GREGORY LEHMAN:super-insulated duplex

Project overview

The goal of this project was to incorporate as many green features as possible while still being cost competitive on the rental market. To get objective performance results we monitored a separate meter on one of the units showing kilowatt hours used for the heaters. The cost for a six month heating season was $185 or averaging just over a $1 per day. See more details on heating performance in the technical section below.

Most green buildings are either high-end custom homes or self-built personal homes. With this project we are providing a low energy home for renters. To keep costs down we did most of the work ourselves and minimized subcontractors.

We broke ground in March of 2007 and completed the project in November 2008. In 2009 we added a rain garden which collects runoff from hard surface areas. In addition, we installed three parking areas on the street paved with permeable pavers which have grass growing up through them.

This project was developed by RGM Properties, LLC which is run by my father, Merritt Lehman, and me. My company, Lehman Design & Mfg, LLC, designed the house and acted as general contractor.

Focus on energy efficiency

Because the house is so compact and highly insulated, we eliminated the central heating system. The air source heat pump, which is like one found in a hotel room both heats and cools. Heat in the lower level is provided by small baseboards in the bedrooms and an electric heater with a fan in the bathroom.

We tracked the performance of one unit from February 1st 2009 to February 1st 2010. The cost to heat the unit came to $185.24 which averages to $30.87/month or $1.03/day. The square footage of the unit is 1150. A separate meter which tracks electric used by the heaters showed 2795.5 kilowatts used during the six month heating season of mid-October to mid-April.

NIPSCO, our utility provider, offers a “good cents” rate for houses heated with heat pumps which during the heating season is $0.055/Kwh after the first 500 Kwh. The first 500 Kwh are at a higher rate, but the other electric use in the house surpasses that number each month. The real cost after the utility company’s three adjustment factors and Indiana state sales tax is around $0.066 per Kwh which is what we used to get our dollar figures.