Are you looking for a unique sustainable material with a low carbon footprint?

In today's episode, we move on to our next sustainable design theme, Earth Building, and investigate rammed earth construction. Architect Steffen Welsch, director of Steffen Welsch Architects, shares the story behind his Butterfly House project, located on an off-grid site in Rutherglen in the hot, dry summer and cool winter climate of north-eastern Victoria.

Today we'll learn about the process, benefits and costs of using rammed earth construction and a wealth of insights and practical information drawn from Steffen's extensive experience.

Australian Architects can earn formal CPD hours by listening to these podcasts and completing an online quiz.

MORE INFORMATION

Find everything you need on the Renovation Collaborative website.

www.renovationcollaborative.com.au

• PODCAST Key points summary, timestamps and resource links
• FREE RESOURCES Transcript edited into clear Q&A.
• CPD Australian architects can find more information on CPD, and
• COURSES Eleven easy to read courses demystifying the entire home design and construction process.

KEY POINTS SUMMARY

1. Rammed earth was chosen for this project because it suits the local continental climate. It optimises energy efficiency by absorbing and releasing heat slowly throughout the day, stabilising internal temperatures. This means it helps maintain a moderate temperature range inside the house by absorbing heat in summer to take the edge off those high temperatures and releasing heat slowly in winter to take the edge off low temperatures.

2. The soil used for rammed earth must be laboratory tested to ensure it is structurally suitable. In Steffen's experience in regional Victoria, there are usually quarries with appropriate soil located within a reasonable distance from most sites. A rammed earth contractor can assist with this process.

3. The rammed earth construction process is relatively simple and dates back over 10,000 years. Plywood formwork boxes are constructed and a rammed earth mix, of dirt, cement, water and potentially other admixtures is poured in and compacted with specialised equipment. At the time the Butterfly House was constructed, rammed earth walls comprised a single solid wall with a thickness of around 500mm. Now, rammed earth walls must include insulation. Their current composition involves an internal layer of rammed earth, a core of thermal insulation and an outer layer of rammed earth, resulting in an overall wall thickness of around 450mm. Alternatively, rammed earth can be constructed as a 200mm thick reverse brick veneer wall.

4. Rammed Earth offers numerous benefits, including thermal mass to stabilise internal temperatures, excellent acoustic qualities, high flame resistance, low embodied carbon and durability and a long lifespan, though it does require extended roof overhangs for protection from weathering.

5. The cost of rammed earth construction is about three to four times higher than that of standard 90mm timber stud frame construction. It's comparable to insulated cavity brick.

And finally,

6. Considerations when using rammed earth include:

• understanding all the benefits and qualities of the material,
• being aware of regulatory issues. It's not covered in the Australian National Construction Code and requires a performance solution report,
• engaging the right expertise early, including a sustainability consultant, rammed earth contractor and structural engineer, and
• co-ordinating all services early in the process.

INTERVIEW QUESTIONS

[00:00] Introduction

[01:00] Tell us about your practice and how you got started into sustainable design?

[05:16] How did you get involved in Architects Declare

[06:50] How did the brief evolve for a rammed earth house in this off grid location?

[09:20] How do you find the right soil?

[11:16] How are rammed earth walls constructed?

[12:40] How thick are rammed earth walls?

[13:48] How does rammed earth improve thermal comfort and energy efficiency?

[16:16] How is rammed earth better environmentally than insulated cavity brick?

[17:37] What is the environmental impact of cement in rammed earth?

[20:04] How to you calculate carbon on your projects?

[24:57] Can you tell us the next steps in the rammed earth construction process?

[28:23] What are lower and upper floors constructed from in a rammed earth house?

[30:11] Does rammed earth need protection from weathering?

[32:06] Does rammed earth need to be sealed?

[33:54] What are the benefits of rammed earth?

[36:46] How does the cost compare to 90mm timber stud frame construction?

[39:00] How does the construction time compare to standard construction?

[39:42] What doors and windows did you use?

[41:40] What materials did you use in the interior?

[42:30] What other environmental choices did you use in this off grid site?

[44:05] What advice would you give to anyone considering building with rammed earth?

[45:50] Key Points Summary

IN THE NEXT EPISODE

Next week we move on to our next sustainable design theme, Prefabrication.

We'll explore cross laminated timber or CLT and investigate its use in a new prefabricated house located on a regional site in Akaroa in the mild temperate climate of east coast, South Island, New Zealand.

I talk to architect Jae Warrander, a director at Makers in New Zealand. Makers is a collaboration between Makers of Architecture and Makers Fabrication. Jae gives us the inside story on his Akaroa Bach prefabricated House.

RESOURCE LINKS

STEFFEN WELSCH ARCHITECTS WEBSITE

Project Page (images) https://steffenwelsch.com.au/projects/butterfly-cost-effective-rammed-earth-house/

PROJECT INFO

Kitchen Cabinets: Hoop pine plywood

Lifecycle Assessment

ESD Consultant: LID Consulting https://lidconsulting.com.au/

LCA Tool: Etool https://e-tools.com.au/

Rapid LCA software https://cerclos.com/products/rapidlca/

OTHER INFO

Williams Boag https://www.williamsboag.com.au/

Denton Corker Marshall www.dentoncorkermarshall.com

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].