Make Tree House Sustainable Again

Make Tree House Sustainable Again

Espen Stalder

Project-Kelowna Passive House 1

Ohio Wesleyan University

Environmental Geography

John Krygier

Spring 2017

Project Summary: 

This project involved looking at ways to make the new SLUs at OWU more sustainable. The Tree House is moving from it’s old house, where there have been modifications made to improve sustainability. Moving into the new house, they’re losing these improvements. OWU is not the best at implementing sustainability, so I looked into ways the house (and future houses) could be built with sustainability in mind. This included researching passive heating, better ventilation, renewable electricity, and other less permanent options such as backyard composting. I found that cost-wise, it’s quite feasible to build one of these passive houses at OWU, as long as the school could be convinced to pay a little extra.

Methods and Results:

Methods-wise, this project was mostly research-based. When I thought of the idea for the project, I thought about creating an official proposal to give to the school that would outline the costs and benefits of a passive house SLU. Unfortunately the designs for the houses had been settled on quite a while ago and construction began right as I started researching. The focus of the project switched to a  more research-based paper. In theory this project can set the groundwork for a future project that can draft an actual proposal, saving some time on research and cost analysis.


Truly Sustainable Housing:

A truly sustainable house would be completely “off the grid.” Everything the house needs or produces would be taken care of without outside interference or effect. Renewable generators like solar panels or wind turbines would supply electricity, water would be taken from rain (ideally) or groundwater (if necessary) at replaceable rates. Heating and cooling would be done naturally using sunlight and the cooling power of the earth, using as little electricity as possible. Ventilation would happen without using too much electricity with the aid of an MVHR (Mechanical Ventilation and Heat Recovery) system. Waste would be taken care of through compost and recycling, with (ideally) nothing going to landfills. Due to city codes and other restrictions, this isn’t necessarily practical for an OWU on-campus house. However, bits and pieces can be taken from this to produce a house that is still much more sustainable than average, maybe even achieving LEED certification.


One of the main components of a passive house is heating. Houses have always been inefficient when it comes to heating, especially back in the days when fireplaces were the primary heat source. Houses from the early 1900s generally are full of drafts and have many places where heat leaks out, such as under porches and through windows. Energy bills to heat houses are often much more expensive than they need to be. Passive houses aim to combat this by designing the house so that it can be heated using natural sunlight rather than electricity or gas, saving homeowners a lot of money.

In the Northern hemisphere, sunlight comes in through the south-facing wall of a house. In a passive house, this wall is as full of windows as it can reasonably be, in order to capture as much sunlight as possible. These windows are often triple-paned, meaning that the heat that comes in has a hard time leaking out as it gets caught between the layers of glass (kind of like a mini-greenhouse effect). When combined with the proper ventilation system, artificial heating becomes almost completely unnecessary. Places at higher latitudes can experience strong temperature differences between winter and summer, which would mean that in summer, these houses would become unbearably hot. To account for this, rooves are designed to keep sunlight out in the summer. The rooves are at such an angle that in the summer, when the sun is higher, sunlight bounces of the roof (where there would likely be solar panels). In the winter, when the sun is lower, sunlight goes below the roofline and into the windows.


The sunlight that does come in during the summer can be countered using standard blinds or other, fancier blinds. Some blinds can block the heat energy from getting in while still allowing light, while some blinds are made from tiny photovoltaic cells that can turn the sunlight into extra electricity. Even with fancy blinds, overheating can still be a concern in warmer climates, especially humid places like Ohio.


Ventilation in passive houses is a very scientific concept that I had a hard time understanding, but I’ll do my best to explain. The two main parts of the ventilation system are the MVHR (Mechanical Ventilation and Heat Recovery) system and the circulation system between rooms of the house. The MVHR draws in air from the outside and brings it to the machine, which is usually located in the basement. The machine transfers the heat of the old air to the heat of the new air mechanically, and brings the new air into circulation. Room by room, a set of filters pumps fresh air into the room (at the bottom) while extracting old air (which rises to the top), keeping a constant fresh air supply going. When the air makes it’s way through every room, it returns to the MVHR where it’s heat is transferred to new air from the outside. The old air then gets pumped back out into the world.


With the MVHR transferring most heat energy from the old air to the new air, not much new heat energy is required. What little is needed can be captured by the south-facing windows, or can be created mechanically. Power for this ventilation system normally would come from solar panels or some other form of renewable energy to maximize sustainability.


Electricity for passive houses is simple: they almost always run off of solar power.  It’s easy enough to mount solar panels on rooves, and with the improving efficiency of solar panels it’s easy to run a whole house off of a roof’s worth of panels, even with the mechanical ventilation system. Oftentimes, energy companies are required by law to buy back any extra power that’s produced by homeowners renewably, and this is true in Ohio. The main electric companies have been fighting to reduce the payments for buying back, but they still do have to buy the extra electricity. It’s not always a lot of money, but it does help the solar panels pay for themselves even faster. Even in the cloudiest of climates, like the Great Lakes or the Pacific Northwest, solar panels can have a huge impact on electricity production, and can reduce electric bills significantly. The ventilation systems can sometimes require a fair bit of power, so having extra solar panels doesn’t hurt. New technologies like solar blinds are in development too, to maximize the amount of solar energy a single house can create.

