewee-sized by Australian standards. For years, the country has held the distinction of having the biggest new homes in the world at an average of 243 square meters (over 2,600 square feet). That's 10 percent larger than the average new home in the United States.
In a press release, the ArchiBlox team explains that the aim of Carbon Positive House is to “give our clients the opportunity to rid themselves of modern day lifelines in a house that has been developed through a collaboration sensitivities and new technologies with like-minded companies.” The firm goes on to explain that Carbon Positive Houses “will make significant contributions within society by addressing the increasing levels of carbon emissions and the high levels of embodied energy that come with the construction of a standard home. These aspects will drive us to balance the amount of carbon emissions released with the equivalent amount sequestered.”
While the home's active elements located up on the slightly pitched roof (a 5.5 kW PV solar system and solar hot water system along with a swath of vegetation for added thermal insulation) is what really helps put the “positive” in Carbon Positive House, it’s worth noting the 829-square-foot home's myriad other bells and whistles.
Key to the home’s passive design strategy is the spacious sun parlor/conservatory. This so-called thermal “buffer zone” takes up nearly half of the home's total square footage and helps to regulate interior temperatures and keep things comfortable in a region with notoriously mercurial weather. (As 1980s Aussie pop group Crowded House has noted, Melbourne is indeed a city with "Four Seasons in One Day.")
Acting as a sort of force-field against the harsh summer sun while also capturing the warmth of the winter sunlight and distributing throughout the home’s interior on chilly days, ArchiBlox describes this north-facing (keep in mind which hemisphere we’re dealing with here) space as both “the lungs of the house” and the “food basket” as it's where occupants can flex their green thumbs and grow a variety of hyperlocal produce within nifty modular planter boxes that, like the home itself, can be easily moved around from one spot to another if need be.
Sporting an absence of mechanical HVAC systems like a furnace or central air conditioning (an in-ground “cool tube” ventilation system help to cool the home during the at-times oppressive hot stretches that roll through Victoria in January and February), Carbon Positive House is also incredibly airtight. Architect Bill McCorkell, who heads the ArchiBlox team alongside builder David Martin, describes the home as being “like a fridge, fully sealed” to the Sydney Morning Herald. “The whole house has been designed to maximise solar gain. There are no fans, it's all just naturally ventilated, cooled and heated."
Other features of this wood-paneled prefab powerhouse include “sliding edible garden walls” that provide shade and help to block solar radiation during the summer; an energy monitoring system; large double-glazed windows; EarthWool insulation; high-efficiency appliances; LED lighting; both rain water catchment and grey water recycling systems; and an overall emphasis on the use of healthy and sustainably sourced building materials that are free of formaldehyde and VOCs.
ArchiBlox estimates that Carbon Positive House, which is also available in a couple of larger configurations and can be built and delivered within just 12 to 28 weeks, will emit 1,016 tons (tCO2e) less greenhouses gases over its lifetime than a similarly sized residence. This is roughly the equivalent of taking 267 cars permanently off the road or planting over 6,000 trees.
During the Carbon Positive House prototype’s eight-day public run at the Sustainable Living Festival, it served as both an Airbnb-hosted sleepover spot and the latest residence of the New Joneses. This low-impact living initiative ("taking green from mung bean to mainstream") from “Buy Nothing New Month” founder Tamara DiMattina challenges Australians to keep up with a whole new breed of neighbor — a neighbor that consumes less, wastes less and “buys experiences over stuff.”
In the case of the Carbon Positive House, the eco-conscious, socially responsible Joneses are also willing to fork over a bit more for a bit less living space: the home starts at $260,000 (a little over $200k in U.S. dollars), not including transportation, site clearing, planning costs and the like. Day bed and hammocks for hanging out in that super-sweet solarium, however, are included with the sticker price.
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