The Lunacy of House Burping
![House Burping Means Opening The Windows To Increase Ventilation, But It's Got Problems. [by Catalina Dondiuc, CC BY 2.0]](https://www.energyvanguard.com/wp-content/uploads/2026/02/open-window-house-burping-luften-ventilation.jpg)
Some years ago in a previous century, I spent the month of January in Germany. It happened to be a winter of extreme cold, with a low temperature of -40 degrees† at one point. And yet, my German companions liked to keep a bedroom window open each night. I was young and hardy then, but it makes me shiver to think of it now. I don’t recall if they called it lüften, but it was certainly akin to that practice. The current misguided fad here in the US calls it “house burping,” a name intended mainly to grab the ever-diminishing attention of social media addicts. So let’s talk about why you should be wary of this craze.
Indoor air quality is more than ventilation
I’ve been hammering away at this for a few years now. Ventilation is only one part of a good IAQ strategy. In my IAQ online course, I cover 7 steps to good indoor air quality. You can get the gist of what I cover from an article I wrote in this blog. Ventilation isn’t even the best thing you can do to improve IAQ.
If you really want a good way to breathe healthier air, do source control first and then add some high-efficiency filtration. Those two address a lot of the most important indoor air pollutants. Yes, ventilation is definitely important, but opening your windows three times a day regardless of the current indoor and outdoor conditions is foolish. You might as well follow a herd of lemmings over the cliff…or believe that lemmings actually do that.
Outdoor air quality matters
Are you going to open your windows for “fresh air” when wildfire smoke has engulfed your home? I hope not. But what about a less extreme case? Let’s say the outdoor ozone level is high. Or PM2.5, the fine particles that make it deep into your lungs, then your bloodstream, and on to the brain or the heart.
Opening the windows when the outdoor air quality is bad only makes things worse.
Comfort problems arise
Last weekend here in Atlanta, we had a low of -9 °C (15 °F) and a high of 2 °C (35 °F). Which three times that day should I have opened the windows? None! I don’t like to freeze inside my own house. Plus, my heat pump is sized perfectly to meet our design heating load, which occurs at -5 °C (23 °F). It would never have caught up with all that cold air coming in.
On a hot, humid day in summer, it’s equally as bad. The air conditioner wouldn’t be able to handle the extra humidity load. The house would be sticky and uncomfortable most of the time. No one wants that.
Humidity gets worse
In winter, cold air is dry air. If you live in a home that has a lot of air leakage, you most likely already have low indoor humidity without opening the windows. Opening the windows not only makes it colder indoors, it also makes it drier. If you like to burp your leaky house, I hope you like 5 to 10 percent relative humidity…and dry, itchy skin, static electricity shocks, and desiccated nasal passages.
I mentioned in the last section the summer humidity problem. You don’t want that either. I monitor the outdoor temperature and dew point to determine if opening the windows is a good idea or not. If the outdoor temperature is moderate and the dew point below 15 °C (60 °F), I open the windows. Otherwise they stay closed.
Energy gets wasted
A lot of house burping critics have already covered this one. Releasing all that expensive air that you’ve paid good money to heat, cool, filter, humidify, or dehumidify is just plain blockheaded. And now it’s more true than ever since utilities are raising rates for homeowners so they can subsidize the cost of energy for data centers. I know the bills for my all-electric home have gone up significantly in the past two years.
What you should do instead of house burping
You want clean air in your home, of course. Who doesn’t? House burping isn’t the solution. Do as much as you can in the 7-step approach to good IAQ, and you’ll get a lot of the benefits—or more—without the drawbacks of house burping. And when you add ventilation, do it with a balanced ventilation system that has heat and moisture recovery. That’s an energy recovery ventilator (ERV), a it’s what I have in my house.
Now, if you want to find out more about ventilation, here’s a perfect opportunity for you. Two weeks ago I gave a talk on this topic at the HVAC Symposium in Florida. They recorded the presentations, and you can get a virtual ticket and watch them all for the low price of $29. There are much better options for good IAQ than house burping.
Allison A. Bailes III, PhD is a speaker, writer, building science consultant, and the founder of Energy Vanguard in Decatur, Georgia. He has a doctorate in physics and is the author of a bestselling book on building science. He also writes the Energy Vanguard Blog. For more updates, you can follow Allison on LinkedIn and subscribe to Energy Vanguard’s weekly newsletter and YouTube channel.
† If you know your Fahrneheit and Celsius temperature scales, you know that I don’t need to give the unit here. The two scales are equal at -40 degrees.
Related Articles
7 Steps to Good Indoor Air Quality
Heat Pump or Furnace: Which Is Better for Comfort?
Ventilating With a Super-Efficient ERV
Photo of open window by Catalina Dondiuc from flickr.com, used under a Creative Commons license, CC-BY-2.0.
