a report from Councillor Dennis J. Carlone and Councillor Craig A. Kelley, Co-Chairs of the Ordinance Committee, for a public hearing held February 5, 2019 to discuss the petition filed by the City Council to amend the Zoning Ordinances in Article 5.000 as it relates to rainwater and flat roofs

ATTACHMENT A 6.7 City of Cambridge 0-7 IN CITY COUNCIL December 3, 2018 COUNCILLOR KELLEY COUNCILLOR ZONDERVAN WHEREAS: Flat roofs and associated central drains on residential three-story homes can lead to more storm water entering Cambridge's sanitary sewer; and WHEREAS: These flat roofs may be on homes that have been insulated or otherwise improved for energy efficiency with the result that snow and/or ice during the winter may build up amounts unanticipated by the original building designers; and WHEREAS: Climate change appears to be bringing more episodes of heavy snow and rainfält. during winter months, as experienced during the winter of 2014-2015 and again ir 2017-2018, and with clogged drains this results in more buildup of snow, ice, and water on flat roofs than may be safe, especially with an energy-efficient building which helps keep rooftop ice and snow from melting away; and WHEREAS: Retrofitting flat roofs to allow angled drainage to the side of residential three-story houses would alleviate snow, ice, and water buildup safety concerns and would decrease the amount of storm water going into Cambridge's sanitary sewer system; and WHEREAS: The expensive alteration of putting a pitched roof on a flat roof could be offset by the added value of increasing interior space in the existing home and possible improving other options for room use; and WHEREAS: The extra height and living space created as a result of installing a pitched roof may negatively impact neighbors; and WHEREAS: The Special Permit process used for other challenging zoning situations may be appropriate in this case; now therefore be it Packet Pg. 251

6.7 ORDERED: That the City Council refer to the Ordinance Committee and the Planning Board, for hearing and report, the proposed amendments to Article 5.000 of the Cambridge Zoning Ordinance: Proposal for converting flat concave roofs to a kind of greenhouse/glass porch Z.O. 5.55 In an effort to enhance the City's commitment to mitigating environmental impacts of certain older types of residential buildings, namely so-called "triple-deckers", while improving the City's storm-water management, modifications to the applicable dimensional requirements of this Article 5.000, in particular regarding FAR and height limitations, may be authorized under the following circumstances: Residential buildings with a flat (concave) roof which may have poor upper-level thermal insulation and/or contribute to important heat island effects, or may suffer from the secondary effects of over- insulation, and on which a drain pipe collects water from the roof and combines it with household waste-water, discharging into a single outflow pipe to the municipal sewer line Provided that the resulting construction will: significantly increase the thermal efficiency of the building entirely eliminate rain water entry from the concerned roof into the sewer system, and said rain water is harvested on the property at the rate of 1/8 gallon per square foot of roof area, with the remainder dispersed at the ground to follow its natural path without direct encumbrance onto abutting properties, the construction of a partial structure relieved from the applicable FAR and height limit may be permitted within the following limits: Additional height not to exceed 10 ft. above the existing roof line of the building • Footprint to be no closer than 3 feet from either long edge or rear side of the building, no less than 6 feet from front/street-side of building, and Additional FAR not to exceed 20% of the existing FAR of the building. Furthermore, in enhancing alternative energy sources (Article 22), additional positive consideration will be given to projects that improve the: installation of solar panels (impractical on residential flat roofs) use of passive solar heating, convective cooling, seasonal shading with natural plants, using rainwater at the roof level or floors below, Least, and lowering bushes and vegetation attractive to pollinating insects at the root harmonization of the new roof profile with the neighborhood architecture. Packet Pg. 252

