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Let’s Stop Using the Word “Breathe” for Buildings


Breathe. It’s a good thing. We need to breathe to live. Breathing consciously relaxes us. And it’s a great song by Pink Floyd from the Dark Side of the Moon album.

Breathe, breathe in the air
Don’t be afraid to care
Leave but don’t leave me
Look around and choose your own ground

Breathing is required of many life forms. But when it comes to buildings, breathing is just confusing.

I hear people use the word “breathe” in the context of buildings quite often. But as is the case with the term “vapor barrier,” I often don’t know what they mean by it. Why, you ask? Well, because people use it in so many different ways. Here are some meanings I’ve heard for the concept of breathing in buildings.

  • Infiltration – “A house needs to breathe.” That’s shorthand for, “I don’t understand the need for airtightness.”
  • Vapor diffusion – Designing assemblies that can dry to both sides is often referred to as allowing those assemblies to breathe.
  • Whole-house Ventilation – Bringing outdoor air into the house is sometimes called letting the house breathe.
  • Vented attics or crawl spaces – Some people think that, similar to the first one above, if we don’t let the structure breathe, we cause problems. Conditioned attics and crawl spaces, in that view, should be avoided.

Joe Lstiburek says, “Words matter.” When we use words with so many different meanings, it creates confusion. If you tell me something about walls or structures or buildings that breathe, which of the meanings above are you ascribing to that word? Or do you have a completely different one?

When someone starts using the word “breathe” in a discussion about how buildings work, or should work, I try to steer the conversation to the concept of control instead. We need to control the flows of heat, air, and moisture. Insulation is what we use to control the flow of heat. The air barrier controls air flow. A drainage plane controls the flow of liquid water. Water vapor is mostly controlled by materials that allow it to move, although in cold climates or with really thick insulation we need to slow down the rate of that movement.

I know we’re never all going to agree completely on a common lexicon. I switched from building envelope to building enclosure a few years ago, but the word “envelope” is just too entrenched to dislodge. That’s OK. At least we know what someone means when they say it (usually).

But “breathe,” in my opinion, doesn’t help at all. Let’s just drop it. Are you with me?


Related Articles

Myth: A House Needs to Breathe

My Choice in the ‘Building Enclosure’ vs. ‘Building Envelope’ Battle

Air Barriers, Vapor Barriers, and Drainage Planes Do Different Jobs

Don’t Talk to Me About Vapor Barriers!


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This Post Has 37 Comments

  1. To go along with your first
    To go along with your first point, I hear “A house needs to breathe” as “I have no idea how to deal with water and air details”.
    Most of the time the word that should be used is dry. A building needs to dry. Many old buildings dried via excess air leakage combined with massive energy use. Once you reduce the energy flow across the enclosure that formula fails.
    Now if we could only convince every building science professional to use “breathe” only in the context of enjoying a day in the mountains…

  2. A word without context is
    A word without context is just a word!

  3. Amen. As a homeowner I paid
    Amen. As a homeowner I paid good money for a home building course around 2001. Instructor very informative about lots of things but repeatedly said “a house has to breathe” and I never got what that meant. He was opposed to too little infiltration and never considered mechanical ventilation. But this raised questions and after a year or two decided it truly meant “dry out after getting wet”.

    He was sincere but old school.

  4. Couldn’t agreed more. The
    Couldn’t agreed more. The way we talk about building science in the industry might be the most important element in changing minds and ultimately the way homes are built. This has been made very clear to me as I’ve started doing newly required code compliance blower door tests here in Michigan. I find myself in front of a great many builders and construction managers, that I otherwise would not have, with a widely varying degree of knowledge and opinions about building science. I realized I had to sit down and (almost poetically) refine the most important points into a two minute conversation, as well as prepare concise answers to the most common questions. Language could not be more important here. It’s also obvious to me at this point that the best thing about these blower door tests is not that we’re reducing air leakage in new homes (4 ACH50 is the broad side of barn) it’s the conversations being started because of them.

  5. “A house needs to breathe.”
    “A house needs to breathe.” That’s shorthand for, “I don’t understand the need for airtightness.”


  6. I don’t think it’s “I don’t
    I don’t think it’s “I don’t understand the need for airtightness” (they do understand) but it’s “all assemblies need to dry out after getting wet because they will accumulate moisture”. Unfortunately it’s not old school thinking, it’s today’s production and sub conventional wisdom. Same argument is used to argue against spray foam.

