Day 6: Net Zero Energy

RNL’s NREL RSF redefined the potential for achieving net zero energy (NZE) status in a commercial office building. Located in Golden, CO and completed in 2010, phase I was the largest office building in the nation to achieve net zero energy status.

The RSF is a 222,000 square foot Federal office building that is designed to be one of the largest net-zero energy buildings of its kind.

The RSF is a 222,000 square foot Federal office building that is designed to be one of the largest net-zero energy buildings of its kind.

Since the RSF we have been quietly building up our portfolio of next generation net zero energy buildings, and are currently working on two that have the potential for making waves in their respective building types. So stay tuned… While we can’t disclose the details of the projects, we can talk about the details of the process. 

Know your Numbers

In theory, any project can reach net zero energy if you buy enough photovoltaics (PV) and find somewhere on the site to put them. Is that the right way to approach it? Absolutely not. Besides, we have yet to find that unicorn of a project with an unlimited budget for on-site renewables. Instead, the key to NZE projects is reducing your energy use as much as possible first, and then making up the difference with on-site renewables. This math game requires knowing your numbers from the very start – the energy use intensity (EUI) of your design as soon as that first Sketch Up or Revit model is made, the amount of PV you will likely be able to fit on the site (and in the budget), and the EUI that you’ll need to hit to make the net zero energy equation work – and checking back in on those numbers regularly. 


While we have energy modeling consultants on most of our projects, it is important for the design team to also know not only the EUI of their design, but also how each component of the design impacts the EUI, where the biggest bang for your buck is in terms of lowering the EUI, and how even the smallest design decision impacts that number.This is especially important during the concept and schematic design phases when the bigger design moves are being made, sometimes in a matter of minutes during a charrette, and where energy consultants may not have started modeling yet. This is where our in-house energy modeling tools come in.

It’s important to know how even the smallest design decision impacts the EUI.

Have Cloud-Based Software, Will Travel (and Design)

The era of plug-ins and cloud-based software has made in-house conceptual energy modeling seamless with the design effort, and portable when traveling to client presentations or project meetings outside of the office; two key innovations. So far we have used Light Stanza, Sefaira and Fenestra Pro to get an early assessment of EUI, daylighting potential, and façade design in our projects.  The promise of every single member of the project team working off of one BIM model is still a ways out from being realized. And that’s fine. For now these software programs allow us, the architects, to know our numbers early on, update them quickly on the fly, and make more educated decisions on the drawing board. 



This case study of the LEED Platinum, Iowa Utilities Board and Office of Consumer Advocate office building, is interesting not only for its high-performance features, but also for discussion of plug loads and glare. Why are these important? As envelopes become higher-performing, and HVAC systems highly efficient, plug loads are becoming a larger piece of the energy pie of a typical building. Where we can design in efficiencies in lighting, envelope, HVAC, water, plug loads really come down to occupant behavior. The electrical engineers can add occupancy-sensor type controls to plug strips and so on, but at the end of the day this significant energy end use is determined by human behavior and dialogue and education from the beginning is key to meeting the energy goals of the building.

“The reason we exceeded our goal is because the occupants got what we were trying to do from the top down…”

“To include everyone in the decision-making process, each section chose an employee to represent them at pre-occu­pancy meetings, which identified strate­gies to reduce loads.”

The result? Modeled plug loads (including data center and fire and security related loads) were 14.5 kBtu/ft2.yr. Actual plug loads from 2014 were just 5.1 kBtu/ft2.yr. But,

The daylight design is also interesting with 95% of regularly occupied spaces daylit. Although there were some teething troubles:

“I characterize our (former) office as ‘a cave down by the river,’” Cooper said. “We had 11 windows in that whole building, and we went from the ‘cave’ and moved in here in January of 2011 when the ground was covered with snow and the sun was low in the sky. We weren’t used to any daylight, and now we had some glare.”

Glare is one of the harder daylight aspects to model, but also the most debilitating if not addressed. Our lighting team is pushing boundaries with the LEED v4 modeling they are carrying out in Light Stanza, so be sure to ask Colin and Shawn about the glare potential in your project. We never want to submit one of our buildings to an architectural journal with the words ‘Accommodations were made as needed’ to describe the post-occupancy cover ups needed!

photo credit: Assassi

photo credit: Assassi


Architect Todd Fix wanted to create a net zero energy passive house that didn’t look like your typical passive house (small windows, thick walls). Mission accomplished.

This is a house for those who are invested in moving parts. Really invested, at $2.5-5mil for construction costs alone.

