Sunday, July 19, 2009

Denver's New Zoning Map is Dropping the Ball on Sustainability

Soon after being named in the top ten cities for sustainability , Denver may damage it's standing because the proposed new zoning code is largely ignoring the benefits of detached accessory dwelling units (dADU's).

First, a little history:

The zoning code rewrite was called for as far back as 1989. Mayor Hickenlooper hired Peter Park to shepherd it in 2004. Meanwhile, preservationists like Jim Lindberg were concerned how the old code was allowing redevelopers to potentially ruin our historic neighborhoods. Blueprint Denver was begun in about 1998 and released in 2002 as the guide for a new code. The Zoning Code Task Force (ZCTF) was appointed in early 2005, consultants were hired, problems identified, and neighborhood contexts were defined.

Along about early 2008, third parties realized that sustainability issues had been heretofore largely ignored by city staff and their consultants. Michael Henry and Don Tressler of INC (InterNeighborhood Cooperation, an RNO), are the most significant of these third parties. Although Greenprint Denver was initiated in 2006 and widely admired, it was two years before Greenprint representatives were spotted at any ZCTF or Blueprint meetings.

At the request of INC, Park then hired Doug Farr to recommend sustainability strategies for the new code. The author wonders why a Chicago based consultant, however well qualified, could be a better choice than a local firm. For example, does Farr know why evaporative coolers are such a great peak power solution for the Denver area? Probably not. It turns out that swamp coolers ARE a zoning issue. No matter, he wrote the book, and made an effort to interview local experts like Michael Tavel.

Also, in the spring of 2007, Bob Sperling and James Van Hemert  and myself organized the Friends of Granny Flats after we realized that the Zoning Code Task Force was almost unaware of the existence and popularity of thousands of historic carriage houses in Denver. We gave a presentation to city staff in April 2007 that was well-received and put dADU's on the radar.

Farr gave his report to the ZCTF in September 2008. At that meeting he was asked, "what are the biggest things we can do in Denver?" His reply, "Two things: Share cars and Solar Access". It looks like the private sector is already targeting the former. By solar access, he went on to explain, on north-south Denver streets it means allowing a taller garage with solar panels on the roof, with laws to prevent future shading of it. After the meeting, he took the concept further and proposed, "for sustainability reasons, the code should require the installation of an accessory dwelling unit whenever these alley structures are built."

(Coincidentally, at the same meeting, the housing affordability consultant, Don Elliot, was asked the same question. His reply, "ADU's, reduction of the minimum buildable lot size, and inclusionary zoning." The ZCTF took the first two choices to heart and they are well-represented in the draft code. The affordability recommendations promised ADU's "in a wide range of districts." The efficacy of Denver's current inclusionary zoning law is unclear.)

After staff parsed Farr's report, they issued the Jan. 14, 2009 sustainability memo , and ADU's are prominent. Mention is made of future study of things like solar fences, kind of a tough putt in urban neighborhoods with mature trees. More on that here and here.

Unfortunately, the proposed zoning map is disallowing ADU zoning over most of the city.

Review the Map . Look for suffixes like -B1, - C1 etc. For example, if your neighborhood has U-SU-C you don't get ADU's, but if you have U-SU-C1, you get 'em. B2 & C2 zoning allows them only on some corners, which is better than nothing, but there isn't any B2 and C2 on the map. Why develop a zoning typology and then shelve it? There are a lot more questions like that once you study the map. Please do, and weigh in .

So, in 2009, after all this work, why is the city offering up ADU zoning in less than 5% of the city?

Edit: As of late August 2009, the areas with ADU zoning shown have increased, but they are still insignificant. There is a small amount of A2, B2 and C2 now shown.
Edit(2) As of November 2009, there is tons of ADU zoning shown. Meanwhile, "Friends of Granny Flats" recommended ADU zoning for ALL single family districts.


  1. Great article Kevin. It is interesting because on one hand we have the solar access group saying that allowing ADU's will block the sun from solar panels on neighbors one story garages and the gardens in the yards to the north of the ADU's. So it all depends on your take of what is green. The City is allowing ADU's where the percentage of neighbors want them. It is a complicated issue that is giving a lot of neighborhoods pause. Areas that have always been single family are cautious to all of a sudden allow rental units in evey household. Right now ADU's are not only carriage houses but also basement apartments and for those R1 and R0 neighborhoods that's a big change.
    Nothing is as simple as it seems.
    Carla Madison,
    Councilwoman District 8

  2. CPD explained to me that ONLY detached ADU's are allowed in SU zones.

    The rationale is that a basement apartment or attached ADU is actually a duplex. Duplexes are not permitted in the SU zones, only in the TU, TH, and RH zones.

    So the issue is complicated, and the proposed zoning is also.

    The rear of the lot is the only place that zoning could hope to regulate the tree canopy, since our street trees are a big part of neighborhood character. Xcel Energy already trims trees in the alley without the owner's permission. Half the cost of PV solar systems are paid for by Xcel, so they will want to keep the shade off their solar panels. That's a simple way to maintain solar access, with no city involvement or neighborhood bickering.

    Anywhere else on the lot, it's just impossible to regulate.

  3. Update: 12/09
    I still can't tell from draft #3 if internal ADUs will be legal. Of course, in most cities with ADU zoning, internal ADUs are encouraged. A converted basement or attached garage is the most economical way to make an ADU, and since ADUs are promoted as providing affordable dwelling units, internal ADUs should be allowed. It should be noted that internal ADUs ARE allowed if the occupant is a family member.