The Basics of Passive House: What You Need to Know

Passive House and Zero Carbon Building Infographic courtesy of Passive House Accelerator.
Infographic courtesy of Passive House Accelerator

WHAT is Passive House?

Passive building is a set of design principles for achieving a precise level of energy efficiency while also creating comfortable indoor living spaces.

The movement began with residential structures as indicated in the name “Passive House”; however, these design standards extend beyond residential buildings. Passive House and Passive Building are used interchangeably for structures of all types – residential and commercial.

Passive building aims to create structures and spaces that are safe, resilient, healthy, durable, comfortable, and affordable. We’ll use Passive House for our purposes here due to our portfolio and expertise.

WHY Passive House?

Designing to Passive House standards is a comprehensive solution that addresses various concerns, offering benefits outside upfront cost concerns. By adhering to these standards, one can guard against future energy cost increases and significantly reduce the overall need for energy by minimizing heating and cooling demands.

This proactive approach not only slashes utility costs but also contributes to a decrease in the carbon footprint associated with traditional construction practices.

In the face of rising costs in recent years, Passive House standards empower individuals to exert control over their utility expenses, providing a long-term strategy for cost management. Beyond financial implications, there is a growing awareness of the environmental impact of our built environment. Passive building practices are crucial in mitigating this impact by substantially reducing carbon footprints, allowing for a more sustainable coexistence with the natural environment, and contributing to a healthier and greener planet for future generations.

Passive House spaces stand out for their energy efficiency and for creating healthier and quieter living environments. The tight envelope of these structures effectively keeps noise and dust outdoors, ensuring cleaner indoor air quality. Furthermore, the third-party verification process ensures that builders construct passive structures according to the design, enhancing their durability and resilience. These structures are less prone to condensation and mold, extending their serviceable life. With such high standards in place, Passive House construction creates homes that endure for a century and beyond, starkly contrasting to the shorter lifespan of 15 to 20 years typical of builder-grade homes.

HOW Do We Achieve Passive House?

There are several basic design/construction principles in Passive House. These principles are the moisture control layers, air control layers, thermal control layers, and radiation control layers.

Moisture Control Layer

The moisture control layer keeps bulk water – think rain or otherwise – out and away from the building and vapor – think humidity, whether outdoors or from cooking, laundry, or bathrooms – contained and out of the building assembly.

It’s known that water, when not managed correctly, can be incredibly detrimental to a building. Consider mold growth, material rot, and conditions that invite bugs/pests. If the space is too dry or too wet (humid), it can promote sickness and create a vapor drive – vapor moves from areas of high density to low density, like pressure – through the envelope.

The moisture control layer will be permeable to vapor to not trap moisture in the wall assembly. A vapor barrier and retarder are two different types of building materials, and it’s essential to know the difference between them as the results of misusing them can be costly and dangerous!

All homes utilize moisture control layers. However, what sets a Passive House apart from the rest is carefully considering the types of products used and their installation. These are verified during design and construction by licensed third-party professionals.

Air Control Layer

The air control layer controls the airflow through the building envelope. We’ve all heard stories about old homes feeling drafty because they leak air! Air leakage is an issue for several reasons, but before we address them, let’s touch on an essential concept: buildings do not need to breathe – they don’t have lungs.

However, because we do have lungs and need to breathe, we need a design that ensures we’re providing continuous, fresh, filtered air into the interior spaces of a building. We want the building envelope to be as tight as possible to control where, when, and what comes into the building.

Condensation on window

By creating tight building envelopes, we’re able to eliminate dust infiltration (think smoke, road debris, pollen, etc.); we’re able to minimize sound traveling through the assembly, thus maintaining quiet indoor spaces; we’re able to keep water vapor (humidity) from traveling through the assembly, minimizing the risk of condensation within the wall (yikes!) as well as preventing additional work for your air conditioning system. If outdoor air leaks into the indoor spaces, air conditioning – whether heating or cooling – will have an increased demand and, therefore, a higher cost of operation.

Consider this scenario: Your home’s interior air has been cooled and dehumidified on a hot, humid summer day. If you open a window and allow that heat and humidity indoors, the interior will also be hot and humid and require additional cooling and dehumidification. The opposite is also true in the winter. These energy losses can add up!

Builders construct homes to Passive House standards with these considerations, subjecting them to rigorous testing to meet specific air-tightness standards. A code-compliant house may be seven times more leaky than a Passive House project!

