This is a two story building with an air handler placed downstairs. This configuration results in negative pressurization of the lower floor in range of 10 Pascals. Unfortunately, this is actually a quite typical condition in hot and humid climate, achieved by combination of factors, such as unbalanced exhaust fans and other HVAC errors and omissions.
Why do I write about it? The measurement was made at the entrance door. The frame of this entrance door could be disassembled with bare fingers – all that was left was an intact paint coat supported by fins of wood growth rings. The rest of the wood was eaten away by termites in a couple of years. It’s a result of sucking hot and humid air around the door perimeter into the cooler environment, creating moist conditions perfect for microbial and insect growth. In this case it was termites, which ate away the untreated wood frame components, made of the average poor quality soft wood sold in home improvement stores under the name of fir-spruce-pine.. They left a pressure-treated wooden buck intact, which indicates the need for pressure treatment of all wood components installed in hot and humid climate.