What does it take to construct a more sustainable built environment? Although there is so much discussion about green construction and despite the carbon emissions targets set on building, at the urban or national level, there is always a concern that the construction sector is not sustainable enough! But what is it that prevents us from designing and constructing more sustainably? In my previous articles, I have gone through technical, behavioral and planning aspects which potentially function as barriers to having an overall more energy efficient construction sector. Cost is a very significant factor and appears to be a barrier to demanding and designing more energy efficient buildings on the perspectives of project clients and professionals. However, there is cause for more optimism in the cost of green construction.
From the perspective of LEED certification, which covers a holistic approach of sustainability, rather than merely energy efficiency, the achievement of targets can vary highly in terms of the cost required. For example, locating the building in a place with better public transportation connections as well as providing bike storage do not come at a significantly higher cost; nevertheless, they do result in carbon savings. In terms of energy efficiency specifically, there are options which do not necessarily increase costs, but can significantly contribute to energy savings. For example, installing light colored roofs and including green spaces in the design, can reduce overheating and hence the energy used for cooling in the summer. Similarly, water use for irrigation can be reduced through the use of plants which need less water, as well as through rainwater collection. Moreover, it is highlighted that, although water expenditures are currently generally low, the lack of resources might increase the cost of water in the future. Therefore, both in terms of energy and water use, the minor increase in capital cost might bring up considerable savings in terms of operational costs, especially if the cost of water and energy increase in the future.
Moreover, the Zero Carbon Hub analysis of the construction in the UK shows that the green buildings’ premium has reduced over time. This is because the delivery of energy efficient buildings is better understood. For example, the increased understanding of reducing thermal bridging and of the associated techniques, resulted in the reduction of these costs. Furthermore, some technologies that used to be innovative and hence expensive are becoming common and their cost is reduced, as it happened in the case of photovoltaics. At today’s prices, the typical additional cost of building a semi-detached house to the Zero Carbon Standard could be less than £5,000.
Furthermore, what is very important is the fact that this initially higher capital cost can result in very considerable savings in terms of the running costs of a household. New homes built to energy efficiency standards could be up to 57% cheaper to run compared to ‘improved’ Victorian homes of a similar size. Similarly, research in the BRE (Building Research Establishment) showed that the achievement of the lower BREEAM (Building Research Establishment Environmental Assessment Methodology) ratings incurs little or no capital cost. Even when higher energy ratings are targeted, the extra cost is usually no more than 2% and it can be paid back within two to five years due to utility savings.
A number of projects have been undertaken to look into the cost of retrofitting homes and the factors that can increase the cost of retrofitting. The main factors causing a cost variation are:
- Use of bespoke products: it typically requires better or specifically trained workforce; hence, not only the product cost, but also the installation costs are higher.
- Procuring products from far away (this is also less environmentally friendly due to embodied emissions)
- Use of poorly designed products incurring additional work and maintenance, also potentially related to poor energy performance
Consequently, avoiding the factors above can keep costs low. Some parameters that can enable the reduction of costs include good communication between project team members, as well as encouraging learning and increasing awareness of the supply chain. Finally, well organized construction and procurement can decrease construction costs. In fact, research by the Building Research Establishment (BRE) has demonstrated that when sustainability strategies are integrated early in the design and procurement processes they add little or nothing to the capital costs.
Promising recent projects have demonstrated that under certain circumstances, careful design and early integration of sustainability strategies can even achieve green construction at a lower cost compared to conventional ones. This is the case of the AIMC4 project, which looks to pioneer the low cost, low carbon homes of the future. The results showed that the cost of low carbon homes achieving energy level 4 of the Code of Sustainable Homes can be reduced by approximately 42% compared to a conventional construction.
Despite the challenges in reducing the cost of green construction, there are significant financial and environmental benefits that can be brought up through this change. The successful projects and examples described highlight that the achievement of green construction at no financial premium is actually feasible.
Image credit by Mattgrocoff via Wikimedia Commons.