It so depends on what you mean. Do you mean 'lowest lifecycle embodied energy'? Do you mean 'Constructed from local and sustainable materials and skills'? Or 'Readily repurposed and long life-cycle'? Or something else entirely?

Normally, I would think of those three things specifically as 'Green Buildings', but there could be more.

I would approach the problem in 3 parts - make existing structures 'Greener', (because there is scads of existing infrastructure, and we've already spent that energy cost to put it there), make new structure 'Green' (far easier to start from scratch), and find ways to retain as much of the embodied energy of end-of-life structures as possible.

Making existing structures Greener means managing the interior environment better - often by changing ventilation, controlling air leaks, insulating, etc. The trouble, of course, is that after the fact, alterations are tricky at best, and hideously difficult at worst. So, I'd recommend the least invasive techniques in most cases. Mini-split AC and Heater units brings heat and cold to where you need them. Insulation (sprayed or applied as panels) to the inside or outside of the building (depending on the desired aesthetics) in a manner to control air leakage and condensation. Use natural light and ventilation wherever possible, and so on.

Making new Green buildings is straightforward. If you're somewhere cold, lots of glass facing the equator and insulation. If you're somewhere hot, lots of shade and ventilation. If you are using AC (eg, hot and humid), then insulate more than ventilate. Anywhere with temperature swings, you need thermal mass. Anywhere dry needs water storage, and anywhere wet can use the water to aid in heating and cooling. And so on. It's about maintaining a reasonable range of humidity and temperature inside the building envelope, while maintaining adequate ventilation, and preventing condensation where it can do damage.

Retaining the embodied energy incorporates Adaptive Management with Reuse. When designing in the first place, think about how the building is going to be dismantled, and how the parts are going to be reused, and how it will be repaired. Do not assume everything will be at the end-of-life at the same time - that never happens in the real world. Transition Engineering understands that everything being built today will get it's first major overhaul in a low-energy-intensity future - energy might be cheap and plentiful right now, but that won't be the case past 40 years from now, and almost all buildings will be designed with an expected lifespan that is twice that or more. So, if energy will be hard to come by, then exactly when we need to keep the embodied energy we have in the buildings, we will be hardest pressed to find high-embodied energy parts. So you have to design the buildings so their elements can be replaced using low-embodied energy alternatives, relatively easily. And that the buildings can be dismantled and high-embodied-energy parts reused at the time of decommissioning.

Nothing to it....

Really ,it is a wonderful discussion ,Douglas Nuttall.

I mean that what steps could be done to make my house or offices satisfying the requirements of sustainability as possible.Also, if my specialization is civil eng.,mechanical eng. ,medicine,etc,can I find a connection or link with sustainability?

Best Regards

Qasim

Ah, that's a different kettle of fish, I think.

Lets start with the definition of Sustainability, from an engineering perspective. We can expand it later if we need to.

We have a description of what Sustainable Development is, provided by the Brundtland Report. We also know what economists mean by Development, so we can work out what they would mean by Sustainability. But we know that engineers will need to have a definition that can direct us to the units of measurement, since we all know that if we can't measure it, we can't design for it.

So, I think Sustainability is the ability of a community to be able to meet all of the needs of all of it's population in 24h/d/ca or less, using only the resources and ecological services from the land that it manages and the skills of the people, in perpetuity.

Said like that, buildings, businesses, projects, processes, and people are too ephemeral to be Sustainable in and of itself. But they can contribute to the Sustainability of the community, by actively working to help the community achieve it's goals.

So that starts with the community goals. What needs that the community have identified can your speciality help meet more efficiently (typical for engineers) or effectively (typical for Human Development professions, like education and health care)? You can't start without the community describing what it thinks it's needs are, and what the symptoms would be of unmet needs.

Human Development people would focus on identifying and removing the obstructions within the self, family, or community that prevent people from being able to meet their needs, and thus increase the freedoms, choices, and capabilities of the population.

Technological Development people would focus on creating or enhancing systems of infrastructure (be that built, green, or otherwise) with the intent of producing a return on their investment of time and resources in the form of time and/or resources into the future, and in so doing, increase the efficiency by which people are able to use their time to convert resources into the means to meet their needs.

So, in your case, the home may be perceived by your community as meeting a need (perhaps of Homeostasis, perhaps of Respect of One's Peers, perhaps something else). The symptom of unmet needs related to housing may be the lack of the availability of an specific area where the internal air temperature and dewpoint can be maintained within a specific range. So then your role could then be to ensure that the people in the community that don't have sufficient area within the building that the target conditions are able to be housed, while ensuring that the resources and ecological services being used by the community can be available in perpetuity.

Every profession would have a different role. Every community would have different definitions, different resources, different symptoms of unmet needs, etc. There will never be a one-size-fits-all solution.