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Should Occupants Have Control of Their Home Ventilation System?

Some installers make mechanical ventilation difficult for occupants to override, but is that the right approach?

Posted on Jan 29 2014 by Allison A. Bailes III, PhD, GBA Advisor

One of the points of contention in the great ventilation debate is whether a home's occupants should control their own ventilation systems. The issue came up again in my recent article, Will a Gas Furnace Dry Out a Home’s Air? I wrote that occupants should have control of their ventilation system and experiment with the rate to help prevent drying out the air by diluting it with too much cold, dry outdoor air. Paul Raymer, a friend and member of the ASHRAE 62.2A standard for residential mechanical ventilation systems established by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers. Among other requirements, the standard requires a home to have a mechanical ventilation system capable of ventilating at a rate of 1 cfm for every 100 square feet of occupiable space plus 7.5 cfm per occupant. committee, then questioned me on that:

"We can make ventilation system controls that do pretty much anything, like vary the rate automatically in response to other factors, but what would those factors be and would anyone be willing to pay for such controls? Do you know of any data that would tell us the percentage of impact from the mechanical ventilation on the RH in the house?"

Why not give control to the occupants?

The issue first came up in this blog about a year ago, though, when Michael Blasnik wrote in one of his comments on my article about blower doors and mechanical ventilation: "I'm also surprised how you (and Joe) are so adamant about mechanical ventilation but then think we can rely on occupants to set their own ventilation rates. That would be a good idea if radon, asbestos, CO, and other pollutants were all smelly — but they aren't."

The Joe he referenced is of course Joseph Lstiburek, PhD, PE. He and Michael went back and forth in what was probably the best comment debate ever hosted by this blog. In one of Joe's comments, he wrote:

"In our experience, the occupant is more intelligent on setting acceptable ventilation rates specific to them than the members of the ASHRAE 62 committees."

Then, last summer I interviewed Paul Francisco, chair of the ASHRAE 62.2 committee, and he told me:

"I don’t believe homeowners should have no control. I also think that homeowners can’t detect a lot of potential indoor air quality hazards and they’re not knowledgeable enough to know what levels of ventilation they need at any particular time."

One of the issues is the same one that has Joe riled up enough to create his own ventilation standard. What ventilation rates should we recommend for homes? Joe has been giving talks about the issue over the past year and says the rates we recommend are based on research about odor control. Dr. Max Sherman of LBNL sees things differently, and I'll come back to the question of optimal ventilation rates in another article.

Whose responsibility is it?

Over the past week, I’ve read a whole lot of comments posted about this question, and it seems there are about as many good arguments in favor as there are in opposition to giving control to the occupants. For example, David Eakin wrote that occupants absolutely should not have control:

"This is not new science. How long have submarines been in operation? How long have modern mining operations been in operation? What about the decades of study and application from NASA? The answer (and probably the solutions) are already old tech. Looks more like politics than science at work in residential air quality."

One pitfall mentioned by several people was the inability of many occupants to understand the ventilation system well enough to control it. This comment on LinkedIn by Ron Bolender is typical:

"My experience is most home owners/occupants don't understand the benefits of their whole house ventilation system, let alone how to control it so it is turned off. When installed in new houses very few builders are doing a good job of educating their purchasers on the purpose of the ventilation system and how to control it. Technical and IT people may be able to read a manual and figure out how to control them at the control panel however, many unfortunately don't know how to control them."

Here’s the thing, though. People will find ways to mess with the system despite the best efforts of the designer or installer. Also, why should professionals tell occupants they’re not smart enough to touch their ventilation system when we allow them to do much more dangerous things, like drive cars? “But, seriously, do any of us think ventilation issues are any more complicated than automobile safety? In fact it's way simpler, and the stakes are not as severe. We can do this -- but not if we try to do it all through the standard alone or through automated technology without user input,” wrote Eric Werling.

