Utilizing several high-performance building techniques designed to make it ultra insulated and efficient, a 4,200-square-foot home in rural Pennsylvania was constructed using a systems-built approach for its three separate living areas.
The LEED-H Silver home in Kennett Square, Pa., features a Superior Walls’ Xi insulated precast concrete foundation, timber framing, and structural insulated panels (SIPs). It boasts a HERS rating of 51, 34 points below the Energy Star target threshold.
By utilizing building techniques known for their superior insulating qualities, project planners achieved optimum energy savings while conserving money and time. Built almost entirely off-site, little waste was generated during construction of what the builder refers to as a “hybrid” home, due to its combination of systems.
“For this project for the biggest bang for our buck, we decided to focus our goals on a systems-built dwelling,” project manager Amy Cornelius says of the $1 million home, adding that it could have been built for about $650,000 with less high-end finishes.
A series of three discrete living areas—living spaces, private spaces such as bedrooms, and utility rooms--built with different combinations of materials helped cut down on energy use. “When the residents are done with one area, you can turn off the lights and utilities and close the door,” says Cornelius, of West Grove, Pa.-based Hugh Lofting Timber Framing.
In addition, the home’s southeasterly exposure takes advantage of cool prevailing breezes; a dense forest to the north helps block cold winter winds. Brick flooring dating back to 1840 and local slate flooring provide additional mass and a 96% efficient Munchkin propane gas combustion boiler provides heat when needed.
“Because of its siting and [envelope], the house stays warmer in winter and cooler in summer than traditional homes in that same location,” Cornelius says. “The owners hardly ever have to run their propane boiler.
Project designers, including architect Matthew Moger of Berwyn, Pa.-based Lyman Perry Architects, aimed to reduce the home’s environmental impact by sourcing local materials, relying on recycled-content materials, minimizing site disturbance, and specing energy- and water-efficient systems and appliances. Indoor air quality and one-level living were also extremely important to the disabled resident and his wife.
Sustainable features include a storm water management plan with bio-swale rain gardens of indigenous plants, a Weston Green Grid vegetative roof over the entry foyer, two 16-SEER variable-speed air conditioning units, and two energy recovery ventilators for improved air quality.
The exterior of the home evokes the look of a historic Chester County barn with rapidly renewable rough-sawn cypress siding and a highly reflective Galvalume standing seam roof. The agrarian aesthetic continues inside with reclaimed antique barnwood floors, a 35-foot-high Pennsylvania bluestone fireplace, and exposed timber framing.
The building techniques used in the project were chosen for their ease of installation as well as their sustainable qualities, Cornelius says. She spoke about the project at December’s Ecobuild America conference in Washington, D.C., along with co-presenter Stewart Elliott of Riverbend Timber Framing.
For example, SIPs—foam core insulation sandwiched between two layers of OSB—are 60% stronger than a stud wall and can withstand 90-mph winds, according to Elliott. In addition, SIPs construction is extremely fast, Cornelius says, noting that it took one week to install Foard Panel SIPs on the Pennsylvania project.
“In the near future, SIPs will largely replace conventional construction,” Elliott predicts. “It provides the strongest structure I can think of, it works for hot or cold climates, and installation is very fast.”
Nevertheless, while the OSB is made out of sustainably farmed crop wood, the foam used in the system is a petroleum product, Elliott notes.
“You can’t put it in a landfill, but you’re putting it to work for life,” he says. “Inside of two years it’s returning a huge savings.”
Professional installation is key when working with SIPs, Cornelius points out, because the panels can delaminate if exposed to moisture.
“You need an air passage, a ½ inch between the panels and the siding,” Cornelius says. “Some manufacturers don’t say that, but it’s something to think about when designing with SIPs.”
There are issues to consider when specing an insulated concrete foundation as well, Elliott says, noting that there are two types: poured concrete blocks or a precast system, which is what was used on the Pennsylvania project.
Both provide an extremely strong, quiet, and super-insulated (R-20 to R-24) foundation, although the block system can take up to two extra days for installation. The presenters recommended professional installation for either type of system.
Last but not least, the “bones of the structure,” its three custom-designed timber frames, are made of FSC-certified Douglas fir, says Elliott. He warned conference attendees to choose a timber frame company carefully.
“There are 250 timber frame supply companies in the country, but not all of them knowledgeable about green building,” he says.
The success of a systems-built dwelling requires a large amount of up-front planning, says Cornelius, who met with more than 20 subcontractors to facilitate the Pennsylvania project.
Regular charrettes, or design meetings, were an important part of the process from the beginning and included the client, builder, architect plumber, electrician, HVAC engineer, sustainable designer, and the LEED verifier.
“We had a group meeting up front at the beginning and met weekly to talk about ways to make the home more efficient,” Cornelius says. “We set the parameters up front.”
For example, during one of these sessions, the HVAC subcontractor realized that a second mechanical room was needed. He alerted the architect who was able to rework the plans before construction began.
“We saved a ton of money by adding that second room into the plan from the beginning instead of finding out about it later,” Cornelius notes. “It was something the architect hadn’t thought of.”
The design-intensive aspect of a systems-built home can add to the cost, which is not much more than a custom home of the same size, Cornelius says.
“The architectural fees up-front are higher, because you have to have complete drawings through the mechanicals,” says Cornelius. “The client conversation you need to have is that you need to spend the money up front to save the money later.”
Also adding to the cost was the $5,000 it took to meet LEED-Silver standards, Cornelius says, adding that most of that was to pay for special fireplace doors. She advised Ecobuild attendees interested in LEED certification to do their homework.
“LEED is all about documentation, keeping your receipts and purchase orders organized,” she says. “If you do it all along, put it into the schedule to document these things, you’re fine. If you wait until the end you’ll never catch up.”
Jennifer Goodman is Senior Editor Online for EcoHome.