Page 24 - Zero Net Energy Case Study Homes-Volume 2

CASE STUDY NO. 6
PASSIVE HOUSE LOS ANGELES (PHLA+)
(Above) Wall section showing the design of the insulation layers in the exterior wall and roof. (Courtesy of PARAVANT Architects)
(Right) View of automatically adjusting exterior blinds in response to solar position. (Photo by Christian Kienapfel)
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Zero Net Energy Case Study Homes: Volume 2
Building Envelope — Insulation and Windows (cont.)
The roof construction consists of a similar combination of types of insulation products, with the blown insulation between the roof joists and rigid insulation board7, which provides the necessary slope for roof drainage in addition to mitigating thermal bridging. The net result is the high overall R-value for the roof assembly of R = 45. The concrete floor has a layer of rigid insulation below the slab, resulting in an insulating value of R = 10.9.
High quality windows and doors with thermal break details are typical of Passive House require- ments. In the case of PHLA+, triple-glazed “tilt and turn” windows8 manufactured in the European Union were selected for their thermal characteristics, air-tightness and for their sound attenua- tion characteristics. The flight patterns for airlines using nearby LAX were about to be relocated above the building site, so the owner opted for the higher grade of window for noise control. (See the discussion in the section below, “Post-Occupancy: Observations and Conclusions”, for the practical issues that this design decision ultimately raised.)
A sophisticated “smart” window shading system9 is employed to shade all the windows automati- cally and admit maximum daylight. This exterior blind system is controlled by sensors located on the roof to respond instantaneously to the sun’s position to change the angle of the blades and the distance between them so that no direct sun reaches the glass. The result is that the house always feels light and open while minimizing solar heat gain.
Building Envelope — Airtightness
As noted in previous case studies in Volume 1, airtightness is one of the keys to minimize en- ergy use in residential construction. Refer to the Sidebar: Airtightness, which summarizes this discussion and defines the airtightness standard for Passive House designs compared to other typical types of construction.
7 SecurShield PolyisoTM by Carlisle. This product is a closed-cell polyisocyanurate foam.
8 Zola clad-wood Arctic line, https://www.zolawindows.com/clad-wood#Slide4
9 Warema external venetian blinds, https://www.warema.com/en/internal-venetian-blinds/exter- nal-venetian-blinds.php