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HomeMy WebLinkAbout07-15-26 Public Comment - S. Boyd - Public comment on NCOD updates regarding height and transitionsFrom:Scott and Frances Boyd To:Frances Boyd Subject:[EXTERNAL]Public comment on NCOD updates regarding height and transitions Date:Wednesday, July 15, 2026 8:53:01 AM CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe. (Submitted to comments@bozeman.net, all others bcc'd) Dear Commissioners and members of the Historic Preservation Advisory Board: I write as a Bozeman resident to comment on the Neighborhood Conservation Overlay District(NCOD) Design Standards now under revision. The updated Unified Development Code alreadyrequires a zone-edge transition, a step-down in building height, where a taller district abuts aresidential lot. That is the right tool, and my request is narrow: that the transition be required aroundthe complete perimeter of every place where the downtown B-3 district, or any commercial district,meets a residential block, in all cases, so that a street between the two no longer removes it, and sothat it applies on every side, not only the side a shadow happens to reach. The reason is old and simple. The first purpose of zoning in this country, before any concern forappearance, was to protect light and air: the sun that reaches a home, and the open sky and breathingroom around it. A tall building set against small houses threatens both. It takes the sun from the homesit shades, and it takes the open sky and the sense of scale from every home it faces, shaded or not. Atransition that reaches only the abutting side, or only the shaded side, protects part of the interface andleaves the rest exposed. To make this concrete, I use one intersection as a running example: the block bounded by West Beall,West Lamme, North Third, and North Grand. Its recent history illustrates the pattern with unusualclarity, and I have been able to model its shadows to scale. But the example is only an example. WhatI ask for is general, and it applies wherever commercial zoning meets residential inside the NCOD. 1. What the neighbors bought, and how the ground rules changed The blocks just north of downtown, in the streets around West Beall, West Lamme, North Third, andNorth Grand, developed as residential neighborhoods of one and two-story houses. People boughthomes there over many decades with a settled understanding of what stood around them and whatcould be built there. Sunlight and an open sky were part of that understanding, whether or not anyonewrote it down. That understanding rested on the zoning. When these homes were purchased, the parcels around themwere zoned for residential use and could hold only residential-scale buildings. Over time, the rules atthe edge changed. In February 2022, the City rezoned the 0.978-acre parcel on the east side of NorthThird Avenue, running from West Lamme Street north to West Beall Street, from R-4, High DensityResidential, to B-3. That half block, which for most of the last century held five single-family housesand a two-story multi-family building, is today a cleared parcel. Under B-3, it may be built to a heightof 90 feet and a width of 250 feet. I want to be fair about this. The rezoning was decided in public, on a recorded vote, with neighborsheard, and I do not ask the City to undo it. Assembling and rezoning land near a downtown is ordinaryand often sound, and I suggest no bad faith by anyone. The point is narrower: the building that maynow stand across the street from these homes is not the building they bought across from, and thechange was made through the City's decisions, not theirs. This sequence, where residential parcels near downtown are rezoned to commercial, and theirpermitted envelope is enlarged, is not unique to this block. It is the general condition that thetransition standard needs to address on every side. The block at Beall and Lamme is simply a clearinstance of it. What they bought across from Now Across the street Five houses and a two-story building A cleared parcel Zoning R-4, residential B-3, downtown business Permitted height Residential scale, about 25 ft 90 feet Permitted building width Residential scale 250 feet Table 1. What the homes around this block were built next to, and what is permitted there now. 2. The two impacts a tall building has on the homes around it A tall commercial building imposes two distinct impacts on the residential neighbors around it. Theyare different in kind, and they fall on different sides. Both are the concern of a transition standard. A. Light: a shadow that sweeps the block, but never reaches the south Bozeman sits at about 45.7 degrees north. On the winter solstice, the sun climbs only to about 21degrees above the horizon at midday, and lower for the rest of that day. A shadow's length is thebuilding's height divided by the tangent of the sun's altitude, which at this latitude gives a simple rule:on the shortest