What is a Passive House? Understanding the Principles Behind This Sustainable Housing Movement
When people think about a home that uses very little in the way of heating or cooling, the result is often not very positive. Older homes without ductwork tend to be drafty in the winter and stuffy or hot in the summer, although they require less energy. The concept of the passive house attempts a return to the low-energy consumption of the past without sacrificing modern comfort.
A Passive House is one that meets some of the highest standards in air quality and energy efficiency. Specifically, it allows homeowners to maintain a constant, comfortable indoor temperature while using 90 percent less energy than the average. The way to achieve this varies based on the property, home type, location, and use. Homeowners have a lot of options to reach the standard, although it usually requires the help of an expert to get there. This guide explains the Passive House methodology and how it relates to home efficiency.
Table of Contents
- What Is a Passive House?
- The Passive House Standard
- Passive House Certification
- Following the Passive House Trend
- Looking for Tax Credits & Grants
- It’s Not All or Nothing: Striving Toward Greater Efficiency
What Is a Passive House?
Passive House is a set of standards for constructing a building that ties to a particular philosophy. The principle, originated in the 1970s, claims that energy efficiency is key to a building’s comfort and operation over its lifetime. Homes with the Passive House classification meet the highest efficiency standards of conventional new building design. Every aspect of the structure is optimized to reduce energy usage below a certain level. The result is a healthy, comfortable living or working space that consumes a tiny fraction of energy compared to nearby buildings of a similar size and function.
The concept of a “passive house” may provide both meaning and a misnomer. The idea comes with a better understanding of what passive and active energy efficiency actually means within a home. In most structures, efficiency comes through production and retention. The building envelope, which describes the ability of the structure's exterior to protect the indoor environment from the outdoors, provides passive efficiency. For example, a furnace is energy-efficient if it uses less fuel to generate heat. A greater quantity of insulation that keeps the furnace’s heat inside longer is a passive form of efficiency.
Although the initial approach to passive houses focused primarily on passive efficiency, the concept has expanded beyond its original meaning. Passive energy efficiency remains a chief component of the standard, but it is not the only measure. Instead, builders can also look at active forms of energy efficiency, like renewable energy production located on the property.
Passive House Construction & Design Features
The construction of a passive house starts with a detailed design. It identifies the assets and liabilities of the region as well as the unique lot. Given a specific set of standards, the chief architect, engineer, or designer uses a variety of methods to achieve desired comfort and near-perfect efficiency. Passive housing generally relates to new construction, but can also apply to existing homes. Common features include:
- insulation well beyond the minimum standards for the climate zone
- ideal ventilation that recaptures conditioned air for use inside the home
- energy recovery at rates of 80 percent or more
- moisture recovery to maintain an ideal range of humidity
- airtightness that allows only a tiny fraction of indoor air to escape the building envelope
- passive heating that makes use of every heat source, including people or pets
- high-efficiency windows to provide strategic management of solar heat gain
Efficiency often starts by relating the indoor air requirements with the structure. As a general rule, homes with a greater surface area tend to be less efficient. This is because there are multiple possible points of failure in every aspect of the building envelope. Designers of passive houses often look to maximize the indoor volume of the house without necessarily increasing the surface area of the structure.
Within the building envelope, there are many opportunities to lose or gain efficiency. Insulation is a good example. Insulation standards are different based on the region and area of the home. Since heat rises, attic insulation is one of the most important components of passive efficiency in areas with colder winters. Passive homes usually feature thicker walls to accommodate more insulation. Innovations in insulation also allow builders to improve the relative insulation without necessarily having to increase the total thickness.
The placement and efficiency of windows is another useful concept for homeowners to understand, when considering passive home designs. The orientation of a window can increase or decrease natural lighting or solar heat gain. Windows that provide extra insulation against heat transfer or that promote heat gain can decrease total energy usage during the winter months.
The Passive House Methodology
The primary goal of a passive house is to balance energy demand with efficiency. It is quite different from many other approaches to efficiency that suppose homeowners can simply pay more when needed, or produce some of their own energy needs. Although Passive House methods often incorporate renewable energy technology to minimize carbon footprint or reliance on the grid, this is not the chief aim. Rather, designers of a passive house work to make the building envelope achieve efficiency goals without compromising comfort.
