By: William Ratsamy

Ecological architecture is a subfield of architecture that seeks to minimize the negative environmental effects of buildings on the planet achieved by utilizing the readily available resources of the local climate. But what can be done in a climate that experiences both extremes of hot summers and cold winters as is apparent in Minnesota?

Climate in Minneapolis, MN

Temperature

Specifically in Minneapolis, Minnesota, the warm season lasts 3.9 months, lasting from May 21st to September 16th. The hottest day of the year is July 17, with the average high being 83°F and low being 65°F. As for the cold season, which lasts 3.3 months, lasting from November 25th to March 3rd. The coldest day of the year is January 22, with the average low being 9°F and high being 24°F.

Daylight

In Minneapolis, the length of the day varies significantly over the course of the year. As of 2020, December 21st was the shortest day of the year, with 8 hours, 46 minutes of daylight. The longest day of the year is expected to be June 20th, with 15 hours, 37 minutes of daylight.

Solar Energy

Similarly to the varying lengths of day over the course of a year, the average daily incident shortwave solar energy also experiences extreme seasonal variation. The brighter period of the year lasts for 3.5 months, spanning from May 4th to August 19th. During this period the average daily incident shortwave energy per square meter is above 5.9 kWh. The darker period of the year also lasts for approximately 3.5 months, spanning from October 28th to February 11th. During this period, the average daily incident shortwave energy per square meter is below 2.6 kWh.

Case Study: UMTC Physics and Nanotechnology Building

Overview

After evaluating the climatic conditions, it is apparent that weather in Minneapolis, Minnesota varies significantly depending on the season. Looking at a local case study, the UMTC Physics and Nanotechnology Building, we see many strategies at play that utilize the existing climatic conditions to reduce energy usage within the building.

To provide project context, the UMTC Physics and Nanotechnology Building is located 115 Union St SE Minneapolis, MN 55455 on the University of Minnesota Twin-cities campus. This building is a 6 story facility used for laboratories and classrooms and was first occupied in 2013. The design team consists of Alliance and ZGF Architects LLP as the architects, Affiliated Engineers, Inc. as the mechanical engineers, Meyer Borgman Johnson as the structural engineers, and Pierce Pini & Associates, Inc. as the civil engineers.

Energy Performance

In terms of energy performance, the SB 2030 standard for energy consumption is 586 kilo British Thermal Units per square foot per year (kBtu/sf/year). The UMTC Physics and Nanotechnology Building, as it is designed, consumes 530.27 kBtu/sf/year. For comparison, the average building consumes 873 kBtu/sf/year.

As a result of the UMTC Physics and Nanotechnology Building’s energy efficiency, the carbon emissions are greatly reduced. The SB 2030 standard for carbon emissions is 163 pounds of carbon dioxide equivalents per square foot per year (lbs CO2e/sf/year). The UMTC Physics and Nanotechnology Building, as it is designed, emits 137.69 lbs CO2e/sf/year. For comparison, the average building emits 243 lbs CO2e/sf/year.

Strategies

The UMTC Physics and Nanotechnology Building achieves these energy goals by integrating a multitude of energy strategies into the building design. Strategies that address domestic hot water, envelope and insulation, HVAC, and lighting. For this blog I will be specifically examining strategies concerning HVAC and lighting.

In terms of the HVAC system, the UMTC Physics and Nanotechnology Building has integrated a chilled beam strategy. There are passive and active chilled beam systems, but essentially warm air is cooled down once it rises and reaches a tube in which chilled water passes through. This system saves energy that would otherwise be used on air conditioning units. The UMTC Physics and Nanotechnology Building also uses an economizer which is a system, frequently placed on the roof, that evaluates exterior air conditions like temperature and humidity through sensor technology. When exterior air conditions are appropriate, the system uses outdoor air to cool a building.

This allows the building to be flexible with energy usage and thus saving energy and money. In addition to this, the UMTC Physics and Nanotechnology Building utilizes an energy recovery system. This system addresses stale and fresh air, as well as heat recovery. Essentially, as stale, interior, warm air exits a building, it is intercepted by fresh, exterior cool air, in which the heat and energy is recovered, thus pumping fresh, exterior, warm air into the building and stale, interior, cool air out.

As for lighting in the UMTC Physics and Nanotechnology Building, the building utilizes occupancy or vacancy sensor devices to detect whether or not a space is occupied or unoccupied. As a result of a space being unoccupied, the sensory devices automatically turn off the light, saving energy. Allowing flexibility in light output, the UMTC Physics and Nanotechnology Building uses stepped daylighting controls. This ability to control the light output saves energy by assessing the existing daylight output in a space and adjusting, possibly, artificial lighting to accommodate. As is apparent on the exterior facades of the building, there are many side windows that provide passive daylighting. In addition to these side windows, the architecture integrates an atria and skylight design. As a result, 85% or greater of the continually occupied spaces in the building are daylit!

Summary

Ecological architecture is a subfield of architecture that seeks to minimize the negative environmental effects of buildings on the planet achieved by utilizing the readily available resources of the local climate. Because of Minneapolis’s significant weather variation, it is important to design with flexibility in order to fully utilize the climatic resources. The UMTC Physics and Nanotechnology Building performs, to some extent, with freedom to allow the climate to affect the interior space. This is seen in the use of economizer and the extensive use of daylight influenced glazing. As an architecture student, I believe that ecological strategies and technologies should be integrated into every building everywhere as they have the potential to save a lot of energy. The main principle to follow is that any design decision must be climate specific.

Sources

https://weatherspark.com/y/10405/Average-Weather-in-Minneapolis-Minnesota-United-States-Year-Round
https://casestudies.b3mn.org/ProjectDetail?id=5007

Click to access adm_apn034en_1209.pdf

What is an Economizer and How Can it Benefit My Commercial HVAC Unit?

https://www.central-va-radon.com/energy-recovery
https://comnet.org/344-daylighting-control
https://www.mortenson.com/minneapolis/projects/university-of-minnesota-physics-and-nanotechnology-building