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Building Naturally

Bridget Freeman-Rock01 October 2019

BB49

The house on the hill

I’m sitting across from physicians Louise Trent and Craig Ellis in their off-grid, strawbale house in rural Hastings, which they share with their three children (and on occasion if the door’s left open, their two free-roaming pet pigs). 

There’s no heating on – outside a brisk southerly, snow on the ranges, but inside it’s comfortable, quiet. My stockinged feet absorb the warmth of the sun-warmed earth floor. I peel off several layers. 

“I spent 45 years of my life living in cold houses,” Craig says, “and it’s not until we moved in here that I could appreciate the insulation and the fact that a house can function well.” Even with a heavy frost, he says, he’s toasty in shorts and Tees, while in hot Hawke’s Bay summers the house remains graciously cool. “It’s bliss!”

For Louise, “The house feels kind of alive – literally, you’ve got that breathable wall, which regulates the temperature. You know from a scientific perspective that the clay expands and contracts, but because it’s so tactile, from a heart feel, it actually feels really organic and alive.” 

She says visitors will often hug the walls.

Theirs is not a proto-type for an eco-house, but a bespoke, handcrafted home, highly idiosyncratic, designed for this family’s needs and whims, and built for generations.

The front door uses repurposed cattle railings from the family farm. The timber was originally brought over from Australia when Louise’s father immigrated. The builder’s vice grips were only meant as a temporary fixture while Craig and Louise decided which door handle to order, but five years on, they’re still to find a better replacement.

It took years of research, hands-on courses and negotiation to come up with preliminary architectural plans, and then a full two years for the redraft, consent and build process – completed in 2016. While the work was project managed and undertaken by professional craftsmen, Craig and Louise were involved every step of the way, and know each nook and cranny intimately and the story and effort behind the crafting.

They see themselves as pragmatists rather than purists – the decision to go off-grid, for example, was dictated by the house-site (and worked out to be significantly more cost-effective) – but the holistic approach is an aspect they truly value.

“The whole building process itself was done off the grid with minimal waste,” explains Louise. “A lot of waste products were composted onto my orchard – the only thing I got from that was the occasional weed! And we’ve got a bit of leftover wood that we’re using as kindling to start the fire. If the house ever got bowled, you’d be able to put half of it in the compost! 

“You’ve got a house that could last 500 years if you really look after it and maintain it, but then it’s also biodegradable – it just makes so much sense.”

Louise, who describes herself as an “active relaxer”, plants around a thousand trees on the property a year – the surrounding paddocks around will one day all be forest. One of her current projects is the development of a drylands garden that doesn’t require watering. 

close-up of the 22m-long (50m2) living retaining wall by the entrance

“We don’t want to be the doomers on the hill,” explains Craig, “but we’ve been tracking the climate emergency for a long time, and it’s not looking great. You could say, we’ve begun adapting.”

House profile

The solid 340m2 timber-structure house was designed for orientation (all rooms are north facing and receive direct sunlight in winter but are shaded in summer) and location (a wind-exposed hilltop on the outskirts of Hastings). 

It incorporates solar-gain, passive house elements: thick strawbale walls (45cm wide) with clay and lime plasters means it’s extremely well-insulated. The thermal mass of the plasters and earth floors retain warmth and double-glazed, vacuum-sealed windows and doors with a heat-transfer mechanical ventilation system in the ceiling ensure a regulated indoor climate.

The house has a dry, even temperature year-round: 18-20C in winter (without heating); 22C in summer (with doors and windows open), even when it’s 30C+ outside. Heating is a wood-fired kitchen range with a wetback for hot water and a small (rarely used) Pyroclassic wood burner in the library. 

Solar panels (like these) are positioned in the paddock rather than on the roof

Materials are predominately locally sourced. The strawbales grown on the Heretaunga plains, lime from Websters quarry across the valley on Middle Rd, clay from Kahuranaki. Macrocarpa from the family farm in southern HB was used for the ceilings, joinery and exterior cladding and gables, with NZ-grown hardwood timbers used for flooring and other features – the stairs, for example, are made from a eucalypt hybrid grown just north of Napier.

