Prioritising health when selecting materials and products is simply common sense, and the best thing about healthy materials – they are also brilliant for the environment.

In today’s episode we move on to our next sustainable design theme – healthy buildings.

We’ll investigate the design of a house on an off grid site located in Mullumbimby in the Subtropical northern New South Wales hinterland. I talk with architect, Michael Leung, the director of Balanced Earth Architects, who will share the inside story on his Sky Farm project.

Today we’ll learn about:

• The key design considerations, materials and products for a healthy home,
• We talk further about the process, costs and benefits of using hempcrete in custom architectural construction, and
• We’ll also cover a wealth of other insights and practical information drawn from Michael’s extensive experience as both an architect and a builder.

Australian Architects can claim formal CPD hours for these podcasts.

MORE INFORMATION

Find everything you need on the Renovation Collaborative website.

www.renovationcollaborative.com.au

• PODCASTKey points summary, timestamps and resource links
• FREERESOURCESTranscript edited into clear Q&A.
• CPDAustralian architects can find more information on CPD, and
• COURSESEleven easy to read courses demystifying the entire home design and construction process.

KEY POINTS SUMMARY

1. Healthy building is about interrogating the detail of materials. Often that's not presented on websites and you have to dig deeper into the Material Safety Data sheets.

After extensive research, Balanced Earth Architects now work with a simple palate of materials and the basics include: hempcrete, recycled timber and other materials from demolition, galvanised steel, timber windows, and natural finishes including clay and lime renders.

2. A hempcrete and lime rendered wall composition prevents mould growth. Hempcrete is vapour permeable, allowing moisture to travel from the inside to outside. In addition, lime render has an alkali surface preventing mould growth.

3. A hempcrete wall is set up as follows:

• It can be constructed on a timber framed or concrete floor.
• In timber framed construction, the joists or bearers may be doubled up to carry more load when the hemp is wet. Then a 10 or 20mm compressed FC board is fixed on top as a base for the hempcrete.
• To build the wall, a timber stud frame is setout 80mm in from the external wall line. The 90x45 stud sits centrally in the 250mm hempcrete wall, allowing 80mm of cover on both inside and outside.
• The entire house is constructed with standard timber stud frame construction. All timber can be untreated pine because the lime in the hempcrete protects the timber, and
• The services are clipped into the stud wall, and the formwork is set up ready for the hempcrete.

4. Concrete interior floor slabs are burnished and then finished with a natural flax seed oil.

Burnishing is a process that creates a smooth, dense and low sheen surface by mechanically trowelling a concrete slab before its fully cured. Unlike polished concrete, burnishing does not grind down the concrete or expose aggregate. The process uses a power trowel or helicopter to compact and smooth the surface to a sleek durable finish.

5. Other healthy internal materials and finishes include:

• Wall linings of pine boards, plasterboard or Villaboard finished with natural clay or lime paints, and natural clay or lime renders.  
• Cabinetry carcasses are constructed from VOC free moisture resistant plywood, painted with natural paint. There is no melamine cabinetry.
• Kitchen benches are made from timber, concrete or a copper treated with natural oils.
• Wet areas avoid tiles on walls or floors to minimise the opportunity for mould growth in tile joints. Instead the walls are finished in a burnished render. Burnishing involves trowelling the fresh render surface until it is completely smooth and all pores and scratches are removed. Bathroom floors and showers are finished with micro cement and sealed.

6. Materials for roof water collection and storage systems avoid chemical leaching and include:

• Galvanized steel roof sheeting, gutters and downpipes.
• HDPE pipes (never PVC).
• Rainwater tanks made from stainless steel or concrete.

7. EMR or electromagnetic radiation exposure is reduced - particularly in bedrooms. All cabling in the house is not within 2 metres of any sleeping head, particularly children. Solar panels and batteries are located on sheds or garages and away from sleeping and habitable spaces, and Internet cabling and plug in connection is provided to avoid WIFI wherever possible.

INTERVIEW QUESTIONS

[00:00] Introduction

[01:11] How did you get started into sustainable design?

[03:40] Tell us about Balanced Earth Architects and Balanced Earth Builders

[08:13] In your experience, is awareness and knowledge about sustainable design increasing?

[09:30] What was the sustainable design brief for this project?

[15:45] What is the Byron hinterland climate like?

[16:31] What were your key design strategies to deal with this subtropical climate?

[18:52] Tell us more about hempcrete construction?

[21:35] Does hempcrete take longer to build than standard construction?

[24:10] How does hempcrete cost compare with other types of construction?

[25:18] Tell us about lime render?

[27:22] Tell us about the other interior materials and finishes?

[29:14] What paints do you use?

[31:33] What materials did you use in the kitchen?

[33:32] What materials did you use in the bathrooms?

[36:39] What are the key criteria to make a healthy home?

[40:54] What did you use for your solar power system?

[42:59] What did you used for your sewage treatment?

[44:26] What did you use for your rainwater harvesting system?

[48:34] What advice would you give to anyone wanting to build a healthy home?

IN THE NEXT EPISODE

Next week we move on to our next sustainable design theme - Delight in your environment.

We'll investigate the design of a small extension to an old timber home and some very important landscape work on a challenging site with overland water flow issues, located in suburban subtropical Brisbane. It's an inspiring transformation from a problem site into a valuable asset that brings joy to the owners and provides a much needed habitat for local flora and fauna.

I talk with architect Tim Benetton, the director of Tim Benetton Architects, who'll share the inside story on his Yeronga House project.

RESOURCE LINKS

BALANCED EARTH ARCHITECTS - Project Page (images) Skyfarm https://www.balancedearth.co/all-projects/skyfarm

BALANCED EARTH BUILDING COMPANY https://www.balancedearth.co/

PROJECT INFO

Georgio Graesan: https://www.giorgiograesanqld.com.au/products/

Hempcrete internal clear finish - Rockcote Repel https://rockcote.com.au/product/repel/

Livos https://livos.com/

Rockcote: https://rockcote.com.au/product-category/natural-materials/

Rockcote Clay & Lime plaster: https://rockcote.com.au/product/otsumigaki/

Micro Cement

Water filter systems: https://watershop.com.au/

OTHER INFORMATION

Luigi Roselli Architects https://luigirosselli.com/

REVIEW

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GET IN TOUCH

If you've got any comments or questions or there's any topic you'd like to know more about, please send me an email at [email protected].