  7. I agree, words matter. I
    I agree, words matter. I have struggled for years with the envelope/enclosure thing. BPI (still) uses “shell”…go figure. As far as the “breathing” thing, my go-to argument for that is to guide the conversation towards control. I often use an airplane as an example where total control of the interior and assembly is critical to life-safety and survival. Thing of a jet traveling 500 mph, 35,000 ft., neg. 50F to neg. 70F outside & 68F to 70F inside, moisture control, etc., etc. Does that enclosure need to breathe?

  8. Does my garage need to br___?
    Does my garage need to br___? I just built a stand-alone, conditioned garage in the midwest. I am planning on putting 2 inches of white foam behind the OSB and sealing it to the studs with expanding foam, so that is a vapor barrier on the outside. I will put 4 inches of fiberglass behind that. I was thinking about a plastic vapor barrier behind the drywall, to keep keep the fiberglass protected from indoor water vapor. But, it sounds like I am better off without it. Is that correct?

  9. I think the sportswear
    I think the sportswear/fashion industry has a lot to do with the word usage. “breatheable” clothes suggest that sweat dries out faster. So it can make sense to use it. I’ve really only heard it used in the vapor drive context. Beyond that, it’s too poetic to mean anything to an engineer.

    Maybe you should write an open letter to Nike.

  10. I still remember the first
    I still remember the first home I ever bought – a spec home in Asheville NC – and the (very popular well regarded) builder said exactly that – “Charles I build my homes so they can breathe!” Gads – If I knew then what I know now……………

  11. The builder/instructor in the
    The builder/instructor in the 2001 course I took, seemed to deny the existence of mechanical ventilation. When a class mate said he wanted a house built with ICF (Insulated Concrete Forms) the reply was “You will be building your own coffin”. He did not seem to like airtight construction, at least not in 2001.

  12. Ooo, that’s good! I may have
    Ooo, that’s good! I may have to steal that one!

  13. Breathing was the reason I
    Breathing was the reason I switched to boxer shorts [;@)

    Good stuff Allison.

  14. Gentlemen, of course you are
    Gentlemen, of course you are all correct, … technically. But you will never succeed in removing a word or phrase from a language (or lexicon). Many a grammar snob have tried to correct incorrect usage, usually to little effect. Instead, I suggest you apply the Jiu Jitsu language technique every time you hear the phrase “A house needs to breathe”. Your reply can be, “Yes, you’re absolutely right! That’s why we install ventilation systems, and design our buildings to dry both to the interior and the exterior, since we know moisture can come from both. What’s your preferred ventilation system? I prefer balanced systems myself, because I hate it when homes hyper-ventilate. Don’t you?!”

    Have a great day, gents!


  15. I think the ‘house must
    I think the ‘house must breathe’ misnomer mostly flows from a lack of understanding of vapor diffusion versus air diffusion. I have a similar reaction when I hear folks use the term ‘vapor barrier’ when they mean ‘vapor retarder’

  16. A “house has to breathe” is
    A “house has to breathe” is from ASHRAE 62-89 and earlier ideas about addressing IAQ. When a homeowner confronts me with that phrase, I ask them if they they are pleased their house is breathing when it’s 20F below zero with a 20 mph wind blowing. Or are they sitting there shivering thinking there has to be a better way.

    Then I ask them, “Do you want Mother Nature to be in charge of your ventilation, or do you want to be in charge?”

    After they answer the latter, then we have a conversation about air-sealing and mechanical ventilation. Works every time.

  17. From an IAQ perspective, I
    From an IAQ perspective, I hear the phrase mentioned more frequently in terms of ventilation. It goes along with the phrase “tight building syndrome”, which applies to early (late ’70s-early ’90s) attempts to reduce energy usage without properly addressing vapor control and ventilation. So it makes sense for “old school” people to use the term, because they learned the hard way (usually by lawsuits) what happens when you insulate a leaky building. My answer is typically, “it needs to breathe through the mouth, which is the ventilation system. It doesn’t need to be perforated.”

