An Investigation of Optimal Pressurization for Buildings in Hot and Humid Climates

Abstract

Buildings in a hot and humid climate usually are kept at a positive pressurization level to avoid infiltration induced issues such as mold growth within building envelopes. This dissertation combines existing models of infiltration and mold growth to predict the influence of pressurization level on the risk of mold growth. The simulation results indicate that a 3 meter high unpressurized building in College Station, TX with 22⁰C indoor temperature set-pint will experience an annual increase in mold index, and 1.5 Pa positive pressurization should theoretically eliminate the long-term risk of an increasing mold index on all walls. The model also indicates that only 1 Pa pressurization is required if the same building is moved to Fort Worth, TX and no pressurization is required if it is moved to Atlanta, GA. Furthermore, a field experiment indicates that the conventional pressurization system fails to pressurize each floor of the eight-floor Harrington Tower building equally due to stack effect; extra make-up air is required to compensate the leaked air through the over-pressurized floors which results in extra energy consumption. An Internal Fan Balancing Pressurization System is proposed to solve this problem. The building energy simulation results suggest that the annual energy cost savings from using the proposed system can range from 3.7% to 6.7% of the total utility bill depending on different assumptions. To verify the feasibility of the proposed system, a scaled three-floor model is developed; on the scale model the Internal Fan Balancing System is able to reduce 28% to 32% of required make-up air flow by keeping better pressurization levels.