<— back to case studies

Case Study

Gainesville, florida

Builder Achieves HERS 53 on First High-Performance Home

In 2012, G.W. Robinson began pursuing ESHP designs after seeing the successful results experienced by other local builders (e.g., Tommy Williams Homes, see PNNL 2011 and 2012). Recognizing the difficulty of incorporating new energy-efficiency features such as ducts in conditioned space into existing home plans, G.W. Robinson took the opportunity to incorporate ducts in conditioned space into a new series of plans it is introducing, called “Generations,” that will include 30 unique house plans all based on three modified ESHP designs and one custom design. G.W. Robinson is initially building four “Generation” homes. Construction began on two of these four homes in early 2013, targeting mid-April for completion so the homes could be included in the Alachua County Parade of Homes in April 2013.

Challenges that G.W. Robinson experienced while building these homes included the following:

Attention to detail when installing soffit framing and electrical wiring. In all cases, duct soffits were very well constructed and duct connections were tight and properly sealed. However, when constructing ducts below the ceiling plane, the primary objective is to achieve a well-sealed air barrier at the ceiling plane formed by the ceiling drywall. In this home, larger than necessary holes were cut into the drywall to accommodate the soffit framing and electrical wires, as shown in Figure 5.

Fortunately, this issue was identified midway through construction and could still be easily corrected by walking the attic floor prior to insulation installation and sealing any identified holes with foam or caulk. A blower door is a great tool to use to identify holes and perform targeted sealing before the attic insulation makes those areas less accessible.

The performance impact of installing ducts in conditioned space is not clear. While G.W. Robinson believes in the concept of ducts in conditioned space, company owner and president Gay Robinson is not convinced they will result in substantial energy savings on top of their already efficient designs. G.W. Robinson typically builds homes with HERS scores of less than 60 and modeling only predicted a HERS score 1 or 2 points lower when ducts in conditioned space were included. However, G.W. Robinson is convinced that building ducts in planned, dedicated, and protected soffits results in a more durable and long-term design and a better product for its customers. These additional values make the ducts in conditioned space make sense for Gay and her company, not necessarily just the energy or cost impacts.

Generations Home Characteristics

Ducts in conditioned space must be part of the design. G.W. Robinson has considered ducts in conditioned space previously, but determined it was too costly to consider if its existing plans needed to be modified. G.W. Robinson’s introduction of a new line of home plans, called its “Generation” series, presented an ideal opportunity to design the homes to accommodate ducts below the ceiling plane in the new designs.

Effective training and communication with tradespeople is crucial to achieving success. A long- time builder in Gainesville, G.W. Robinson has long-standing and cooperative relationships with its subcontractors. G.W. Robinson also engaged and met with all the subcontractors prior to construction to explain the construction schedule so everyone was on the same page, knew what was expected of them, and knew what was coming. That way, even subcontractors who weren’t familiar with specific high-performance features could anticipate what was coming. Because of the relationships that G.W. Robinson has built and maintained over the years and the best practice of meeting as a team to review schedules, roles, and responsibilities, the company was able to build its first home with ducts in conditioned space with little to no difficulties. “We made some changes,” noted Gay Robinson, “and it required more trips [for some of the subcontractors]. It wasn’t perfect, but we didn’t have to take anything out…and people were ready for it.” G.W. Robinson also follows up with a meeting involving all the subcontractors and tradespeople after construction is completed to review how the job went and identify areas for improvement. This should ensure G.W. Robinson’s next home construction goes even more smoothly.

G.W. Robinson’s positive experience with high- performance homes and ducts in conditioned space is made clear by their plans to continue using ESHP designs in its “Generations” series. G.W. Robinson also plans to modify some of its Classic designs to bring the ducts into conditioned space as well, although the proven performance information in occupied homes is what will really convince owner Gay Robinson of the long-term value of ducts in the conditioned space.

Lessons Learned

• Ducts in conditioned space and the ceiling air barrier were instrumental in achieving moderate air leakage rates and scoring well on the HERS Index, although additional can lights penetrated the ceiling in many locations.

• Training was important for the installer to achieve best practices. Involving the builder, designer, and building science consultant in the training of all onsite workers helped to meet efficiency goals.

• Design decisions made in the field can dramatically influence energy performance. In addition to the recessed can lights, changes for this house included the addition of a swimming pool pump, downgrading the AC system, and installing a smaller PV array.

<— back to case studies