Making the Invisible Visible: Designing for energy efficiency with insulation

Photo courtesy Paul Filitchkin

By Tara McClinchey
Buildings are energy hogs. Nearly half the total energy consumption of commercial and industrial buildings in Canada is used for heating and cooling spaces, which contributes to 42.9 per cent of the sectors’ greenhouse gas (GHG) emissions. Thus, important measures are taken to reduce the energy consumption of buildings, with a special focus on heating and cooling loads. This has presented a challenge for design professionals over the last few years. How can a building be designed to maintain its exterior beauty while nevertheless still significantly reducing its energy consumption?

The high-rise buildings dominating most downtown cores across Canada may be pleasing to the eye, but what really counts is hidden behind the walls. Not only do wall assemblies including fibreglass, rock, and slag wool (i.e. mineral fibre) insulation provide peace of mind with effective moisture and fire protection, but they also have much to offer by reducing a building’s energy consumption.

For example, they can offer savings on utility bills, which can then be invested in business growth opportunities or improved competitiveness, such as reduced prices for consumers or higher profits for shareholders. (These savings vary, as explored in the seller’s fact sheet on R-values. Higher R-values mean greater insulating power.) Highly insulated and well-ventilated buildings can also provide its occupants improved indoor air quality (IAQ), which could have an impact on health, well-being, and overall productivity.

The market for energy-efficient buildings is expected to grow. These code requirements are becoming more stringent, and energy efficiency labels on buildings are growing more recognizable. Canada has adopted a benchmarking system—making it easier for building owners to track and assess their energy consumption, and to compare their performance with other buildings of a similar type. It is important buildings are designed not only to look esthetically beautiful, but also be energy efficient. This means taking mineral fibre insulation into consideration when designing the building envelope.

Examining the energy efficiency code requirements
The commercial building sector is changing as more jurisdictions across Canada move to adopt the 2011 National Energy Codes for Buildings (NECB) or their own energy efficiency codes (e.g. Supplementary Bulletin 10 [SB-10] of the Ontario Building Code [OBC]). While the 1997 Model National Energy Code for Buildings (MNECB) was the first to introduce energy efficiency standards for commercial, institutional, industrial, and large residential buildings, it is the 2011 NECB that has been effective at setting a precedent for more stringent minimum energy requirements in much of the country. This has put Canada in the running with other countries leading the way in energy-efficient construction.

Taking a holistic approach to design, NECB allows designers to take either prescriptive, trade-off, or performance paths. In other words, there is some flexibility in design, as long as the building does not consume more energy than it would have otherwise. A building designed with more windows, then, would be required to compensate for its higher ability to transmit heat (known as the heat transfer coefficient, or U-value) by increasing the level of insulation, for instance, in the remaining parts of the building envelope.

The national energy codes are typically revised every five years, and the next version of the NECB is expected later in 2015, but has minimal changes to energy efficiency. The plan for the version after that (to be released in 2020) is to improve energy efficiency by 20 per cent. Currently, there are numerous proposals being discussed that would affect the building envelope and required insulation levels, including lowering the maximum U-values for each climate zone, limiting trade-downs in the performance and prescriptive paths, and reducing the number of skylights allowed.

As the provinces and territories adopt the revised NECB, once high-performing buildings might lag behind new buildings. Therefore, designing buildings with insulation levels beyond what is required by code can offer building owners added value in the long run. Voluntary programs, such as building certification and benchmarking, can also provide designers the motivation to do just this, which, in turn, increases the supply of energy-efficient buildings on the market.

The market for energy-efficient buildings and certifications
Building certification has done a lot for raising awareness and opening up the demand for ‘green’ buildings that are said to be more energy-efficient than those built to code. Most people could probably identify the Energy Star label or recognize the Leadership in Energy and Environmental Design (LEED) plaque on a building. Some will even pay a premium to occupy spaces in green-certified buildings with the understanding they will save money on their energy bills and that they can advertise they are doing their part to help the environment. Certain businesses will also pay a premium for the added benefit and competitive advantage of attracting people who want to work in healthier and environmentally responsible offices.

However, spotting an energy efficiency label on a high-rise building made with large window areas raises some questions. Such as, how much energy will the building conserve? Is it actually more efficient than the uncertified ones?

For such a building to merit a strong energy label, the interior must compensate for the poor efficiency of the building envelope. However, what happens when the interior mechanicals (i.e. HVAC and hot-water systems) are not well-maintained, or a subsequent tenant replaces parts of the building interior? It is suggested the most durable, sustainable contribution to a building’s energy efficiency is its well-insulated envelope rather than its interior features.

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