With Louisiana’s summer weather starting to bear down on it, a 1,200-sq.-ft. house in the south-central part of the state designed to meet Passive House standards has so far been performing as designed.
GBA posted an item about the project back in February, as construction neared completion. The house has been variously dubbed “the 204House” or the “LeBois House.”
The project architect, Corey Saft, a professor of architecture at the University of Louisiana, provided us with energy efficiency details about the three-bedroom, two-bath house and said he was aiming for LEED Platinum certification as well as certification by Passive House Institute US. Given Louisiana’s relatively long hot-and-humid summer season, achieving the latter goal seemed like an especially interesting challenge, as one observer, GBA Advisor Carl Seville, noted in the comments section of the post.
Taming the cost of dry comfort
But a recent story on the project posted by The Independent Weekly, which serves the Acadiana region of south Louisiana, explains that the house, while still awaiting word on LEED certification, was certified in June by Passive House Institute. Just as important, the house continues to provide a high level of interior comfort to its three occupants – students attending UL’s architecture school – and the home’s utility bills hovered near zero in March and April (minus 62 cents, then $5). Over the course of a year, Saft estimates, utility costs likely will average less than $25 a month.
“There was a sense of relief, really,” Saft told the paper. “You don’t want to be too optimistic. I mean everything you read says one thing, but usually it never comes out that good. So I was definitely pretty surprised. It was hoped for, I wouldn’t say anticipated. It’s the first time this was done in a hot, humid climate where everything kind of worked out the way it was supposed to.”
Insulation, airtightness, and an ERV
The shell of the house features R-28 Icynene LD-R-50 walls and an R-55 Icynene LD-R-50 roof, with 2×6 and 2×8 advanced framing. The exterior walls are wrapped in 1-inch polyisocyanurate, the roof in 2-inch polyiso. Siding is pre-painted fiber cement board and white standing-seam metal panels, with a 1-inch space between the siding and polyiso to help “shade” the walls and prevent heat and moisture buildup. R-21 extruded polystyrene (XPS) was used for the basement/crawlspace walls, and R-16.5 XPS under the slab. The house is fitted with SeriousWindows’ 501 series vinyl-frame windows, with SeriousGlass 8 double-pane glass.
During full summer heat, the house will lean heavily on its energy recovery ventilator, an UltimateAir RecoupAerator, to reduce humidity and air temperature, but it also is equipped with a 1-ton ductless mini-split air conditioner with a single vent.
On pricing and appraisals
Saft said he aimed for affordability, and in fact construction and materials costs – including a 3.25 kW thin-film photovoltaic system – came to a pretty reasonable $120 per square foot, although the architect emphasized in the Independent Weekly story that, as has been noted time and again by green builders, projects with high-performance features are still not abundant enough in most markets to appraise realistically.
“If you’re rich and you want to make a zero energy house, it’s not that hard. But the trick is to make it standard practice,” Saft told the paper. “For me, it’s making it cheap and staying inside the realm of standard practice, and that hopefully will inspire other people to do it. Hopefully, little by little, projects like this will help establish some precedents.”