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ventilating after weatherization

CC.Rob Member Posts: 128
Question on what cfm needed to provide adequate ACH following weatherization/insulation.

before = 2100 cfm @ -50Pa

after = 1400 cfm @ -50Pa

Building volume including basement 25.3k ft^3

Numbers I'm getting from ASHRAE 62-89 not particularly helpful, other than showing there should be supplemental ventilation. Have programmable, var spd fan. Not sure what to set it for.

Help appreciated.


On a hydronically-related note, the supply temps used for a given load have dropped by about 12-15% (smart control system using ODR/IDF).


  • BillW
    BillW Member Posts: 198

    How many people are in the living space?  Is it a home or a commercial building?The number of air changes/hour vary based on occupancy & activities, for example cooking, which generates smoke, odors and water vapor.  The typical ER/HR ventilator delivers approximately 200 CFM on high speed.
  • CC.Rob
    CC.Rob Member Posts: 128

    4. residential.

  • don_9
    don_9 Member Posts: 395
    Occupied mode

    I often hear you would need an airchange every 5-6 hrs.Usually even in a tight home due to wind and stack effect you will find you'll get plenty of ach.lots of times in the winter if you have mouisture on the windows you need fresh air.

    Summer time when its hot and no wind to be found is the time you need to pump fresh air into the home.we been getting more into co2 montoring and adjusting the fresh air off those numbers.you could add a co2 sensor and control your fresh air system thru that during occupied mode.

    Every year that goes by i find myself getting into airside system analysis and i find its to be a exciting field.Glad to see you wethead are coming along,and into the airside of the business.
  • croydoncorgi
    croydoncorgi Member Posts: 83
    edited July 2010
    Ventilation testing??

    (see my comment about Passive House ventilation in the Newsletter thread...)

    Good to know that controlled ventilation and related issues get properly handled (at least some of the time) in the US.  In UK, it's not well-done at present!

    How does the testing system operate in the US?  Big fan and instrumentation put into a door opening when construction finished?
  • Brad White
    Brad White Member Posts: 2,398
    edited October 2010
    A little late to the party, but

    Rob, congratulations on the significant improvement with infiltration!

    I ran your figures using ZipTest Pro from Rick Karg up in ME and within that figured for ASHRAE 62.2 which is the residential side of ASHRAE 62. (62.1 is commercial.)

    With some assumptions for your building height and floor area, I get a mechanically delivered CFM of 30 minimum and this assumes an infiltration credit of 28 CFM. In other words, if your house were perfectly air tight, (never going to happen), you would need only 58 CFM.

    Truth be told, most HRVs are larger than that, and if used to exhaust a bathroom as a recovery source, that is not a bad place to start. 

    This reflects minimum ventilation for habitation, but does not address what might be needed to avoid affecting combustion air (should you have a large kitchen range hood for example.) The numbers are just a baseline.

    I hope this helps.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • Brad White
    Brad White Member Posts: 2,398
    Building Leakage Testing

    I suspect that building leakage testing is the same here as in other countries. I use a Minneapolis Blower Door setup and as you stated, it is fitted to a door and instrumented. I use an automated program which samples across about ten Pascal levels, 60, 55, the benchmark 50 and so on downward in 5 Pa increments to form a curve.

    The technology was originally from Europe, Sweden principally, and is now fairly universal. It is also a whole lot of fun, if you ask me!

    I often combine blower door testing with IR thermography. The two together enhance each other nicely.

    The other part of the testing is telling how much supplemental ventilation may be needed for habitation and to avoid back-drafting of combustion products. All good things.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • CC.Rob
    CC.Rob Member Posts: 128

    Hi Brad,

    Great to see you back on the Wall. 30 cfm is exactly what my local guru came up with. Probably using the same software....

    We used that figure as the starting point for the end of last heating season, and it seems to work well.

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