I question the claim ‘Being in an all-glass house also dramatically cuts the amount of electricity needed’ when you consider peak winter and summer temperatures. But all is forgiven by this feature “Underneath the house, a "microclimate pool" cools the house by evaporation. If the house is built on the beach, it will have a custom slide inside that leads directly down to the sand.” If I had $5mil to spend on a house, then hell yes it would be built on a beach. 

image courtesy of

image courtesy of


A modular, sculptural approach to shade structures. Elegant and simple yet highly functional – Shade! PVs! Directional Breezes! Let’s hope the solar geometry math was right and they work. Phoenix is not a city you want to mess around with when it comes to shade. My one question is if there is a lot of reflection (and glare) off the metal? Field trip the Phoenix office…

photo credit: Matt Winquist

photo credit: Matt Winquist


We all have our own personal sore points with the LEED rating system, but for some reason the bike rack credit seems to be one of the more highly divisive. Why all the hate for bike racks? This post does a great job of reminding us that LEED is about more than just building energy use. 

“The energy content of the gasoline used by the typical office commuter each year is comparable to the energy used by his or her share of the building where he or she works.”

photo credit: Todd Dwyer

photo credit: Todd Dwyer


This article talks about how lessons learned from the one-off net zero energy buildings of today can be applied to creating the net zero energy cities of tomorrow. Interestingly it uses NREL as a case study:

 ‘For NREL, the architects transitioned to “masters of collaboration,” synthesizing and corralling information from a web of experts—engineers, builders, and various consultants.’

Well-deserved praise. And a good reminder of the key to delivering projects of the calibre of the RSF – integrated design teams. It would have been nice if the author had actually mentioned RNLs name at any point in the article… Rest assured as soon as I cast eyes on the article it was retweeted, tagged and hashtagged before you could say ‘master who?’


‘Imperative 11, Red List, within the Living Building Challenge requires that manufacturers disclose the ingredients in their products to ensure that they are free of Red List chemicals and materials. Declare supports the Living Building Challenge by providing a transparent materials database that project teams can select from to meet Imperative 11'

Declare is a searchable database of products that do not contain any Living Future Red List Materials. This is a valuable resource for our WELL projects that are under the same material ingredient requirements.

Clicking on the product database, and filtering for CO, shows there are no products with final assembly in CO that are free of Red List materials, but CA has 9. We have the power to change that! Many of the manufacturers in the Declare database are there because they re-examined their ingredients and formulated a healthier product so it could be used on a specific LBC project. The web site has a template form that can be sent to manufacturers explaining the need to declare/disclose their ingredients and remove known carcinogens

National Renewable Energy Laboratory | RNL Design

National Renewable Energy Laboratory | RNL Design

Mirror, Pods, and Printed Panels...Not Your Grandma's PV Panels

For a while developments in solar panel costs have been getting all the attention, but recently innovations in solar panel applications are getting their time in the...sun. This article describes three different applications: 

photo courtesy of Ripasso Energy

photo courtesy of Ripasso Energy

1000 sqft solar mirrors that generate enough energy per year to power 24 homes, but require much less land (and no water!) compared to conventional concentrated solar systems.

A system designed to generate continuous solar energy, day and night, rain or shine, by connecting 4 - 8 PV panels to a 6'x8' 'Power Pod' that contains a turbine generator

Printable, flexible, organic PV panels ranging in size from the back of a smartphone to a large window - these have been in development for years but are only now becoming commercially


photo credit: Wai Ming Ng

photo credit: Wai Ming Ng

Another innovative use of PVs. It's a contemporary stained glass window, energy source, and phone/tablet charging station all in one. 


Still on the topic of community-scale issues: With the goal of making solar more accessible to a wider range of US communities, including low-income households and people who rent rather than own, the White House announced a new initiative to ramp up community solar projects across America, and install 300 MW of renewables in federally subsidized housing developments by 2020. When would we consider community solar? In multi-family housing projects where the budget, or the building design, doesn't support on-site PV but partnering with a 3rd party to provide residents with a community-based PV system makes a good business case (selling point).

performance-based design

Back again to the new Cornell Campus on Roosevelt Island… This time an interesting interview with the key players from Morphosis, Arup and Cornell University on the performance-based design approach on the net-zero energy Bloomberg Center.

From the beginning, we knew that we had to tackle the PV surface area issue. PVs are becoming more efficient, but they’re reaching an efficiency plateau, so we have to deal with the horizontal surface. That translated into a building that had a particular form, a certain type of massing. In lieu of having a tower, it required a form factor that is lower and broader. That also allowed us to create a walking building, which reduces the number of elevators, which further reduces energy consumption. It gives the opportunity to lay down a larger field of PV solar panels. It’s all integrated. The PV canopy, in many ways, defines the building identity and the overall masterplan.

photo courtesy of Cornell University

photo courtesy of Cornell University