Reduce and replace: how to curb residential greenhouse gas emissions

Last Friday, the Intergovernmental Panel on Climate Change released its fourth report on the impact of anthropogenic greenhouse gases on the planet. According to the report, there is now unequivocal evidence that global warming is being caused by human activities and that the impact will be felt for centuries.

A week or two before the release of the IPCC report, Conserve Nova Scotia announced its "EnerGuide for New Houses" program, intended to encourage new-home builders to reach the EnerGuide 80 rating (that is, the R2000 standard) by 2011. Conserve Nova Scotia's central argument for constructing a home to the EnerGuide 80 rating is, "When you build to 80, you also cut about 5.6 tonnes of greenhouse gas emissions from entering the atmosphere every year".

This argument is based on two assumptions. First, the new home is the same size as the original. Second, the source of heat remains unchanged: if electric, both the original and new home are electrically heated; if oil, the original has an inefficient furnace, whereas the new has an efficient one. If these two assumptions are met, and the home achieves an EnerGuide 80 rating, the saving will be about 5.6 tonnes of carbon dioxide.

However, when many people build a new home, it is typically larger than the original. In these cases, the home may achieve the EnerGuide 80 rating, but its size means it will meet neither the energy nor the greenhouse gas reductions predicted. There is also a trend for people building EnerGuide 80 homes to opt for electric heating rather than oil; in these instances, greenhouse gas emissions can actually increase if the electricity supplier relies heavily on coal (which is the case in Nova Scotia).

The Conserve Nova Scotia website gives more details of the program, stating, "The average energy rating of a home in Nova Scotia is 67. Beginning in 2009, all new homes could be required to achieve an energy rating of 72. In 2010, the minimum rating would increase to 77. In 2011, the minimum would be 80".

At first glance, using a graduated approach to introducing EnerGuide 80 seems reasonable in that it allows builders to learn the standard; however, these numbers are misleading.

Although the average EnerGuide rating for homes in Nova Scotia may well be 67, this number takes into account all homes, including poorly insulated ones built prior to the 1960s; looking at only newly built homes produces a considerably different number. According to NRCan's CANMET Energy Technology Centre, in 1997 the average newly constructed conventional home in Atlantic Canada achieved an EnerGuide rating of 72.3, while R2000 homes received an EnerGuide rating of 80.1. In other words, since 1997, most new homes probably met the 2009 target and those built to the R2000 standard already exceed the 2011 target!

Despite these shortcomings, Conserve Nova Scotia is offering a $350 cash incentive to cover the cost of the energy audit of any new home that achieves a rating of 77 or better, while homes with a lesser rating get half the amount. Homes built to the EnerGuide 80 rating, regardless of their energy consumption or greenhouse gas emissions, receive an additional $500, bringing the total to $850.

It is important to understand that "energy efficiency" does not necessarily mean a reduction in energy consumption. The first step in curbing greenhouse gas emissions is to reduce the amount of energy consumed.

The greater the reduction, the better, because the second step in curbing emissions is to replace most, or ideally, all, existing fossil-based energy for heating with as much indigenous, non-fossil energy as possible.

So how can new-home builders reduce and replace?

When it comes to new homes, reduction can be achieved in a variety of ways; for example, exceeding the EnerGuide 80 rating or, in keeping with declining household size, building smaller, low energy consumption homes. The simplest and most cost-effective form of energy replacement is to employ (free) solar energy and to require that new homes be constructed on an east-west axis to maximize their solar gain through south-facing windows.

Rather than paying $850 for the construction of new homes that may consume more energy and emit more greenhouse gases, Conserve Nova Scotia should champion the immediate introduction of reduction and replacement legislation: building codes (new homes exceed the EnerGuide 80 rating) and municipal bylaws (new homes maximize solar gain). The $850 can go towards assisting low-income Nova Scotians reduce their home energy consumption.

(And if it turns out that climate change is a left-wing hoax, there's no need to pity anyone living in a home that has reduced its energy consumption and replaced imported fossil fuels with solar, since they'll be the ones laughing all the way to the bank as energy prices continue to climb.)

Published Chronicle-Herald - 15 February 2007