We can make this work

The real problems, it seems to me, are inadequate education and lack of good control options. Of course occupants need to have control. When they turn their HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. systems off and open the windows, the ventilation system needs to go off, too. When they’re having the extended family over for Thanksgiving, they should be able to crank it up. No, they can’t smell radon or carbon monoxide, but that’s a job for more than just the ventilation system.

No matter how sophisticated a ventilation system we put into a house, though, the occupants exert control in another way: They have a big impact on the source strengths of many of the pollutants, especially in older homes in which the building’s materials aren’t off-gassing much anymore. What are they keeping in the home or garage or crawlspace? What are they doing in the home?

There’s just no way a one-size-fits-all approach can work. Few occupants can afford to have their local ventilation pro make regular visits to make sure they’re getting the right amount of ventilation. The solution is to recognize that occupants will be in control no matter what we try to do to prevent that. We need better system designs and better controls to help them get the best possible results from their ventilation systems.

Will some of them do stupid things, like turn it off and never run it? Absolutely. Some people never change the filters in their air conditioner or the oil in their car. We need controls for the users on the lowest end that have feedback equivalent to the oil and temperature dummy lights on the dashboard of their car. For more interested and sophisticated occupants, devices like the Fantech controller shown above are one of the best solutions.

We can make this work! The question about who has control isn’t really the relevant question. The real question is, who will seize the opportunity to improve ventilation systems and controls so that residential indoor air quality starts to realize the gains that are possible?

 

N.B. If you're going to the ACI national conference in Detroit this year, I'll be a co-moderator of a panel on this topic: The Ventilation Standard Debate -- Real Housewives of 62.2. Duncan Prahl of IBACOS put it together and is the other moderator. The panelists will include Joe Lstiburek, Paul Francisco, Michael Lubliner, and Don Stevens. You really don't want to miss it!

Allison Bailes of Decatur, Georgia, is a speaker, writer, energy consultant, RESNET-certified trainer, and the author of the Energy Vanguard Blog. You can follow him on Twitter at @EnergyVanguard.


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  1. Fantech
1.
Wed, 01/29/2014 - 20:56

Controlling our ventilation system
by Elizabeth Kormos

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We have a gas fired hydronic air system (NUAir Enerboss) with an integrated HRV. The system has boost switches which allows us to up the ventilation as needed when we have odors in the house from cooking, etc. We also know how to set the thermostat to run the system continuously (recommended on other posts except in very humid summer conditions) or we can set it to cycle on and off for different intervals or turn it off altogether. I think it is patronizing to say the homeowner shouldn't be able to control their own HVAC system. The builder/HVAC installer should educate the homeowner on the recommended settings but ultimately it is the homeowner's house. Would you want someone else to dictate the temperature in your house? Easy to use intelligent controls are the answer.


2.
Thu, 01/30/2014 - 01:02

Edited Thu, 01/30/2014 - 01:06.

Control of HVAC
by Dennis Heidner

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There is an interesting overview report that was published earlier this week on the EIA website. I found it quite amazing that only about 1/3 of the houses have programmable thermostats. Many houses have fixed (non-programmable) thermostats that maintain the same set points year round, day and night.

It appears that in many cases the person that determines the set point -- and perhaps the ventilation rates will be the installers. Not the home owners - (apparently unable to program the thermostat or the video recorder), but the person that chose the thermostat may have done so based on lowest cost to their company and their highest margin...

If that is what is happening - perhaps letting ASHRAE set the ventilation rates is the more intelligent move after all. Or perhaps we add "Basic programmable thermostats" to one of the required classes before graduation from high school....

EIA fact sheet: (January 28, 2014 -- for when it is archived).

http://www.eia.gov/todayinenergy/detail.cfm?id=14771


3.
Thu, 01/30/2014 - 08:27

Edited Thu, 01/30/2014 - 08:51.

Domestic Measurements and Controls
by Kevin Dickson, MSME

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Elizabeth has touched on the simple ultimate solution to the ventilation problem. For temperature, we measure it, then set it to where we are comfortable.

