We see them all the time – various types of stationary or rotating ventilators on roofs.

The general rule for attic ventilation is that a minimum of 1 square foot of vent area is needed for every 150 square feet of attic space. That amount can be cut in half to 1 square foot of vent area to every 300 square feet of attic space if the ventilation is balanced on the roof with 50% of the ventilation placed low on the roof, near the eaves and the other 50% placed high near the ridge or peak … A few common types of vents used in roof ventilation systems include static vents, ridge vents, and gable vents.1https://www.prestigeroofinglv.com/about-roof-ventilation-and-cooling/

I will be focusing on the static vents


In 1925 the Kansas State Agricultural College id a series of Comparable Tests of Automatic Ventilators.

They cover – plain stationary, stationary siphoning, plain rotary and rotary siphoning ventilators. What caught my eye was the drawings with basic dimensions. This I could use to create 3d models that approximate the ventilators.

Plain Stationary

Here we have some drawings (Fig. 7) taken from the KSAC article. Dimensions are on a separate chart.

Fig. 1

Left are pictures of  plain stationary ventilators (Fig.1). This helps make sense of the drawings (some sense at least)

These all simply vent the attic space while preventing rain from entering.

Table V
This chart shows the dimensions (Table V). The Type as it says, referees to the drawings in Figure 7.This provides an excellent starting point to create 3D models using the drawings and dimensions.

Table V Scaling

Table V-S

This is all well and good as I have drawings with dimensions. I now needed to scale these and threw all of the data from Table V into an Excel spreadsheet and came up with a .. call it .. Table V Scaling. I have the scaled dimensions in inches and mm and at the bottom I can change the scale to get an immediate update.

O scale : Type A Version 1