This methodology is revolutionary to a degree in that it focuses on passive energy efficiency. Proponents of this approach believe that the building envelope must be the most efficient before any other considerations (e.g. efficient appliances or renewable energy sources) can be added. This calls for attention to problems like thermal bridging that are common even in new, efficient constructions. Solving issues that decrease heating and cooling efficiency with improved ventilation maintains a more-constant temperature, humidity, and indoor air quality. As a result, it also dramatically decreases operating costs.
Passive House design standards can be difficult to achieve, and for good reason. With a standard build, developers evaluate the needs of people in the area and their target demographic. They use this research to create a design that will work well for most residents who might be interested buyers. There may be some degree of customization.
A Passive House Planning Package is far more complex. Instead of aiming for a general level of efficiency, designers start with a very detailed set of end goals. The design process is data-driven and requires a comprehensive plan. This includes features such as:
- orientation and size of the structure
- strategic positioning of windows and surrounding trees
- expected energy needs at a very fine and detailed level
- higher quality building materials, and usually more of them
The level of research needed for the initial PHPP requires an expert who has experience with passive house standards. Someone who is designing a passive house may run predictions on the amount of heat they expect to be generated by the residents living in the home, or an exact number of lightbulbs. They can anticipate the volatile organic compounds that might result from furniture or paint choices, and accommodate it into the ventilation needs of the space.
For a good analogy, home buyers might think about the effort needed to build a wine cellar or indoor greenhouse inside a home. The room requires careful attention to:
- temperature regulation
- variations based on anticipated use of the space
Passive house design demands just as much attention, but for the entire home. Each part of the house contains a thorough analysis of potential energy use and efficiency. The result is a structure that operates flawlessly and primarily behind-the-scenes, with ideal comfort in every room.
The Passive House Standard
More than simply a philosophy, a Passive House is a specific set of standards. If builders, architects, or property owners want to build a passive house, they must consider the standards in every aspect of the structure. As a general rule, the chief designer or architect of the space will prepare a Passive House Planning Package (PHPP). This outlines the expected heating, cooling, and dehumidification load of the building. It also identifies the intended ways to minimize wasted energy and reduce energy consumption.
Depending on the structure’s layout, energy requirements, and other factors, it may also include plans to supplement with renewable energy produced on-site. Passive houses do not need to generate their own renewable energy in order to meet the standards. In fact, the philosophy strongly encourages developers to consider efficiency before solving for demand with additional energy production. New standards separate the program into three separate classes: Classic, Plus, and Premium. These classes help developers to organize how they plan to balance demand with supply. Each one requires careful attention to both aspects.
Classic, Plus & Premium
In the past few years, the Passive House Institute has created a series of classes that provide an updated methodology for identifying a passive house. This update comes largely as the result of innovations in renewable energy sources available on an individual property, like solar panels. The classes also help to ensure that builders follow the letter of the standard as well as its spirit. This is why demand and production remain separate. By requiring builders to continue to adhere to strict standards in efficiency and construction of the building envelope, they can minimize attempts to bypass concerns about demand in favor of production.
The new classes also change the way energy production and demand are measured, by ground area instead of floor area. This marks a shift in the way that developers looking for this certification should compare production with demand. In the past, the standard measured energy demand in terms of square meters of floor area. By this standard, a building with one floor had a higher efficiency than townhomes or a multi-story condominium. This gave an unnecessary and possibly undue edge to single-floor buildings, when experts argue that they are not particularly efficient.
Passive House Classic involves a building that is highly efficient but does not necessarily produce its own renewable energy. This class concerns homes that have a renewable primary energy demand of 60 kilowatt-hours or less per meter squared of ground area. Since heating is the largest source of energy consumption for the typical home, there is an additional requirement for it. Specifically, any building with the Passive House classification must keep its heating energy demand at 15 kWh/m²a or less. This limitation requires architects to consider heating specifically. It means that they cannot try to balance out higher heating consumption with lower demand during the rest of the year.
A home in the Passive House Plus classification has a lower net energy demand than the Classic level, at least partially due to renewable energy production. The goal is to provide for the entire building’s energy consumption on an annual basis. Although this energy generation typically comes from solar power, it may also come from other sources, like a wind turbine. Designers often add a hot water recapture system to retrieve heat from used water, as a means to cut down the load. The home must produce at least 60 kWh/m²a of renewable energy, in exchange for 45 kWh/m²a or less in primary energy demand.
