Passive House in Different Climates

The Path to Net Zero

Mary James, James Bill

• Publisher: Routledge
• Year: 2016
• ISBN:
  9781317446279
• Edition: 1
• Topic: Architecture
• Subtopic: Architecture General

Passive House in Different Climates introduces the seven Passive House principles, to help you create super-insulated, airtight buildings that require minimal energy use to heat, cool, dehumidify, and ventilate, with superior indoor air quality and year-round comfort. Seventeen case studies in four climate zones---marine, cold and very cold, mixed-dry and hot-dry, and mixed-humid and hot-humid---and in ten countries, show you how to achieve net-zero energy regardless of where you're building or what type of building is required. Includes more than 150 color illustrations.

1 Seven Principles of Passive House Design

DOI: 10.4324/9781315696553-2

Fig. 1.1 Courtesy Ann Vogt

A thorough understanding of the following Passive House (PH) principles, which are briefly summarized here, is essential for constructing a PH building. Successful completion of a PH project generally depends on all members of a design and construction team being familiar with these principles and committed to their implementation. As important as understanding the technical aspects of the PH process is, an interdisciplinary approach with good communication and coordination among team members is also critical.

Fig. 1.2 Courtesy Ann Vogt

Fig. 1.3 Courtesy Ann Vogt

1. Superinsulate the entire envelope of the building—walls, roof, and foundation or crawlspace (Figs 1.1, 1.2, and 1.3). The level of insulation will depend on the local climate and the building’s design; the appropriate level can be determined by using the building energy modeling software, the PHPP. In milder climates, superinsulating a building may translate to little additional insulation compared with a conventionally constructed building, depending on the building’s features and the quality of the other components. In especially favorable climates, such as San Diego, California, insulation may not be needed at all under the slab. In colder climates, such features as the size of the windows on the north façade will greatly influence the amount of insulation required in the building assemblies. And, the ratio of exterior envelope to conditioned interior space is critical in determining how much insulation will be needed. Large multifamily buildings, even in cold climates, may have insulation values that approach the levels found in typical construction.
   There are no requirements for the type of insulation used. Passive House buildings have been constructed using such insulation materials as cellulose, blown-in fiberglass, mineral wool, expanded polystyrene (EPS), cork, and even sheep wool, among others.
   From an environmental perspective, the choice of insulation materials will contribute greatly to the overall embodied energy of the building. As there is generally more insulation in PH walls, there is generally more embodied energy and carbon in the walls as well when compared to a conventionally built house. The payoff for this embodied energy is the energy savings over the lifetime of the building, which reduces the total embodied and operating energy. In most cases, the annual energy use of a conventionally built house quickly results in its total embodied and operating energy outpacing that of almost all PH assemblies. If reducing the embodied energy or carbon of a PH is a goal, then avoiding the use of spray foam insulation made with a hydrofluoro-carbon (HFC) blowing agent is advised, as is minimizing the use of such energy-intensive materials as concrete and even oriented-strand board (OSB). Recently, polyurethane foams made with more environmentally friendly blowing agents have hit the market.
2. Eliminate thermal bridges, or areas with relatively higher thermal conductivity than surrounding areas. Thermal bridges, such as the studs in a highly insulated wall assembly, provide easy pathways for heat loss in a structure, diminishing the actual, delivered R-value of the assembly. They can also cause moisture problems if warm, moist air condenses on a cooler surface. Common thermal bridge locations include rim joists, parapets, and footings at or below grade. However, these and other thermal bridge details can be designed in such a way as to minimize or even eliminate thermal bridges (Fig. 1.4). Special attention often must be paid during construction of these details to make sure that they are built as specified and not altered to fit the contractor’s usual practices.
3. Create an airtight structure. A continuous air barrier layer around the entire building envelope reduces the need for heating and cooling, eliminates drafts, and makes the building more durable. Achieving the airtightness criterion is often the biggest hurdle for novice PH builders and designers. When it comes to airtightness detailing, simplicity and consistency are characteristics that increase the likelihood of getting these details implemented correctly by the construction crew (Fig. 1.5).
   As Terry Nordbye, certified PH tradesperson and airtightness specialist says, “Achieving the required 0.6 ACH₅₀, or the EnerPHit standard of 1.0 ACH₅₀, for Passive House is a mundane, inglorious journey into an acute focus on sealing such minor gaps as a ¹/₃₂-inch space between two objects. Strategies for air sealing have to begin at the desk of the architect during the design phase and the specifications for air sealing should be on the plans and deciphered with the builder, and preferably with the building team, before a hammer is ever picked up.”
4. Specify mechanical ventilation with heat or energy recovery, depending on the local climate (Fig. 1.6). A mechanical ventilation system supplies fresh air and exhausts stale air in specified volumes, providing for excellent indoor air quality (IAQ). When adding in either heat or energy recovery, the recovery efficiency is essential to reducing a building’s overall conditioning energy use, as is the efficiency of the fan motor, because the mechanical ventilation system is likely to be running 24 hours a day every day of the year. The efficiency of the ventilation system becomes increasingly critical to achieving low overall energy use as the scale of the PH project increases. In a multifamily building, each apartment will require fresh air, and often multiple systems are employed to meet these needs.

