At last week’s Construction Tech we welcomed Trey Farmer and Nikki Kruger of Therma-stor to talk about the technical, technique, and the technology of dehumidification of Passive House buildings in hot and humid climates. In addition to having Nikki take us as deep into the weeds of building science as we’ve ever ventured in a Construction Tech episode, we also heard from Trey about his experience living in a Passive House home in Austin, TX, throughout February’s power crisis.
To recap, millions of people in some of the most southern regions of the United States experienced a wave of three consecutive winter storms and extremely cold temperatures back in February. In Texas, some days were the coldest on record, and at one point it was actually warmer in Anchorage, AK (61.21° N) than it was in Austin (30.26° N). (A comparable comparison would be Saint Petersburg (59.93° N) and Cairo (30.04° N).) While most states saw only limited power outages, the energy infrastructure in Texas experienced widespread failures, largely due to poor planning and even worse policy decisions. For most homeowners and renters, this meant they had to experience those freezing temperatures without power and without heat in homes that had been built without significant insulation. One can guess what happened to many water pipes.
The situation was very different for Trey. He watched the chaos unfold from the comfort of his Passive House retrofit, which was certified under PHIUS+ 2018 pilot program and achieved a final score of 0.4 ACH50 after some help from AeroBarrier. (Prior to the retrofit, the home, which had originally been built in 1914, had a 16 ACH50.) Though he did lose power for three days in February, the temperature inside his home only dropped from revealing that his home only dropped to 62° F (about 17° C). The only concern was that CO2 levels in their bedroom increased the second night to 3200 ppm, which is significantly lower than the OSHA limit of 5,000 ppm, but still higher than where it ideally would be.
Nikki, meanwhile, talked about the importance of dehumidification systems not only in Trey’s home, but in all homes, to keep them at optimal levels (approximately 50% relative humidity). Air conditioning units can be used to eliminate moisture problems in the summer, but shoulder seasons sometimes do not get warm enough to warrant turning on the A/C, but may still see relatively high dew points. This means more than just discomfort. It means mold. This can be particularly problematic in very tight homes.
To learn more, check out the video above. You can find some of the links that were shared in the chat below:
Ductwork for ERVS, Dehumidifiers, and Forced-Air Heating Systems (Green Building Advisor)
Controlling Humidity in Warm Climates (The Journal of Light Construction)
Faster Horses & the Future of HVAC (Positive Energy)
ZERH Webinar: Lazy Air Conditioning: HVAC and Humidity Control (Text Only) (Office of Energy Efficiency & Renewable Energy)