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Thank you for posting! I saw an article about this fad in the Washington Post this morning and thought it was absurd…and was pretty sure Allison Bailes would debunk it. Now I’m certain it’s 100% crazy.
Yeah, once I searched online and kept pulling up site after site praising the the practice, I knew I had to cover it.
Amen!
Thank you, we know there’s a better way, but those cultural or “traditional” ways are hard to break…
I too wrote about this in a blog post for Passive Buildings Canada:
https://www.passivebuildings.ca/articles/2r9h9bu2s96pavjg26ouc61zthelgx
Nice article, Greg! Those of us who understand building science need to keep fighting back against the lunacy of house burping.
I’m questioning at what point the ERV is economically viable. Adding up HDD and CDD and the cost of heating and AC tells me how much the ventilation air costs if it’s not conditioned. Toss in the cost to running these fans and you can figure a payback period for a given unit. If you can’t DIY the installation, suddenly the payback is much longer. If one simply opens a window with a MERV-5 screen filter (the best I know about that doesn’t require adding another fan to get airflow) while running the exhaust fan, balanced ventilation without pollen can be achieved.
I have a question about the calculation of heat loss via ventilation: I saw it’s 1.08*cfm*HDD*24 BTUs for the year. If the ventilation air leaves the house before transferring its heat to anything inside, wouldn’t the heat transfer to the house be less? Could that be calculated without setting up a thermometer on the outgoing air?
The point of an ERV is to retain as much heat or cool from the outgoing air so it’s not entirely non conditioned. But yeah there is an issue with the cost of purchasing installing and operating an ERV that just thinking about those numbers It may be more cost effective to just crack a window somewhere or put a small return duct to outside the house with a good filter and call it done.
And also an ERV is not installed to save energy it’s to increase indoor air quality by wasting as little extra energy as possible.
I always get a kick out of the building science guys that keep saying houses don’t need to breathe then they put in an ERV. The proper statement is houses need to breathe where and when we need them to not randomly on their own.
In commercial settings like say in a restaurant they put in make up air units which are basically just regular RTU units but they pull air directly from outside before cooling it and feeding it inside. Yes they also can heat but in most cases they run in cool mode in the winter as well to flush heat out of the building. Many restaurants will even have the AC run in the dining room in the winter as they heat from the people inside etc bring the temps up inside.
But opening all the windows for a while in winter feels good, i.e. it adds to indoor comfort. I don’t know why. Maybe it’s just that we don’t like things to be the same all day. But the fact that it feels good while failing to score well against our IAQ KPIs suggests to me that there’s something missing from our KPIs.
I am not sure what “feels good” means when opening the windows in winter means, but I suspect you have other IAQ problems that need addressing.
SJR: I agree with RoyC. Your “feels good” may well be someone else’s “I’m freezing in here!” Also, what KPIs are you referring to? We have relatively inexpensive IAQ monitors now that can tell us if common indoor air pollutant concentrations are above recommended safe levels. Mine look good most of the time without opening windows.
It feels good perhaps because denser cold air carries more oxygen and you get a bit of an oxygen rush?
Why would cold air contain more oxygen?
RoyC, I said denser cold air, not air with different oxygen ratios. And it’s likely more adrenaline from the momentary cool air on your face than increased blood oxygen saturation from a few percent jump in the O₂ mass being breathed in.
Paul, sorry about misinterpreting your comment. I did some quick calculations and air at 32 F is about 8% denser than air at 70 F. I wonder if that does make a difference.
But back to the original discussion, when I want “fresh” air, I go outside.
Well, RoyC, you’re doomed, because we’re being told that going outside might be worse than staying in.
because cold air is denser.
This is a timely topic for me. I just got back from the ASHRAE Winter meeting where the SSPC 62.2 standard committee (Ventilation and Acceptable IAQ in Residential Buildings) sort of addressed this issue. For a long time, this standard has required “ventilation openings” in “habitable spaces”. What this means in our language is that bedrooms have to have operable windows. This is not for evacuation reasons. There is no requirement for opening these windows. This requirement is just there in case you have an unusual event (painting, cleaning, etc.) that requires additional ventilation. It is causing problems now due to large commercial buildings being converted to apartments where some of the bedrooms might have fixed glass or no windows at all. I wonder if the thinking behind the original requirement was this “burping” mentality.
RoyC, in single-family residential at least, operable egress windows are absolutely a requirement, and yes, it is outside of 62.2 context, but I thought I’d apply some brakes on this runaway fixed window train.
ASHRAE 62.2 also puts a minimum size limit on the bedroom window requirement. It has to be at least 4% of the floor area or 5 sq. ft., whichever is greater. I can live with the fire escape argument in the codes, but not the IAQ logic in ASHRAE. ASHRAE SSPC 62.2 tends to overthink many of the things in that standard.