ATTACHMENT B Climate Change City Council, 5 February 2019 Residential flat roof conversion proposal now? on the built environment Who else is worried about Why Worry about Flat Roofs Climate Change and its impact 2/5/2019

drain ssions into sewer roof = clogged roof: snow melts Well insulated flat Poorly insulated flat roof is insulated Goal A: Minimizes greenhouse gas Objectives for 2020 says 14.1% of Cambridge's greenhouse gas emissions from all measurable sources So the incentive is not to insulate a flat roof What the Climate Protection Action Committee Goals and http://www.cambridgema.gov/CDD/climateandenergy/greenhousegasemissions/communityemi Central drains on a flat roof clog when a flat all roof water Roof drain collects https://boston.uli.org/wp- (emphasis added) floodproofing will need to become cost of doing nothing could be profoundly new strategies for building envelopes and Actions to prevent and reduce damages from and property, they are a sound investment...." disruptive and exponentially more expensive. showers, etc. content/uploads/sites/12/2012/04/UL1_LivingWithWater-Final1.pdf Tie-in to toilets, commonplace. While building a more resilient extreme weather events not only protect people community will require investment over time, the removing water from local ecosystems drains that combine rain with sewage, "Careful planning will be required to maintain the adding to our WRA treatment load and Additionally, many flat roofs have center continuity and quality of the urban experience, and What the Urban Land Institute Says 2/5/2019

experience) https.//cxtcnsion.inois.cau/icr/storinwater.cim runoff." (emphasis Kelley's) 6,000ct/yr of rain* the rain and sending it off site as storm water "Recently, more community storm water plans A single Triple Decker gathers And 1/3 of sewer input for a three-family water from the site. This policy involves keeping building could be RAIN! (Nicolai Cauchy's discharge. One basic starting point for such a plan is for homeowners to reduce runoff from have incorporated the concept of "no net loss" of their individual lots. Many simple yet effective as much as possible, rather than simply collecting What the University of Illinois Says and using the rain that falls onto a site on that site *Ref.: 1500s.f. area; 4' annual rainfall; 7.5gals/c.f.; sewer tax $8.3/Ccf (Ccfa100c.f.); Typical Triple Decker consumes 130Ccf/yr (FY2010) methods can be used to help reduce individual drain 2/5060689) • damaging flooding *There are different schools of thought on this Currently.... environment • snow and ice buildup on the roof and Insulated flat roofs are likely to result in* accumulated ice and snow (wet snow is heavier- • structural challenges due to the weight of https://www.accuweather.com/en/weather-glossary/wet-vs-powdery-snow- Who else is worried about storm water and its impact on the built potential associated ice dams in the center 2/5/2019

roof conversion heating and cooling. Protect neighbors by: natural paths "without direct per guidance of the Special Permit incentives (or at least covers costs) for FLAT ROOF AMENDMENT encumbrance onto abutting properties" 1. Requiring a Special Permit prior to any FLAT ROOF AMENDMENTS 2. Retaining stormwater onsite or following greenhouse gas emissions associated with Via extra FAR and/or height relief, provides with better insulated pitched roots thus cutting residential property owners to replace flat roofs many flat roofs zoning discussions recommendation 3 September, 2013) Modestly recharges groundwater (noted in PB Separates household sewage and storm water incentives (or at least covers costs) for A larger discussion of environmental Are intentionally narrowly defined* benefits versus personal costs versus thus cutting down on MWRA sewage by the subject of post-Envision Cambridge increased density versus neighborhood removing the central drain associated with 1. Manages storm water onsite or off per Special Permit FLAT ROOF AMENDMENT Via extra FAR and/or height relief, provides FLAT ROOF AMENDMENTS *7 June, 2016 PB recommendation raised this concern- "there should be a expectations versus..... somewhat failed in residential property owners to pitch flat roofs, the Brown Petition and may, or may not, be broader consideration of the types of public benefits that could be achieved" 2/5/2019

ice/snow buildup construction costs insulation of residential flat roofs by "Increased size and height" • Incentivize greenhouse gas reducing Concerns about relaxing Z.O. limits Impact on neighbors and visual aspect- - Reducing concerns about clogged drains and • Minimize rainwater discharge into sewage - Create FAR/height options to compensate for Purpose of ZO Amendment 5.55 and maximize its return to local ecosystems Rainwater (gutters at diverted to the ground eliminated! gambrel) or use on roof recycled for Central Drain Front view from 40ft away Illustration of one design option Visual representation: minimal impact Side view from 15ft away cooling heating Shading enhance seasonal High-level cover with pollination Convective Passive solar ventilation and Vegetative roof flowering plants 2/5/2019

