Energy-Efficient Remodel Delivers More Space, Lower Bills

Carl Seville—principal of Seville Consulting— is a green builder, consultant, educator, and writer on sustainability with over 28 years of experience in the construction industry. The moment Seville walked into this 1918 house in the Druid Hills historic district of Atlanta, he knew it would be a great green renovation and addition project. Below, Seville describes how he doubled the size of his house and made it over 60 percent more efficient.


Project Challenges: Accomplishing More with Less
Starting with the original three bedrooms and two baths, my goal was to expand the house to a total of five bedrooms, including a new master suite, a new family room and kitchen, and a screened porch, incorporating green building features and techniques throughout the project. I was able to accomplish these additions with only a small first floor addition and three new dormers in the attic.

I found myself using primarily standard products and techniques rather than cutting-edge technology. Due to the high initial cost and the limited financial incentives, I did not include solar hot water or electricity generation in the project. My costs were approximately $450,000, which allowed for significant donations and discounts and took into account the fact that I would be acting as the project manager and general contractor. Jimmy Carrion of SawHorse served as the architect.

When making all major decisions, I considered the main tenets of green building: energy efficiency, health, durable construction, and sustainable materials. Using energy efficiency as my guiding principle, I sought out materials and techniques that would provide me with an efficient house.

Our approach to this project was strongly influenced by building science—the study of the house as a system. The key concepts of building science are the movement of air, heat, and moisture in and out of buildings. I believe selecting healthy and natural materials, while important, serves little purpose if the underlying building is inefficient, unhealthy, and not built durably. These green materials are wasted in poorly performing buildings, often negating the extra value that they bring to a project.

Design: Keep Heat In, Moisture Out
Seeking to reduce the environmental impact of the project while providing the additional space desired, I worked with my team to develop a design that retained the entire existing foundation, the first-floor framing, and the majority of the first-floor walls. The new second floor was created almost entirely within the existing roof volume, reducing the amount of demolition waste.

All homes can develop problems if exterior moisture is not carefully controlled. Rainwater that enters the wall cavity can cause wood rot and mold. To eliminate this possibility, I installed a Tyvek water-resistant house wrap on all the new walls, with Grace Vycor flexible flashing tape around the door and window openings carefully integrated with the house wrap, to shed the water that inevitably wicks through the stucco and brick veneer. Most people don’t realize that the exterior finish on a house, whether it is brick, stucco, or siding, does not keep moisture out of the structure. It is the barrier behind the siding that keeps the house dry.

Energy-Saving Systems and Appliances
I selected spray foam insulation from Icynene to create a completely sealed and insulated thermal envelope, including insulating the attics, basement, and crawlspaces. This allowed me to reduce the size of the heating and cooling systems, as they did not have to overcome the extreme temperatures found in typical vented attics and crawlspaces. My HVAC contractor carefully sized the systems, insuring that the equipment maintains proper humidity levels and runs as efficiently as possible year round. Energy Star appliances, tankless water heaters, and dimmable compact fluorescent bulbs further reduced energy usage.

I incorporated various water-saving techniques, including dual-flush toilets and Metlund on-demand hot water pumps. When hot water is needed at a sink or shower, we press a button that draws water from the heater while circulating it back down the cold water line and delivering hot water to the fixtures in a matter of seconds. I ran across an interesting challenge with the tankless water heaters: They require a minimum volume of water flowing through them before they will turn on, and the pump was not able to draw enough volume to start the heater. I needed to relocate the pump to a larger water line that provided adequate water flow.

Results: A Healthy, Energy-Efficient Home
The spray foam insulation that makes the house energy efficient also improves indoor air quality by keeping pollutants such as pollen and auto fumes out of the house. Combining the air sealing with efficient HVAC systems, high-quality filters, and fresh air intakes creates indoor air so clean that dusting is rarely needed.

Another benefit of careful air sealing is humidity control. In houses that are not well sealed, moisture in the air flows freely, allowing the house to become humid in the summer and dry in the winter. In a well-sealed house, moisture in the air does not flow into and out of the house easily, which keeps it drier in the summer and more comfortably humid in the winter.

In a house as tightly sealed as mine, however, it is important to avoid introducing pollutants into the air, as they do not disperse as quickly as they would in a leaky house. I selected low-VOC paints and floor finishes, limiting the toxic chemicals present in the house and further improving the indoor air quality.

My house was tested with a blower door both before and after the work to check the amount of air leakage and confirm the performance improvement. Before the work, the house tested at 0.76 ACHnat (Air Changes per Hour at natural pressure). After completion, the results were 0.24 ACHnat, well below the maximum allowable 0.35 of the program.

The house is comfortable in all seasons and the air is fresh and clean. After analyzing my utility bills, I determined that the completed project is over 60 percent more efficient. Although the house is more than twice as large, it uses less energy than before.

Resources
Carl recommends the following resources and consults them for his own projects.

Building America
Building Science Corporation
Energy and Environmental Building Association
Energy Star
Environmental Design and Construction Magazine
Green Builder Magazine
Home Energy Magazine
HousingZone Green Building Forum
Natural Home Magazine
Sustainable Buildings Industry Council

For more links, visit the Building America website.