A House Needs to Breathe…Or Does It? Unpacking Building Science Myths
Is your home healthier, safer, and more sustainable when it's airtight? Discover the real meaning behind 'a house needs to breathe.'
By Allison Bailes
What does it mean when people say “a house needs to breathe”? For generations, builders, homeowners, and even some professionals have repeated this phrase, but few stop to consider what ‘breathing’ means for buildings. Dr. Allison Bailes confronts this myth head-on in his influential book A House Needs to Breathe…Or Does It?, challenging common misconceptions in home construction and operation. This article delves into the key themes of Bailes’s work, exploring the underlying science, persistent myths, and best practices for creating homes that are not just durable, but also healthy, comfortable, and energy-efficient.
Understanding the Myth: Does a House Need to “Breathe”?
The phrase “a house needs to breathe” is familiar to anyone involved in building or renovating homes. But, as Dr. Bailes emphasizes early in his book, houses don’t actually need to breathe—people do. The belief that homes should be intentionally leaky and allow outdoor air to pass through walls and attics is not just misleading; it can be actively harmful to both the building and its occupants.
In many cases, when people talk about houses “breathing,” they’re referring to two distinct concepts:
- Leaky Buildings: Allowing uncontrolled outside air to enter a house, often through cracks, poorly sealed windows, or wall penetrations.
- Drying Out: Ensuring that moisture doesn’t get trapped inside building assemblies, which can lead to mold, decay, and other issues.
These are valid concerns—homes must handle moisture appropriately—but confusing “breathing” with leakage is a serious mistake. Instead, modern building science emphasizes the difference between airtightness and ventilation.
Why the Myth Persists: History and Habit
The myth arose from the experience of drafty, older homes, which relied on incidental gaps and cracks for ventilation. For years, these natural leaks seemed to “refresh” indoor air, but they often did so unpredictably, bringing in pollutants, causing comfort issues, and wasting energy. As we began to build tighter, more energy-efficient homes to save on heating and cooling, a backlash emerged, arguing that “tight houses don’t breathe and are unhealthy.” However, random leaks do not provide good indoor air quality—they just make a home inefficient and uncomfortable.
Bailes’s work is essentially an attempt to replace folk wisdom with facts grounded in physics, chemistry, and decades of research.
The Core Principles of Building Science
Bailes’s book is celebrated for its clear, often humorous approach to the sometimes daunting topic of building science. Central to his explanation are several key principles:
- Houses are Complex Systems: Homes involve interacting components—enclosure, HVAC, plumbing, electrical systems, and people—each contributing to building performance.
- Air Sealing is Essential: Air leaks can account for a significant portion of energy loss and can allow moisture, dust, and pollutants to move through walls and roofs.
- Humidity and Moisture Control: Moisture mishandling is a primary cause of poor indoor air quality, mold growth, and even structural failures.
- Controlled Ventilation: Instead of relying on random leaks, proper ventilation systems deliberately introduce, exhaust, and filter air for comfort and health.
- Building Science is for Everyone: Homeowners, contractors, builders, and renovators all benefit from a basic understanding of building science concepts.
What others are reading
Key Areas Covered in the Book
- Air leakage, insulation, and airtightness
- Heating, cooling, and indoor environmental control
- Moisture management
- Mechanical ventilation and filtration
- Common construction myths and errors
“A House Needs to Breathe”: What Builders and Homeowners Get Wrong
One of the book’s central arguments is that confusion about what “breathing” means leads to poorly built, unhealthy, and inefficient homes. Build tight, the science says, but ventilate right. Dr. Bailes makes this clear in his famous analogy: “You don’t ventilate your lungs by poking holes in your chest; you do it with your nose and mouth.” Similarly, you don’t ventilate a house by leaving gaps in the building envelope—ventilation must be deliberate, controllable, and designed.
Bailes identifies several dangers of misunderstanding ‘breathing’:
- Uncontrolled air leaks can bring in allergens, dust, and outdoor pollutants.
- Energy waste from unplanned heating and cooling loss.
- Moisture movement that can lead to mold, rot, and decay.
- Missing real indoor air quality issues by trusting unpredictable, leaky paths for fresh air.
Modern Air Tightness: Too Tight for Comfort?
Many people believe that making a house too airtight causes indoor air quality problems or moisture issues. Bailes’s answer is no—a house cannot be too tight as long as it is ventilated properly.
Airtight homes:
- Reduce energy usage by preventing warm or cool air from leaking out
- Protect wall assemblies by keeping moisture-laden air from passing into cold spaces where it may condense
- Ensure that the location, amount, and quality of incoming air can be controlled by design, not by accident
Problems arise only when homes are airtight but not ventilated. Thus, the solution is not to build leakier houses, but to install and use mechanical systems that provide fresh, filtered air as needed—regardless of outdoor air conditions.
Ventilate Right: Mechanical Ventilation Explained
To maintain good indoor air quality, modern homes depend on mechanical ventilation—systems that reliably remove stale air and bring in filtered outdoor air. These range from basic exhaust fans to whole-house heat recovery ventilators (HRVs) or energy recovery ventilators (ERVs).
- Balanced Ventilation: Supplies and exhausts air in equal measure, maintaining indoor pressure and comfort.
- Exhaust-Only Systems: Use fans to pull indoor air out and rely on makeup air entering through controlled inlets.
- Supply-Only Systems: Bring in outdoor air actively via ducts or fans; less common in residential than balanced.
- HRVs and ERVs: Transfer heat (and moisture in ERVs) between incoming and outgoing air streams, maximizing energy efficiency.
