public library poor comfort€¦ · com/blackbox/ public library – poor comfort the black box...

FOR MORE INFORMATION, VISIT: HTTP://BUILDEQUINOX.COM/BLACKBOX/

Public Library – Poor Comfort

The Black Box IAQ™ is a tool for improving energy efficiency as well as diagnosing indoor air quality problems.

In this case study, we were asked to help determine comfort conditioning problems in a new library. The

building is a beautiful “prairie” style design with 12,000 square feet of space. As summer approached, the

building’s air conditioning system was unable to maintain comfortable humidity and temperature conditions.

The library board and staff were being run in circles as the architect, building contractor, and HVAC (heating,

ventilation and air conditioning) sub-contractor pointed fingers at each other, a typical situation building

owners and homeowners are placed in when things don’t work correctly.

We used our BB IAQ air analysis algorithms to determine comfort level and air exchange activity, and found a

surprising result. The library had an enormous flow of fresh air pouring in from the fresh air supply system.

Commercial buildings, unlike homes, have mandated fresh air requirements. In this case, the fresh air supply

systems had not been properly commissioned, resulting in too much fresh air flow that overtaxed the air

conditioning equipment.

We used the Black Box IAQ™ to adjust the building’s fresh air supply system in a series of steps over several

weeks such that fresh air flow adjustments didn't overshoot our air quality goal. With the BB IAQ test, we

could see that the primary pollution generation times reflected patron usage in the early morning, noontime,

public school dismissal time, and early evening hours. As we adjusted the building fresh air flow schedule,

humidity levels were reduced to 50% from the 70 to 80% relative humidity levels previously experienced.

The attached BB IAQ™ report, taken this past summer, a year since the original tests, shows how the building

is operating today. As indicated in the report, the fresh air supply could be further reduced, however, it has

been left at a relatively high level (but only 33% of the original setting) in order to ensure sufficient fresh air

during high occupancy events. The library staff reports comfortable conditions in the building along with a

20% reduction of air conditioning cost relative to the previous summer’s utility cost. And, the summer of 2012

was a record breaking hot, humid summer!

The Black Box IAQ™ testing provided us with the guidance improve energy efficiency while maintaining

excellent indoor air quality. Without this guidance, a lot of finger pointing would still be occurring.

CASE STUDY

Test Number: Black Box Case Study 3Name: Public Library

Email address: [email protected] Location: Central IllinoisBox Location: commons

Report Date: 8/23/2011

Use our building energy modeling software to design a healthy, comfortable, efficient home.

A free version is available at www.buildequinox.com/zeros

CERV: Monitor pollutant levels, get fresh air, and recover energy.

Learn more at www.buildequinox.com/products/cerv

pg. 1-1

Overview: This Black Box IAQ™ report provides an assessment of indoor air quality (IAQ) over the tested time period for the designated space. Black Box IAQ™ measures temperature, humidity, carbon dioxide (CO2), and volatile organic compound (VOC) levels. Based on these measurements, the air exchange rate and pollutant generation rates are determined. The report is divided into two sections as follows:

Section 1: Test Summary Information Reports the measured and calculated values of temperature, humidity, CO2, VOCs , and air flow rate for the measurement space. A determination is made as to whether the levels are acceptable or not. Unacceptable levels suggest corrective action.

Section 2: Recommendations Test results for the measured CO2 and VOC levels are plotted against the calculated air flow rate through the space. Suggested changes to the air exchange rate are given and the impact of changes to the air exchange rate on pollutant levels are provided. Trends in radon gas levels due to changes in air exchange rate are also discussed.

Black Box

Indoor Air Quality Report

* Disclaimer: This test is provided for informational purposes only. Results are dependent on a number of testing conditions. It is vital to appreciate that a test result only gives a “snap-shot” estimate for a single time period and a single location under conditions at the time of testing – how well it represents other locations and times is uncertain since the amounts and types of pollutants and air flow rates in the environment is always changing.

www.buildequinox.com ©Build Equinox 2013 Rev 1.9.2, Report # Black Box Case Study 3

Air Exchange rate per occupant(cfm/person)

pg. 1-2

Low Air

Flow

Optimal Air

Flow

High Air

Flow

Air Exchange 39.9 cfm/person

1: Test Summary Information

0

20

40

60

80

100

60 65 70 75 80 85

% R

elat

ive

Hu

mid

ity

Temperature (F)

Comfort Chart Slacks & Long Sleeves ComfortRegion

Shorts & Short Sleeves ComfortRegion

Room Condition Data Points

Average Room Condition

Temperature and relative humidity measured during the test period are shown in the above figure. The two regions represent different comfort levels of clothing for sedentary (eg, office work activity) persons. Room conditions falling mostly within the comfort regions provide confidence that building conditioning systems are operating appropriately. Extended periods of high indoor humidity can be an indirect indicator of mold, a known component of poor indoor air quality.

Measured Temperature and Humidity Levels:

Air flow to the measured space results from either controlled ventilation or uncontrolled infiltration through cracks and inadequate sealing around doors and windows. The Black Box IAQ™ analysis calculates the space air flow rate and is reported in two ways: 1) as cubic feet per minute (cfm) and 2) as cfm per equivalent person (cfm/equiv. person) as shown above. It is important to point out that the calculated equivalent person is not the same as the number of occupants. The equivalent person number is based on typical pollution generation rates per person but can be different from the number of occupants due to occupant activity such as cooking using gas cooktops or actual occupancy time in the tested space. Air flow rates less than 15 cfm/equiv. person contribute to “stale air” and higher levels of indoor pollutants. Air flow rates greater than 25 cfm/equiv. person are higher than needed to maintain adequate indoor air quality and thus increase the heating and cooling energy required to condition the space.