day, at midday, a shadow is about two and a half times the height of the thing castingit, and longer still in the morning and afternoon. Building height Midday shadow, December 21 25 ft (two-story house)65 ft 35 ft 92 ft 47 ft 123 ft 60 ft 157 ft 90 ft (B-3 maximum)236 ft Table 2. Length of the midday winter-solstice shadow, by building height, at Bozeman's latitude. The shadow is not aimed at one set of homes. It falls to the northwest in the morning, swings to thenorth at midday, and reaches the northeast by mid-afternoon, so the neighbors to the west, the north,and the east are each reached at some hour of the day. The one direction the shadow never reaches isdue south, because the winter sun sits in the southern sky. The homes on the south side of a buildingkeep their sun. The figure below shows the sweep for the example block, drawn to scale on the City'sown aerial photograph. Winter-solstice shadow study, full-block B-3 build-out at Lamme, Beall, Third, and Grand, shown as an illustration of the light impact. The permitted B-3 envelope (90 feet tall, 250 feet wide, drawn at a 10-foot setback) is shown on the block as cleared today. Shading is the computed shadow between 9 a.m. and 3 p.m. on December 21, at 45.68 degrees north, with the solar-noon extent marked. Base aerial and scale: City of Bozeman GIS. Homes Sun lost Solstice daylight lost Days per year in shadow West of North Third Morning about 24%year-round, in the morning Across West Beall (north)Midday up to 100%about 211 days, at solar noon East of North Grand Afternoon about 22 to 30%about 187 days, at 3 p.m. Table 3. The homes reached by the shadow, and how. The south side does not appear, because no shadow falls there. How far this departs from what stood before is worth stating plainly, because it is the measure of thechange. What stands on the block Days per year the homes across WestBeall are shaded at solar noon The historic block face: five houses and a two-story building (about25 ft)0 days A mid-rise building under the former R-4 zoning (about 50 ft)125 days (34% of the year) A 90-foot building under B-3 211 days (58% of the year) Table 4. The change over time, in days of midday shadow. These shadow figures are computed from standard solar geometry and are solar-noon maxima. They should beconfirmed by a formal study for any specific building, which is one of the things this letter asks the City to require.The order of magnitude is not in doubt. B. Air: a wall that is felt on every side, the south included The second impact does not depend on the sun at all. A wall 90 feet high and up to 250 feet long, setagainst one and two story houses, is a large object in a small-scaled place, and it is a large objectwhether or not it casts a shadow on any particular home. This is the “air” in “light and air”: the opensky above a property, the space around it, and the shared sense of scale that a neighborhood of houseshas. A home on the south side of such a building keeps its sunlight, because the sun is in the south andthe shadow falls away to the north. It does not keep its sky. The geometry of this is as simple as the shadow's. The top of a 90-foot wall, seen from a home acrossa 60-foot street, rises about 56 degrees above the horizon. Seen from a home at an abutting edge,perhaps 20 feet away, it rises about 78 degrees, nearly straight overhead. Since the sky runs 90degrees from the horizon to the point overhead, a wall reaching 56 degrees fills well over half of thevertical sky in that direction, and a wall at 78 degrees fills almost all of it. That is the impact thesouth-side neighbor receives in full, with no shadow at all. Distance from the wall Angle the top of a 90-ft wall reaches 20 ft (abutting edge)about 78 degrees 40 ft about 66 degrees 60 ft (across a street)about 56 degrees 100 ft about 42 degrees Table 5. How high a 90-foot wall rises into a neighbor's sky, by distance. Horizon to overhead is 90 degrees. 3. The Code requires a transition where lots abut, but a street removes it The updated Unified Development Code is not silent on this interface. Its zone-edge transitionstandard (BMC § 38.260.070) requires a step-down in building height where a taller district abuts aresidential lot. That is the correct tool, and I credit the Code for having it. The problem is not that theCode ignores the edge. The problem is where the requirement stops. The transition is triggered by abutment, by a shared lot line. A residential lot that sits across a streetfrom the commercial parcel does not abut it, and the requirement does not reach it. In practice, a streetremoves the transition. The neighbor who faces the building across sixty feet of pavement is owednothing, while the neighbor who shares a side line is owed a step-down, even though the building, itsshadow, and its wall are the same in both cases. How the residential lot sits Transition the Code requires Sharing a lot line with the commercial parcel (abutting)A step-down