CASE STUDY. Two Dogs and Two Cats Insufficient Air Exchange with High CO2

Transcription

1 FOR MORE INFORMATION, VISIT: CASE STUDY Two Dogs and Two Cats Insufficient Exchange with High CO2 A Black Box IAQ was placed in the main living area of a pre-1900 home. The house had been refurbished with a high efficiency gas furnace (external combustion air) and had vinyl siding installed within the past five years. Two occupants live in the house with two mid-size dogs and two cats. The occupants work during the day. Page 1-2 of the report shows reasonable comfort exists in the house, with the average temperature and humidity in a range where short sleeves and shorts would be comfortable for most people. The data was collected during early summer. flow was found to be low in the main living area of the house, resulting in higher than desirable carbon dioxide concentrations. The air flow rate dial below the comfort chart on page 1-2 of the report shows an air exchange rate that is less than the 15 to 25 cubic feet per minute per person air exchange rate needed to keep pollutant concentrations acceptable. Page 1-3 confirms that carbon dioxide levels are high due to insufficient air exchange rate. VOCs (Volatile Organic Compounds) are less than 1,000ppm, indicating that other sources of pollution such as fumes from off-gassing of home furnishings, cleansers, cosmetics, and cooking odors are not significantly adding to VOC generation beyond that of the occupants (human and pets). When VOCs are from human and animal metabolism, VOC concentration will be less than that of carbon dioxide because VOCs more readily react and breakdown, and because VOCs are absorbed into building and furnishing surfaces. Page 2-1 contains a table with summary information and suggestions for improving air quality. Because carbon dioxide concentration is greater than desired, the table suggests increasing the air exchange rate to a level that will reduce carbon dioxide concentration from the measured average level of 1,599 ppm to 1,000 ppm. Assuming that VOCs are generated at a similar rate as measured during the test, VOC concentration will also be reduced from 601 ppm to 501 ppm. The table on page 2-1 recommends doubling the flow of air through the space from 19 to 38 cfm (cubic feet minute). The best method for improving air quality is with fresh air ventilation. Fresh air ventilation systems, such as our CERV fresh air conditioning system, efficiently exchanges energy between fresh air and exhaust air streams while managing air quality. Page 2-2 includes two plots that graphically display the test measurements and changes in pollutant levels due to the suggested ventilation modifications. The top figure shows the measured carbon dioxide and VOC concentration levels and the air exchange flow rate as solid markers. The hollow markers show the change in carbon dioxide and VOC concentrations after the air exchange flow rate is adjusted. Increased ventilation decreases carbon dioxide to 1,000ppm and with an associated decrease of VOC pollutants.

2 Indoor Quality Report Test Number: Black Box Case Study 6 Name: Two Dogs Two Cats address: test@buildequinox.com Test Location: Central Illinois Box Location: living room Report Date: 6/1/2012 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. Use our building energy modeling software to design a healthy, comfortable, efficient home. A free version is available at CERV: Monitor pollutant levels, get fresh air, and recover energy. Learn more at * 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. pg. 1-1

3 % Relative Humidity 1: Test Summary Information Measured Temperature and Humidity Levels: Comfort Chart Slacks & Long Sleeves Comfort Region Shorts & Short Sleeves Comfort Region Room Condition Data Points 20 Average Room Condition Temperature (F) 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. Infiltration or Controlled Ventilation Flow Rates: Optimal Flow Low Flow Exchange 10.7 cfm/person High Flow Less than to 25 Greater than 25 Exchange rate per occupant (cfm/person) 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. flow rates less than 15 cfm/equiv. person contribute to stale air and higher levels of indoor pollutants. 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. pg. 1-2

4 Measured CO2 and VOCs Levels: Optimum Optimum Excess Dilution Poor Quality Excess Dilution Poor Quality CO2 Level ppm average VOC Level ppm average Less than 800ppm ppm Greater than 1000 pollutant ranges 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 Conditioning Engineers) recommended ranges. CO2 and VOC Levels: 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. pg. 1-3

5 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 Average level Estimated level during test period after adjustment CO (ppm) (ppm) VOC (ppm) (ppm) Calculated level Recommended during test period adjusted level Recommended action to achieve adjusted level Space 18.9 (cfm) 37.8 (cfm) Add or increase controlled ventilation Flow Rate 10.7 (cfm/equiv. person) 21.4 (cfm/equiv. person) 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 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. 2-1

6 Radon (pcurie/liter) Carbon Dioxide & VOC (ppm) Carbon Dioxide (CO2) and Volatile Organic Compounds (VOCs) 2000 CO2 & VOC Characteristics 0.5 equiv. person 1 equiv. person 2 equiv. person equiv. person max CO2 & VOC levels preferred lower range limit your space VOC your space CO2 adjusted VOC adjusted CO2 Preferred Range Controlled Ventilation or Infiltrated Flow Rate (cfm) Radon Level Trends versus Flow Rate 10 pci/sec radioactivity flow 20 pci/sec radioactivity flow 50 pci/sec radioactivity flow 100 pci/sec radioactivity flow maximum radon level Current Exchange Rate Adjusted Exchange Rate Acceptable Levels Controlled Ventilation or Infiltrated Flow Rate (cfm) pg. 2-2