How Much Noise Should You Accept in Your Home?

CC BY 2.0. A ventilation system in a Passivhaus/ Lloyd Alter

"People should not be forced to choose between intolerable noise or poor indoor air quality in their homes." Architect Mark Siddall points to a study he was on the team for: How loud is too loud? Noise from domestic mechanical ventilation systems. It is relevant to the Passive House crowd and anyone working in high performance or multifamily housing. They are writing from a UK perspective, but should be particularly interesting for North Americans, who are inured to high levels of noise because most live in homes with forced air heating and air conditioning systems that have a constant background noise, usually about 35 dB.

Some Noise Is Beneficial

The study notes that in the US, "It is speculated that a possible reason for the higher permissible sound levels from mechanical services is due to the greater cultural acceptance of this type of noise, with mechanical services having greater penetration in North America."

decibel scale

Decibel Scale/via

It is a fascinating topic because it is all so subjective. Low level background noise can mask sounds from neighbours or embarrassing noises; when I renovated my house I specified remote fans in the bathrooms so that they would be silent, but due to space limitations they couldn't fit them in; I got noisy standard fans instead. Now, however, I realize they are actually better because they mask sounds, as well as moving air.

element hotel times square new york photo

My house has radiators so there is no noise from the ventilation system, but, being used to silence, I have trouble sleeping in hotels. The worst I ever stayed in was a so-called "green" hotel in New York; I looked up the specifications of the incremental heating and cooling unit and it was pumping out 65 dB, as much as a vacuum cleaner. Who can sleep in that? When I travel, I often turn off the hotel room ventilation because of the noise, only to wake up later from the discomfort of an overheated room. (It's one benefit of getting older; I wear "hearables" now and have a volume control for my head.)

The study authors mention a UK hotel chain that sets limits of about 24 dB because of its "money-back guarantee if residents do not have a good night's sleep." I wish they included the brand name.

The study authors note that "the Passivhaus standard for noise from the ventilation system is ≤ 25 dB(A)." As is so common with numbers in the Passivhaus world, "the authors have not been able to determine how this value was determined," but it works, and the authors "are not aware of any noise complaints from ventilation system in Passivhauses in the UK."

The Absence of Sound Can Be Disturbing


Big bedroom in Cestaria/CC BY 2.0

This is actually a testament to the quality of Passivhaus mechanical designers, because Passivhaus buildings are so quiet that you hear everything. When I stayed in a Passivhaus flat in Portugal I found the silence in the bedroom to be almost eerie, and I was almost relieved when the ventilation system came on, to know that there actually was sound at all.

The study notes that, without any real standards or understanding of the issue, contractors pretty much ignore the issue. "Here noise levels remain unregulated; there is little incentive to take appropriate steps during the design, specification, procurement, installation and commissioning to ensure that suitable levels are achieved."

This can be a real problem in modern sealed and insulated houses:

Many residents in parts of Europe and beyond are dissatisfied with their ventilation systems due to the noise. This dissatisfaction causes them to reduce or disable entirely the operation of those ventilation systems. This represents a potential health hazard in modern air-tight homes, as infiltration cannot be relied upon to achieve adequate IAQ [Interior Air Quality]. Excessive noise levels and unacceptable quality of noise are separately reported as issues leading to interference with ventilation systems.

It is also a big problem in multifamily housing, where the bathroom exhausts are a key component of building ventilation and have to run all the time. In one study of buildings in Toronto, Ryerson University's Mark Gorgolewski found that 27 percent of respondents disabled their continuously running bathroom fans (needed for apartment ventilation) because of noise.

There Are Wide Variations in Noise Tolerance

The authors propose a maximum limit of 30 dB in bedrooms, with a "prudent limit" from mechanical systems of 24-26 dB, noting this "is unlikely to cause an adverse reaction from most occupants while falling asleep, but that 20% of Finnish respondents found this too noisy."

Decibel meter

Decibel Meter Pro on my iPhone in my bedroom/ Lloyd Alter/Screen capture

This is really low; I just tested my bedroom with nobody home but me and nothing running but the fridge, a floor away, and it higher than that. The authors conclude with the obvious: "People should not be forced to choose between intolerable noise or poor IAQ in their homes."

People in North America are doing this all the time, with useless noisemaker kitchen exhausts and bathroom fans. They have big round noise pipes connecting all the bedrooms together to the furnace and AC fans. It's amazing that anyone can sleep.

noise reduction

© nk Architects

We have noted before that Passivhaus buildings are really quiet. It's another reason that it is time to demand the Passivhaus standard for everyone. I wrote earlier that "you come for the energy and carbon savings but stay for the comfort, security and quiet." But it's not just the walls, it's the ducts and the HVAC design. It's the whole package.