in height at the edge Across a street from the commercial parcel None Table 6. The gap. The transition is triggered by abutment, so a street between the two removes it. It is worth being clear about how this gap came to matter, because it is recent. Until 2015, the NCODDesign Guidelines applied to the B-3 commercial character area without exception, and their building-form provisions constrained height there. The extensive heights now permitted were not achievableunder the Guidelines as they then applied, and so the concern in this letter was largely moot: thebuilding that creates it, tall enough to shadow the homes across a street and to wall off their sky, couldnot be built in these blocks. The Code therefore had no need to measure light and air, or to carry atransition across a street, because the impact did not arise. In 2015 the City adopted Subchapter 4B ofthe Design Guidelines, a carve-out for the B-3 commercial character area, adopted expressly toaccommodate contemporary development of greater height and density. That change is what made thetall building possible, and it is what turned a dormant gap into a live one. The height arrived. Themeasure for its impact did not, because the Code had never needed one. The street does not earn that exemption. At this latitude, sixty feet of right-of-way cancels only abouttwenty-three feet of building height for the winter sun, and it does nothing at all for the wall's visualmass. If anything the across-street neighbor is more exposed than the abutting one, because nointervening building stands between the wall and the home. The shadow study is the illustration of thepoint: a full-height building reaches well past the far curb, onto homes a full street away. The street separates them on a map. It does not separate them in winter, and it does not separate them from thesky. The exemption for streets is also not the only narrowing to avoid, and the shadow should not be readto invite one. Because the sun impact reaches the west, the north, and the east across the day, and thesky-and-scale impact reaches every side, the south included, the transition owed across a street isowed on every bearing. The conclusion is not that only the shaded homes to the north need atransition. It is that every home around the perimeter does, whether the Code reaches it today or not. The fix is therefore not a new regime. It is to remove the street from the trigger, so that the transitionthe Code already requires at an abutment is required equally across a street, around the full perimeterof every place where commercial meets residential, on every side. 4. What I ask I am not asking the City to forbid tall buildings, and I am not opposed to housing or density. Thehomeowners on these blocks did not expect that nothing would ever be built across the street. Theirexpectation, which the City itself created through decades of residential zoning, was more modest:that whatever was built would step down to meet the neighborhood it joined. The Code already honorsthat expectation at an abutment. I ask that it honor it around the whole perimeter. I ask the Commission and HPAB, in preparing the NCOD Design Standards, to take three steps. First, extend the zone-edge transition the Code already requires at abutments so that it also applies toresidential lots across a street, and so that it applies on every side of the interface, not only the sides ashadow reaches. A step-down toward the residential edge should be required around the completeperimeter of every commercial-residential interface, in all cases. This is the central request: it closesthe street gap, and it reaches the sides a shadow never touches. Second, for the sun-facing sides, require a winter-solstice shadow study as a submittal for anybuilding above a defined height (for example 40 feet), measured at the winter solstice, when the lossis greatest. This is the light half of the analysis, and the figure above is an example of it. It documentswhy a street is not the separation the current trigger assumes. Third, require depictions from the affected homes on every side, the shaded ones and the south-facingones, showing the permitted building in place as it would be seen from the front windows and doorsof the neighbors. This is the air half. It lets the Commission and the neighbors see both the shadowand the wall before either is built, and it keeps the south-side homes, which no shadow reaches, frombeing left out of the record. None of this stops a project. It measures one before it is built, and it lets the decision be made with thefull cost in view. Sunlight and open sky are the two things a tall building takes from the small homesaround it. The sun it takes from some sides, the sky from all of them. A transition required around thewhole perimeter, and not removed by a street, is the honest response to both. Thank you for considering this comment, and for the work of updating these standards. Sincerely, Scott Boyd