Don’t Blame the ASHRAE 62.2-2010 Standard

I have to interrupt my series on Homeowner’s Energy efficiency to say a couple of things about the ASHRAE 62.2 Standard.ASHRAE Guy

Change is always a problem.  The fact is that any change requires some rethinking and relearning.  Building science is changing all the time.  We are learning more.  We have better tools and better materials.  Buildings are getting more energy efficient and tighter.

The fact is that the ASHRAE residential ventilation standards have changed regularly.  The Standard is on a three year update schedule.  What is being referred to as the “simpler” ASHRAE 62-89 Standard is one, very small component of that standard referring to the sizing of a whole building ventilation system.  It is sort of like saying a house is simple when you only look at the insulation in the attic.  The fact is that the ASHRAE 62-89 Standard is 26 pages long.  The ASHRAE 62.2-2010 Standard is 14 pages long.

The ASHRAE 62-89 Standard is no longer supported by ASHRAE partly because of its complexity, but if you were to truly follow that procedure you have two choices in sizing the system: The Ventilation Rate Procedure or the Indoor Air Quality Procedure.
There are three steps involved in the first part of the Ventilation Rate Procedure, determining if the outdoor air is acceptable for ventilation:
1.    The contaminants in the air outside do not exceed the levels in an accompanying table and consider the size of the local community whose population is less than 20,000 and there is adequate air monitoring for three consecutive months.
2.    If the outdoor air contains any of the contaminants in the table, you can refer to another table.
3.    If you still can’t determine the quality of the air, you can perform air sampling based on NIOSH procedures.
The next part allows you to treat the ventilation air and suggests how you might accomplish that, and allows you to vary the ventilation rates during certain periods, like rush-hour traffic.
Once you have reached that point, you can refer to Table 2.3 from which you can extract the magical “0.35 air changes per hour but not less than 15 cfm per person” along with a few notes.  Also in this table are the continuous and intermittent ventilation rates for kitchens and bathrooms (which haven’t changed) along with 100 cfm per car in a garage (which is also in the IMC).

If you want to go through the second procedure – The Indoor Air Quality Procedure – you’ll need to find a copy of the 62-89 Standard.

Note there is nothing in the 62-89 Standard about calculating a Building Airflow Standard, Building Tightness Limit, Minimum Ventilation Level, etc.

The two main points of the 62.2-2010 Standard are:
1.    A whole building ventilation system to refresh the air in the house;
2.    Local exhaust ventilation to take pollutants out at the source – bathrooms and kitchens.
To calculate the whole building ventilation rate you need to know the floor area and the number of bedrooms, and you can look at the chart and figure out the CFM to meet the whole building ventilation rate.  Or if you want you can use a pretty simple formula:
0.01 x floor area + 7.5 x (number of bedrooms + 1)

Local exhaust is the same as it was in the 62-89 Standard:
Room            Continuous      Intermittent
Bathroom     20 cfm              50 cfm
Kitchen         5 ACH              100 cfm

Both Standards talk about reducing the impact on atmospherically vented combustion appliances – nothing new there.

When you buy a new combustion analyzer, it has all sorts of capabilities, but maybe all you need it for is to measure CO in the flue and you can stop there.  It comes with a detailed manual and you might even be able to take a course on how to use it to do lots of other things that are built into its sophisticated electronics.  The ASHRAE 62.2-2010 Standard can be used to simply size mechanical ventilation to cover two basic functions and you can stop there.  At the same time it has a lot of flexibility built in to fine tune the ventilation rates for a variety of applications.

If anyone can guarantee me that he or she can build me a house with the right materials and perfect indoor air quality in any location in the U.S. to surround and protect my grandchildren that will never have bad indoor air quality that will affect their health any day of the year as long as they are living there, then I will agree that you don’t need to apply any mechanical ventilation standard.  The ASHRAE 62.2-2010 Standard doesn’t guarantee perfect indoor air quality and states that clearly, but it isn’t complex to apply, and it is constantly under consistent and predictable review and welcomes input for improvement.


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3 Responses to “Don’t Blame the ASHRAE 62.2-2010 Standard”

  1. John Krigger Says:

    Hi Paul,

    Change isn’t so much the problem as change without improvement. Can we really get any more precise than 0.35/15 cfm? If not, why do we need all the new calculating, training, reasoning, and interpretation.

    Your Pal, John

    • praymer Says:

      John – I am with you about precision, but I’m not sure that the formula 0.01 x Afloor + 7.5 x (Bedrooms +1) is any more of a precision hurdle than 0.35/15. The measuring devices are all around plus/minus 10% but I do think that the installed system testing is a really good thing. I also think it is really good to ask people to document the system. We need the training, reasoning, and interpretation because it’s what we do! Geez, at least we’re talking about ventilation.

      Your BFF, Paul

  2. Ventilation Requirements for Weatherized Homes | Says:

    […] connect quickly and thus take some of the impact out of Krigger’s blow. His article, titled, Don’t Blame the ASHRAE 62.2-2010 Standard, disputed Krigger’s claim that ASHRAE moved away from simplicity when they revised the […]

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