Mount Angel ID Roundtable - Part III

Part III of III- Building Envelope (see Part I and II)

The following article is the third installment of a three part series drawn from a roundtable discussion that occurred in August 2007 about integrated design, among principal project team members responsible for design of the Annunciation New Center for Theological Studies graduate theology building at Mount Angel Abbey. The cross-disciplinary collaboration among project team members was a hallmark of this project, but specific areas of responsibility are indicated for each of the panel participants.

Father Michael Mee served as the Chair of the Building Committee and became involved several years before the actual design process started, as the Monastic Community and Building Committee composed their ideas about project aspirations.

Kent Duffy, FAIA is a Principal of SRG Partnership, Inc., the project architect, and served as Principal in Charge and Project Designer.

Michael Hatten, P.E. is a Principal of SOLARC Architecture and Engineering and was the mechanical engineer and energy engineer for the project.

G.Z. "Charlie" Brown, FAIA, is a Professor of Architecture at the University of Oregon and Director of the Energy Studies in Building Laboratory (ESBL). Under his leadership the ESBL designed, built, and monitored the performance of a full-size classroom prototype, in order to facilitate project team investigation and evaluation of daylighting, night ventilation of building mass, integration of mechanical and electrical systems, and to inform and define the passive systems approach that was incorporated into the project.

Building Loads

Mount Angel Exterior

Mike Hatten ("MH"): Here are a few glimpses into our integrated design thinking. We moved from an understanding of the loads to the system concepts. Initially, we were trying to imagine what would happen at night during the cooling season, what would happen during the day, and what would happen during the transition from night to day. Those of you who have been working on LEED projects and projects where there's formal commissioning have begun to ask these kinds of questions.
 

Outside air ventilation is the most significant building load, with significant implications for how we address systems concepts. As a general principle, one may want to seriously consider dealing with ventilation in a separate, dedicated way, not just as part of a set of mixed air dampers with air handlers on the roof. In fact, that approach did get expressed in this design, as heat recovery ventilators. Each classroom has its own dedicated heat recovery ventilator. And then for the more complex and integrated spaces-the offices and corridors-there is a building level heat recovery ventilator on the roof that provides ventilation air to some of the other building spaces.

The heating load for this building is almost all about ventilation, easily seen when we graphed heating and cooling loads. We're actually seeing between 70 and 80 percent effectiveness in the heat recovery ventilators that went into this design, reducing the effective heating load to about one-quarter of what the actual load is.

Kent Duffy ("KD"): The building has a modest heating system to provide perimeter heating to meet the remaining heating load. There is no active cooling system. We have made some corrections this summer because we had trouble in the winter with some air infiltration that was greater than we expected. So, there's slightly more perimeter radiant heat than what we included in the original design, and we're working to seal infiltration sites.

As we began to get some experience with this building-it happened to come on line right at the beginning of the heating season-we quickly found out that our assumptions of how much outside air would move through this passively functioning building differed from how much was actually circulating, a very cogent, specific example of where the real world meets integrated design assumptions - in this case, the infiltration component of the building loads.

There is a conference room on the classroom level (the second floor), with a shaft that goes all the way up, through the building, to bring daylight into the conference room, but it's also the ventilation path for the entire second floor to ventilate out the top of the building.

MH: The doors on either side of the classroom windows are manually opened and they have continuous louvers, top to bottom. Above the window is another set of dampers, which are automatically controlled, allowing air to move above the plane of the ceiling and through the room, cooling thermal mass in the floor and the roof. The air flows through the entire volume of the room and vacates through turbine ventilators on the roof above the corridor. We have thermal mass and ceiling fans, a combination that increases comfort range. You normally design a space to allow the temperature in summer to float up to about 78 degrees, but we have actually designed to allow the temperature to get to 83 degrees while maintaining comfort equivalent to what you would have at 78 degrees.

G.Z. "Charlie" Brown ("CB"): The ASHRAE comfort zone is defined so that when building conditions are maintained within that zone it can be expected that 20 percent of the occupants will remain uncomfortable. So designers also have to manage expectations about what a building can actually achieve.