Reaching the Passive House Premium classification often requires extra considerations for energy production and the building envelope. This class calls for a building to keep its energy demand under 30 kWh/m²a, with energy production greater than 120 kWh/m²a. It means that the home is producing more energy than it consumes. As a general rule, builders need to significantly expand their efforts to achieve it. For example, they may need to move to the highest grade of windows or cover a larger surface of the roofing structure with solar panels.
Passive House Certification
With such a high level of research and expertise needed to create the design, home buyers need to find someone with appropriate experience in the Passive House standards. Designers of passive houses also need to know which products are most likely to meet their design plans. There are a variety of certifications available for professionals and products to make it easier for people to find what they need. Property owners can often do a search to locate professionals in their area with the necessary qualifications.
Builders in the U.S. must also decide if they want to apply for certification through PHI or PHIUS, which are two unique certifying organizations. There is a pre-process involved, wherein the designer or consultant submits their PHPP for review and approval before construction begins. The processing fee is based on the total square footage of the building. It usually takes several weeks for the initial design to be reviewed and approved or rejected. The rater may make recommendations and require the designer to submit revisions before approval.
Once the PHPP is approved, the designer must arrange for a series of on-site visits during construction. At each of these points, a rater may tell the designer to make changes to meet the standard. At the end of the process, the building receives a final assessment and processing of the certification.
PHIUS and PHI
The concept of the passive house began in Germany. A significant amount of homes that meet Passive House standards are located there. As the movement gains interest and recognition on a larger scale, however, more industry experts are shaping the way that the Passive House methodology affects regional building preferences. Originally, the PassivHaus Institut (PHI) had a U.S. branch called PHIUS. In 2011, these two organizations split formally over a variety of differences. Builders in the U.S. can apply to certify with either or both organizations, which keep their own standards.
Regional temperature variation is probably the easiest for home buyers to understand. In theory, a passive house that meets the PHI certification does not need a heat source most of the time. If it requires one at all, use is extremely minimal. This is also true for cooling. PHIUS recognized that the geography and size of the U.S. meant that they could not expect residents of areas with extremely hot or cold weather to meet the same standards as those living in a milder climate. As a result, PHIUS standards allow different maximums in heating and cooling load dependent on the area.
In addition, PHIUS makes different allowances related to the unique features of the U.S. climate and energy market. For example, PHI only allows solar panels as a renewable energy source available for thermal energy. By comparison, PHIUS permits solar and wind. PHIUS bases its limits on source energy on the actual energy lost during transit. PHIUS advocates argue that PHI assumed a greater degree of efficiency in transport than actual, making it harder for designs to meet the standard.
Another obvious distinction is based on the size of the home and the number of residents. U.S. houses tend to be larger than European housing. And in some regions, average family size is significantly larger as well. This makes efficiency more difficult to achieve when related to a standard that assumes a small house and family. PHI standards require that homeowners have an annual energy demand of less than 120 kWh/m²a. PHIUS establishes a different limit based on household size, 6200 kWh per person per year. For a four-person family, the total is similar between the two certifying organizations.
Following the Passive House Trend
Although the Passive House trend is currently strongest in Europe, it is gaining momentum in the U.S. as well. Homeowners are focusing more on energy-efficiency and their carbon footprint, especially as it relates to the construction and operation of the building. This often leads to better comfort and long-term energy savings, with systems that are designed to work better and last longer. The Passive House standard comes originally from Germany, but its requirements often fit easily into U.S. building codes.
The flexibility that builders and homeowners have in the way they approach solving the problems posed by energy demand encourages creativity and innovation. It can be a very difficult standard to achieve, particularly in areas with a higher seasonal energy consumption rate due to excessive heat or cold. However, for home buyers willing to make the investment, it may yield impressive returns.