On the one hand, yes, it’s hard to fix stupid, especially when it’s -9 °C and the entrenched traditions dictate user behavior.
On the other hand, there is nothing wrong with a bit of lüften, as long as one is aware of their surroundings, such as air temperature and relative humidity, PM2.5 levels, etc.
Now, “aware” is a tricky thing, at best. Allison, it would be very useful to mention monitoring tools, especially for indoors. Live outdoor data is usually available.
Another aspect is filtration. That ERV incoming air filter better be higher than Merv 8, otherwise we’re likely concentrating PM2.5, not diluting.
Also, no matter how good that Merv filter rating, gaseous outdoor pollutants like ozone, NOX, CO, or VOCs will not be filtered out by a regular filter, and activated carbon version might not be sufficiently effective or last very long (and will not filter CO).
There is some work to do, especially addressing outdoor sources.
Knowing what outdoor air we’re bringing in is especially important in locations where, for example, certain well-known building science enthusiasts pull out the ERV filter on their own home to show us the thick layer of highway smog on them.
It’s a strange practice and I have heard of it many times in Europe. In some parts they believe that being cool and comfortable in the summer can make you sick. Interesting old wives tales are still believed there.
In England they have trickle vents to help dry out the house year round because they have been insulating their old houses and air sealing them and they already had massive interior moisture problems before that. They have no means of humidity control, no means of air filtration or air movement and they hang their clothes on racks inside the house. So it’s very common for them to have what we would consider massive amounts of mold and they routinely wash their walls with bleach water to kill off the mold.
They are starting to require small wall vents that act as a very compact ERV but look like a round exhaust fan. I think in the future we are going to see a massive number of British houses need major repairs as interior humidity rots what wood framing is in their houses.
We only open our windows when the temps/humidity/pollen make sense. Like today it was 70* and nice low humidity which is rare for us here in TX as the humidity is usually high even when it’s cold.
CO2??
The article is silent on carbon dioxide?
We are in a fairly tight old house.
CO2 can get to >1,000 sometimes in some rooms.
We open windows to get the CO2 out… when it isn’t smoky outside!
Yes we are in a sort of mediterranean climate in Australia… so often not extreme temps.
Hi Again,
If something just feels good, we’re probably all guessing at the reason. My guess is that it’s partly the need for variety, partly the pleasure of experiencing the outdoor sounds and smells indoors for a few minutes. Some people love a blast of cool, scented air for a few minutes, others hate it. But I suspect that few people respond well to day-long sameness
Regarding the KPIs, all I’m saying is that we need to design to enable the things people enjoy in addition to the things our measurements say are good for them. I’m all in favour of better, measured IAQ, but let’s remember that a home is to be enjoyed, with or without analysis.
Meanwhile we could all also press our authorities to pay more attention to outdoor air quality and noise pollution. It’s not just the indoors that should be habitable.
There are probably few places in the continental US where we could live today to fall under the new WHO guideline of 5 µg/m³ mean annual exposure to PM2.5. This study raises some questions about anthropogenic vs natural sources of PM2.5 and attainability of such a standard: https://news.mit.edu/2022/rethinking-global-air-quality-guidelines-0607
That got me curious. Take Okinawa, Japan, for example. One of the world’s highest concentrations of centenarians. A small skinny island separated from mainland by several 100’s of miles of sea. Prevailing winds between N and NE: https://weather.directory/jp/okinawa/wind Yearly mean PM2.5 is around 12µg/m³. Yearly contribution to PM2.5 by Gobi desert dust from the mainland falls somewhere around 5-10%, however in the spring it’s 20-40%. Majority of PM2.5 pollutants come from transboundary transport from the continent. It also turns out that industrial pollutants hitch a ride on the seasonal Gobi dust.
Does that mean that the effects of the rapid industrialization of China in the last 50 years or so haven’t shown up in the centenarian population of Okinawa yet? Is there something about the homes of those Okinawans? I have no idea, but before we jump to “lunacy” conclusions and generalize, maybe we need to limit those conclusions to a more specific geographic and environmental context?
I need to go for a walk.
My theory is that during winter, lüften feels comfortable for the same reason radiant heating is more comfortable than convective heating, everything else being equal: cold air in the face is invigorating, but the room surfaces are still warm so the radiative temperature that your body “sees” is in the comfortable range.
One way to test this theory is to see if Germans who have convective heating lüften more often than those who have radiant heating. If the theory holds, then the “crazy” idea of a subfloor heating system that uses an indoor HPWH as the heat source might not be so crazy after all.
I’ve been opening my windows (in a Pacific Northwest cold snap) because of high CO2 levels. Routinely over 1500ppm! (Echoing Tim Forcey in an earlier comment)