   

   Fig. 1.4 Courtesy Anne Vogt

   

   Fig. 1.5 Courtesy Anne Vogt

   

   Fig. 1.6 Courtesy Korin Krossber for PlanOmatic

   The local climate will largely determine whether a heat recovery ventilator (HRV) or an energy recovery ventilator (ERV) should be specified. ERVs are more typically used in climates with greater humidity, as the enthalpy core in an ERV conserves moisture, as well as heat, limiting the outdoor humidity from entering a building during humid months and conserving the indoor humidity during dry months. In warmer marine climates, in buildings where leaving windows open does not trigger safety or allergen concerns, the mechanical system may be turned off during the warmer, summer months, but this approach can lead to problems with poor IAQ. Studies of pollutant exposures from cooking and off-gassing of materials have highlighted the importance of appropriate ventilation rates in airtight homes. While a mechanical ventilation system that runs continuously does incur an energy penalty, installing such a system in an airtight house on balance saves energy in most situations and climates. A simulation study by researchers from Lawrence Berkeley National Laboratory investigating the energy losses and savings from installing mechanical ventilation in 50,000 virtual airtight homes across the United States found that adding ventilation would increase residential site energy demand by 0.07 quads annually, but that improving the airtightness of all homes to meet current average retrofit performance levels would decrease demand by 0.7 quads annually. Upgrading all the homes in the study to be as airtight as the top 10 percent of similar homes would double the savings, leading to roughly $22 billion in annual savings in energy bills.
5. Install high-performance windows and doors. Well-insulated windows and doors that seal tightly significantly reduce thermal losses through the building envelope, virtually eliminating the cold drafts and convective heat losses commonly felt when sitting near low-performance windows. High-performance windows typically have U-values of 0.4 to 0.6 for the glass, translating into R-values for the whole window that are greater than 7.0. The solar heat gain coefficient (SHGC) for such windows can range from 0.3 to upwards of 0.7, with the appropriate SHGC dependent on local climate and the façade on which a given window will be installed. While the original high-performance windows tended to have bulky frames, the newest designs feature slim frames with maximal glazing area. Such products are widely available throughout Europe, and increasingly on other continents as well. The PHI, which was founded in Darmstadt, Germany, in 1996 to conduct research and promote the design and construction of highly energy-efficient buildings, instituted a certification program for PH components in 2000, including windows, doors, and solid-wall components. In 2013, manufacturers in 22 countries—mostly in Europe, but also in North America and Asia—were producing 232 PH-certified transparent components, of which 119 were PH-certified windows. As the availability of high-R-value windows has expanded in the United States in the last decade— albeit still mostly imported from Europe—the price has started to drop as well, making the creation of very high-performance envelopes more cost effective. And, as the high-performance window market matures, it is becoming easier to find windows whose designs are fine-tuned for specific climate zones. Quadruple-pane windows are now available for extremely cold climates, as are well-insulated, low-SHGC windows for warmer climates.
6. Minimize energy losses and manage energy gains. This concept seems straightforward and even obvious, but many, if not most, buildings are not designed with energy impacts in mind. Designers of PH buildings must assess the extent to which various factors—including the local climate, available solar resources, window placement, internal plug loads, and more—will affect the energy balance in a building. For example, in warm, humid climates, shading to limit direct solar gains is essential for dampening peak cooling loads, not only in the hottest months but also in the swing seasons. In heating-dominated climates, strategically placing more windows on the south-facing façade can go a long way towards reducing heating loads. In an office building internal plug loads can dominate the energy balance, sometimes leading to year-round cooling needs even in cooler climates.
7. Use the PHPP for energy modeling. The PHPP is an extremely detailed building modeling tool, created by the PHI, that integrates local climate data with data on every element of a building to forecast its energy use. The accuracy of the PHPP has been validated many times by comparing modeled energy use to monitored energy use in projects in Europe. As with all modeling tools, the assumptions built into the model need to be understood when applying the tool to new environments. In the United States, for example, consumption by miscellaneous electrical loads can outstrip the assumptions built into the PHPP. In one PH built in Washington State, the heating and cooling loads were exactly as predicted, but the difference in actual compared to predicted electrical loads was another matter—a 70 percent increase over the PHPP-modeled results. Designers of PH buildings can work with clients to lower consumption; they might also tweak the forecasted energy assumptions in order to get more realistic estimates for sizing on-site renewable energy systems. Owners and occupants of PH buildings, if motivated, can bring total loads more in line with predicted loads by buying and installing only very efficient appliances, using high-efficiency lamps such as light-emitting diodes (LEDs), and consistently using power strips to turn off miscellaneous loads when not being used. Another important consideration is that the PHPP is a static model, not a dynamic one, and tends to dampen peak loads. This modeling approach works well in heating-dominated climates, because airtight, well-insulated buildings both buffer indoor conditions from outdoor temperature changes and conserve heat, thus dampening peak demands. However, the PHPP can underestimate peak cooling demand in warm, humid climates; in these climates it might be advisable to also use a dynamic simulation model to forecast comfort conditions for occupants throughout a building during worstcase conditions.