There are many reasons property owners might want to consider the Passive House approach to building. It can be tailored to suit virtually any climate or weather concerns. Although it is often more expensive, increased demand for sustainable construction may make it more affordable. Homeowners who consider building or upgrading to the Passive House standard may enjoy the following benefits:
- ability to customize based on use
- dramatically lower energy costs, as much as 90%
- increased indoor air quality through improved ventilation
- less reliance on the local grid
- focus on renewable energy over fossil fuels
- greater home comfort
Owners of passive houses often notice that their maintenance needs are also lower. Systems that require a lower load tend to break down less often and may last years longer. This lowers repair and replacement costs over the life of the equipment.
For homeowners who intend to sell the home within several years, resale value may also present a big advantage. Home buyers of today consistently indicate a preference for homes that feature better energy-efficiency. Though this is generally at a lower level than a passive house, and tend to include minor improvements like efficient windows, air sealing, or Energy Star appliances. A passive house certification may exceed most efficiency standards, setting a property apart from the neighbors.
For most people, the biggest disadvantage to building a passive house is the initial investment. Experts estimate that the additional requirements for the standard may cost property owners about 10% more than the cost of a typical home. How quickly they recoup their investment in lower energy costs depends on the building and its heating and cooling load. People who live in areas with extremely hot summers or very cold winters may stand to benefit more and break even faster than those in a relatively mild climate.
Interested buyers are also dependent on the knowledge and experience of the architects and builders in their local area. Germany boasts tens of thousands of passive houses and have the experts to go with them. Outside of that country, however, understanding of the standard may be few and far-between. Property owners may need to search extensively for a designer with experience creating plans for passive houses. They should be prepared for the possibility of having to go outside their own area to find one.
As with any other energy-efficient design, use also affects the result. Residents of each unit need to know how to operate the controls ideally, and be willing to make changes as needed. Over time, the structure may develop problems that alter the heating, cooling, or ventilation needs. Thermal bridging, or displacement of insulation, is a good example. Homeowners must understand what is likely to happen as the house ages and how they can maintain higher levels of efficiency.
Many of the myths concerning passive houses relate to outdated perceptions people hold about some of the individual standards. Common myths may say that passive houses:
- are too stuffy
- cost too much
- limit innovation
- are too specific
- only work in certain climates
- take too long to recoup the price
In fact, most of these are misconceptions or outright misunderstandings. For example, homeowners often worry about a building being too airtight, thinking that each room will feel very stuffy. However, this often relates to the way they have used buildings in the past. With ideal ventilation that operates independently, every room has a regular supply of fresh air.
The Passive House standard actually sets few requirements for builders. They only need to achieve certain levels of efficiency and airtightness. The choice of materials and building styles depends on the architect’s and engineers’ imaginations, limited mostly by the lot and the property owner’s expectations.
Proponents admit that passive houses cost more, but argue that it is a worthy investment. On average, a passive house might cost an additional $30,000 to build, on top of a $300,000 house. However, this is not a significant deviation from other efficient building designs, or the regular improvements that homeowners might expect to pay over the first 10 years of owning a home.
Your Mileage May Vary
As with any other custom building design or retrofit, homeowners should keep in mind that their experience is likely to differ from others. Passive houses present a world of opportunity confined primarily by a buyer’s budget, local climate, and housing needs. People who live in Minnesota are going to have different needs than homeowners in Florida.
The benefit of the Passive House standard is that it is customizable by definition. It does not presume that homeowners can achieve a certain efficiency with the same equipment and building approach, regardless of energy load or use. The Passive House Planning Package identifies from the beginning what the lot needs to meet the standard, and proposes clear solutions to those problems from the outset.
Looking for Tax Credits & Grants
Since a passive home does not need to use particular types of building approaches or equipment, homeowners can often take advantage of a variety of tax credits to help them pay for it. The availability of credits, tax deductions, or grants is heavily region-specific. For example, the United Kingdom offers a grant program of up to £2,500 toward the construction of an efficient home. The United States currently features credits on the installation of solar, wind or geothermal energy, but they are phasing out by 2021.
Although many of these funding options are nationwide, homeowners should look for options at the state, city, and utility level. At a higher level, people may be able to take advantage of credits or funding on installation or a new build. As they get to the municipal or utility level, replacement may also offer options. For example, a utility might feature a credit on the bill for a homeowner who switches to a smart thermostat. Homeowners may want to ask their local utilities and browse their state energy office websites for more information.