For CO, we already measure it by law (CO detectors). We can "set" it by having the ventilation come on as required to lower the CO to a preferred setpoint.

For humidity, we can measure it and set it.

For CO2, we can measure it and set it.

For VOCs we can measure it and set it.

The ventilation rate is moot, the "stats" control the cubic feet of fresh air per hour as required by the setpoints.

Today's standards are just guesses, so we just need the technology to catch up. There's no ASHRAE standard requirement for temperature because we can set it to where we want it.

In the 1890s we had steam heat but no automatic control. Before thermostats, we opened a window if we got too hot. With ventilation, we are still in the 1890s. Today's debate about ventilation rate is moot once the technology catches up.

Today's thermostats don't go below 55F. Tomorrow's "CO stat" won't allow a higher reading than, say, 3ppm. There's your tamper proof safety control because we "can't trust the occupants".


4.
Thu, 01/30/2014 - 08:53

Reply to Dennis Heider
by Kevin Dickson, MSME

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It's not that homeowners or occupants are too stupid to set a programmable thermostat, it's that it's very low on their priority list, and they don't understand how much money they could save.


5.
Thu, 01/30/2014 - 09:48

Edited Thu, 01/30/2014 - 09:57.

I think you're right, Kevin
by Rob Wotzak

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I've got two cars that get about the same fuel economy. One has a trip computer that shows current and average MPGs, the other has no such computer and has a broken odometer. While driving the one with the trip computer, I can get obsessive about how much fuel I'm using, while in the other car I don't even think about it.

I believe that same could happen in houses; the easier we make it to monitor and control the performance our houses, the more likely homeowners will bother to notice and do something about it. Not everyone will care and be actively involved, but I'm sure some people would.

That said, the sensor-activated automated controls would make a lot of sense. There seems to be an explosion of interactive home controls coming onto the market this year. At first I might assume that regulating health, safety, and energy wouldn't be as sexy to consumers as controlling TVs, music players, window blinds, and lights, but if Google is willing to shell out big bucks for a company that makes smart thermostats and smoke detectors, it seems that smart ventilation controls might not be too far off. It sure would make sense to have them.


6.
Thu, 01/30/2014 - 10:54

Engineers designing thermostats should go back to school
by Patrick McCombe

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"Or perhaps we add "Basic programmable thermostats" to one of the required classes before graduation from high school...."

I think a better option would be send all the current thermostat designers back to school. Maybe they could design products that are easy to use without costing $250. My programmable stat doesn't have a weekend setting or occupancy sensor, so it turns off the heat when we're sitting around on Sunday and Saturday mornings. Now that's stupid. I finally made all the set points all the same and I set it back at night and when we go to work. I wonder how many people do the same with their setback and old-school thermostats?


7.
Thu, 01/30/2014 - 18:30

Great article
by Derek Roff

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Thanks for your comments and information, Allison. I found this article to be useful and informative. I'm reminded of the debate over PCs vs mainframe computers in the early 80s. Central IT favored terminals hooked to a mainframe, because they didn't believe that users could make intelligent decisions about hardware and software choices. Thirty years later, we see that they were right, in part. PC users have wasted countless hours and dollars in poor choices. But they have also created a fantastic leap forward in technology and information, supported an incredible improvement in hardware and software, and encouraged interface improvements that have revolutionized most aspects of modern life.

As Patrick indicates in comment 6, many programmable thermostats have an interface that would have been embarrassing in a computer program of 1985. Users can handle dozens of sophisticated apps on their smart phones. If they don't/can't handle most HVAC controls, the fault lies chiefly in the devices and interfaces, rather than in the users.


8.
Fri, 01/31/2014 - 13:28

Joe Lstiburek Comment
by Terry Lee

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I question this comment from the link above, why?

"On the topic of CO2 or relative humidity sensors controlling the ventilation systems, Joe wrote a while back, “CO2 and humidity are not good proxies for good air quality. They are better than nothing. But not much better.” So the BSC standard has no provisions for changing the ventilation rate based on those factors."


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