Archive for February, 2003

VENT RECKONER 1980

5 February 2003

Some things are made overly complicated for no-good-reason.  I found this to be true of the Building Standards Consolidated Regulations with respect to fresh air ventilation rates.  It was pretty daft to be honest.  I looked at the process and knocked up a chart on the drawing board back in 1980.

[Picture of ventialtion chart from 1980]

In those days I stamped things with a rubber stamp.  Well, I was a teenager! LOL! This is called a Regchart because it is based on regs.

The vent rates entirely depend on what the space is used for. In the regs there is a wee table and easy enough to pick a rate from it — it’s reproduced on the chart — a bar is 0.5, a disco is 0.7… and office is 3.7.

This means that in a bar, each person is allocated a floor area of 0.5m2 which obviously lets you know the maximum number of people allowed in the space — the so-called “Occupancy Load Factor” — just divide the value from the table (0.5m2 per person in this case) into the floor area of the room. Once you have the number of people you need to provide fresh air for, you then look up another table, it will be 28, 20, 17 or 12 cubic metres of air per person per hour.

Then you multiply the number of people by the volume per person per hour to get a total volume per hour.  When you divide into this the volume of the room, you get the per hour air change rate.

What a palaver!

What I used to do was cancel out the floor area, so everything depended on the height of the room.

I could find an air change rate, for example, by just doing this:

28/ (1.9 x room height).

The company I worked with at the time used to still use the old Imperial System, so this wee chart had CFM and room ceiling heights in feet.

Ah, it’s funny looking back all those years, but that was what it was like back then — you had to find a way to work, and I had to figure out vent rates in CFM from SI regulations, and the only way I could keep sane was to draw a graph!

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