  18. Everyone here is missing the
    Everyone here is missing the point of what constitute the term “a breathable” building. First let me state that the major issues in a wet structure is not rain or snow, but a little, tinny sliver of space between the cold air and the warm air, this is where condensation is formed, this area shifts based on climate and how the wall structure is designed and built, how much insulation is used, if the insulation is properly installed and last but most important id where that vapor or air barrier is located. Thus the term breath is used to indicate that moisture, just like the moisture from you breath when you exhale, escapes the exterior wall structure. I guess i am from the old school, I have seen and witnessed an entire building covered in mold because of a vapor used improperly.
    In conclusion by making the building breathable: 1. you focus on the wall assembly, 2. we talk about the movement of water vapors, 3. we address condensation points. and 4. use proper, and due diligence when it comes to insulation installation. installation

    1. Good point. Another aspect
      Good point. Another aspect many here are missing is the fact that all this stuff looks great in text books and data sheets and drawings but remember, that’s a static representation of the condition of the building after the last nail is hammered in. If left exactly as it was intended then these “super tight” buildings should perform as intended. But that’s not real life. People use their homes. 2 days after they move in the cable company starts whacking holes everywhere trying to get Wi-fi up and running. Kids punch holes in the wall. The wife hangs mirrors, pictures, and shelving. Eventually there will be some renovations which leaves gaps and cracks in the once perfectly sealed exterior walls leading to exactly what Jurij spoke about. I’m guessing many on this forum are designers but I’ve ripped apart hundreds of homes ranging from 2 to 150+ years old. Not much moisture problems in the old ones and you’d be surprised at how low of an energy bill a homeowner can have with a 100 year old house with virtually zero insulation but new windows and doors.

  19. Perhaps builders have an idea
    Perhaps builders have an idea that “air tight” homes have a small margin of error with regards to moisture problems and commissioning a properly built/designed ventilation system is next to impossible.

  20. That is an excellent analogy
    That is an excellent analogy – I have used it, too. I stole it from Doug Rye after attending one of his seminars. He was using it in the context of foam vs fiberglass insulation, thickness of insulation & discussing air tightness. What do you think the wind chill temp is on the nose of that airplane? He would start by describing the conditions & let you try to figure out what he was talking about before telling you that he was talking about an airplane. Very effective. He could sell ice to Eskimos in an airplane. It really gets folks thinking.

  21. A new home I just moved into
    A new home I just moved into has ant problems. I would like to air seal (aka caulk) along the interior baseboards (baseboard trim as been removed in remodel, so would be easy right now) but my husband literally said to me, “but the house needs to breathe!” I explained that anywhere ants come in, air comes in, and it’s not necessarily the air we want coming in. We live in San Diego and have our many doors open nearly year round. Do you think caulking around the baseboards would be an ok thing to do? More importantly (debatable), will it keep the damn ants out?!

  22. Houses need to breathe, I
    Houses need to breathe, I think of allowing energy to move. Example: Don’t TRAP moisture in building assemblies. I don’t like to use the word CONTROL. When you control something it usually doesn’t like to cooperate. Talk your child they can’t have something or ordering someone around to do something they don’t want to do. I prefer to use the word, manage. It is our job to manage energy transfer. We know we can’t stop(control)it,but to limit it’s movement as best possible in a certain type of climate. Just my 2 cents for today.

  23. @Michael, you can manage
    @Michael, you can manage moisture with ventilation and the appropriate selection of cladding/wall/ceiling materials based on vapor permeance. Occupants need to breathe, not the house.

  24. I’ve been coming across so
    I’ve been coming across so many inspectors and builders lately who keep telling me a home needs to breath, it was on my list to write something up clarifying the topic. Now i dont have to!

  25. Houses need to breathe, but
    Houses need to breathe, but they do not need dozens of open mouths to do so, in simple terms a 3 bedroom property needs just 3 tiny mouths and one slim exit slit based uder the roof ridge tiles to breathe. Over ventilation is the problem, that and in older homes the absence of a roofing felt and loose laid or wind lifted roof tiles. Ventilation can be a river, a stream or a trickle and lets not forget that homes and buildings can suffer like people from the wind chill factor, heat is not lost, more often than not its blown away.

  26. Hi Dale … I’m a home
    Hi Dale … I’m a home inspector in Ohio and former Builder. My experience is that using “mother nature” for ventilating homes is far superior than mechanical systems in the “long hall” … as mechanical failure and/or changes in climate, building techniques and other variables change. What may work in one area of a state may cause environmental havic in another. The old saying “don’t mess with mother nature” really plays out over time as mechinac systems fail, not installed right, or were just a stupid idea and made into someone’s code model and Will take “forever and a day” to get changed.

  27. I am in the curious business
    I am in the curious business of explaining people’s houses to them. Yes, I am one those functional morons generally called “home inspectors”. I like the OP’s idea, but have learned that one should use whatever terms are available to make a customer understand a concept. Developing hard lines for word use smacks of clerisy. Most homeowner’s are not engineers and expecting them to develop into one is unrealistic. Or so it seems. Words mean something. Use one’s that people understand, however disconnected they may seem from our limited perspective. People understand “breath”. Get them to that point, at least, and worry about VR’s, VB’s, WRB’s for another time.

