See also:  “Housing Units” and “Housing Density” – Why these are terrible ways to measure housing success.

“Dwelling Units per Acre”

This is another odious term that planners use. You’ll find it in key spots in the December 2021 draft Gateway plan, both as a phrase (or abbreviated as “du/ac”) and as a number that’s derived from “dwelling units per acre.”

Since the aim of the Gateway plan is to provide housing for lots of people, then we’d want to see as many dwelling units per acre as possible, right?  To achieve more dwelling units per acre, we can do two things:  Build taller apartments or have more units on a floor (or both). And how do the number-crunchers make more units on a a floor?  They make smaller units.

Perhaps you are understanding why I despise the counting of housing by “units” and “units per acre.” The numbers may satisfy some engineer or bureaucrat’s job to have a document filled out and completed, but it has very little to do with the actual needs for homes.  It’s just a shell-game, swapping one thing for another.  But it does not create more housing for people.

One other way to look housing density is by Floor Area Ratio, abbreviated F.A.R. or FAR. In creating apartments, we want some outdoor open space — that is, we don’t want the building to go all the way to the edges of the property. If, say, the building takes up half of the property and goes up 2 stories, then the FAR is 1. If the building was half of the property and went up 4 stories, then the FAR is 2. That’s the total floor area of the building divided by the parcel size.

The advantage of FAR is that we’re not counting “housing units” — we’re counting the area of the building. The developer could make a blend of studios, one-bedroom, two-bedrooms, three-bedrooms — and the FAR figure would stay the same. 

With the “housing units per acre” designation, a building with all micro-studio apartments would have roughly twice as many “units” as a building that had a blend of housing sizes. There could be twice as many units — but it wouldn’t be providing more housing. The developer makes more money but people who want to live in a space bigger than 400 square feet would be out of luck.

We don’t want to use Floor Area Ratio to determine the design of buildings, just as we don’t want to use “dwelling units per acre” as any measurement of achieving our goals. There are other factors also that add up to encourage good design.

I remember reading years ago about how central planning was done in Russia during the 1960s and 1970s. Factory production and Housing production were controlled by government officials, who gave orders to the factory and construction management on how much of this or that they were required to make. One year the powers-that-be recognized that there wasn’t enough window glass in the country, so they ordered the glass factories to increase production by 25%, as measured by thousands of square feet of glass per month. So what did the glass factories do?  They made the glass thinner.  That would enable the factories to increase their output — as measured in how many square feet of glass they were making — without having to make more actual glass.  The glass was so thin that it often broke during transportation, before it even got to the construction sites.

That would be like saying “Let’s promote more units per acre” or “Let’s encourage greater densities, and get more housing that way.” We’d get more units, but we don’t get more housing.

A similar bungle happened in Russia with molded rubber parts.  The central government required factories to increase the number of “units” they made every month.  Just like what I’m describing here with making lots and lots of studio apartments to satisfy an invalid measurement — the molded rubber factories made lots and lots of doorstops.  Because then they could say that they made lots of “units.”  And at the same time, tractor tires were impossible to buy, because no factory wanted to make them, since each tractor tire only counted as one “unit.”

To paraphrase what I’ve written elsewhere: We do not want encourage developers to build studio apartments.  We want a blend of all housing sizes.  We don’t want a goal of building, say, 500 “units” and having them be substantially made up of studios.

Using the terms “housing units” and “dwelling units” and “dwelling units per acre” is the wrong way to measure housing. Again to remember:

The goal is to create homes for people.
Let’s not forget this.