Buildings currently account for 40% of the total energy use in the United States, but we’re seeing many organizations working to change that statistic by building more sustainably and reducing their carbon footprint. Whether it’s through simple updates like installing occupancy sensors for lighting and Energy Star appliances or through a third-party certification like the International Living Future Institute Zero Energy Building Certification to validate their efforts, becoming more energy efficient is a top priority. One such organization, Mass Audubon, has committed to achieving net zero energy on all future building projects, and Chapman had the opportunity to work on one of these projects at their Drumlin Farm Wildlife Sanctuary in Lincoln, MA. With their new Environmental Learning Center, Mass Audubon was seeking not only to achieve net zero, but also to create a building that would serve as an energy efficiency model for the organization’s future projects.
The concept of a net zero building is simple enough – the building produces as much energy as it consumes annually – but constructing one can be considerably more complicated. When the project’s successful outcome is riding on the care in which your building is constructed and its end performance, the details can seem overwhelming. Our experience on the Drumlin Farm project taught us that success lies in the team’s attention to detail, and we’d like to share our top tips to achieve net zero energy:
Given that the success of Zero Energy Building Certification is determined by quantifiable results, you’ll want to assemble your team early and set clear expectations from the beginning. Plan to dedicate a lot of time up-front developing a deep understanding of every design detail and reviewing them with the subcontractors to ensure that they have reflected them in their pricing and carried enough money to get the job done. At Drumlin Farm, for example, we met with the owner and the foreman of the framing company before awarding the job, doing a plan review and directing their attention to the many air sealing details that they would have to execute.
Collaboration is key with any construction project, but it’s even more crucial on a net zero building. Success depends on everything being done right the first time, and we found this was best achieved through constant onsite collaboration. Have the architect confirm you are building to their specification before you move on to the next step, work with manufacturers to verify that you are using their products in the most effective manner. During the window sealing at Drumlin Farm, the architect and tape manufacturer were onsite and worked with us when we installed and air-sealed the first window; this added collaboration helped us achieve the needed results.
Selecting the proper materials upfront can help avoid a lot of headaches. Review your materials menu to verify that the products specified are suitable for the building’s environmental conditions and determine whether there are alternatives that could help achieve better results. Drumlin Farm’s tight schedule required that the building envelope be sealed in the middle of winter, so our team undertook extensive research to identify products that would work in extreme weather conditions. Finding products with the smallest environmental impact is also important. At Drumlin Farm, we insulated between the studs and rafters with dense pack cellulose (recycled newsprint) because its global warming potential is more than 95% lower than spray foam insulation.
The success of net zero construction is dependent upon envelope and air sealing details that keep air from entering or leaving the building through the floor, walls, and roof. To ensure that the building is extremely air tight, you need an incredibly attentive site supervisor who will study the drawings and develop a sound plan to accomplish the architect’s vision. At Drumlin Farm, our site supervisor worked tirelessly with our subcontractors making sure every precaution was taken while constructing the tightly air sealed envelope and even jumped in to self-perform some tasks when needed to ensure the building was properly sealed.
The tightness of the building envelope is measured by a blower door depressurization test that, if sealed to net zero standards, will exceed code air leakage standards by 300%. At Drumlin Farm, we tested at multiple stages so we wouldn’t have to re-do work. For the final test air leakage through the building envelope was not to exceed 646 CFM at 50 Pascals of air pressure produced by a blower door fan. The result we achieved was one-third of that allowed – 224 CFM at 50 Pascals – and a true testament to our careful preparations and attention to detail throughout the job.
By taking the extra time to consider every detail our team was able to achieve great results at Drumlin Farm. More than meeting all of the standards for a Zero Energy Building Certification by the International Living Future Institute, Mass Audubon’s new environmental learning center will likely exceed those original expectations and prove to be net positive.