Wrightsoft Infiltration info?
Gwisejr
| Posted in Green Products and Materials on
Does anyone know how to interpret Wrightsoft’s Infiltration calculation method? I’ve attached the forms that my builders hvac guy sent to me. In the infiltration section, it just says Method: Simplified, Construction Quality:Average and fireplaces:1..
I just want to know what that means in their expected ACH50 number.
Thanks..
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I'm not sure if Manual J uses the same AIM-2 infiltration calculation method as Canada's F280-12, but I think they are similar. The category "Average" constitutes 4.55 ACH in the AIM-2 method.
There is a way to enter exact blower door numbers, if you have an expected target ACH.
EDIT: I looked it up, they are totally different. Disregard
I don't think they correlate the ACH they use for load calcs to a blower door result (ACH50) directly, at least not using the Simplified Method. Table 5A in Manual J gives infiltration numbers for the 5 categories of tightness (Tight, Semi-Tight, Average, Semi-Loose and Loose) for 5 different size buildings (based on floor area). For your 2738 sf and Average, it's 0.32 ach for heating and 0.16 for cooling.
Very rough rule of thumb, multiply ACHnat by 10 to get blower door ACH50.
So, roughly speaking, the heating ACH50 calculation would yield ~ 3.2ACH50 and cooling ~ 1.6ACH50?
Page 6 of your pdf report shows its using 0.37 and 0.16 (ACHnat numbers), which accounts for adding a little for the fireplace in the heating season.
Anyway, yes roughly 3.2 (3.7) and 1.6 ACH50 would be the roughly equivalent blower door results. More the 3.2-3.7 probably, since the winter numbers assume more stack effect leakage which the pressure of the blower door simulates a bit better than the summer numbers (sorta guessing here but it sounds feasible). But short of changing the model to use the Blower Door Method there's not direct conversion, that I'm aware of anyway.
If you're planning to be substantially tighter than 3-4 ACH50, make sure the HVAC guy updates these loads accordingly.
Here is a great article that might better help you understand your report.
https://www.energyvanguard.com/blog/how-read-manual-j-load-calculation-reports
From the article: "Infiltration. Did they use a simplified input method? If you're building a new house and meeting a code that requires 7 air changes per hour at 50 Pascals (ACH50) or better, the entry should be ""tight" or maybe semi-tight." Better would be to use an actual blower door number. For example, if your code requires 3 ACH50, enter that into the calculation. If you're going for Passive House certification, enter 0.6 ACH50 or 0.05 cfm50/sf of enclosure."