Peter Amerongen is fond of saying "concrete is one of the most energy intensive things we do". Or something to that effect. By "we", he means humanity, and he's right:
Cement is the principal ingredient in concrete[, and] cement manufacturing accounts for approximately 7% to 8% of CO2 globally, and approximately 1.8% of CO2 emissions in Canada" (source ).
The concrete used in the Millcreek NetZero Home (MCNZH) will be composed of about 50% fly ash (a waste material from coal-fired power plants) to minimize the use of cement. We're still using too much concrete, but since my family is spending its life savings on this house, we weren't willing to experiment when deciding how to add mass to the home to store solar heat .
Still, reducing our use of concrete is a priority, and were doing it in a couple of ways:
Old sidewalk blocks have been removed and stored so they don't get broken during demolition and excavation
The old garage on the site - we like it and we're keeping it!
The greening of concrete is an area that needs desperate attention - it's a brilliant building material that is used in almost every building we put up. However, it's an environmental nightmare. That's why concrete houses are not at all green (contrary to claims made by the likes of Con Boland ), and we should strive to reduce its use as much as possible.
In our next house (ha ha), maybe we'll figure out a better way to store solar heat than in concrete floors. There's a guy who's building in the Garneau neighbourhood who's storing it in pop bottles filled with water. Now that's a benign source of solar mass.
In the meantime, we'll do our best to minimize our use, even if it just means reusing old concrete blocks and not tearing down the second building on our building site.