zero net energy (zne) 2020/ 2030-the future of building design and construction

​Are you prepared for the future of building design and construction? Ready or not, here it comes. Starting in the year 2020:

• All new residential construction (single-family and low-rise multi-family) in California will be required by code to be zero-net energy (ZNE) and include photovoltaic solar panels
• All new commercial construction in California will be required by code to be zero-net energy (ZNE) by 2030
• 50% of existing commercial buildings in California will be required by code to be retrofitted to ZNE by 2030

WHAT DOES ZERO-NET ENERGY (ZNE) MEAN AND HOW WILL IT IMPACT THE FUTURE OF BUILDING CONSTRUCTION?
Currently, residential and commercial buildings attribute to the consumption of approximately forty-percent of the total energy consumed in the United States. The strategic plan in California will endeavor to mitigate this issue by requiring the new construction of residential buildings to be ZNE by 2020, and commercial buildings by 2030.
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A ZNE building translates to the total amount of energy consumed by the building on an annual basis being offset by the creation of an equal amount of on-site renewable energy, resulting in a zero-net. So, what does that really mean? The daily building operations require the consumption of energy (currently, predominately in the form of fossil fuels). These building operations are commonly related to building systems, such as mechanical systems (heating, ventilating and cooling), electrical systems (lighting, equipment, appliances, etc.), plumbing (water heating). So how do we offset this required energy consumption in the form of on-site renewable energy production, and what are the forms or solutions for producing on-site renewable energy? Before we touch on that subject, let’s focus first on an even more predominant subject. Why not first significantly reduce the amount of energy required by a building. YES! Of course. This raises the concept of the three-tier approach to building design.

​THE THREE-TIER APPROACH
1. TIER 1-BASIC BUILDING DESIGN TECHNIQUES
​Some simple, thoughtful and conscious building design concepts can contribute to a very significant effect on the reduction of building energy consumption. The main concepts are heat retention, heat rejection and heat avoidance. Basically, the goal is to keep building occupants in the thermal comfort zone, so we seek strategies that retain heat when conditions fall below the comfort zone, reject and avoid heat when the conditions rise above the comfort zone How do we employ these concepts with basic building design techniques? The answer is often more rudimentary than one may believe. 

Chart courtesy of Climate Consultant, developed by the University of California Los Angeles, Energy Design Tools Group, Copyright © 2016 The Regents of the University of California

Shown above is an annual temperature range chart for San Francisco. The horizontal grey band represents the comfort zone. As we can see from this chart, in San Francisco we are mainly concerned with the concept of heat retention. 

• Site Analysis and Building Orientation

An analysis of the existing site and climate conditions, including reviewing prevailing wind conditions, as well as strategic building orientation, including glazing orientation will potentially contribute to a sizeable amount of building energy reduction and thermal comfort.

• Building Form

Basic building form, based on existing site climate conditions will have a significant impact on the thermal comfort demand and reduction.

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• Superinsulated walls, roof and floors

It was not that long ago that many buildings were built without any wall insulation. We have since learned and there are now codes governing minimum insulation requirements. However, we can exceed the code requirements by providing increased insulation R-values in walls, floors, ceilings and roofs, effectively significantly reducing heating or cooling demands.

• Building Envelope Colors

Even a concept as basic as exterior (or interior) color(s) can play a significant role in energy consumption or reduction. Dark colored building cladding or roofing will absorb more solar energy, which may be beneficial when we seek to retain heat, can be a significant disadvantage when we seek to reject or avoid heat.
 
These are just a few basic impactful basic design strategies to consider. There are many others, including vegetated roofs. These are just a few basic strategies.

2. TIER 2-PASSIVE STRATEGIES  
Similar to basic design techniques, passive strategies engage manageable design components that can greatly alter building energy consumption. Some principle concepts are:

• Daylighting

If we increase the amount of natural light (directly or indirectly) into a building, we can significantly reduce the amount of artificial light required and also provide benefits to building occupants, in the form of health and mood benefits. But wait. If we increase the amount of sunlight into a building, we will also increase the need for cooling. This is not necessarily the case, along as we employ thoughtful and conscious design decisions. How? Well, back to tier one-proper glazing location, orientation and size. This is also where a sun chart is becomes a valuable tool. We can allow for direct natural light when we desire direct natural light (heat retention) or we can allow for indirect or filtered natural light to gain the benefits of natural light, but exclude the heat gain. How? With proper analysis of sun chart and site conditions, we can properly design elements such as roof overhangs, fins, clerestories, light shelves, louvers, etc.

• Winter Solar Heat Gain

We can include elements that harness the benefits of direct solar heat gain in winter months, when heat retention is desired to achieve remaining in the comfort zone. Such elements include a trombe wall, thermal mass elements, sun room or space, etc.

• Passive Cooling Techniques

We can employ passive cooling techniques such as night-flushing, passive radiant cooling, evaporative cooling and earth cooling to reduce or even eliminate the need for mechanical cooling energy demands.

3. TIER 3-ACTIVE STRATEGIES/ MECHANICAL EQUIPMENT 
As shown on the psychrometric chart, in a location such as San Francisco, tiers one and two can attribute to approximately seventy percent comfort hours. At the time we reach tier three, we would only need to focus on the remaining thirty percent. So how do we account for this remaining thirty-percent?

Chart courtesy of Climate Consultant, developed by the University of California Los Angeles, Energy Design Tools Group, Copyright © 2016 The Regents of the University of California

• Photovoltaic solar panels

Starting in 2020, all new low-rise residential buildings will be mandated to include solar panels. When we think of photovoltaic panels, we often think of the ubiquitous roof mounted arrays. However, there are also building-integrated photovoltaics (BIPV). These type of integrated systems can replace traditional roofing, cladding, glazing or canopies.

• Geo-Exchange Heat Pump

In very simple terms, heat pumps move heat from the building interior to the ground in summer months and in winter months from the ground to the building interior. These are typically open loop or closed loop systems.

• Wind turbines
• Biomass Energy
• Hydroelectric Energy

Chart courtesy of Climate Consultant, developed by the University of California Los Angeles, Energy Design Tools Group, Copyright © 2016 The Regents of the University of California

Ultimately, there is a view of ZNE as a negative connotation. These buildings will sacrifice budget, sacrifice function and aesthetics or project objectives and requirements. In contrast, we have the opportunity to design and build buildings and infrastructure that not only improve quality of life for occupants, but are also sustainable, that are not viewed as “downgrades”, for the sacrifice of sustainability, but as desirable “upgrades”, without sacrificing budget, function, aesthetics and actually increasing occupant comfort. We can design and build buildings that are ecologically beneficial, sustainable, harmonious and alluring ecosystems.
 
Ready or not here it comes 2020.

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