Does Size Matter When Building Green?

31 May 2018
Posted by: Annabelle Numaguchi, Evolution and NZGBC Homestar Assessor
Time to read: 2 mins.

Does Size Matter...

When Building a High-Performance House?

 

What does a green home look like?

This is not a trick question like “What colour is the White House.”  Clearly, the term green home refers to a house that has sustainable elements, which includes a good thermal envelope.

So, what does an energy-efficient home look like?  There is no one answer. 

A thermally-efficient home does not come in a one-size-fits-all package.  An eco-friendly home can look like any other home; it simply performs better.  

Whilst the greenness of a home is determined by its performance, not its aesthetics, many eco-friendly homes do follow certain design principles.  

The sooner energy-efficiency is integrated into the building process, the better the outcome.  Many green homes follow the basic principles of optimal-size-to-occupant density, insulated thermal mass, good orientation and minimal wall-to-floor ratio. 

A good example of this last element is Evolution’s Show Home in Christchurch.  A rectangular shape is optimal for heat retention, which makes sense.  The less surface exposed to the outside elements, the slower the heat loss.

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The placement of the windows in this home is another ideal design feature that improves performance.  The majority of windows face north to maximize solar gain.  Conversely, the covered deck provides natural shading when the sun is high, which keeps the home from overheating in the summer.    

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Evolution Show Home at 15 Dove Grove, Westmorland Heights, Christchurch

Whilst there are definite guiding design principles, the question arises “Do energy-efficient homes have to look alike or come in a certain size?”  The answer is absolutely not.

There is no exact formula that dictates the shape or size of a home.  A home fulfils many needs for its owner, from comfort to investment, and the design needs to meet them in a balanced way.

For example, a tiny home requires less energy to operate, but may not provide adequate space for the needs of a family of four. 

It’s generally true that a larger home will require more resources to maintain an even, comfortable temperature, but these needs can and should be mitigated with higher specifications in the design and construction of the thermal envelope. 

A high-performance, 300m2-residence can be built to use less energy to heat and cool than a standard 200m2 home built to minimum code. 

Whilst there are simple, smaller designs that maximize efficiency, the size and floor plan of our homes are determined by factors outside of building science.  The desire to build a larger home can be motivated by a need to house multiple generations, to serve as a family legacy, for aesthetics or for entertainment purposes. 

No matter the size of the house, incorporating high performing methods and materials will benefit the outcome from whole-life cycle to occupant health to less drain on shared resources.

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Residence in Lakeside Estates, built by Evolution, a division of Rilean Construction

A good example of this balance is the residence we recently completed in Lakeside Estates, which includes Photovoltaic panels, triple-glazed windows, airtightness and Mechanical Heat Recovery Ventilation (MHRV).

In other words, well-built homes, whatever the size, last longer, are healthier to live in and cost less in money and impact to the environment.

Building an energy-efficient home starts at the design phase.  Whilst it should influence the design, it does not dictate the look of the house.

 

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