The NexusHaus: Big Problems, One Bold Solution

The future of Austin might lie inside a granny flat. 

A team of students at the University of Texas is collaborating with the City of Austin and the Technical University of Munich in Germany to fix four of Austin’s biggest problems – low access to local food, high energy demands, strained water resources, and a lack of urban density – all with one very tiny house. 

Details of the project were revealed in February during UT’s Energy Week, a five-day examination of the latest research findings, emerging trends and new technologies in the world of energy.  The project has been dubbed the NexusHaus, for its ability to merge solutions to several of Austin’s problems into one building. The NexusHaus is a 850 square foot, solar-powered house that will be showcased at the U.S. Department of Energy Solar Decathlon in October so that it can compete against 20 other collegiate teams in this prestigious design competition.

However, the NexusHaus team wants to take it one step further. They are designing the entire house with Austin in mind, so that after the competition, it can be returned the city and used as a model for future environmentally sustainable design. They actually want someone to live in this house, and then they want to the house to be replicated and sold at an affordable price so that it can be utilized all across Austin.

“The idea is to increase density and growth in Austin, while keeping it sustainable and minimally impactful on local resources, both water and energy,” said Charles Upshaw, co-captain and project engineer of the NexusHaus project. 

Of course, the NexusHaus is no silver bullet, and it is still in its early phases, but the ideas that it puts forth are exciting. Austin is going to have some big issues to tackle over the next few years and if it wants to prevent the mistakes that have hurt other cities, while maintaining the character that makes Austin so great, it will need to think up some big, bold, and new ideas. The NexusHaus is a good place to start that creative thinking.


The Problem: Lack of density within city limits and a limited housing supply.

If you live in Austin, you don’t need to be told that the city is growing fast. You can see it each and everyday, when you look up at the construction cranes that have taken over downtown or find yourself trapped in a long line of traffic on MoPac. Austin has lead the nation in population growth over the past four years, pushing 110 people and 70 cars into the city per day. The decade ending in 2010 saw a 37% increase in population, according to the Austin Chamber of Commerce, and more and more people seem to moving here each day.

All of these new people have to live somewhere, and as they continue to pour in, they typically have one of two choices to make – they can choose to live on the outskirts of the city (which contributes to urban sprawl) or they can find a place in the city center (driving up rents and pushing longtime Ausitnites out of their homes, which in turn, contributes to urban sprawl). In fact, according to a 2009 research study, housing costs have risen by more than 85 percent in Austin since 1999, precisely because of the confluence of these two problems – too many people moving into the city and not enough affordable housing to accommodate them. 


The Solution:

The members of the NexusHaus team don’t think that it has to be this way. In fact, they are designing the micro house precisely with east Austin in mind, where they see the problems associated with a population boom and a limited housing supply most acutely. 

 “Lower income families that are looking to stay in their homes might be able to add one of these [NexusHaus units] and rent it out, and the rented income might be able to cover the cost of increases in their property taxes,” Upshaw said.

The goal of NexusHaus is not just to increase density, but to do so within the context of Austin’s existing neighborhoods. It’s a goal that is supported by an existing partnership between the Austin Community Design & Development Center (ACDDC) and the Center for Sustainable Development at UT, called the Alley Flat Initiative. The idea is that by utilizing the more than 40,000 lots that by city code are large enough to legally accommodate a granny flat/alley flat/accessory dwelling unit, density could be increased without completely destroying existing neighborhoods, while at the same time, providing an additional revenue stream for residents struggling to stay in their homes because of rising property taxes.

“It would be a way to increase density in neighborhoods without just scraping houses and putting up condos,” Upshaw said. 


Problem: High energy demand and a desire to reduce greenhouse gas emissions from power generation.

Texans use a lot of energy, especially during summer afternoons. That’s when everyone gets home from work, turns up the AC, and cooks dinner. In the utility industry, this phenomenon creates something called peak load. In order to ensure reliability, utilities must build enough power plants to meet electricity demand at its highest possible level, despite the fact that peak load only lasts for a few hours or less a day, during just a few months of the year. 

The way that utilities have traditionally met this demand is through “peaker” plants that can turn on and off quickly and supply energy only as needed. In Austin, our peaker plant is the Decker natural-gas fired power plant located on the east side of the city. It is also the city’s oldest power plant and is pretty inefficient. Austin Energy staff are currently working on a plan to replace Decker with a new, highly efficient natural gas-fired power plant to serve as the utility’s new peaker. Like all things related to natural gas, the new plan is of course, controversial, especially amongst the city’s environmental community. They claim that the plant will be too expensive, use up too much of the region’s precious water resources, and damage Austin’s greenhouse emission reduction goals. The fight against the new natural gas plant has turned intense, but the utility seems pretty intent on seeing that it gets built. A viability study is planned for the spring. 



Regardless of what comes out of the fight over Austin Energy’s new natural gas plant, the NexusHaus could help. Equipped with its own solar array, and designed to hit its maximum production levels during peak load hours, the NexusHaus could provide some much needed relief to the grid. Here is how it would work – Solar is already pretty well equipped to help offset peak load demand. During the summer months when Texans are kicking their ACs into overdrive, the sun is usually shining, making solar a great electricity resource during this crucial time. If the NexusHaus becomes widespread throughout Austin (as its creators envision), then its collective mass of solar power could significantly help to reduce demand on the grid from electricity (demand that is met by burning additional fossil fuels). 

