Net-Zero-Ready Home in New Zealand

It’s the little things that add up. There is no truer statement to be said for a net-zero-ready home, where all the small, and big, details add up to create a high-performance building.

Net-zero is not a new concept; its roots go back decades. However, the net-zero concept has gained steam in recent years. This interest is driven partially by more stringent energy building codes and partially by environmentally conscious consumers.

Before we delve further, here is a common definition of Net-Zero as it pertains to buildings per the Merriam Webster dictionary, “producing enough energy … to offset any energy consumed.” [i] Net-Zero also goes by the monikers of Zero Energy Building or Zero Net Energy.

So, how do you get to net-zero?

The path to net zero is different for every project and can be very complex. In an effort to keep this explanation simple, we will focus on a few steps that are commonly contemplated during the design and construction of net-zero buildings.

First off, let’s start with the building’s orientation on the property. The best placement is one that takes advantage of the land’s natural attributes. For example, leveraging natural breezes and incorporating areas of cross ventilation within the home can save on mechanical cooling costs. Incorporating design elements that can take advantage of the sun’s path over the course of the year is another way. One way to do this is to incorporate south-facing glazing under a deep overhang. This will allow the home to gain warmth during winter months when the sun is lower on the horizon while staying cooler during the summer.

The path to net-zero continues during construction with the air tightness of the building envelope a primary concern. The best analogy we have heard about this is from architect Vicki Yuan of Lake|Flato Architects who credits a trusted mechanical engineer for the concept. Yuan says, “’You want to think about your building like a human body: You want to breathe through your nose or your mouth—not through your skin.’” [ii] In other words, eliminate air leaks through the walls and roof, or skin, of the building.

Once the building’s orientation is set and the building envelope is as air tight as possible, you can then focus on elements like glazing, the HVAC system, and other areas to improve energy efficiency of the home.

Design of the Mosgiel Residence

Located in New Zealand, the 142 m² (1,528 square foot) Mosgiel Residence incorporates net-zero principles into its design and construction. This net-zero-ready home is designed to be ultra-efficient, with the goal of being net-zero in the future.

To start, the home’s orientation takes advantage of the site’s westerly winds while limited glazing on the southern exposure. Both of these design elements keep the home cooler during the hotter months.

Next, the building envelope fully encompasses the home. It starts with expanded polystyrene insulation (EPS) under the concrete slab. Then, the home uses the Insulspan® Structural Insulated Panel (SIP) building system with 6-½” panels on the exterior walls and 8-¼” panels on the roof. It also includes 8-¼” panels for the floor decking and 4-½” panels for the interior walls. When the benefits of the panels, sealant used during installation, and high expansion foam to fill any joints combine, the air tightness of the Mosgiel’s Residence building envelope is phenomenal.

To help meet the goal of net-zero, careful attention was also paid to the home’s windows and doors. Most of the windows and doors are set under deep eaves and overhangs to provide natural shading. In addition, the windows are triple-glazed while the sliding doors are double-glazed. This added glazing helps to mitigate the natural heat transference that occurs through glass.

The home features a high-performance HVAC system by Mitsubishi, which includes an air exchanger. The air exchanger brings in fresh air and exhausts stale air from the home. Other high-performance items in the home include Bosch appliances and water saving toilets.

The Final Results

As a result of incorporating net-zero principles into the design and construction of the home, the Mosgiel Residence has realized an 84% savings in monthly power costs when compared to a typical New Zealand home of this size and is net-zero-ready should the owner decide to go to the next level. And, that’s money you can take to the bank.

Learn more about how you can get to net-zero with SIPs. Starting a net-zero project? Request a quote today.

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Resources

[i] net-zero, https://www.merriam-webster.com/dictionary/net-zero

[ii] How to Design a Net-Zero Home: Net-zero-energy buildings are key in a path to a greener future, by where does an architect begin? AD PRO breaks down the process, https://www.architecturaldigest.com/story/how-to-design-a-net-zero-home

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