Table of contents

• Cover
• Half Title Page
• Title Page
• Copyright Page
• Table of Contents
• Acknowledgments
• Introduction
• 1. Seven Principles of Passive House Design
• 2. Applying Passive House Principles in Different Climates
• 3. Evolving Passive House Standards
• Marine
• 4. Cohousing for Seasoned Folks, Portland, OR
• 5. Orchards at Orenco, Hillsboro, OR
• 6. Renovating a Family Pharmacy, Clonmel, Ireland
• 7. The Existing District of Tomorrow, Kerkrade, Netherlands
• Cold and Very Cold
• 8. TAO House, Taos, NM
• 9. Building with Straw, Bad Deutsch, Austria
• 10. Warren Woods Ecological Field Station, Three Oaks, MI
• 11. Kolla School, Kungsbacka, Sweden
• Mixed-Dry and Hot-Dry
• 12. Conversion of an 1880s Hay Barn
• 13. Taller Passivhaus México, Mexico City, Mexico
• 14. Casa Troni-Brien, Lo Barnechea, Chile
• 15. Library of Villamediana de Iregua, Villamediana, Spain
• 16. Adjoining Office and Residential Buildings, Zhuozhou, China
• Mixed-Humid and Hot-Humid
• 17. A Brooklyn Row House Revived, Brooklyn, NY
• 18. Mamaroneck EnerPHit House, Mamaroneck, NY
• 19. Ivy City Passive Townhouses, Washington, DC
• 20. Zero Energy Design House, Iksan, Korea
• Bibliography
• Index