Jan. 13, 2017
Driven by tougher building codes, homes are becoming tighter, with less air flowing through cracks and crevices around windows, doors and other ill-fitting parts.
While that's a huge improvement for energy savings, tighter homes present challenges in ensuring indoor air quality.
The U.S. Environmental Protection Agency reports that the air within homes and other buildings can be more seriously polluted than the outdoor air in even the largest and most industrialized cities. Other research indicates that people spend approximately 90 percent of their time indoors. For many people, the risks to health may be greater due to exposure to air pollution indoors than outdoors.
That's why Joseph Lstiburek, Ph.D. and P.Eng., and the founding principal of Building Science Corporation, has been on a crusade to ensure that building codes and home builders lead to homes with the best approach for indoor air quality and ventilation.
His work with industry partners through the U.S. Department of Energy’s Building America program led to significant research into the wetting and drying of walls and, ultimately, to a major code change relaxing the requirement for vapor barriers in the International Residential Code.
The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) residential ventilation standard 62.2 (“Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings”) was first published in 2003.
At the time, the standard was 7.5 cfm per person plus 1 cfm per 100 square feet based on the assumption that the number of occupants in a home equals the number of bedrooms plus one.
In 2013, ASHRAE 62.2 was updated to a new formula. Under the new formula, high-performance homes were required to be ventilated at a higher rate: 7.5 cfm per person plus 3 cfm per 100 square feet. For a tightly built 2,400-square-foot home with three bedrooms, the minimum airflow rate jumped from 54 cfm to 102 cfm or 89%. There's a question in the industry whether that standard provides the most efficient performance for removing pollutants and saving energy.
In a recent exclusive interview with ProudGreenHome.com, Lstiburek discussed the challenges and some of the barriers facing the industry through building codes and guidelines that actually may be leading to worse indoor air quality.
PGH: How do you see the current approach to indoor air quality as set out in the International Energy Efficiency Codes and ASHRAE 62.2 guidelines?
JL: The codes focus on dilution, ventilation and air exchange. But the approach should have always been on source control. And the irony is that this has been known for 150 years. If a building smells like manure, the first thing to do is remove the manure, not ventilate the building better to get rid of the smell.
My approach is dilution is not the solution to pollution, source control is. And the motto for years residentially has been, build tight and ventilate right. And so what we're really doing is building tight and over ventilating.
And people are putting in higher levels of insulation, what could be bad about that? The codes decided to err on the side of caution and call for higher ventilation rates. The problem is that higher levels of ventilation lead to humidity problems and mold in commercial and residential buildings south of the Mason-Dixon Line and of Interstate 35 in Texas.
In the North, it causes problems in wintertime because the higher levels of home ventilation lead to excess dryness in wood floors that split, and the furniture is cracking and the people indoors are uncomfortably dry.
To solve this problem, the codes say to add humidification, and humidification is basically aerosolized bioweapons. It's incredibly unhealthy. So the high levels of ventilation are leading to problems in cold climates in the wintertime and problems in hot humid climates in the summer.
PGH: So what's the best ventilation system to deal with moisture and odors in the home?
JL:Not all ventilation systems are the same. Exhaust ventilation is not as effective as balanced ventilation. Air distribution is more effective than no distribution. So a balanced system with distribution is significantly better than an unbalanced system without distribution.
However, this is not recognized in the codes or in the ratings. We're not encouraging good systems. We're encouraging bad systems because the good systems aren't given credit for their goodness.
PGH: So how does this situation affect homeowners who buy houses built to these codes?
JL: We believe that people are stupid and are incapable of selecting a ventilation rate. It's just like the old days when we had thermostat police. By law we're going to set this as your interior temperature. Remember Jimmy Carter in his stupid sweater?
We now have ventilation police. We're being told that we're too stupid to figure out that some houses need more ventilation than others. You know if you're stripping furniture in your house or rebuilding a carburetor in the dining room and growing marijuana in the bathroom, you're going to need a higher ventilation rate than somebody who doesn't do stupid things in their house.
So why should there be just one ventilation rate based on the worst-case scenario for 2 percent of the population.
All the energy we've saved with all of the insulation that's been installed, we're wasting with these high ventilation rates. So with the energy saving mentality we mistakenly think that we can dramatically improve the air quality because we're not focused on the contaminants in the first place.
PGH: What's the best alternative to an unbalanced ventilation system?
JL: You have you have a balanced ventilation system that provides a means of distribution. It doesn't have to be an ERV or HRV; there are other variations that you can have.
You can have the air being pulled out of the bathrooms and are being supplied to the air handler and having it operate so many minutes every hour, then you're getting balanced ventilation.
Sucking air in to the house and blowing it out at the same time is better than just sucking in air and better than just blowing it out. Sucking and blowing at the same time with mixing is the best. And you also want to have really good source control.
PGH: What is the importance of proper ventilation for indoor air quality?
JL: This is not complicated. Things that kill you are more significant and things that make you sick and things that kill you quickly are more important things that kill you long term.
So what kills you the quickest is releasing carbon monoxide. So you want sealed combustion furnaces sealed combustion water heaters and you don't want to have your house under negative pressure if you have an attached garage because you don't want suction from the garage into the house.
So you know you want to have a balanced ventilation system if you have attached garage. Then look at what makes you sick over the long term, things like radon, pesticides and herbicides stored inside.
So you want to passively vent your areas under your foundation to the atmosphere for radon and then you want to make sure that you have the ability to control the humidity in the summertime.
The problem is that if you build an energy-efficient house to the 2015 IECC and it's smaller than 1,500 square feet, you're going to probably need to put in a dehumidifier because the air conditioning system doesn't run long enough to dehumidify the house.
PGH: What should builders do to ensure they deliver a home that performs properly?
JL: My advice to them is to install the ventilation system that meets the code and commission it at half the rate and instruct the occupants on how to operate it. The problem is the Energy Star program says you have to follow ASHRAE and so does RESNet, and I tell builders to ignore Energy Star.
If we give control of the thermostat to the occupant, why can't we give control of the ventilation system to the occupant? Design a system that can operate at a higher rate and give the occupant the ability to operate it at whatever rate they want.
So I say rise up and rebel, it's time to take control of your ventilation.