Passive Design Approach to the Learning Environment

• By Mike Dieterich
• 10/01/16

PHOTOS PROVIDED BY MIKE DIETERICH

Passive design strategies reduce upfront costs, operating expenses and required maintenance. They are as intelligent as they are cost effective. Passive design features, like additional insulation, light shelves, shade walls and innovative heating/cooling design reduce the amount of energy that an HVAC system needs in order to adequately heat or cool a space. Less demanding HVAC systems have lower upfront installation costs and are cheaper to operate. Money saved can then be put towards adding even more energy saving features to a building. A return on investment can be calculated to illustrate the value of an energy efficient system.

This article features research from the D.C. Public Schools (DCPS) Modernization Program. This is a multiyear study that will be revisited as new technology is developed. Retrofitting and building measurements were used to establish benchmarks. After being commissioned, optimization research was conducted to enhance performance and optimize efficiency.

The DCPS Modernization Program used energy audits and the Collaborative for High Performance Schools (CHPS) Operational Report Card (ORC) to establish its data points. The ORC evaluates a learning environment’s performance by measuring its indoor air quality, energy efficiency, visual quality, acoustics, thermal comfort, water conservation and waste reduction.

Indoor air quality measures an interior environment’s temperature, relative humidity and its carbon dioxide (CO2) and carbon monoxide (CO) levels, in parts-per-million (ppm). CO and CO2 levels are compared to those found in the surrounding outdoor environment.

Energy Star’s Portfolio Manager was used to measure and compare each school’s energy consumption to a national standard. Our analysis collected energy consumption data at 15 second, sub-metered intervals, which helped us determine the spikes, baseloads, peak loads and start/finish times for each piece of equipment. By adjusting start times and temperature points, we reduced energy consumption by an additional 20 percent.

Energy audits also use thermography to discover air leakages. This is done by assigning an estimated R-value to a building’s envelope. Thermographs of the envelope are then taken and analyzed to determine the relative temperature differences (hot vs. cold) of an envelope’s features. Significant temperature differences indicate leakage points. Common leakage points are around window and doorframes, hollow wall cavities, attic spaces and other holes cut into the envelope. After being identified, leakage points are properly insulated and sealed.

Our project measured light levels at desk height, in nine locations throughout each classroom. Measurements were taken three times during a school day to determine how the light level changes in a classroom. Levels are measured in foot-candles (FC). Acceptable levels are between 35 and 50 FC. Most spaces were over lit or inappropriately lit for their purpose. Changes made to light distribution and fixture type cut back on the number of lights that each building needed by 30 to 40 percent.

The two acoustic properties we studied were background noise and sound insulation. Background noise is the sound level in a room in which no sound is intentionally made. Sounds from an HVAC system, mechanical equipment and the outdoors contribute to a room’s background noise level. Learning becomes difficult when levels breach 45 decibels. Measurements should be taken with and without the HVAC system running to determine the amount of background noise it contributes.

Sound insulation is the amount of sound that is transmitted between adjacent spaces. It is measured between a classroom and a hallway, and between two adjacent classrooms. Proper building design results in a reduction of at least 40 dBA between a classroom and a hallway and at least 45 dBA between adjoining classrooms.

Water use is measured by counting the number of fixtures in a building and then observing each fixture’s flow rate. This metric helped us determine whether high-flow fixtures needed to be replaced by ultra-low flow fixtures. In Washington, D.C., storm water management is key to site success. D.C. requires all water from a 1.2-inch rain event to be reusable. This can be accomplished via green roofs, greywater toilet flushing, and bio swales.

To determine waste production, we recorded the amount of waste that each school sent to a landfill, recycled, or composted. Our analysis enabled more appropriately sized waste receptacles to be installed and strategically placed to better accommodate the creation of a zero-waste school.

Occupant satisfaction is an overlooked, but equally important metric. To measure satisfaction, a survey, with questions relating to each of the aforementioned categories, was issued. If over 20 percent of responses to questions about a specific category indicated dissatisfaction, we revisited our approach to that category. (See chart 1 below.)

