There was a time when the term 'LEED' - short for 'Leadership in Energy and Environmental Design' - was reserved almost solely for construction-related manuals and trade publications. Not so anymore. Take the example of a February 2009 Toronto Star headline, LEED-ing the way, for a story about Canada's first residential development built entirely to LEED Platinum specifications.
The story and headline underscore the fact that despite the relative newness of this green rating system in Canada - it was adapted from the U.S. version and implemented here in 2004 - it has become widely recognized among Canadians whose awareness of all things green continues to grow.
While there's no doubt LEED ratings have established important benchmarks for smarter, more environmentally-friendly construction (as have similar systems such as Green Globes and Canada's more consumer-focused EnerGuide), many within the building industry will agree that quantifying green value can be challenging within the confines of LEED. To accurately measure environmental impact, it's often necessary to look more closely at a building's sustainability and ongoing lifecycle assessment.
"LEED is in fact a fairly primitive and not very flexible tool for green measurement," says Bill McEwen, Executive Director of the Masonry Institute of British Columbia. "The goal now is to look at lifecycle assessment - an overall view of environmental impacts, including the long-term maintenance and cost associated with a building."
Speaking about concrete masonry and, specifically, concrete block, McEwen notes that block earns high marks in two key areas of LEED measurement: regional material, and recycled content. 'Regional material' refers to material sourced within 800 kilometres of the building site. 'Recycled content' refers, in the case of block, to the replacement of some of the cement and aggregate (sand and gravel) in a block mixture. About 20 to 25 percent of the cement content can be replaced with supplementary cementing materials (SCMs - typically ground blast-furnace slag in eastern Canada, and fly ash in the west). Aggregates can also be replaced with various recycled materials. There is now lightweight block produced in Ontario that in some cases is credited as having 100 percent recycled content.
All of which can contribute significantly to a building's overall LEED rating - ratings are calculated not by the greenness of individual materials alone, but on their contribution pro-rated by dollar value relative to the cost of all the building materials.
This perhaps raises the question: what if one green material is less expensive than another?
"It's perhaps a back-handed compliment," says Bill McEwen, "that concrete block is a low-cost material relative to the performance and durability it delivers."
Durability, meanwhile, is one area in which concrete block outperforms pretty much all other building materials. However, in comparison to categories such as energy, which can earn a potential 10 points out of a total of 70, durability receives only one point under LEED Canada specifications. (Under the U.S. LEED rating system, it receives no recognition at all.)
"A building that lasts a hundred years makes more sense environmentally than a building that lasts 50 years and then has to be replaced," says Bill McEwen. He points out related advantages such as minimal maintenance and the fact that block needs no additional interior finishes or exterior cladding - benefits that translate to lower costs, fewer materials, and fewer resources required for upkeep.
These are important considerations in assessing a building's sustainability, yet they're not recognized under LEED.
And there are other characteristics of block that, while having a low or no profile under LEED, add green value and/or increase the sustainability a structure. For example:
- Thermal mass - Concrete block helps maintain indoor temperatures by moderating the temperature swings that cause furnaces and air conditioners to kick in.
- No VOCs - Concrete block contains no volatile organic compounds (VOCs-potentially harmful gases that contribute to smog and can cause respiratory problems). Ironically, concrete block and floors earn no LEED points for indoor environmental quality, and in fact would need to be covered by a low-VOC material (such as paint or carpet) in order to qualify.
- Fire safety - Concrete block doesn't burn, and therefore saves lives when used as a firewall, and can be re-used when the flames are finally extinguished.
Block also surpasses most other materials when compared as a sound barrier. Bill McEwen notes that this particular quality has made concrete block a favoured material of some large-scale residential and hotel property developers.
"You really have to look at the big picture and weigh all the benefits of a building material," says McEwen, adding that calculating those benefits is not as straightforward as it might seem. Steel, for instance, can incorporate lot of recycled material, yet be shipped from China, leaving behind a sizeable carbon footprint.
And while McEwen doesn't discount the importance of LEED in promoting green construction, he does note that there is sometimes a tendency toward "chasing LEED points" and thinking short-term.
He adds, "The farther down the road you look, the more sense masonry makes."