  28. Hurrah Allison!
    Hurrah Allison!

    I’ve been saying for a long while that “Houses don’t need to breathe but they do need to be able to sweat!” i.e., there’s no upside to air infiltration in building assemblies, but drying potential is crucial.

  29. An ERV allows fresh air in:
    An ERV allows fresh air in: breathe in. Fans in bathrooms remove moisture: breathe out. …. what’s the problem with the analogy? I like it. Build tight/ breathe right.

  30. Anytime I see someone trying
    Anytime I see someone trying to control language I am suspect of their intent. I am sure at some point in JLC’s history the term “breath” was acceptable so let us get to the issue which this article never actually did. All you did was talk about controlling language and not what the problems of moisture being held in walls really create.

    So how about talking about how we control moisture transfer in lieu of language.

    I have been in the industry for almost 40 years and mostly what I have heard is talk. Thankfully companies like Dupont (Tyvek) are contributing with solutions. As usual, the internet just likes a good discussion while the real world moves.

  31. Michael – Yes, leaving a
    Michael – Yes, leaving a house leaky enough to “breathe” works, sort of. The problem is over ventilation during extreme hot or cold or windy weather, and under ventilation during calm 72 degree days. This is why balanced ventilation in a tight home is best for comfort and energy savings. However, in poor housing stock, many houses are tightened up just enough to avoid adding whole house mechanical ventilation, especially when the occupants are unlikely to service the equipment.

    If our country adopted the old school ventilation habits of countries like Sweden and Norway, we would be practicing vädra. Vädra is the habit of opening the windows of a house one or more times a day to exchange the air. It is performed in many homes in Scandanavian countries year round. They make their homes quite warm and tight, but if they don’t have an HRV, they regularly upgrade their indoor air.

  32. Can anyone help me with my
    Can anyone help me with my knowledge of cold attics vs warm attics spaces and which is best? In Europe and England, attic spaces are bitterly cold in winter. I view these bitterly cold roof spaces as a ‘magnet’ that draws heat out of a property. I claim no matter how thick a layer of fiberglass insulation laid on the attic floor does not stop heat loss and this is a myth. When a house breathes it loses valuable heat, and these costly heat losses are out of proportion to the so called gains and benefits. All views and comments will be appreciated that question for/or against whether a cold attic space is preferable to a warm attics space with some consensus of which is best? and is increased breathabilty a by-product of increased heat loss?

  33. @Bob, you’ll find other
    @Bob, you’ll find other articles on this site that focus on this question, but consider that in cold weather, a vented attic won’t be any colder than the outside, and in fact, it’s often quite a bit warmer than the outside due to solar radiation on the roof. On the other hand, as long as ceiling is properly sealed and ducts located inside conditioned space, a conditioned attic will actually increase the seasonal heat load since there’s more surface area exposed to the cold. Conversely, if you don’t do a good job sealing the ceiling, or there’s no other way to get the ducts inside, then a conditioned attic solves these problems. It’s as simple as that.

    you wrote: “is increased breathabilty a by-product of increased heat loss?”

    If by breathability you mean infiltration, then I would say just the opposite: increased heat loss is a by-product of increased breathability.

  34. Tony, there’s no need to get
    Tony, there’s no need to get yourself all worked up over this. No one is “trying to control language” here. I simply made a suggestion because the word “breathe” when used in the context of buildings is confusing. You don’t agree. That’s fine. Use whatever words you want.

    But someday, when you’ve gotten yourself into a state of kenopsia, you may wish for a bit of tuttadit. From there, the usual progression leads to kairosclerosis. That’s all I’m saying.

  35. I was so blown away with ‘air
    I was so blown away with ‘air in equals air out’ that all I could think of was breathing BUT your recommendation is well received here; clarity in communications contributes to the success of goals and I want us to control our buildings!

  36. We are designing a house to
    We are designing a house to be built in a warm temperate mediterranean type climate, dry summers and wet winters, in South Africa. I really want to do it right, and am an engineer myself. But I am so confused. I really want to implement the best strategy but everythng on the net seems to be for colder climates. How much airtightness and vapour control is really required for milder climates? Is there any documentation out there for us to read?
    HRV systems are not commonly used and would it really be necessary? Just want to walk around in a t-shirt all year round……

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