A comparison of Resistance Values for some typical wall construction

The onslaught of increased energy costs has brought government code bodies to the forefront and within a relatively short period of time thermal resistance requirements for building envelopes began reflecting these higher costs for electricity and heating fuels.

The era of cheap and abundant energy has come to an abrupt end.  It is now the time to develop effective conservation goals through knowledgeable, innovative, imaginative building designers and craftsmen.  In order to do this there are a number of things to keep in mind.

First of all, to do a good job of saving energy it is important to be concerned with thermal performance of the entire building, not just a component or a system.  Every aspect has to be taken into account and standards that take this overall “thermal performance” into account are ideal.  This approach gives designers and builders freedom to use their skills and ingenuity and encourage such things as:

• 1. Proper solar orientation of the building on its site
• 2. The geometric shape of the building (ratio of length to width)
• 3. The number of stories for a given floor area requirement
• 4. Mass and colour of exterior walls
• 5. Shading or reflections from adjacent structures
• 6. Opportunities for natural ventilation; wind direction and speed
• 7. Reduced air infiltration and efficiently sized mechanical equipment
• 8. Proper insulation

A true “performance standard” would establish an annual energy budget and then allow designers, builders and owners to achieve this energy budget in the manner best suited to their requirements.

The sun’s energy rays can be used to advantage to reduce energy costs.  There are both “active” and “passive” solar collectors.  “Active” solar collectors collect energy from the sun and then use mechanical equipment such as pumps or fans to distribute that energy.  “Passive” collectors simply collect the sun’s heat and store it until it is released by radiation or conduction.  No materials serve as “passive” collectors better than masonry - concrete block, brick or stone.

Massive walls of masonry keep buildings warmer in winter, cooler in summer because they are passive solar collectors even when not designed as such.  Furthermore, the increased mass of masonry can reduce and shift energy flow peaks and so reduce the size and capital costs of heating and air conditioning systems.

Insulation, when properly used, is the construction material most widely incorporated to conserve energy.  However, it is important to determine the ideal thickness of insulation to achieve cost efficiency.  The law of diminishing returns as applied to insulation thickness is a primary factor to consider when establishing the optimum RSI value.

Insulation affects only the loss or gain of heat through conduction.  Heat conduction through walls accounts for about 10 percent of a building’s overall energy usage.  Air infiltration through cracks and inadequately sealed openings of windows, and doors, through cracks and inadequately sealed openings, is estimated to account for 25-30 percent of the thermal loss in buildings.

Furthermore, effectiveness of insulation depends on the wall to which it is attached and masonry is still one of the best-suited materials for the skins of buildings as it guarantees minimal air transfer through the envelope.

Keeping to a strict energy budget for building is important today and will be even more so tomorrow.