Natural Ventilation: A house needs to breathe…?

Many still believe that a house needs to have air leaks in order to breathe through “natural ventilation”

The myth that “a house needs to breathe” is still considered fact by many. 100 years ago houses did not have thermal control via insulation. Back then, air movement in the building assisted with drying the structure out in the wet season using natural ventilation. This was 100 years ago and today our standards for comfort and health are much greater. We no longer burn wood or coal as a primary heat source. We also don’t want to give half our paycheck to the utility company to have conditioned air and hot water.

This pandemic has brought to light many building science principles include ventilation and air filtration. The experts recommend that we wear a mask that filters the air before it reaches your nose or mouth and gets transported to your lungs when pathogens or harmful particulates are in the air. OSHA even requires this for our workers. Especially when working around materials such as drywall that have silica that can cause lung damage. Most prefer a tight fitting mask to one that allows particulates to enter your lungs.

Education is the key

Several weeks ago I engaged with several builders on a forum. One of them brought up the antiquated concept that that building must be leaky to breathe. I was polite and stated that the current consensus is that we must “build tight (no holes) and ventilate right.” Not to mention that the energy code also requires insulation and air sealing to reduce the energy needed to operate the house and keep it comfortable.

Inspired by the exchange that I had on the forum, I added this topic to a new “Green Myth Buster” series that I created for a green building website called Rate It Green. My friend, Dan Edelman from ROCKWOOL was kind enough to share some of his thoughts on the topic. We successfully debunked the claim that “A House Needs to Breathe.”

Consider “controlled ventilation” instead

Like your body, you want to control where the air comes into the house. A mask that has holes in it is not affective. When you bring “fresh air” into the built environment you want to be able to control where it is coming in. Air coming in from a musty crawlspace or attic that is full of coal residue should not be considered FRESH.

Current building codes and green building standards state that air should enter into the structure through a controlled ventilation system. The air will be filtered (for pollutants) and the air could be conditioned as well. Fresh air brought either directly into the HVAC system OR a balanced air system such as an Energy Recovery Ventilator should be installed. Cold air in the Winter or “hot and humid” air coming in during the Summer will increase the heating or cooling needed to condition the air. Conditioning air for humans to be comfortable is one of the top demands on our energy supply.

Top Ventilation Solutions

Most of the top green building programs require “whole house ventilation” systems to be installed. Some newly constructed homes may reap the benefits of updated building codes and new building science techniques recommended by green building programs. We build to the standards set by EarthCraft House and LEED for Homes. These same whole building ventilation strategies should be implemented when design HVAC systems for existing homes as well. We recommend finding and sealing all of the air leaks, improving the insulation then designing the ventilation system. If these steps are completed out of order, then the HVAC system may not work properly.

Balanced Ventilation- Neutral Pressure Systems

Neutral Pressure Ventilation Systems brings in fresh air from the outside while expelling polluted air from the inside. Systems such as Energy Recovery Ventilators are able to exchange the energy from the conditioned and humidity so the “fresh air” comes into the structure at a similar temperature and humidity level as the existing air in the house. I have an article and several videos listed below that explain the science behind ERV’s.

Balanced Ventilation- Positive Pressure Systems

Positive Pressure Ventilation Systems bring fresh air from the outside directly to the return side of the HVAC system. This air is filtered and conditioned as it mixes with the existing conditioned air in the house. If the humidly levels are not ideal, humidity control systems can either add or take away humidity from the incoming air depending on the time of the year.

Let us help you fix your home [holes & ventilation]

Our team can help make your house more comfortable, healthy and energy efficient whether we are designing a custom new home or renovating an existing structure.

Contact us today to get a free phone assessment of your needs so we can schedule the appropriate next steps to solve your problems.

Additional Resources

Here is an article that I wrote for a Green Building Website called Rate It Green that explains ERV’s in more detail:

https://www.rateitgreen.com/green-building-articles/demystifying-ventilation-and-energy-recovery-ventilators-ervs/146

Videos that we have created on related to this topic:

Zip System and Air Sealing Techniques

Energy Recovery Ventilator unboxed and explained

Positive Pressure System- Aprilaire

ROCKWOOL Insulation outside the air barrier

Other Resources:

Rate It Green: Green Building Material Directory

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