Princeton University

School of Engineering & Applied Science

What to do about old energy inefficient homes: a case study

Prof. William K. George, Jr., Visiting Professor, Mechanical and Aerospace Engineering
Friend Center, 109
Monday, March 31, 2014 - 7:30pm

Approximately 25% of our energy usage in the USA is residential, and substantially more if personal transportation is included. Clearly the most straightforward solution to increased demands for cleaner energy, less CO2 production, and the demands of climate change is to use less energy at home, and produce it with renewable resources. This is relatively straightforward in new construction, but quite difficult in old. This presentation will be about the experiences of the lecturer (and his wife) converting a 1929 classic bungalow in a historic district into a Zero Energy Home.
The 46 solar panels (44 grid-tied, two solar hot-water) could provide only about 20% of the annual energy previously used in the home. So in order to provide enough energy for heating and cooling using a highly efficient inverter-driven split-system heat pump HVAC, low energy appliances, electric automobile charging for a Chevy Volt and a surplus to offset other carbon uses, aggressive reduction in winter heating and summer cooling demands was necessary. Ample use of insulation and radiation barriers were crucial, but complicated by the historic district requirements which limited exterior changes. The most difficult problems were controlling leakage air flow while providing proper ventilation, and solving the problem of vapor diffusion and condensation in the structure (especially the masonry parts). Use of innovative techniques and materials (including aerogel and smart materials) provided the solution. The methodologies employed can be readily applied to improve millions of existing homes or in new construction; and if employed would substantially reduce our future energy needs. A smart grid which can utilize home energy sources and local storage opens even more possibilities.