Thermal Control Layer

People often simplify the thermal control layer by considering it merely as the insulation in walls or roofs; however, this layer comprises more than just those elements.

Passive design considers the thermal control layer to include the entire building envelope assembly – roof layers, wall layers, and even windows, foundations, and floor layers. All these assemblies have some level of thermal insulative value. The most significant concept to understand here is that we want to keep the indoors warm when it’s cold out and the heat outdoors when it’s hot out.

It’s important to note that windows disproportionately affect a wall’s insulation value; continuous insulation is much more effective than cavity insulation; and thermal bridging should be eliminated. Homes built to Passive House standards will have at least 75% more insulation, and the windows will be 100% more insulative than a code-built home.

Radiation Control Layer

The radiation control layer is another vital component but often one of the least considered. Radiation refers to solar radiation or heat from the sun. The most common architectural component used for radiation control is interior blinds. Unfortunately, when using blinds, once the radiation is indoors, the heat accompanying it is also indoors.

Open concept Living-Dining space optimizes natural light and panoramic views of Pier Cove Valley - Bridge House - Fennville, Michigan - Lake Michigan

In a Passive House project, the design team creates sun angle models and takes measures to minimize glazing where it’s not optimal (both East and West-facing) or reduce heat gain during the warm months.

Engineers create energy models for mechanical systems to ensure right-sizing, avoiding unnecessary oversizing. The typical rules-of-thumb in code-built homes often result in oversized systems that run inefficiently and cost more to install.

Architects carefully consider window placement and utilize external shading devices to manage a structure’s unique design and site location. For example, using triple-pane windows instead of double-pane windows will help reduce the amount of solar radiation let into a space.

Utilizing external shading devices – ubiquitous in Europe but oddly not common in the United States – allows us to keep radiation out at times that we don’t want/need it, and having the ability to open and close them means we can allow radiation into the building in the colder months. By controlling the amount of radiation entering the space, whether keeping it out in warm months or allowing it indoors during cooler months, we can reduce the load on the mechanical systems; reduced effort by mechanical systems means less energy usage means less cost!

WHO Benefits from Passive House?

Everyone benefits from Passive House! Because the construction industry significantly impacts energy usage and carbon emissions, making greener improvements affects everyone from both a cost standpoint and a health standpoint.

Passive House buildings maintain a healthier environment by providing continuous, fresh, filtered air. Additionally, Architects design these structures to eradicate the growth of mold. They’re more comfortable than traditional buildings because they have superior (thicker and more sustainably sourced) insulation, high-performance windows, and eliminate thermal bridging, creating more even temperatures indoors.

Existing Site Views to the West - Forest Gallery House - Fishers, IN

Passive buildings are quiet, have no dust, and keep pests and bugs out, thanks to their robust building envelopes. And maybe most importantly, they’re energy-efficient and have predictable energy performance.

After being built under the guidelines of Passive House, passive structures can “sip” energy, meaning relatively small solar arrays can often support them and rely very little on our current-day energy grid. They use as much as 85% less energy than traditional buildings! Although, generally construction is improving, it’s common to see about a 60% reduction in energy usage. Passive House buildings benefit users’ health, wallets, and the planet.

WHO Certifies Passive House Buildings?

Because the process of creating Passive Houses is controlled and measured, it provides a predictable outcome. To ensure that passive design principles are followed and met, several third-party organizations provide certification of both structures and professionals.

Phius and PHI are the prominent organizations that certify buildings and projects. Phius and PHI also provide certification for professionals. Organizations such as Emu Passive and Passive House Network also offer professional certifications. These professional certifications include design consultants, builders, energy raters, energy verifiers, and tradespeople. This network of professionals has enabled an ever-increasing number of projects to be built and certified.

Passive House Institute US (Phius) Logo
Passive House Institute Logo

WHERE Can I Learn More About Getting My Own Passive House?

Are you ready to embark on your Passive House journey? Connect with us now! We don’t just design; we craft personalized solutions tailored to your unique needs.

As a Certified Passive House Builder, we bring your dreams to life and seamlessly manage the entire construction process. Our simplified setup empowers us to continually assess costs, putting you in the driver’s seat. Plus, enjoy the ease of streamlined communication with a single point of contact – we’re here to listen, guide, and make your Passive House dream a reality!

Interior - HAUS Studio Space - 101 S Harding St - Suite C, Indianapolis, IN 46222

Written by Paul Reynolds.