Recognizing a housing crisis in New England, where many renters and homeowners pay over a third of their income on housing, much of which includes homes that were built before 1950 and are extremely inefficient, the ∆T90 team at Norwich University in Vermont designed a high performance, affordable solution that has been accepted in the Solar Decathlon 2013 that takes place in October 2013 in Irvine, California.

Addressing concerns that include inefficient heating systems, insufficient insulation, and leaky construction of door and window assemblies that contribute to fuel costs that are sometimes equivalent to mortgage payments, the ∆T90 team took “an unapologetic design position” to deliver a modular home that is tailored to the northeastern region of the United States.


The 1000 square foot, solar-powered ∆T90 house provides two bedrooms and one bathroom with an improved cost-to-benefit performance ratio while raising the expectations of what can be achieved in an affordable, high-performance home. The solution is designed to maintain an interior temperature of 70 degrees Fahrenheit, even when outside temperatures drop to 20 degrees below zero, all while achieving net zero energy usage.

The team of students constructed a building envelope that slows the rate of heat energy transmission by incorporating passive and active systems. The exterior wall includes 14 inches of insulating materials. The need for a mechanical room is eliminated by the utilization of a ductless mechanical systems and an instant water heater.

The estimated base cost of the ∆T90 home is $195,000, which is affordable to Vermont households that earn 20 to 30 percent less than the state’s median income level, to prove that solar energy can be affordable.