KD: The analogy that I always use is, if you're in the sun, you would feel hot. And if you walked under the shade of a tree with dappled light and a gentle breeze blowing across you, you would feel comfortable. It's the same air temperature, but you would be comfortable. It's a matter of tuning the comfort of people rather than adjusting the building temperature.

Classrooms

MH: So, in a classroom at Mount Angel, during a summer night, in cooling mode, the automatic louvers open up, both on the outlets and the inlets, and we're bringing air through to cool thermal mass in the floors and ceilings, in preparation for the next day where we'll be seeing the cooling loads.

There are some interesting transitional issues that are layered into those automatic controls. One is that we are trying to sense mass temperature in several places in the floor in this building to tell these various automatic controls when to stop the night ventilation mode so we don't overcool the classroom. We are also locking out the heating, because we intend to depress the first few hours' temperature below the mid-60s-we don't want the heating system to come on the following morning. So, two pieces are there-the mass temperature sensing and lockout of the heating system the following morning-to really make this night flush system work without incurring an energy penalty.

When we get to a summer day, we automatically close two of the louvers. Additional louvers are manually controlled, so there is an expectation that occupants, as they become more aware of the dynamics of the room, begin to understand how to manage some of the elements of the comfort system in this room. Occupants can also manipulate the ceiling fans and use the cool surface temperatures to help maintain comfort.

CB: The automatic louver system is designed to handle enough ventilation and enough cooling of the mass on an average cooling day, that you won't need the manual windows at all. You only need to employ the manual windows when you have an extreme day, when they would be opened to increase ventilation. The reason why there's an automated component and a manual component is because the manual windows are a lot cheaper to build and they're not used very much and the penalty we pay for not having them used properly is small compared to potential problems with additional, more complicated automation.

KD: And I would go one step further to mention that each classroom is a stand-alone system, you can operate an individual classroom while the other classrooms remain in an unoccupied mode. Every classroom has its own ventilator.

Offices

Mount Angel office

MH: I just want to mention a little about the offices. From my perspective, as one of the designers of the natural ventilation cooling system, the offices and the office wing were a significantly more complex undertaking (than the classrooms).

To really figure out how air is going to move from inlets in the offices to outlets located in conference rooms is really an integrated design challenge because there are code issues that have to be dealt with by the architectural designers. We need to have a way to transfer air from multiple rooms- via transoms, using hallways, open doors, and ultimately exhausting through outlets located in conference rooms. The complexity of the required airflow is significant and it's one of those issues that, if you're going to tackle integrated design challenges, you really need to get the whole team sitting around the table and engaging in a series of discussions of how "smart" your air is going to be.

Ventilation in the offices is done passively. The offices are not served by heat recovery ventilators, all the windows are operable, and all of the office occupants have control over a dedicated air inlet damper, as well. So they can use both the windows and their dampers to bring in fresh air as needed.

KD: There are manually operated transoms above the office doors and so it's up to an office occupant to open them for air circulation. Or, if you have too much ventilation, you close the transom. If you're here during the day and your door is open, it's no problem. But the big thing with night flush is to move air through the office at night when you're not here. So, it's important to leave the transom open and also to open the air inlet damper under the window.
Air is drawn through each of the offices in independent patterns, and each office operates as an independent system. So, you can have people occupying offices on different schedules all summer long without trying to make all this space operate at the same temperature.

Article by Jeff Cole, Konstrukt, Inc for BetterBricks. For details about Mount Angel Abbey, please see an overview brochure on the Annunciation New Center for Theological Studies developed by SRG Partnerships, Inc.

Photos of Mount Angel building are credited to Lara Swimmer Photography.

Drawing and schematics were taken from a presentation given by G.Z Brown, University of Oregon, Energy Studies in Buildings Lab and Mike Hatten, Solarc Architecture and Engineering, Inc. entitled "How to Use Performance Modeling to Support the Integrated Design Process - Case Study: High Performance Classroom and Mount Angel Academic Building."

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