Hi Ed, and thanks for the links. I did read through them.
From your first link;
"ABSTRACT
This report was commissioned by the New York State Energy Research and Development
Authority and the New York State Department of State to review the history and state-ofthe-
art of attic ventilation and air sealing. It includes a mathematical model that is used to
examine the complex relationships between such variables as attic bypass leakage area,
outside air temperature, household moisture production, and venting area. The primary
recommendation is to reduce heat and moisture flows into the attic by permanently sealing
all air leakage paths between the house and attic, especially in climate areas that experience
sustained periods of low wintertime temperatures. It concludes that current attic ventilation
codes, which omit reference to considerations of climate zones, are of marginal utility to the
building or retrofit industry and are in need of revision. Recommendations for further
research are included."
"Nonetheless, building codes, HUD standards, and ASHRAE "past practice"
recommendations have led to relatively uniform attic ventilation standards. These
standards usually require attics to have one square foot of net free vent area for every
300 square feet of insulated ceiling area. In many areas, twice as much ventilation
(a ratio of 1 in 150) is required in buildings with flat roofs and cathedral ceilings or if
there is no vapor barrier. These standards were developed in the 1940s based on
limited field experiments. "
"The primary research on ventilation air flows was performed in 1962 by a research
engineer for a company that manufactures attic vents (Hinrichs, 1962)."(not particularly unbiased, I am still looking for a copy of this paper)
" In reality, there is no guarantee that providing a specified area of passive ventilation openings will yield some desired level of ventilation. Predicting ventilation flow rates is difficult due to difficulties in modeling site-specific wind patterns, especially at shielded sites, and the
unpredictable effects of wind speed and direction on a given system of vents. "
" The American Society of Heating, Refrigeration, and Air
Conditioning Engineers (ASHRAE), a major building science organization, altered its
description of venting standards from"Recommended Good Practice" to "Past
Practice" in 1981, and has made no new recommendations since then. "
I will stop there.
Your second link/report is from 1985. Nothing new there, although I like the illustrations, (they are about as sophisticated as mine)lol.
The IBC codes are based on the same old studies reffered to in the above paper and on manufacturers installation instructions.
Not sure what to make of the swine barn referance.
"Leaving a door open in summer will “short-circuit” the system and actually increase effective temperature by reducing airspeed."
Wouldn't that be the same as opening a soffit vent???
I am still looking for a recent scientific study that uses computational fluid dynamics for it's modeling of wind and airflow around buildings and in attics.
And I have seen many referances to the "short circuit" of ventilation systems. But I have never seen any scientific study that illustrates or tests the idea.
I have seen a study that shows that airflow through an attic is not laminar, but turbulent. Which adds another variable to the equation. I'll see if I can find and post it.
I do appreciate your time and effort. I'm not trying to be bullheaded. Just trying to figure it out.