Manuela is an entrepreneur Italian Architect in love with Australia and with the environment. Actually, my new friend C. from the Earth Carer Course told me about her amazing self-built eco-efficient straw-bale house in Hilton and you can easily imagine that I was really keen to interview her and to know more about it 😉
I got in touch with Manuela, who kindly invited me to visit her house and to meet her family, while having a great chat about her experience as Architect. I discovered that she graduated in Italy and in 2007 she firstly moved to Perth to work for an architectural firm. She was already really passionate about sustainability and energy saving design.
Then, in 2012, she spent a couple of years back in Italy, where she had the opportunity to improve her knowledge and building experience with straw-bale constructions. Subsequently, in 2014, when she came back for good to Perth with her partner, they had no doubt: they decided to buy a piece of land and to build their own house, a straw bale house!
The construction system easily reminds us the “Three Little Pigs” fairy tale, but in reality is a very solid and energy efficient house. Indeed, people around the world have been building homes using straw for centuries. There are straw bale houses in Europe and America that are now over 100 years old and in excellent condition. (1)
From a construction point of view, it is important to clarify the difference between hay and straw: straw is the stalks or stems of grains like wheat, barley, or oats after the grain has been harvested. Hay is grass or legumes that have been cut and dried and is generally used as animal feed. (2) Straw-bale construction is a building method that uses bales of straw (commonly wheat, rice, rye and oats straw) as structural elements, non structural building envelope and insulation, or both. (3)
This building system has many pros from an environmental point of view including:
renewable nature of straw
high insulation value
compostable if dismantled
Particularly, WA farmers have abundance of straw as they harvest it twice a year and it is usually used for mulching and to create animal bedding or otherwise it gets burnt. It makes straw bales very affordable, with a cost of $4 each approx.
Manuela’s house is a new construction located in Hilton. Being a granny flat, it is a small one storey house (approx. 75 sqm) but really well designed, featuring one spacious bedroom and one bathroom, a nice open plan living area with kitchen and a mezzanine level as a studio/guest bedroom. The living area can expand towards the back garden through bi-folding windows, adding high quality extra space to the house.
From a technical point of view, she decided to have a wooden structural frame installed by a certified company and assessed by a structural engineer and to use straw bales to create the non structural exterior and interior walls. I was really impressed to know that she built the straw bale envelope all by herself and that it took only 2 months for a team of 4 people! Manuela explained me in detail how they built it and all the challenges they faced along the path. I don’t want to get too technical, but if you want to know more feel free to ask me more questions about it 😉
As a brief overview, I can tell you that water is the main challenge for straw bales, in the form of rising damp, rain and condensation. Luckily, different strategies have been successful in other projects, therefore straw bale buildings can last more than 100 years with same maintenance as wooden buildings.
Choosing a breathable wall render mix is also very important, because it will protect straw bales from the rain and possible vermin attack, as well as allowing the wall to release any condensation. From an energy saving point of view, straw bales have excellent insulation properties, among the most cost effective thermal insulation available. They also offer good sound insulation and compliant fire resistance.
On the other hand, straw bales have very low thermal mass, being composed, by volume, mostly of air. However, the cement and earth renders typically used on straw bales result in finished walls having appreciable thermal mass, which is very important to guarantee high level of indoor comfort. Indeed, Manuela told me that during summer time the indoor temperature is pretty good till 6 pm, when it gets up to 27C…but then she can open the windows and enjoy the Fremantle Doctor. It means that last summer they NEVER had to turn the aircon on!
During winter time, the indoor temperature is usually around 19 degrees, meaning that she doesn’t need any heating. If outside is really cold (ie 6 degrees with no sun), the indoor temperature can reach 17 degrees. Only in those special occasions, as she has little children, she turns on the reverse cycle heater for only 1 hour to achieve 19 degrees and after she turns it off, the temperature remains above 18 degrees for the WHOLE DAY thanks to the well insulated envelope!
I can’t stress enough how cold is my house made of double bricks… with 15 degrees inside at 7 am!!! If I want to “survive”, I turn the heating system on till I reach 19 degrees and when I turn it off, within 15 minutes the house is cold again, mainly because walls are cold (non insulated) and windows are not properly sealed.
Manuela’s house is a great example of energy efficient and sustainable home that can be built in WA. She successfully registered her house for the 2017 Sustainable House Day on Sunday, 17th September, in order to promote and raise sustainability awareness within the Community. I really suggest you to visit her house together with other more “traditional” buildings, in order to see with your own eyes that energy efficient homes are “normal” houses that can be made by many different materials, including double bricks with well thought insulation.
The main difference is that in an energy efficient home you will live better from an indoor comfort point of view, you will pay nearly zero a/c and heating bills and building or renovating your house won’t cost you a fortune!
Thanks to Manuela for her availability to meeting me and sharing her experience with Think About Sustainability. You can read more about her project on her website TerraDesignLab.