All paints and oils are non-toxic, sourced from the Natural Paint and Natural House companies.

Personal, creative features include a living retaining wall carpeted with hand-propagated succulents; an experimental green roof on the upper-story craft room; a hand-sculptured adobe window-seat; fresco paintings around the outside entrance and tadelakt (a traditional Moroccan, waterproof-plastering technique) in the bathroom.

The house is fully off-grid – powered by solar panels in the paddock and a small wind turbine. Rainwater is collected in 30,000 litre tanks and a dam. Waste water (including sewerage) is treated with a worm-based composting septic tank system.

clay plasters lend themselves to artistic features, such as this tree, sculptured by Louise and friend Nadine; close-up detail of timber, carpeted in an array of different succulents; pet kune kune pigs Fuji and Blacksie.

Climate-conscious construction

Pat Mawson, chair of the Earth Building Association of NZ (EBANZ), and Nils Rock (master carpenter and licenced designer) have been building “natural, handcrafted homes” in Hawke’s Bay together for a decade (strawhomes.co.nz), including the Roy’s Hill house showcased here. 

The living room marries clay, earth and stone features with untreated NZ-grown timbers.

While there’s a growing awareness of energy-efficient housing, they believe this shouldn’t be the prerequisite goal but an integrated outcome of more overarching considerations: the materials used, smart design and construction methods that take into account the whole life-cycle of the build

A big factor that receives less attention, they say, is the ‘embodied energy’ of products, in other words their carbon footprint (processing, transport, etc). Cement, for example, is a massive contributor to atmospheric carbon – it’s the third largest emitter of CO2 in the world after the US and China and the most widely used substance (save for water). Yet there are less destructive, time-tested alternatives.

New Zealand’s earth-building standards (which encompass cob, adobe, rammed- and poured-earth structures and centre around performance and pragmatic tests) are amongst the most comprehensive in the world. While the original aim was to provide a healthy, low-cost housing solution for young families and a guaranteed pathway for compliance, they’ve also been used to build luxury mansions, and more recently in Nepal and Haiti for massive rebuilding projects.

The living room marries clay, earth and stone features with untreated NZ-grown timbers.

But the standards have hardly been touched for 20 years and need revising, especially with new research and the learnings that have resulted from the Christchurch and Kaikoura earthquakes (those houses built to the earth-building standards, by the way, performed well). If they’re not updated, says Pat, they’ll become redundant. 

While MBIE has a regulatory duty to maintain them, and initially agreed to their rewrite, the ministry withdrew funding part way through, leaving the work to EBANZ and other volunteers, who set up a fundraising drive to complete it by September.

“We need the standards,” says Pat, “they’re a really positive way of making changes. So we’re doing it anyway.” 

Strawbale falls by default into the ‘alternative solutions’ bracket of the Building Code (requiring a design-led, non-generic approach with demonstrable proof and input from appropriate experts). 

But if approved, the new revised earth building standards will include guidelines on strawbale and light earth materials (such as hemp-crete, woodchip, or even pumice, composites, which are usually packed around a non-loadbearing timber structure, and bound with clay or lime), which will give councils valuable information and help smooth that consent process through. 

In the case of the strawbale house showcased here, back in 2014 the clients had to pay a substantial amount of money for the plans to be peer-reviewed because the local council didn’t have the in-house expertise to assess it.

According to the NZ Green Building Council, New Zealand’s built environment is responsible for 20% of the country’s carbon footprint; emissions from the construction industry rose 66% in the decade 2007-2017. 

The lime-rendered exterior walls of this north-facing house reflect back the HB light, while (BELOW) Fuji the pig has a snooze by a Jeff Thomson cow sculpture that lived with Louise in her student flat in Wellington in the 1990s and has spent time on a hill in Bayview overlooking the sea.

Pat and Nils see natural building as an important tool in the toolbox that should be better supported if we’re to transition to a zero-carbon future. 

Currently, it seems there’s a lack of interest, and yet, there’s such opportunity. 

They’re calling for the Government to take a more considered look at building and where those carbon changes can be made and to back natural building or methods that are sequestering carbon, considering the whole life-cycle of products, and inter-generational ways of building.

