A green roof is the per­fect roof

Winnipeg Free Press - Section G - - HOMES - MIKE HOLMES

WHILE you were watch­ing cov­er­age of the 2010 Olympic and Par­a­lympic Games, did you no­tice the roofs of the Olympic Vil­lage? They’re green, and I think they rep­re­sent ex­actly the kind of de­sign we need to be in­cor­po­rat­ing in all de­vel­op­ments, es­pe­cially large ones in ur­ban ar­eas.

Now that the games are over, the Olympic Vil­lage will be an ur­ban cen­tre, in­clud­ing res­i­den­tial, re­tail, com­mer­cial and pub­lic space, and it was built sus­tain­ably. They’ve in­cor­po­rated many meth­ods for con­serv­ing wa­ter and en­ergy, in­clud­ing ground-source heat­ing, heat trans­fer from sewer lines and stormwa­ter man­age­ment us­ing swales planted with na­tive veg­e­ta­tion. The most vis­i­ble are the green roofs.

The de­sign­ers of the Mil­len­nium Wa­ter de­vel­op­ment were re­quired by the City of Van­cou­ver to make sure the to­tal roof area was at least 50 per cent green. That adds up to al­most 300,000 square feet of green roofs in this project alone. That’s a bold move on the city’s part, and one I think should be re­quired ev­ery­where.

Re­cently, Toronto be­came the first city in North Amer­ica to adopt a by­law that re­quires and gov­erns the in­clu­sion of green roofs in new de­vel­op­ment. That ap­plies to new res­i­den­tial, com­mer­cial and in­dus­trial build­ing per­mits over a cer­tain size. That’s re­ally a step in the right di­rec­tion. Green in more ways than one A green roof is the per­fect roof. They are ‘green’ and can save you money on your heat­ing and cool­ing bills. They clean the air, pro­duce oxy­gen and na­tive habi­tats for wildlife. They can also pro­vide ad­di­tional liv­ing area for your home, which al­lows you to re­duce the foot­print but still have more space.

The roof sys­tem used at Mil­len­nium Wa­ter is an ex­ten­sive ‘blan­ket’ type of sys­tem de­vel­oped over the past 40 years in Ger­many by Xero Flor. It in­cor­po­rates the veg­e­ta­tion, wa­ter re­tain­ing fleece, drainage bar­rier and root bar­rier in one. The plants are grown in fields, then rolled up and trans­ported to the rooftop and in­stalled. It’s a light­weight sys­tem that can be used in many homes.

The roofs are planted with a mix­ture of se­dum and drought-re­sis­tant suc­cu­lents that flower in the sum­mer and go dor­mant in win­ter. They are tough. They tol­er­ate ex­tremes in tem­per­a­ture — they can take the heat of sum­mer and cold of win­ter — and they don’t need ir­ri­ga­tion once they are es­tab­lished. (In Van­cou­ver, they won’t have a prob­lem get­ting ir­ri­gated by na­ture, I’ll bet). Stormwa­ter Runoff A green roof re­tains stormwa­ter and de­creases the rate of runoff — it slows the wa­ter down as it per­co­lates first through the green roof be­fore it goes to the drain.

They also store wa­ter in the plants, then release the mois­ture slowly back into the at­mos­phere. Any ex­cess wa­ter that does run off the green roof has been fil­tered nat­u­rally by the plants. Re­duce Waste A green roof will out­last tra­di­tional roofs by decades. Since the ac­tual roof mem­brane is shielded from the sun’s UV rays, and pro­tected from wind, tem­per­a­ture ex­tremes and ther­mal stress of a freeze-thaw cy­cle, the roof will last longer. That means all the cost of re-roof­ing (con­sumer cost, cost to the en­vi­ron­ment to cre­ate new roof­ing ma­te­ri­als, and the cost to dump the old roof into a land­fill) are re­duced. Ur­ban Heat Is­land The tem­per­a­ture in a city can be 10 or 20 de­grees higher than the tem- per­a­ture around it —that’s the ‘heat is­land’. The build­ing ma­te­ri­als such as con­crete and as­phalt shin­gles ab­sorb so­lar ra­di­a­tion and them re-emit it. Green roofs ab­sorb that same so­lar en­ergy and use it to grow the plants. That process also cools the air through evap­o­ra­tion. On a hot sum­mer day, the tem­per­a­ture of a green roof can be cooler than the air tem­per­a­ture. (On a tra­di­tional as­phalt roof, the sur­face tem­per­a­ture is usu­ally many de­grees hot­ter than the am­bi­ent air tem­per­a­ture. Go fig­ure.) Re­duce heat­ing/cool­ing costs Green roofs help in­su­late build­ings, es­sen­tially by shad­ing the roof sur­face and by pre­vent­ing heat from mov­ing in­side. That keeps the in­te­rior tem­per­a­ture cooler. It also keeps the roof sur­face tem­per­a­ture more con­stant — it doesn’t get ex­tremely hot or ex­tremely cold. That takes a strain off the heat­ing and cool­ing sys­tem, and saves money. More than just good looks A green roof pro­vides an oa­sis for wildlife — birds and in­sects can live on it. And I think green roofs just sim­ply look good.

— Canwest News Ser­vice

‘Green’ roofs re­duce heat­ing and cool­ing costs, con­vert CO2 to oxy­gen and can

in­crease your home’s liv­able space.

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