Sustainable low carbon house design & affordability trade offs due to budget

Hi all, I just started writing this; it is a work in progress/brain dump. I will finish and add photos and show how to utilise PlusSpec to deliver more sustainable buildings. You’ll find it an interesting read on how & why many are not producing more sustainable projects.

Personally, I like the idea of building a home from locally available and sustainable materials, rich in texture and high in durability and insulative properties. My “perfect home” would be carefully solar-orientated to make the most of the winter sun & omit the hot summer sun. The internal walls would be natural thermal batteries that store and release energy, and the windows would all be triple-glassed with reflective coatings where required. The roof would collect solar, which would be stored for later use, and I’d have a zero-dollar energy bill and zero drain on the grid… In a perfect world, right?

Although all good intentions are present, we all trade-off at some stage for various reasons. I have listed several below.

  • Budget
  • Durability
  • Time constraints
  • Legislation and building code
  • Availability
  • Newer technology on the horizon
  • Knowledge or information availability

As a result, in most cases, homes are built to a budget with standard construction methodologies that meet the status quo of minimum finish. For example, Lightweight timber or steel wall framing with lightweight cladding or more durable and generally more expensive single and double masonry walls. The reason is that our industry has been using these construction methods for years, and trades are trained in the installation, and as a result, they are more efficient to build.

Where do you get the best bang for your buck?

  1. Solar orientation and window placement give the highest bang for your buck.

Where can savings be made? Living rooms on the sunny side and utility rooms that can be closed off on the hot summer side make for a better, lighter, healthier home. More importantly, it reduces the running cost of a house by reducing lighting and air conditioning load for extended periods.

  1. Colour choice and material in connection with solar orientation. For example, darker colours absorb heat, so it makes sense to add darker colours to materials that store thermal mass where the winter sun will connect and where the summer sun will not.

Where can savings be made?

Adding a lighter colour to areas like the roof or walls that get full sun in summer makes sense.

  1. Conductivity: the energy transfer through a material with the least degradation/resistance. The reason they make pots and pans from metal is metal quickly and efficiently transfers heat from the heat source to the cooking surface. Don’t get me wrong, steel has its benefits, but I would never build a home with external or internal steel wall frames. Steel frames will not hold higher compression loads and will collapse faster than a wood/timber frame in the event of a fire.

Where can savings be made? Wood/timber frames will resist the transfer of heat or cool and, when insulated correctly, will significantly reduce transfer of the elements. A wood/timber wall frame is also considerably quieter to live in; just as energy transfers through steel, so too does sound. Contrary to popular belief, cutting down trees actually helps the environment by storing carbon and enabling the regrowth of new trees that absorb more carbon. In short, wood is good.

  1. **Air leakage **. You can spend a fortune on Double glassed, Low E, thermally broken windows and wall insulation to have it negated by gaps between windows and wall frames or floor substraights.

Where can savings be made? Sealing such gaps with the appropriate sealers during construction can significantly increase the effectiveness of insulation and reduce draft/ambient temperature transfer. I’m not saying you should go to the site at the pre-internal lining stage with 10 silicone tubes and seal every window to the wall frames, as that could cause significant issues. You should research the proper sealant for the right area and consider having it professionally installed. FYI, my biggest concern with sealing around windows is settlement and, as a result, placing load on windows/doors and breaking glass by limiting the ability for movement. Everything must flex and have a tolerance allowed for movement over the lifespan of a building.

  1. Waste of time and resources : Errors with material over or under order, rectification during construction, delays and construction costs are critical factors for higher housing costs. Although designers and builders don’t publicise this, most, if not all, businesses add a contingency to projects to allow for error, which can be 10 to 15%. As a result, we are trading off more sustainable building methodologies and practices. In my opinion, all industry participants should be looking closer at implementing emerging technology that reduces error & increases the efficiency of project-specific design and construction. The building industry is one of the least efficient industries in the world. In many cases, the design and procurement of a non-standard home or building can cost 20 to 25% of the total construction cost.

Where can savings be made?

Halving the cost of pre-construction and increasing the ability to build without error, over-order, redesign, or modification onsite can free up financial resources to spend on more sustainable building methods and products. Easier to use and cost-effective 3D Virtual construction CAD technology enables the industry to reduce the cost of housing by significantly increasing the visibility of detail and selection, including solar orientation, sun and shading. Virtual construction aids designers, contractors & tradespeople in seeing a project and remedying costly errors caused by oversight or miscommunication. Moreover, Virtual construction software such as PlusDesignBuild will deliver an accurate bill of quantities that can be assigned to specific prices by specific suppliers/product manufacturers which aids the ability to send projects out for multiple bid requests and enables admin people to associate localised standards and specifications to orders.

  1. Virtual Value engineering

Designing or alteration of a design or its structure with the intent to deliver a similar or greater outcome in less time and at a lower cost. On every project I design and build, I always look for better ways to construct. In fact, I always look for better way to do everything, which can be very consuming or taxing as it keeps me awake most nights.

Where can savings be made?

The initial design must have sufficient detail to aid the process of Value Engineering. When traditional project delivery methods are used, this process can be costly, so the answer is to ensure your project is designed using Virtual Construction software. Why? Because virtual construction software adds the essential details right from design conception. Optimised and automated communication of design deliverables associated with traditional construction methodologies makes value engineering feasible and solutions more apparent. Even to the untrained eye.

Here are a few examples of value engineering a design

In my own house, I designed and installed a rudimentary mechanical ventilation system that transferred heat and cool to different zones of the home according to temperature; the goal was to deliver more desirable hotter or colder air to internal rooms with greater thermal storage properties, in this case, solid brick. Was it a success? Well, yes and no. The execution and quality of the componentry could have been better, and the data recording and analytics could have been more scientific. Yet, the initial findings were as expected: reduced power was required to run the home. One of the main things that skewed the result in my favour was unintended, but it was a great learning experience. First, a bit of background. I designed the house to make the most of the lower winter sun. The main structure on the northern wall (southern hemisphere) was made from recycled, heavy section bridge timbers in which we painstakingly recessed double-glassed, argon gas filled, Low E thermally broken glass, which was purchased from a demolition auction and sold/recycled due to scratches in the tint in its original installation of a commercial building in Sydney. At this stage, I needed more understanding of what reflective coatings did and how they worked, I wrongly assumed that the coasting reflected both ways and, as a result, randomly installed the glass. I continually admired the abundance of light streaming through the windows as winter arrived. I was amazed at the amount of heat being generated, so much so that it was as if there was some mistake or another heat source, as the results exceeded logical expectations. Low E coatings are made to be directional and reflect heat ( a mistake on a window receiving winter sun). When reversed, they amplify or magnify the sun’s energy to deliver energy in the form of heat. So, in short, if you get sun on the glass in winter when you need heat, turn the coating to face the inside. But be careful, as it gets scorching. Eg 15deg Celcius outside is 40deg Celcius inside.

More later…