Sustainable design

So you want to build an ecological home?
There’s a good deal more to it than installing solar panels, geo-thermal cooling systems and energy-efficient appliances.

To build a truly sustainable home, one has to start with a sustainable design.

Sustainable designs certainly incorporate renewable energy technologies and minimize the use of fossil fuels, but these are only one part of a much bigger picture.

A sustainable design aims to work with the natural elements and conditions first and foremost, to create the right conditions in which high-tech, low-energy appliances and systems can work optimally.

Beyond energy efficiency, “green” designs also take into account the sustainability of materials and finishes, the overall durability of construction and the longevity of the design for the future residents.

Passive cooling

In a hot and humid climate like Cayman, where utility costs are high, keeping interiors cool for less is top on most people’s list of priorities.

Reducing the energy needed to keep the hot air out and the cold air in is therefore one of the most important aspects of an ecological home.

A sustainable design aims to do this first of all by passive means, explains James Whittaker, CEO of NEXT Development & Design, a design-manage-build firm creating energy-efficient homes in Cayman.

This means examining the paths and patterns of sun and wind and using them to the home’s advantage, before even considering mechanical systems.

“We look at the sun and how it sits with the orientation of the land and we look at the wind flow and direction,” says James.

“Where you have big windows framing a picturesque view, you want to avoid the sun shining in through those windows, so you put in large overhangs and porches.”

At the eastern and western ends of a house, where the low angle of the rising and setting sun makes overhangs redundant, the landscaping is designed so that trees and vegetation will passively shade these areas.

Wind flow and direction are also analyzed, he adds, to determine how breezes will enter, circulate through, and exit a building, helping to cool interiors when air-conditioning systems are turned off. Orientating the house so that the long sides face into the prevailing wind maximizes their cooling effect.

“If you can use the design to passively cool a house, you have created something that is already energy efficient,” James says.

Before air-conditioning was available in Cayman, homes were designed along these principles for generations, he points out, so, in some respects, it is a return to traditional ways.

But these time-tested methods can now be enhanced with new materials and technologies: by building with Insulated Concrete Forms, hurricane-rated, insulated windows and spray foam, it is possible to create an airtight, well-insulated envelope that adds to the passive cooling abilities of the design.

Water efficiency
Rainwater harvesting is another area in which traditional practices are being revived. A growing number of new developments are being designed with rainfall catchment and storage systems to reduce their need for city water. While it is not considered safe to drink, rainwater can be used to flush toilets and water gardens.

At Camana Bay’s 18 Forum Lane this concept has been scaled up to a 50,000-gallon cistern, which has dramatically improved water efficiency.

Landscape designs that make use of endemic, drought-tolerant plants can further reduce water consumption. Choosing trees and shrubs that are readily available locally and that are well adapted to the climate, and positioning them in such a way that they will shade a building, are also essential aspects of a sustainable design (see page 124).

Creating a well-insulated, energy- and water-efficient framework lays the essential groundwork for a sustainable home. Once this is in place, one can add a range of energy-efficient mechanical and technical systems, from geo-thermal cooling to solar panels, LED lighting, WaterSense-rated bathroom fittings and Energy Star rated appliances.

“The mechanical systems that are available are not the foundation of a sustainable design: they are the icing on the cake,” James explains.

“Eighty percent of the battle to create an energy efficient home is in the design itself.

“Take your average 3,000-square-foot home as an example,” he says. “Your CUC bill might be around $800 per month, but if that house had been designed sustainably, the utility bills could come down to as low as $200 per month.

“If you then look at installing a solar system to cover that energy demand, you’re looking at a much smaller solar array which is far more affordable and relatively easy to install.”

Computer modeling

Although much of sustainable design is grounded in common sense, computer software now makes it possible to maximise the benefits.

Design Cayman, for example, uses sun-path diagrams to map the movement of the sun over a development throughout the day, and throughout the year.

By predicting where the shadows will fall and where there will be more heat gain, they can calculate where additional insulation or shading will be required.

NEXT Design & Development uses energy modeling to calculate exactly how energy-efficient a home will be, how much CUC bills will come to, and what steps will need to be taken to reach net zero – the point where no utility bills are generated.

By entering certain variables it is possible to accurately predict how much insulation is needed and which air-conditioning units represent best value for money, before the home is built.

Future-proofing

Sustainability encompasses durability, and a sustainable house should be built to last. That doesn’t only mean that it should be able to withstand hurricanes and flooding, and make use of materials that will not degrade over time, but that it should be designed with longevity in mind.

“When we design a sustainable home, we spend hours with the family who will be living in it to understand their lifestyle, their needs and how these might change over time, so that we can future-proof it and create a home they will live in forever,” James explains.

Although the use of renewable energy and low-consumption appliances has been steadily increasing in Cayman in the past few years, the concept of designing-in sustainability from the earliest stages is still a relatively new one.

It’s a more holistic approach than traditional design, taking into account lifestyle, the health of the home, the impact on the environment and more.

By considering all the factors – environmental, economic, and social – that add up to sustainability, a green design results in more than an energy-efficient house. It results in a comfortable, livable, long-term home. 

 

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