Hidden 密度: The Growing Case 对于adu
我们可以称它们为巷道住宅、奶奶公寓、地下室套房，甚至是fonzie公寓 whatever name you give them, 北美各地的市政府正在放松对附属住宅单元(ADU)的限制，作为一种缓解措施 growing housing crises’.
An accessory dwelling unit is an additional, self-contained unit added to an existing property, 通常上面 what the 分区密度 would otherwise allow. The addition of these units is a form of small-scale urban infill, 在不改变社区特征的情况下，为社区增加“隐藏密度”. 单元要么添加到现有结构中，要么隐藏在后院, leaving the original streetscape intact. 自20世纪初以来，这些附属单位已经大量建造, but often without permits and counter to a city’s zoning code. In the city of Los Angeles, 例如, there were 644 permitted ADUs constructed between 2003 and 2016, but there are an estimated 50,000 illegal units 穿过城市.
来自旧金山规划的一段视频描述了他们扩展的ADU项目.
Vancouver as a Case Study
Vancouver has often been held up as the poster child 对于adu. Vancouver began to legalize its 地下室套件 in the 1980s. According to a 2016 study by the Sightline Institute, 35% of single-family houses in Vancouver have an ADU, 要么是地下室套房，要么是后院小屋(温哥华市称之为“巷道之家”)。. These additional dwellings provide the city over 26,这在北美的许多城市仍然是非法的. As a point of reference, there are about 310,000 “dwelling units” in Vancouver according to the 2016 census. ADUs account for 8% of the available housing in the city. 与此形成鲜明对比的是, Seattle had developed only 1,到2016年，adu将达到300个，尽管其市政边界内的单户住宅数量是现在的两倍.
Even with all this additional housing stock, 温哥华仍然面临着住房危机——与20世纪80年代提出adu的最初案例时讨论的住房危机相同. ADUs are not a cure-all solution, but at 8% of the housing stock, they are certainly mitigating what could be an even larger problem. These additional units have helped the city in at least three ways: 1. 利用现有的，未充分利用的空间，很容易转换成新的住房. 允许“就地养老”或同一家庭内的代际住房. 让想要住独户式住宅的家庭以更合理的成本享受同样的生活方式.
An example of a Vancouver laneway home. 图片来源: City of Vancouver.
California Goes Full Legalization
在看了像温哥华，加州这样的成功案例之后 took great strides 在全州范围内创造一个更容易建立adu的环境. 1月1日起st在美国，2017 adu在全州范围内是合法的，个别城市不能禁止其建设. 另外, regulations on mandatory parking minimums 对于adu are now illegal, 这是一个城市“允许”ADU建设的传统方式，但在实践中却不可行.
adu现在是通过增加供应来解决经济适用房短缺问题的可行工具, without changing the look and feel of a neighbourhood. And with statewide approval, 独户房主将无法向市政府施压，迫使其对自己的社区实施限制. 小规模的填充物可能会在整个州急剧增加(如果你愿意在你的新房子里安置洛杉矶许多无家可归的居民中的一个的话), the County of Los Angeles might even pay for it’s construction).
The Future of Single Family 住房
而西海岸正朝着快速建设这些单位的方向发展, 许多其他北美城市都在努力争取通过限制ADU的政策. 例如, 卡尔加里目前有一个个案申请程序，单位必须得到市议会全体成员的批准, making the process discretionary and time consuming. 他们一直在努力寻求共识来修改他们的政策，现在正在考虑将其提交给全市投票 upcoming municipal election. What is preventing more cities from embracing hidden density? Carbondale, a small city in Illinois, recently scrapped 这完全是在"保护单户社区"的基础上试图使套房合法化. 这是最常见的担忧，在公开听证会上一次又一次地提出. 但是，由于其固有的隐藏密度，adu是否会对单一家庭社区造成伤害? Or is this yet another case of NIMBYism? 当adu被证明是在现有城市结构中创造大量住房的有效策略时, 未来，像温哥华和加州这样的政策将席卷整个大陆，前景一片光明.
