At­tached hous­ing key to a clean, dy­namic city

The Province - - EDITORIAL - JOSEPH DAH­MEN and JENS VON BERGMANN Joseph Dah­men is an as­so­ci­ate professor at the UBC school of ar­chi­tec­ture and land­scape ar­chi­tec­ture. Jens von Bergmann is the pres­i­dent of Moun­tainMath Soft­ware and An­a­lyt­ics.

Ren­o­vat­ing sin­gle-fam­ily homes isn’t the an­swer when it comes to re­duc­ing car­bon emis­sions. In­stead, Van­cou­ver needs to com­mit to build­ing en­vi­ron­men­tally ef­fi­cient, four- to five-storey row hous­ing. This will re­duce over­all emis­sions while cre­at­ing vi­brant neigh­bour­hoods that in­crease hous­ing sup­ply.

Last year, we pub­lished a study that looks at the car­bon im­pli­ca­tions of tear­ing down sin­gle-fam­ily homes and re­plac­ing them with newer, more ef­fi­cient struc­tures of the same type. What we found sur­prised us. For a typ­i­cal wood frame, sin­gle-fam­ily home in Van­cou­ver, car­bon payback av­er­ages 168 years.

The car­bon payback for new struc­tures drops to around 30 years af­ter 2025, as­sum­ing that the City of Van­cou­ver im­ple­ments the ag­gres­sive per­for­mance tar­gets they have iden­ti­fied. But un­der cur­rent per­for­mance stan­dards, each time we tear down a func­tion­ing home and re­place it with a new one, we in­crease our over­all car­bon emis­sions.

The car­bon payback pe­riod for ren­o­va­tions to ex­ist­ing sin­gle-fam­ily homes is un­likely to be much bet­ter. Older wood frame houses in Van­cou­ver are of­ten built with­out in­su­la­tion, base­ments, or seis­mic pro­tec­tion. Deep ren­o­va­tions to these struc­tures of­ten re­quire re­plac­ing all but the shell of the build­ing, which is sim­i­lar to tear­ing houses down and re­build­ing from scratch. Pre­serv­ing her­itage struc­tures com­mem­o­rates our shared his­tory, but it’s a cul­tural rather than an en­vi­ron­men­tal pri­or­ity.

In light of these find­ings, it’s un­for­tu­nate that our study has re­cently been cited by Van­cou­ver Coun. Colleen Hard­wick in a mo­tion that sug­gests lim­it­ing new con­struc­tion in favour of ren­o­va­tion. This mo­tion stems from a mis­un­der­stand­ing of our re­search.

In Van­cou­ver, homes are be­ing torn down and re­placed for rea­sons that have noth­ing to do with en­vi­ron­men­tal per­for­mance and ev­ery­thing to do with eco­nomics. Put sim­ply, a cheap house con­structed on an ex­pen­sive build­ing lot has lit­tle chance of sur­viv­ing when the prop­erty changes hands. Rad­i­cally in­creas­ing land values pro­duce a tear­down cy­cle as new own­ers de­mol­ish ex­ist­ing homes and re­build com­men­su­rate with the over­all value of their prop­erty, re­sult­ing in spi­ralling car­bon emis­sions.

Ris­ing prop­erty values also makes it likely that to­day’s new sin­gle-fam­ily home is next year’s tear­down. Re­plac­ing one ef­fi­cient home with an­other of­fers di­min­ish­ing en­vi­ron­men­tal re­turns: the car­bon payback in this case can eas­ily stretch to 500 years or more.

As long as we keep re­plac­ing car­bon in­ten­sive sin­gle-fam­ily homes with more of the same, we can’t use the tear­down cy­cle to ad­dress the over­all car­bon emis­sions of build­ings or af­ford­abil­ity con­cerns. Even with laneway ini­tia­tives and sec­ondary suites, sin­gle-fam­ily zoned ar­eas of the city have barely main­tained their pop­u­la­tion.

In­stead, we need to loosen zon­ing so that sin­gle-fam­ily homes can be se­lec­tively re­placed with eco­log­i­cally and eco­nom­i­cally sound, fourto five-story row houses and town­homes. This will di­ver­sify our hous­ing op­tions, re­duce car­bon emis­sions, and cre­ate dy­namic neigh­bour­hoods like those found in Ber­lin, Paris, and Mon­treal. At­tached hous­ing in these cities al­lows more peo­ple to live in prox­im­ity to jobs and ameni­ties, de­creas­ing their re­liance on cars and ac­com­mo­dat­ing fam­i­lies. De­sign­ing sim­i­lar hous­ing for Van­cou­ver can do the same here.

Van­cou­ver is en­ter­ing a new phase of ur­ban de­vel­op­ment. Pro­vid­ing sus­tain­able hous­ing to one mil­lion new res­i­dents mov­ing to our re­gion by 2050 will re­quire let­ting go of older sub­ur­ban mod­els of de­vel­op­ment built on car­bon-in­ten­sive sin­gle-fam­ily homes punc­tu­ated by clus­ters of glass tow­ers.

De­sign­ing high-per­for­mance at­tached hous­ing us­ing lam­i­nated tim­ber and other emerg­ing struc­tural prod­ucts made of sus­tain­able tim­ber grown in B.C. can se­quester car­bon, add valu­able jobs to the B.C. econ­omy, and de­liver on Van­cou­ver’s green am­bi­tions. The higher value of these struc­tures also will de­crease the like­li­hood that they’ll be torn down be­fore their car­bon debt is paid off.

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