Proper ventilation:
- Controls humidity, reducing the risk of mold and dust mites
- Removes pollutants such as volatile organic compounds (VOCs), particulates, and excess carbon dioxide
- Promotes health and comfort for occupants
Deconstructing Building Science Myths
Bailes uses wit and clear examples to bust common misconceptions in the industry. Some of the most persistent myths include:
| Myth | Reality (per Bailes) |
|---|---|
| Houses need to be leaky to be healthy. | Airtight houses with controlled ventilation are healthier and more comfortable. |
| Insulation stops air leaks. | Insulation slows heat flow but does not block air; air sealing is separate and essential. |
| Old houses “breathe” and don’t have moisture problems. | Old houses often have hidden rot and mold due to uncontrolled air and moisture movement. |
| New houses are stuffy and dangerous due to tightness. | Modern houses are stuffy only if not properly ventilated; tightness enables high air quality with the right system. |
Integration: Building Homes as Systems
Bailes repeatedly makes the point that building a house is not about optimizing one part in isolation. Every component—from the foundation and walls to HVAC systems and windows—must work together for the house to function as a healthy, efficient, and durable whole. Errors often happen when builders, designers, or homeowners focus on individual parts (like R-value of insulation) while ignoring the broader building system.
- Building Envelope: Needs to be continuous and well-sealed
- HVAC Systems: Should be properly sized and integrated into airtight design
- Moisture Management: Includes vapor barriers, drainage planes, flashing, and ventilation
- Behavior of Occupants: Even the best systems can be defeated by poor user habits
As every house is unique—built in a different climate, on a different site, by different people—Bailes advocates for careful planning and rigorous execution to avoid common pitfalls that lead to discomfort, inefficiency, and expensive repairs.
The Role of Design and Retrofitting
With the climate crisis and cost of living on the rise, there’s greater focus on both new construction and retrofitting existing homes for better performance. Bailes highlights several approaches that can dramatically improve a home’s comfort and efficiency:
- Comprehensive weatherization: Sealing leaks, adding insulation, and controlling moisture
- Electrification: Moving away from fossil fuel heating equipment toward electric heat pumps
- Upgraded ventilation: Integrating mechanical systems with filtration for best air quality
- Smart design: Considering climate, site, and orientation from the outset
These strategies are increasingly affordable and can radically reduce household greenhouse gas emissions, improve health, and even lower maintenance and utility costs.
Who Should Read ‘A House Needs to Breathe…Or Does It?’
Although written in accessible language, Bailes’s book is best suited for:
- Contractors and builders looking to enhance their understanding and avoid classic errors
- Homeowners and property managers seeking to make informed decisions for retrofits or renovations
- Architects and designers wishing to design modern, sustainable homes
- Students and enthusiasts interested in building science fundamentals
The book is widely recommended within the trade for its clear, reference-style organization and the author’s ability to make complex topics understandable—sometimes even entertaining.
Dr. Allison Bailes: Making Building Science Accessible
Dr. Bailes is a physicist, building science educator, and author respected for his ability to translate complex science into practical knowledge. His blog, Energy Vanguard, is widely read by builders and energy professionals. In A House Needs to Breathe…Or Does It?, he compiles more than a decade of insight, myth-busting, and advice on healthy home design.
- Known for his direct communication and humor
- Advocates for evidence-based construction practices
- Passionate about dispelling myths that persist in the building trades
Frequently Asked Questions (FAQs)
Q: Does a house actually need to “breathe”?
A: No. Houses themselves do not need to “breathe”; it is the occupants who need fresh air. Properly sealed and insulated homes with mechanical ventilation create the healthiest environments.
Q: What is the difference between ventilation and air leakage?
A: Ventilation is the controlled, intentional exchange of indoor and outdoor air—typically via mechanical systems. Air leakage is uncontrolled airflow through gaps and cracks, leading to energy and comfort problems without reliably improving air quality.
Q: Can a house be too tight?
A: No—as long as proper mechanical ventilation is installed and operated, there is no such thing as a home being “too tight.” Problems only arise when tight construction lacks deliberate ventilation.
Q: How does moisture get managed in modern homes?
A: Moisture is addressed through exterior flashing and drainage, interior vapor barriers as appropriate (by climate), airtight walls, and, most importantly, ventilation that removes excess humidity before it causes problems.
Q: What steps should a homeowner take to improve air quality?
A: Start with sealing obvious leaks, upgrading insulation, and ensuring the home has a high-quality ventilation system—ideally a balanced or heat-recovery type. Regular maintenance and avoiding indoor pollution sources (smoking, toxic products) make a big difference.
Additional Resources and Further Reading
- Energy Vanguard Blog — Ongoing myth-busting articles from Dr. Bailes
- U.S. Department of Energy: Building America — In-depth resources for pros and homeowners
- ASHRAE Residential Ventilation Standard — Industry standard for designing healthy ventilation
- Weatherization and retrofit contractors — For audits and improvements
For those inspired to learn more, Bailes’s book and blog provide a thoughtful, research-based entry point into the rapidly evolving world of building science.
References
- https://building-performance.org/bpa-journal/house-breathe-book/
- https://www.youtube.com/watch?v=UTBNNhUH5V8
- https://www.goodreads.com/book/show/75412283-a-house-needs-to-breathe-or-does-it
- https://www.energyvanguard.com/book-house-needs-breathe-or-does-it/
- https://energyvanguardstore.com
- https://positiveenergy.pro/building-science-podcast/2020/3/31/house-needs-to-breathe-allison-bailes
- https://www.thriftbooks.com/w/house-needs-to-breathe-or-does-it–an-introduction-to-building-science/37571392/
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