Sources of emissions
Buildings

Energy consumed by DUSP's buildings causes the release of 390 MTCDE per year, which represents 30% of all emissions from the department. Most of this energy is supplied by the MIT Cogneration Plant, which is much more efficient that a conventional power station. The energy is supplied as chilled water for cooling, steam for heating and electricity for lighting, computers, etc.

The approximate value of 390 MTCDE represents emissions due to energy consumption of space occupied by DUSP, using a universal value per square foot of office space across MIT. For comparison, the total energy used and resulting emissions produced by each building was calculated and proportionally assigned, to give a lower estimate of 345 MTCDE. The complete methodology is given below.

In addition to 'top down' calculations of emissions from supply, some estimates of the impact of computing on energy consumption are made. This approach may provide a better guide for action since it highlights specific sources that could be reduced.

Calculating floor space occupied by DUSP

The buildings database provided by MIT facilities gives floorplans and the MIT buildings database provide information on the floor area of each building on campus, with information on the occupant by department1 1. See floorplans.mit.edu. For rooms in buildings 3, 7, 7A, 9 and 10 only, this list was manually reviewed and corrected (e.g. where studio spaces are listed as occupied by the architecture department instead of DUSP). 1 2. Corridors running between DUSP rooms shared with other departments (e.g. the AVT lecture theatre) were classified as having 50% use intensity (equivalent to being half their size if entirely used by DUSP)

Total floorspace occupied by DUSP

Building	Space in use (sq ft)
3	1,690
7 (7 + 7A)	3,785
9	17,265
10	5,649
Total	28,389

Calculating emissions with the MIT-wide office space value

Classifying space use in different buildings is not necessary to use the overall MIT-wide value for MTCDE per sq ft. 3 3. This value is given in Tiffany Groodie's comprehensive analysis of energy use, available via DSpace. Groodie, T A, A methodology for assessing MIT's energy used and greenhouse gas emissions. ME SM thesis 2004.. Based on emissions of 0.013 MTCDE per square foot, the total emissions from DUSP's spaces are 390 MTCDE. Although this value is useful as a summary of emissions, it does not provide any distinction between the types of spaces in use or point to specific sources of heating or cooling as large energy drains.

Calculating emissions from facilities department data

For each building on campus, electricity, steam and chilled water come from the MIT Cogeneration Plant on Vassar Street. Quantifying emissions from the plant is complicated because a single fuel produces multiple outputs - e.g. gas is burned to generate electricity, steam is a by-product and this steam is also used to create chilled water. Consumption of supplied utilities is metered for each building. The student-run energy mapping project4 4. See energymap.mit.edu and the MIT facilities dept are collaborating on a data display web page for the meter readings, showing consumption in watts per square meter on a monthly basis since July 2002.

Sample utilities consumption chart for Building 9

Using charts for the four DUSP buildings,consumption for each building was manually interpreted to show data points per month per utility. From this, a monthly average watts per square meter was derived, and a total watts per building5 5. Information from the facilities department is provided in watts per square meter for each building's entire floor space, including circulation and areas with low power consumption (e.g. janitors' storage space). Using these values to calculate power consumption in DUSP's rooms will result in an underestimate of energy intensity, because the greater power consumption in classrooms is not taken into account. To remedy this, the total power consumption of each building was divided by the active floor space (classrooms, offices etc), to give a measure of W/m^2 of intensely used spaces. The floor area of rooms occupied by DUSP was then scaled by this value to provide a total energy consumption.

Derived energy consumption of utilities in different buildings

Building	Steam	Chilled water	Electricity
3	0.51	0.44	0.82
7	0.86	0.97	0.86
9	0.65	0.34	0.81
10	0.51	0.28	0.79

For each utility product, greenhouse gas emissions per floor area can be calculated, based on two sources in Groodie, 2004: the total amount of each utility supplied to MIT, and the emissions resulting from it. Since we know the amount of energy used in each building, we can assign the correct proportion of MIT's total GHG emissions to DUSP. Final emissions calculated by this method are 345 MTCDE, which is reasonably close to the rougher value worked out above.

	Steam	Chilled water	Electricity
Total MMBTU produced	1,629,112	38,557	578,118
Total GHG emitted	106,220	25,752	60,257
Watts consumed in DUSP spaces	18,207	11,900	23,095
MMBTU of DUSP spaces	544	356	690
% of MIT total consumption	0.03%	0.92%	0.11%
MTCDE due to DUSP consumption	35.5	237.6	72.0

The actual value of energy consumed by DUSP's activities in office, classroom and meeting spaces is probably higher than either estimate, since these values were calculated for core spaces only and do not include occasional use classrooms in other buildings, spaces occupied by cross listed courses, resources dedicated to DUSP in other parts of the campus, etc.

Limitations and alternatives: Assessing energy consumption and emissions from the bottom up

Even a building-level assessment of energy consumption and emissions from utility data is not sufficiently detailed to provide guidance for energy reduction, because DUSP's energy use is mixed with other occupants of the same building. This distorts the representation of emission measurements due to DUSP alone. A more action-centric measure of energy would be entirely bottom up, assessing lighting fixtures, fancoil heating/cooling units, computers, printers, kitchen facilities etc. As part of this audit, data have been collected on the computing facilities of DUSP. The next step is to combine this with information or estimates on other energy uses to provde a bottom up assessment of energy consumption.

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