Date of Award

Spring 1-1-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Shelly L. Miller

Second Advisor

Lupita Montoya

Third Advisor

Marina Vance

Abstract

Low-energy home design is becoming more common in new and retrofitted homes, and energy-efficient designs often sell at a premium [1]. This perceived and realized value of reducing energy use in homes is important as the need to reduce fossil fuel use becomes increasingly critical. Energy efficiency measures, like tightening the envelope of a home saves energy, but can impact the indoor air quality. We monitored the indoor air quality of nine tightly constructed homes, one tightly constructed public library, and one conventionally constructed home, and performed a repeatable cooking activity to observe the impact and response to the resulting fine particulate matter (PM2.5) emissions. We compared the PM2.5 concentrations from the cooking activity while operating the mechanical ventilation systems at default rates (~0.1-0.3 h-1) and in a temporary boost mode (~0.3-0.8 h-1). We also measured the concentrations of total volatile organic compounds (TVOCs), formaldehyde, radon, and bedroom carbon dioxide (CO2) levels. Results show that fine particulate matter concentrations are generally low indoors, but a cooking event drastically increases concentrations and levels are slow to decay. Median time above 35 µg/m3 after cooking was 4.7 hours. Overall, there was not a significant difference between operating the ventilators at standard rates and utilizing the temporary boost. Completely-mixed flow reactor models of select tested homes show that installing and using a directly-exhausting range hood could reduce peak PM2.5 concentrations by 75% or more. Current ventilation practices in these buildings may not be adequate for these common polluting events. TVOC concentrations were generally low with a median average of 459 µg/m3. Formaldehyde was above the California Office of Environmental Health Hazard Assessment (OEHHA) chronic limit of 9 µg/m3 across all tight buildings with a median value of 30 µg/m3 . Carbon dioxide levels in bedrooms were high at night (>1000 ppm) in six of the homes, indicating that current bedroom ventilation practices are not consistent nor adequate. Bedroom air exchange rates (AER) determined from carbon dioxide decay ranged from 0.08 to 0.30 h-1 with a median value of 0.12 h-1.

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