• FAR no impact on natural light existing FAR and 6' (front) Even adjacent to a third floor dormer, • VISUAL IMPACTS • Maximum roof height • ZO 5.55 limits height gain to 10' for light/view • ZO 5.55 suggests a limit of 20% over • Setback requirements of 3 (sides and rear) Addressing local impact concerns In other City areas where triple deckers are Minimal impact on neighbor's natural light or view concentrated the crown overhang determines angle neighborhoods neighborhoods and present well Concerns about relaxing Z.O. limits disrupt the prevailing character of some Mar the iconic image of triple-deckers and 2/5/2019

conditions are met: (BZA) neighbors by allowing a change in zoning Concerns about relaxing Z.O. limits may grant a special permit for alteration of a Example of Special Permit Creating value for certain residents but not their single family or two-family, detached dwelling to provide one accessory apartment if the following • 4.22.1 In all districts the Board of Zoning Appeal applicability via a special permit (PB Memo 7 June, supports this amendment provisions of Section 5.28.2. before? YES! emissions and managing storm water, like the policy The public policy behind minimizing greenhouse gas zoning district as set forth in the following convert an existing principal-use structure behind, for example, maximizing housing opportunities, to Residential Use Where it is proposed to designed and built for non residential use to uses not otherwise allowed in the applicable residential uses or to certain non-residential relief to unique properties- Section 4.30 - Table of Use Regulations, such • 4.29 Conversion of Non Residential Structures this- granting specific zoning Have we done something like uses may be allowed after issuance of a special Example of Special Permit (PB) permit by the Planning Board consistent with the 2/5/2019

sewer system, and that Gutter harvest ran perior plane Provided that the resulting construction will allows heat in winber • significantly increase the thermal efficiency of the building Language- requirements ZO 5.55 is good common sense Flat Roof Zoning Proposal's per square foot of roof area, with the remainder dispersed at the ground to follow its natural path without direct encumbrance onto Innovation, Ecology, and Economies • entirely eliminate rain water entry from the concerned roof into the • said rain water is harvested on the property at the rate of 1/8 gallon design scale - Drawings not to exact primarily for suggestions building. the building building, and municipal sewer line height limitations, may be authorized under the following In an effort to enhance the City's commitment to mitigating and height limit may be permitted within the following limits Language- background • Additional FAR not to exceed 20% of the existing FAR of the water management, modifications to the applicable dimensional requirements of this Article 5.000, in particular regarding FAR and side of the building, no less than 6 feet from front/street-side of Language- new allowances namely so-called "triple-deckers", while improving the City's storm- Flat Roof Zoning Proposal's Flat Roof Zoning Proposal's household waste-water, discharging into a single outflow pipe to the environmental impacts of certain older types of residential buildings, • Footprint to be no closer than 3 feet from either long edge or rear Residential buildings with a flat (concave) roof which may have poor • Additional height not to exceed 10 ft. above the existing roof line of the construction of a partial structure relieved from the applicable FAR on which a drain pipe collects water from the roof and combines it with effects, or may suffer from the secondary effects of over-insulation, and upper-level thermal insulation and/or contribute to important heat island 2/5/2019

architecture. with natural plants, insects at the roof level, and • using rainwater at the roof level or floors below, • harmonization of the new roof profile with the neighborhood Language- considerations • installation of solar panels (impractical on residential flat. roofs) Furthermore, in enhancing alternative energy sources (Article 22), Flat Roof Zoning Proposal's • planting flowering bushes and vegetation attractive to pollinating • use ot passive solar heating, convective cooling, seasonal shading 2/5/2019