But that’s not all. NexusHaus takes this concept one step further with an integrated rainwater thermal storage system that shifts cooling to off-peak hours. This helps to reduce energy consumption by about 80 percent during peak hours, potentially allowing excess power to be fed back onto the grid.


Problem: Drought and a dwindling water supply.

It’s no secret that central Texas is in a drought. Last month, the Lower Colorado River Authority, which manages the region’s water supplies, announced that Austin’s current drought is the worst its been since the Highland Lakes were constructed, almost 100 years ago. The Highland Lakes (which includes Lake Travis and Buchanan) are the primary water source for the city of Austin and they are 36 percent full.

What’s worse, despite fairly successful conservation efforts, the situation is not getting much better, because of what those in the water world call, inflows. Simply put, inflows are the amount of water flowing or feeding into the Highland Lakes. These inflows come from the Colorado River, and according to Robert Stefani, head of the auxiliary water program with the City of Austin, the river is “basically dead.”

At UT’s Energy Week Conference, Stefani explained that the Colorado River is essentially Austin’s only source of water, which means that we are tied to the health of the river, and unfortunately, the health of the river is not looking good. 

The city’s water utility, Austin Water, has some pretty startling statistics on this. Of the top 10 lowest inflows in the history of the lakes, five of them have occurred in the last eight years (2006, 2008, 2014, 2013, 2011). And these inflows aren’t just coming up a little short. In 2011, which was the lowest year for inflows ever, inflows only totaled about 10 percent of what they normally do. That's 90 percent short. 

So what is the City of Austin doing about this? Over the past 20 years, the city has tried out a variety of different water conservation efforts, all of which have been pretty successful. Austin’s per capita water use has dropped by 22 percent since 2006, according to Austin Water, and even though Austin’s population has grown since then, overall water use has not. This is really, really good news, but as Stefani explained at UT Energy Week, in light of the current situation, it just isn’t enough. It is time to go after more innovative and untapped sources of water conservation.


Austin Water is now venturing into uncharted territory with its conservation efforts. “People don’t know what to do with conservation once you give out 100,000 [low flow] shower heads,” Stefani said, “because nobody ever thought you’d give out 100,000 shower heads.”

But these ideas have already been exhausted, and the city is looking toward bigger and better options. One thing they have already done is code reform, which sounds boring, but could actually hold the key to a lot of untapped potential. Austin now has one of the most progressive plumbing codes in the country, Stefani said, because it allows for all kinds of greywater and rainwater reuse. 

This includes collecting rainwater for actual residential drinking water use, which became legal last year, but has not yet been done within city limits. NexusHaus would change that. The NexusHaus design includes an innovate rainwater catchment system that can serve as a mini reservoir to help reduce flooding during heavy rainfall, and also be treated onsite to be used for drinking water. Once built, this will be the first residential potable rainwater system (new construction) in the city of Austin, providing a valuable model to other developers and homeowners as to how this can be done.

“The house itself provides the City of Austin a model for advanced conservation,” Stefani said. “It provides a platform, or a template, for what can and can’t be done.” 

Stefani continued on to say that the city needs early adopters like the NexusHaus to provide a valuable proof of concept to the community and show that innovate water conservation efforts are possible. If all goes as planned with the NexusHaus, it will use 50 percent less potable water than the average home. In these drought-stressed times, a savings like that could be huge.


Problem: Limited access to local food and inequality in our region’s food system.

Austin is home to a $4 billion a year food economy, the headquarters of one the nation’s largest grocery stores, and a serious food insecurity problem. According to a City of Austin report, 25 percent of children in Travis County are food insecure, which means that they lack consistent access to a food supply. So even as celebrity chefs open new restaurants on every street in town, regular Austinites find themselves without access to a healthy meal, or even a meal at all. This dichotomy is an important thing to think about when exploring the city’s food systems, explained Edwin Marty, the City of Austin’s food policy manager, during a panel discussion at UT’s Energy Week.

“Not only can you get any kind of food in Austin, you can get any kind of food infused with any other kind of food… but it’s important to recognize that not everybody in our community is benefiting from our food system,” Marty said.

Another problem with the system is its effect on the environment. Worldwide, agriculture accounts for 80 percent of fresh water use and is also a major contributor to global warming. According to the EPA, agriculture accounts for a full 10 percent of the country’s greenhouse gas emissions. Austin can help to negate these interlocking problems of inequality and environmental degradation, Marty said, but only if it has control over its own food system. Right now, only .8 percent of the food we eat in Austin is locally produced. 


Addressing these compounding problems with the city’s food system is going to necessitate innovative solutions. Austin cannot just blindly increase local food production, without thinking about the effect that it could have on the local environment. “It’s pretty difficult to imagine a scenario where we increase local food production without simultaneously increasing the demand on our water supply,” Marty said.

The NexusHaus tries to fix this problem by utilizing an aquaponics ecosystem that uses fish, microbes and plants to produce more food with less water. Here’s how it works – Ammonia rich waste from a fish tank is used to fertilize a plant bed. In turn, the plants help to filter the water, so that aerated, clean water can reenter the fish tank. This concept of using nutrient-rich, recycled water to grow food allows the aquaponics system to use 90 percent less water and produce 10 to 20 times more food than conventional farming methods. 

This is where the nexus in NexusHaus really comes into play. By including a water-saving, food-producing aquaponics system, the NexusHaus solves a variety of problems plaguing the Austin community all at once. It helps chip away at inequality, offering Austinites the chance to grow their own healthy, organic food right in their own backyard. And it does that without placing too much of an additional stress of the city’s environment or local water supply.


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