This is part 2 of Energy Saving Ideas.  With all of the snow that we have had around Calgary this year, I thought it would be a good idea to go over some of the easy and cost effective ways to reduce your carbon foot print.  What follows are some energy saving ideas that most everyone can implement.  These systems are standard design protocol for our office.

Occupancy Sensors  

An occupancy sensor is a lighting control device that detects occupancy of a space by people and turns the systems on or off automatically, using infrared or ultrasonic technology. Occupancy sensors are typically used to save energy, provide automatic control, and comply with building codes.

Typically occupancy sensors are used to control lighting systems, but they can be used to control HVAC systems, plumbing systems, etc. typical examples are

  • Turn lights on when you walk into a room.
  • Turn the heat up in a room when it is occupied. This is similar to the night set back concept from last month.
  • Turn on hot water heaters when a space is used.
  • Turn on automatic flush system on plumbing fixtures.
  • The hotel industry uses occupancy sensors quite extensively. When a room is not rented, it is put into a hibernation mode. 
Can you really save with sensors?

Here's an example: In standard 3 storey office building, lights are left on in the bathrooms on every floor for 24 hours a day. If sensors were installed, the on-time would be reduced by at least 12 hours, a 50% savings.

At an estimated 500 watts per bathroom and 9 cents per kWh, the annual savings works out to be $219, or enough to buy 7 more sensors. The chart below shows the possible reduction in on-time gathered in a survey of a large corporate headquarters.

Area type and % Reduction
Locker room - 65%
Large work room - 55%
Rest room - 50%
File room - 45%
Small work room - 40%
Corridors - 25%
Small offices - 22%

Free Cooling for HVAC Systems  

Free cooling is an economical method of using low external air temperatures to assist in chilling air or water systems, which can then be used for air conditioning systems

In heating, ventilation, and air conditioning (HVAC) in winter months, buildings' interior spaces may need cooling, even while perimeter spaces may need heating. Free cooling is the production of air conditioning without the use of refrigeration equipment, and can be used generally in the late fall, winter and early spring,

When utilizing free cooling as a cooling source in an application, the use of ecologically harmful refrigerants can be reduced. Free cooling is also a way to cut down on electricity costs; in some cases the cut might exceed 75 percent. Reducing electricity consumption also has an environmentally friendly effect, as electricity power production often involves air pollution.

How does it work?

Cooler outdoor air is mixed with the warm return air from a space. The amount of cooler outdoor air is controlled so that the air temperature of the mixture is at the optimal supply air temperature for air conditioning. Through a controller, modulating dampers are controlled to provide this optimal mix. As the air is already at the required discharge temperature, the compressors on the air handling unit do not need to operate and the only cost is to run the blowers. There are times when the outdoor temperature is ideal and can therefore supply 100% fresh air to the space - at no cost. The more fresh air the better the environment for the occupants.

It is a win - win situation.

Free Cooling for Chilled Water Systems

As mentioned above, free cooling can use a chilled water system. It is basically the same principle as the HVAC systems. With cooler outdoor air temperatures, circulate water through an outdoor "radiator" to cool the water down the required temperature. This chilled water can then be circulated through chilled water coils in the HVAC system to provide air conditioning to the spaces. The compressors of the chiller do not need to run - saving money. Of course, in a climate such as Calgary, we always need to be concerned about freezing issues, so you must ensure that safeguards are put in place.


We are finding that building envelops in newer buildings are being constructed very well and there is not the infiltration and heat loss that you would normally have seen in older structures. As a result, there is a significant cooling load in the winter months. Systems must be put in place to provide air conditioning during the winter. One of the most economical ways to provide this air conditioning is with the use of free cooling systems.

If you would like more information on this, please contact our office and we would gladly discuss this further.