In previous issues we have highlighted the benefits of reverse brick veneer construction, especially for residential dwellings. Unlike the vast bulk of Australian brick homes, RBV, as it is often referred to, places bricks with their thermal mass inside the house and protects them from absorbing the hot Australian sun with an external cladding/insulation sheath.
Properly designed windows allow low angled winter sun deep into the building where its heat is trapped in the bricks and slowly released as passive heating to inner rooms. The more directly overhead summer sun is kept away from the internal brickwork by appropriate eaves, screening and the cladding/insulation exterior, negating the need for energy intensive air-conditioning.
But for all its benefits, RBV has been a little too out there for mainstream builders. Now though, Cameron Rosen’s Sustainable Building Management and Consultancy, known as Australian Living, may just make RBV seem almost ordinary. It has taken the idea to the next level with a building method he dubs ‘reverse masonry veneer’. But we’re getting ahead of ourselves.
Rosen believes sustainable design should adhere to the five 'p' principles: proper preparation prevents poor performance. Or, as he says, “the intention to design sustainably has to be there before pen is put to paper”. Five must be his lucky number, for it is also the street address in Rose Bay, Sydney, of the innovative Eco-Challenge where Australian Living has dared four families and four architects to design the most sustainable house they can afford. Five is also the number of his key considerations required for sustainable home design.
The first key we’ve already mentioned — design intent, or designing with the end in mind. Secondly and crucially important is thermal comfort. Rosen engaged thermal consultant, Graham Hunt, who listened to the four home owners on what they expected from their new homes before advising how best to optimise each dwelling’s respective insulation needs and its location.
“We isolated the crucial living areas — sleeping and living — that need to be kept at optimum temperatures from service areas such as bathrooms, that do not need such a high level of thermal comfort,” Hunt says, pointing out that insulation employed on the project was twice that for most new homes. Rosen expects the temperature in living spaces to stay in the comfort range of 19°C to 22°C.
To finesse the detail of his own house as one of the four in the Eco-Challenge, Rosen collaborated with Pidcock Architecture and Sustainability. Katherine Madden, associate director at the firm, says “Working with Cameron we were able to establish some design parameters so that building could be comfortable thermally in both summer and winter. The challenge of such a long and narrow site meant thinking of a solution that would bring the winter sun deeper into the floor plan, whilst shading it from the harsh summer sun.”
Once he knew how much insulation was required for thermal comfort and where it was most effectively positioned, Rosen moved onto his third key consideration — materials choice. He sought out all options that might yield the results his thermal comfort standards required. This lead to some first time residential applications of materials and methods normally confined to commercial buildings.
For example, the Rosen house avoids clay-fired bricks and opts instead for a prefabricated Ritek hollow wall system which is filled with Boral’s Envirocrete with its 30 per cent recycled content (60 per cent cement replacement with flyash and a 20 per cent aggregate replacement mixed with recycled water). Envirocrete was also deployed in the foundation slabs and plunge pools. The recycled nature of Envirocrete has been calculated to have saved the houses 14 tonnes of GHG emissions — a year’s worth of emissions.
The prefabricated Ritek wall, which acts as formwork for the Envirocrete, allowed the ground floor wall of the four homes to be constructed within a week. Using such a wall system, Rosen believes he has arrived at the “most recycled masonry structure you can build” while avoiding the 5 per cent to 10 per cent of brick wastage common to traditional brick veneer construction.
The design of Rosen’s house used the Ritek/Envirocrete wall only where thermal modelling indicated the benefit of thermal mass. As noted earlier, this thermal mass is inside the building, not exposed on the exterior — it is hidden by another innovation in residential design, Kingspan Kooltherm insulation panels. These rigid panels contain a Polyisocyanurate (PIR) rigid insulation core with autohesively bonded facings on both sides. This panelling was used as veneer over the Ritek walls and acts, as Rosen puts it, ”as a ring of protection or like a woolly jumper, so to speak”.
Madden from Pidcock is also enthusiastic about the product. “The beauty of the Kingspan insulation product used at Rose Bay is that it not only acts as the insulant, it is also resistant to the passage of water vapour and is ready to take the render finish — very mulitfunctional!,” she says.
“Having the insulation on the external skin also means that you are not limited to the amount of insulation that you can add as with a cavity wall where the thickness of insulation is determined by the width of the cavity.”
And speaking of width, Rosen notes “our RMV system is the thinnest structural thermal wall on the market with a cross section of only 235 mm and combining materials for a performance of thermal mass and R4 insulation“.
There is a great deal more material creativity at play in the Eco-Challenge project, but we are too constrained for space to delve into it here. However, we did enquire why Rosen thought it has taken so long for the residential market to be alerted to new material approaches.
“Technology has finally caught up to ancient design principles that we forgot in the eighties. The proceeding generations have accepted air-conditioning as the solution,” he says. “Now we have the modelling ability and materials available to construct to a higher level of comfort home that controls itself naturally. We need to re-educate the market place.”
And part of this new thought process involves the fourth key, the adoption of permaculture principles, such as having a garden which is 80 per cent edible, installing fruit trees that not only provide food crop but offer a privacy hedge and aesthetic greenery, or diverting greywater and stormwater to feed the garden only to the degree that moisture monitors indicate it is required.
We asked Pidcock Architecture & Sustainability what lesson it had taken away from the Australian Living Eco-Challenge. “We were very lucky to have such an engaged and interested client such as Cameron, and the fact that he was the builder as well made it all the more interesting and informative. We now collaborate with our builders much earlier in the project phase, so as to help realise the best design outcome for our clients,” Madden says.
This early engagement of people provides a neat segue to Rosen’s fifth and final key for sustainable home design: “the variable factor — the resident”.
Buildings are, after all, not mere inanimate objects. They are systems that intimately involve people. A house doesn’t care it if is cold or hot, but people do. That is essentially who homes should be designed for.
And in the case of Rosen’s home, he has risen to his own eco-challenge, scoring the equivalent of a NSW BASIX 8 star rating for thermal comfort, and that might be the best result that is economically feasible. Pidcock’s Madden says: “For every extra dollar spent to improve the rating [after the 8 star rating was achieved], the return was more difficult to achieve.”
