Tag: green architects charlottesville va

26
Jun
2017

Zero energy homes | the Passivhaus approach to reducing energy bills in homes

The focus of this discussion is achieving a zero energy home through the Passivhaus approach.

True or false – adding insulation has diminishing returns? True, doubling the thickness of a roof insulation doubles the cost while halving the heat loss/gain, and half of a half is a quarter and half of that an eighth…. So, “How low should we go?” as some have asked. The idea behind the Passivhaus program, developed in Germany, is to break through the cost barrier by sealing and insulating the bejesus out of an envelope till the need for mechanical equipment is eliminated (apart from fresh-air delivery).   What about the applicability of the system to the mid-Atlantic region? According to Galen Staengl, Passivhaus-certified energy consultant, “It’s still an open question as to where the cost/performance balance is struck in in our region where cooling and dehumidification are also required.” Even with the adaptability of the approach to different climates still being explored, the program offers valuable insight into how we might crack the zero energy code.

The Passivhaus program is performance-based. To achieve the 4.7 kBtu/ft/yr goal, recommended R-values for walls are R-40, for roofs, R-60. At the Hickory Hall project at the College of Emory & Henry in Virginia consulting engineer Staengl says this is achieved with a wall system comprised of 2×6 studs with cellulose insulation and 2 1/2″ of EPS insulation outside of the sheathing – all building techniques well understood by contractors and resulting in a cost increase of only 5%. The Contracting firm of Structures Design Build, located in Roanoke, Virginia alters the DNA of the typical wall section by adding a modified Larsen truss outside of the studs and sheathing. The truss, truss joists turned on their side with the webbing removed, is filled with cellulose.

The Passivhaus approach doesn’t stop at the envelope. In the US, where the climate varies from hot to cold and somewhere in between, and where some parts see enough humidity to wilt Blanche Dubois’ curls, energy-efficient lighting and equipment, especially hot water heating, need to be addressed.   And of course, all the other aspects we’ve discussed above are thrown into the stone soup of the Passivhaus approach resulting in a HERS rating of between 20-30.

One of the challenges of the application of Passivhaus approach in the US is availability of cost-friendly materials. Triple-pane windows, a must for the approach, are just beginning to show up in the marketplace. Happily many of the major window manufacturers are getting on-board and Marvin, Pella and Milgard all offer triple pane options. In Europe where energy codes now mandate a Passivhaus approach, triple pane windows have become the norm — and costs are lower than for double pane — the more stringent codes in Europe are affecting a radical change in the marketplace.

In addition to the significant energy savings of the Passivhaus approach, consider the indoor climate. A recently completed home in Virginia Beach uses triple pane windows and the temperature of the glass is ten degrees warmer in the winter. The increased

Triple Pane Windows

Triple pane windows in this home reduce energy bills and increase comfort. The temperature at the windows is 10 degrees warmer in the winter.

comfort associated with a well-designed envelope is palpable and a nice side benefit to reduced energy bills.

26
Oct
2015

Lewis & Clark Exploratory Center of Virginia: Engaging people is key to a building’s success

We design with the philosophy that engaging people in our buildings is key to a project’s success.  We think a lot about how to create opportunities for discovery, for collaboration, for a conversation with nature… Take for example, The Lewis & Clark Exploratory Center (LCEC).  We designed the roof as an vegetated garden/overlook to the Rivanna River.  This is where a visitor first arrives and the roof signals the building’s larger goals: to connect to the Lewis & Clark story, and to engage the visitor with nature.  The vegetated roof is to be planted with species gathered by the explorers on their journey west.  The overlook, with a replica of a ship in the foreground and the Rivanna in the background, recalls to the visitor that the exploration was carried out by river.  The building also teaches about water, how precious it is, how it is the source of life: the roof water is directed to a riverstone channel that flanks the stairs descending to the exhibit space.  Water is collected in a basin at the entry below and the visitor crosses a bridge to enter the building – again, references to Lewis & Clark’s river journey as well as modern concerns about the environment and the importance of water quality.  The building is designed to achieve LEED Silver, and its many sustainable features are teaching examples for visitors.  Best of all though is how active the center is with community activities.  The building teaches about the Lewis & Clark’s journey, about nature while serving as an ideal setting for the activities organized by LCEC.  It is gratifying to see our goals realized.  IMG_1463IMG_1478