Other Sustainable Projects:

There’s a few smaller things that can be done with the house that aren’t necessarily permanent features, or aren’t realistic to use at OWU. Backyard composting is easy to do and doesn’t take up much space. Many if not all of the SLUs already do it in some form. Food scraps at the SLUs go into a bucket under the sink, which is then taken to a proper compost pile. This would happen at the new Tree House whether they want it or not. What can be improved at the SLUs is the recycling. As it is, the recycling isn’t able to take many types of plastic. Only two specific types work with the SLU recycling. Ideally, most types of plastics as well as more kinds of materials besides plastics and paper would be able to be recycled at the new SLU. I’m not sure who would be in charge of this, I’m assuming it’s due to limitations with the school’s recycling partner.

Rooftop gardens are another sustainability project that’s catching on in big cities. While it wouldn’t be practical at OWU, especially not on a normal house with plenty of space around, rooftop gardens are quite beneficial to the buildings below them. They can grow food, act as natural cooling systems (kind of like old Viking sod rooves) and give people in urban high-rise environments like New York or Chicago some form of green space right on top of their work or home. The new SLU wouldn’t need a rooftop garden, but a backyard garden certainly wouldn’t hurt. It could serve both as a place to grow food and a place to compost, and add some scenery to a backyard that doesn’t really have anything besides a treeline. Rooftop gardens could in theory be put on top of the flat-roofed buildings on campus like the library or the science center, though it would likely be too expensive for the school to go for.

Rooftop gardens and another newish feature called vertical gardens also serve as important habitat for city wildlife. Vertical gardens stretch along the sides of buildings, usually as little terraces. Birds can nest in them, and squirrels can climb up to rooftops without having to rely on dangerous electrical lines. Urban wildlife tends to be pretty neglected and vertical and rooftop gardens are a way to counteract that.

How It Would Work at OWU:

Passive housing is a good idea anywhere, but would be especially good for OWU. There’s a strong environmental studies department here, and most of the students seem to be pretty environmentally conscious. Passive housing on campus could help attract new students, especially for the new environmental science major.

Ohio, and the campus itself, is decently well suited to passive housing. The new SLU has it’s south-facing side against the street, meaning there’s less obstacles like trees or other buildings blocking the sun. There can be some wild temperature swings monthly, weekly, and daily, meaning heating costs are constantly fluctuating. A passive house would not only greatly reduce the heating costs but also even the heating out (at least in older buildings, it’s either very hot or very cold at any given time). This would save the school a decent amount of money, with heating bills for the average passive house being around $300 a year (as opposed to the Ohio average of around $782 per year).

The Great Lakes region is one of the cloudiest areas of the country, but even with that, solar power is fully realistic. A standard solar array in Columbus is enough to power  about half of the yearly electricity usage. In private homes, this is mostly limited by cost. The school would in theory be able to put enough solar panels atop new SLUs to fully power them, but could just as easily get by with a standard array. The area can also get sticky hot in the summer, which a truly passive house isn’t necessarily able to handle. The MVHR can also serve as an air conditioner provided it’s given some cold air initially to work with. While it’s more expensive, it would be a nice thing to have (the new SLUs they’ve built already have air conditioning so in the same standard these passive SLUs would too).


On average, building a passive house is around 5-10% more expensive than building a standard house. The larger the building, the less expensive it is proportionally, so a passive duplex (SLUplex as they call them here) would be around 6-7% more expensive than a traditional duplex. This isn’t terribly expensive all things considered, especially when considering how much money it saves. With heating only costing around $300 a year, and with solar energy covering most if not all of electricity consumption, the average passive house can save owners up to $170,000 over 30 years. Since OWU’s living quarters seem to last quite a while (Stuy has been around for something like 80 years), this could be a big thing for the school. $170,000 per unit ($340,000 per duplex) with multiple duplexes would give the school quite a bit of extra money to work with.


Most of the benefits have already been outlined in this report. The SLUs wouldn’t rely on natural gas or coal-fired energy to heat and power themselves, instead using renewable sunlight as a heat source and as a source of electricity. Net energy costs would be at least cut in half, but ideally net energy would actually be a positive, with the SLUs producing enough power to sell back to electric companies, helping to pay off that 6-7% extra faster. Environmentally, the passive SLUs would have a much smaller footprint than a normal house, which besides the obvious benefit to the environment could potentially attract new students to the school. The SLU wouldn’t need to look much different architecturally as passive components can be built in to the house without being noticed. Overall, a passive SLU would be a great idea for the school, and a further project to actually submit a proposal would be a good step in making the school aware of passive houses and all the benefits that come with them.

Works cited:

Anderson, Elizabeth. Tree House resident

Badescu, V., & Sucre, B. “Renewable energy for passive house heating: II. Model.” Energy and Buildings, 2003.

Database of State Incentives for Renewables and Efficiency. “Ohio Programs.”

Earthship Biotecture. “Radically Sustainable Buildings.”

Environmental Protection Agency. “Backyard Composting: It’s Only Natural.” NSCEP, 2010. (hyperlink cuz the link’s too long).

Figueiredo, A., Kämpf, J., Vicente, R. “Passive house optimization for Portugal: Overheating evaluation and energy performance.” Energy & Buildings, 2016.

Kuzman, M.K., Groselj, P., Ayrilmis, N., Zbasnik-Senegagnik, M. “Comparison of passive house construction types using analytic hierarchy process.” Energy & Buildings, 2013.

Mullins, Seamus. “Rosslare Case Study, Passive House Cost Analysis.” 2010.

Passive House Institute US. “What Is a Passive Building?”

Passive house Pty Ltd. “Ventilation & Heat/Energy Recovery.”—heat-energy-recovery

Rodriguez-Ubinas, E., Montero, C., & Porteros, S. “Passive design strategies and performance of Net Energy Plus houses.” Energy & Buildings, 2014.

Schneiders, J., Feist, W., & Rongen, L. “Passive houses for different climate zones.” Energy & Buildings, 2015.

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