How much space is needed between naturally ventilated buildings?

Separation distances between buildings are not always the primary consideration when anticipating building a new structure, but poor planning will lead to headaches later. Typically a 50-60 foot space between buildings is recommended for fire safety, however often that distance is less than appropriate for ventilation or other reasons. Poor planning and reduced separation distances leads to issues like snow drifts in inconvenient locations, difficulty in mowing, and seasonal odor and dust concerns near the house or other high use areas. In naturally ventilated livestock barns reduced separation distances lead to another issue, reduced ventilation.

There is an equation to determine the separation distance needed for an upwind structure to not influence the natural ventilation available to the downstream structure. The first step in determining the space needed between structures is to determine prevailing summer and winter wind directions. The equation for determining separation distances between naturally ventilated structures is based on the height and length of the upwind structure. In the Midwest it is common for summer winds to come from the South and winter winds to come from the North. With this typical wind pattern, the equation described below will need to be calculated based on each season. If both structures are naturally ventilated, each structure should be considered in the upwind position, and the larger of the two separation distances calculated should be used for planning purposes.

Separation Distance (ft) = 0.4 * Max Height (ft) * √Length (ft)

I find this equation to be quite thought provoking. Not only does this equation show the influence building a new structure may have on natural ventilation, but modifying existing structures can also influence natural ventilation available. When making changes to existing structures (adding height OR length to a structure) or adding larger trees to a windbreak should all be approached with caution. If ventilation is unintentionally reduced in a naturally ventilated structure, it is very difficult and expensive to gain back the necessary ventilation capacity.

Equation and Information from:

Lemenager, R., D. Jones, D. Buckmaster, W. Field, T. Glanville, L. Horstman, K. Johnson, J. Loven, G. Selk, T. Stewart, and R. Williams. Cow-Calf Production in the U.S. Corn Belt. MWPS-66. Ames: MidWest Plan Service, 2011. Print.