Credits and grants are highly variable, depending on the design of the passive house. Programs often have deadlines or phase-out dates that require implementation within a certain amount of time. Larger systems tend to offer the biggest reward, given the higher investment. Homeowners should keep in mind that every little bit counts. Saving $25 or $50 on a variety of smaller components can add up to bigger savings once the total bill comes due.
It’s Not All or Nothing: Striving Toward Greater Efficiency
Given the variability of designs in passive houses, homeowners have a lot of possible directions they can take. Because of the high standards, it is often harder for home buyers to meet the needs of a Passive House design, even with new construction. However, it is not necessary to reach the qualifications of certification to receive some of the benefits of home efficiency. A passive house focuses on comfort without loss of efficiency. Many aspects of home construction can work toward this goal without having to create a PHPP and seek PHI or PHIUS approval.
It is important to consider safety with any kind of home renovation/upgrade. Increasing the air-tightness or altering how a building is ventilated should be done carefully and with the supervision of a licensed professional. Of course, smaller changes such as utilizing efficient appliances around the house can be accomplished with ease.
Homeowners who cannot buy a Passive House may want to consider these tips as part of a broader plan of better house operation and a smaller carbon footprint.
Features for a New Build
Even if property owners planning to build a custom home are not looking for a passive house, they can still improve passive efficiency. The design of the house can dramatically affect the problems posed by efficiency. Larger homes as well as open-concept homes tend to be the least efficient, for example. This is because they have higher needs to condition the air per person and a higher surface area. Ideally efficient homes may be smaller and have a higher ratio of volume to exterior surface area.
Orientation and window choice is key. Homeowners in an area with hot summers should avoid putting most windows to the south, as a way to minimize solar heat gain. By comparison, owners of properties in the northern U.S. may want southern-facing windows, as a way to increase solar heat gain in the winter. Homeowners should choose efficient windows with a low-e coating to minimize heat transfer. Double or triple-glazing reduces noise and also increases efficiency.
Efficient heating and cooling also helps a great deal. Heating, water heating, and air conditioning are the largest energy costs for residential buildings. Extra insulation is a minor investment with a decent return. The right choice in material will help people cut down on heat transfer without having to make the walls bigger. With efficient HVAC appliances and sealed ductwork, homeowners can reduce wasted energy spent and improve their home comfort.
Adapting an Existing Home
Fortunately, homeowners do not have to rebuild their homes to become more efficient. People may wish to consider making the following upgrades:
- improve insulation beyond the local building guidelines
- select PHI-certified windows
- install solar panels
- seal air leaks
- replace outdated furnaces, heat pumps, and air conditioners with Energy Star models
- seal or repair ductwork
- install a programmable or smart thermostat
- replace incandescent bulbs with LED lights
- install a zoned heating and cooling system
- choose water-saving fixtures and toilets
Put together, these improvements can help property owners save thousands of dollars over the lifetime of the equipment. The bigger the investment, generally the larger the reward. People can often justify the initial expense by considering how much less they will spend, or their improved comfort.
Homeowners who wish to take it to the next level may seek EnerPHit certification. This is not quite as strict as PHI certification. Instead, homes must create a heating demand of 25 kWh/m²a. This still requires a heavy amount of research into the home’s existing energy usage, with a plan to solve the most common problems. It may also call for significant changes to the building’s structure, such as the exterior walls or foundation.
As a relatively recent standard, the Passive House movement takes advantage of greater attention to sustainability and energy efficiency. Homeowners worldwide recognize that they stand to save a lot of money and make their homes more comfortable if they invest in efficient building designs and technology. For many properties, it is not enough to simply buy efficient appliances and hope for the best. A better understanding of the way a house passively maintains (or loses) efficiency helps people create a more complete package.
Passive House standards aim to cut down on energy by 90 percent while maintaining ideal home comfort and indoor air quality. A system of requirements based on insulation, management of heat transfer, air filtration, and conditioning requires a detailed plan that identifies all considerations from start to finish. Even if homeowners do not ultimately seek this certification, the increasing popularity of the approach drives manufacturers of mainstream building products and equipment to a higher expected standard of efficiency. Although passive houses are few and far-between throughout the world, that may not be the case in just a few short decades in the future.
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Listing information last updated on October 17th, 2019 at 7:37am MDT.