Natural building tips

There’s an art and science to building well, and when working with natural materials no one recipe or single ingredient. But here Nils and Pat offer 10 things to consider for your new build or renovation.

1. If you can’t avoid, then at least reduce the use of cement – cement is right up there with oil and coal, in terms of CO2 emissions. There are additives such as fly-ash that can be used to dramatically reduce the cement component of concrete and these will become more readily available options if people keep asking for them. Or better still, consider an earth floor, or timber floor on piles.

2. Strawbale walls have a high R-value, so great energy-efficient properties, and they also act as a carbon sink. As a renewable by-product that can be locally sourced, strawbale walls store carbon and can ultimately be composted. Contrary to myth, strawbale houses perform really well in fires, the sealed straw is too tightly packed to burn. If they’re well designed they’re very durable and can last a long time. 

3. Clay, clay, clay. It’s vapour permeable, and absorbs and releases moisture very readily – storing excess moisture safely until it has a chance to dry again. As a plaster it allows walls to ‘breathe’, while maintaining healthy humidity levels and stable temperatures within the house. Clay can often be sourced locally, using only the energy it takes to dig it out of the ground. It’s non-toxic, easy to repair, biodegradable, and beautiful too! You can plaster with clay over standard gib and other materials on interior walls.

4. Consider solar gain and bringing thermal mass into the house – you can retrofit an existing structure with adobe-veneer walls, for example, or create an adobe-brick or earth-bag wall behind a fire place or an earth floor where the winter sun shines in. 

5. Favour bio-based materials like wool and timber over fibreglass and steel – you can still build conventionally that way if you choose, but you markedly decrease the carbon footprint of your house and they work better from a building-science perspective with moisture. Use locally sourced, or recycled products where possible. Timbers like macrocarpa and eucalyptus are more enduring and require less treatment than pine – by supporting these you also support alternate timber forestry.

6. When using natural materials, design is crucial. Orientation and location are essential considerations – maximum sun in winter, minimum sun in summer, protection from elements. Be innovative and smart with eaves and roof pitch.

7. Design for deconstruction not disposal. Can materials be separated out, taken apart? While you can salvage matai flooring from an old state house, for example, the customary building practice now is to glue it to concrete, and you can’t get it back – once you get it off the concrete it’s totally destroyed. If you nailed the wood to joists it can be later repurposed.

Tadelakt lime plaster is used in the bathroom for wet-area surfaces (seen in
the shiny turquoise and yellow patina here) – a tradition Moroccan waterproof plastering technique.
BOTTOM: There’s attention to detail in every corner along with carefully curated, personal
precious things. Louise’s collection of French antique tiles are paired with artisan ceramic tiles made in Auckland; the kitchen benchtop is a handmade polished concrete block inset with greenstone off-cuts and hand-picked river rock; the collection of vases on the window sill are
tiny antique glass bottles dug up from an old dump on the farm by Louise as a child.

8. Polystyrene is often used to build air-tight, energy-efficient, passive houses, but it’s a material that embodies a lot of energy through its production process. It’s quite poisonous as a waste product (can’t go into landfill) and while it can be theoretically recycled, without local facilities it’s impractical. Polystyrene alternatives for sub-flooring include Cupolex pods (recycled plastic domes), wool insulation (under timber) or even pumice and mussel shells. For walls strawbale, LEM (light earth materials, like hemp-crete) or straightforward wool insulation can give you comparable R-values (contingent upon thickness and design).

9. If building air-tight to conserve energy, you’ll need to consider ventilation. If using mechanical ventilation, choose a heat-recovery system that genuinely exchanges air rather than recirculates it, not a positive-pressure HRV system (which may work in an old, drafty house, but can cause damage in energy-efficient designs).

10. Interior furnishings, such as carpets, and paints can be hugely toxic and carbon-emitting. If you’re refurbishing that may be the best place to start in creating a healthier, more climate-neutral living environment. See naturalpaint.co.nz.

Disclaimer: The author is married to builder Nils Rock, hoping one day to get a strawbale house of her own.

Bridget Freeman-Rock01 October 2019

BB49

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