Money saved by following our model was put towards the installation of additional, passive energy saving features in each building, which further reduced HVAC demands and their consequential costs.

On page 16 is an image of Powell Elementary School. During the addition a shading devise was installed as a passive solar design adding 10 percent in energy savings. An East West Building Orientation saves five percent. The solar chimneys reduce energy consumption in excess of 10 percent, depending on weather conditions. Low-flow plumbing fixtures decrease water usage by 50 percent, saving $3,007 ($5.60/1,000 gal). The value of these features becomes clear. This also becomes part of the curriculum where teachers can use the school building for real world lessons in mathematics, science, engineering, art, and writing.

Watkins Elementary School, image below, incorporated a shade wall into the retrofit of
Cost of Shades (50 percent): 10,750 square feet x $25/square foot = $268,750
Savings in HVAC Initial Cost: 28 tons x $8,000/ton = $224,000
Savings in HVAC Operating Cost: 28 tons x 1,500 hours per year x 0.75 kw/ton x $0.15/kwh = $4, 725/year in electricity.

• Total Net Savings= $41,495
• Savings to Investment Ratio (SIR) = 1.93
• Annual Internal Rate of Return (AIRR) = 5.74 percent
• Simple Pay Back (SPB) = 10 years
• Life Cycle Emission Reduction: 932 metric tons C02; 3 metric tons S02; 1.4 metric tons NOx

PHOTOS PROVIDED BY MIKE DIETERICH

The planning process has been augmented such that passive design features are now discussed at the outset. The short-term cost of implementing these features is justified by the long-term savings they yield. The sustainability, via passive design, approach has been quantified and it demonstrates drastically decreasing operating costs.

This is a two-step process. The first step incorporates sustainability into the design, as discussed, reducing the overall baseline of energy consumption. The second step comes down to how a building is operated. This is best shown through the Sprint to Savings competition run by Jamie Donovan using building optimization planning and management.

The Sprint to Savings energy competition challenged participating DCPS schools to reduce their electricity during the fiveweek competition period (Dec. 1 to Jan. 4). Their performance was compared to a weather normalized baseline period (Oct. 15 to Nov. 30), since the primary goal of the competition is occupant engagement and education, for a fair and effective competition design.

Using data from the competition, we compared the average daily kilowatt hour (kWh) consumption during winter break compared to daily consumption during the first three weeks of December. As a whole, the 25 schools included in the competition reduced kWh consumption during winter break by about 17 percent compared to the preceding three weeks.

A further analysis of five schools reveals that they were successful in turning things off during unoccupied periods during the competition period. As graph 1 shows, these schools had significant reductions during each weekend during the competition and for winter break. The well-defined peaks between days 1-5, 8-12 and 15-19 represent occupied weekdays when, consumption would be at its highest. The troughs — day 6-7, 13-14 — represent the weekends. The curves flatten out at day 20 with the beginning of winter break and remain low. These curves are exactly what we like to see.

In contrast with the top five schools, (see graph 2 above), the five schools at the bottom of the table were less successful in shutting down over winter break. By looking at the load profiles of these schools and analyzing the data, these buildings are consuming electricity at nearly the same rate during weekends and holidays as they are when the building is fully occupied during the week. This is particularly true for Cleveland and Bruce Monroe @ Parkview, indicated by electricity use curves that are essentially flat with no troughs or peaks.

The take away is: a) improving shut down performance during unoccupied times and; b) implementing tighter HVAC scheduling on a permanent basis. If the bottom five schools realized electricity reductions over winter break consistent with the competition average — 17 percent, the five schools would have reduced their spending by $8,012, or $5,718 above their actual spending.

Making permanent scheduling changes at these five sites presents a significant saving opportunity. A 20 percent reduction would save the city $210,000 per year — or $1 million over five years — in electricity costs. A 10 percent reduction would achieve a savings of $118,965 per year — or nearly $600,000 over five years — across these five facilities.

The 20 percent reduction target is not arbitrary. Implementing scheduling/controls changes at facilities that currently have no or limited schedules in place should yield at least a 20 percent reduction.

This article originally appeared in the issue of .