Infiltration or Controlled Ventilation Air Flow Rates:

Less than 15 15 to 25 Greater than 25


Air pollutant ranges

pg. 1-3

Excess Dilution

Air

Optimum Air

Poor Air

Quality

VOC Level

469.0 ppm average

Excess Dilution

Air

Optimum Air

Poor Air

Quality

CO2 Level

713.8 ppm average

The dial graphs above show the level of measured pollutants during the test period. The table below categorizes the measured levels ranging from “very good” or low pollutant levels to “very poor” or high pollutant levels based on ASHRAE (American Society of Heating, Refrigeration and Air Conditioning Engineers) recommended ranges.

The most common source of indoor CO2 generation is human and correlates with human respiratory activity. Indoor combustion of natural gas, such as from stoves and fireplaces or improper flue venting of gas water heaters and furnaces, is a large contributor of CO2. Indoor CO2 levels that are unusually high may cause occupants to grow drowsy, get headaches, or function at lower activity levels. The ASHRAE recommended CO2 upper limit is 1,000 parts per million (ppm).

VOCs are also emitted from human respiration, but additionally as gases from certain solids or liquids. VOCs include a variety of chemicals, some of which may have short- and long-term adverse health effects. VOCs can be emitted by a wide array of products including carpet, furnishings, paint, cleaning solutions, cosmetics, and building materials among many others. Natural gas combustion and cooking/food preparation are also sources of VOCs. VOCs should also be kept below 1,000 ppm.*

*VOC measurements are correlated to a CO2 reference as the amount of VOCs produced in proportion to human CO2 production.

CO2 and VOC Levels:

Measured CO2 and VOCs Levels:

Less than 800ppm 800 - 1000 ppm Greater than 1000


Average level Estimated level during test period after adjustment

CO2 713.8 (ppm) 1000.0 (ppm)

VOC 469.0 (ppm) 531.9 (ppm)

Calculated level Recommended during test period adjusted level Recommended action to achieve adjusted level

Space Air 116.2 (cfm) 60.8 (cfm) Seal space or reduce controlled ventilation

Flow Rate 39.9 (cfm/equiv. person) 20.9 (cfm/equiv. person)

pg. 2-1

2: Recommendations The interaction between pollutant level and air flow rate to the space is described in more detail in this section. The first table below summarizes the average measured values of CO2 and VOCs during the test period and estimated levels after adjustments are made. The second table summarizes the calculated values of air flow rate to the space during the test period; recommended adjusted level of air flow rate to keep CO2/VOC levels below 1,000 ppm. Controlled ventilation adjustments are based on cfm values.

As air flow rate to the space increases, pollutants are diluted. Conversely, decreases to the air flow rate concentrates pollutants.

Summary Information from Your Test

The following plot provides additional details showing how air exchange flow rate, pollutant generation, and pollutant levels are related. Current pollutant levels and air exchange flow rates are shown with solid symbols for CO2 and VOCs. Also plotted on the figures are lines showing the relative pollution generation rates (equivalent people generation rates for CO2 and VOCs). Hollow symbols show how the suggested air exchange flow rate will impact pollution levels in the space.

The suggested change in ventilation is based on CO2 and VOC levels. Whichever is greater is used to determine the suggested ventilation change. If the concentration level is greater than 1,000 ppm, an increase in room ventilation is suggested. If the concentration level is less than 1,000 ppm, a decrease in room ventilation and/or infiltration is suggested. A second plot provides guidance related to trends in radon levels due to adjustments in ventilation and/or infiltration levels. Radon testing must be conducted by either certified radon technicians or by individual homeowners using state approved testing methods. The red, horizontal line in the plot marks the maximum recommended level of radon per EPA guidelines. If you have conducted a certified, state approved (where applicable) radon test concurrent with the Black Box IAQ™ test, your radon level should be plotted on the solid vertical line marked "Current Air Exchange Rate". For example, a reading of 4 pCi per liter would be a point located at the intersection of the solid vertical line and the horizontal red line. Increasing fresh air ventilation air flow may reduce radon levels, while decreasing air infiltration air flow may increase radon concentration. The second vertical (dashed) line represents an adjusted air flow rate recommended for maintaining reasonable levels of CO2 and VOCs. The curved lines represent different rates of radon flow into the tested space. Drawing a line that follows the nearest curved line from the current radon level plotted on the solid vertical line to the dashed vertical line shows the expected trend in radon due to air flow adjustments. See our case studies and informational reports for additional guidance. Conducting a second radon test after any changes to the ventilation and infiltration characteristics is recommended.


pg. 2-2

Carbon Dioxide (CO2) and Volatile Organic Compounds (VOCs)

400

600

800

1000

1200

1400

1600

1800

2000

0 20 40 60 80 100 120

Car

bo

n D

ioxi

de

& V

OC

(p

pm

)

Controlled Ventilation or Infiltrated Air Flow Rate (cfm)

CO2 & VOC Characteristics 0.5 equiv. person

1 equiv. person

2 equiv. person

4 equiv. person

max CO2 & VOC levels

preferred lower range limit

your space VOC

your space CO2

adjusted VOC

adjusted CO2

Preferred Range

0

2

4

6

8

10

12

14

16

18

20

0 20 40 60 80 100 120

Rad

on

(p

Cu

rie/

liter

)

Controlled Ventilation or Infiltrated Air Flow Rate (cfm)

Radon Level Trends versus Air Flow Rate

10 pCi/sec radioactivity flow




maximum radon level

Current Air Exchange Rate

Adjusted Air Exchange Rate

Acceptable Levels


public library poor comfort€¦ · com/blackbox/ public library – poor comfort the black box...

Documents