How Buildings Waste Energy During Winter: 3 Common Issues

Topics: HVAC, Energy Efficiency, energy conservation, efficient heating, energy savings, building efficiency

Michael Tobias
Author : Michael Tobias on December 18, 2020

HVAC represents the largest share of energy consumption in most residential and commercial buildings, and space heating in particular is the top expense during the winter months. You can expect the highest heating bills with cold weather, but an excessive cost may indicate issues that require attention.

The heating cost a building depends on three main factors: the efficiency of the space heating system, the effectiveness of the building envelope in keeping the heat inside, and a proper configuration and thermostat setting. Even the most efficient geothermal heat pumps will waste energy in buildings with many air leaks, and a high thermostat setting will increase energy consumption regardless of system efficiency.


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This article will describe three common issues that increase building energy consumption during winter, and recommendations to fix them.

Issue #1: Air Leaks in the Building Envelope

03 subtitle 1 air leaks

Space heating systems keep building interiors at a higher temperature than outdoors, and air leaks make this task more difficult. When plenty of cold air is allowed into a building, it has the same effect as using the air conditioner while the heating system operates! For instance, if a commercial building loses 60,000 BTU per hour due to air leaks, the space heating system must provide that amount of additional heating. This will increase the consumption of gas or electricity, depending on the types of heating equipment used.

Some air leaks are evident when standing close to doors or windows, but others are more difficult to find. Energy consultants use special methods to find air leaks more easily:

  • Thermal imaging is a powerful tool, since it makes temperature differences visible for the human eye. For example, a draft of cold air in a building area that is not occupied may remain hidden for a long time. However, a thermal imaging camera will show cold areas in a darker color than their surroundings. Thermal imaging also detects poorly insulated areas as cold spots in the building envelope, even when there is no air leakage involved.
  • Pressurization tests can also detect the building areas affected by air leaks, and they also allow an estimation of leakage in cubic feet per minute (CFM). The blower door test is the most common method, where air is injected or extracted and the effect on indoor pressure is observed.

Older buildings tend to have more air leaks, but even a recent construction may be affected. Finding and sealing air leaks is strongly recommended, since you will also save on air conditioning during summer.

Issue #2: Heating Systems with Low Efficiency or Poor Maintenance

03 subtitle 2 heating system low efficiency

For a given indoor area and outdoor temperature, an inefficient heating system will consume more energy and dollars. Low efficiency can be caused by a lack of maintenance, or simply by the technological limitations of older equipment.

The best starting point to improve a heating system is getting a professional inspection by HVAC engineers. This will reveal if low efficiency is caused by lack of maintenance or equipment features, to plan the most effective actions.

  • Damaged insulation on air ducts or hydronic pipes is an example of a maintenance issue that reduces heating efficiency. The necessary repairs are not complex, and can be scheduled with minimal disruption for occupants.
  • When the heating equipment itself has low efficiency, building owners should consider an upgrade. For example, a boiler with an Annual Fuel Utilization Efficiency (AFUE) or 95% will consume around 30% less fuel than a unit with 67% AFUE. Waiting until the summer is recommended, since an upgrade during winter will leave the building without heating.

An inspection of the building envelope is recommended before any heating system upgrade. You can achieve even greater savings by fixing issues related with insulation and airtightness first.

Issue #3: High Thermostat Setting and other Configuration Issues

03 subtitle 3 thermostat

According to the US Department of Energy, a thermostat setback of 7-10°F for 8 hours per day will reduce HVAC costs by around 10%. However, many thermostats are set at a high temperature all winter long, making the heating system consume more energy. Finding the ideal setting for a commercial building is a challenge, since individual preferences vary when it comes to thermal comfort. However, Lawrence Berkeley National Laboratory (LBNL) found that the best temperature for human productivity is around 22°C (71.6°F). The WELL Building Standard suggests an indoor temperature variation of 3°C (5°F) to offer thermal comfort for more people.

In addition to temperature, there are other equipment settings that affect heating performance. Some examples are damper positions, boiler pressure, ventilation rates, operating schedules, air duct pressures, etc. These types of issues can be detected with a professional energy audit.

Conclusion

Building owners can expect to spend more on heating during winter, but the cost should not be excessively high. In many cases, a high heating bill can be attributed to building envelope deficiencies, low overall efficiency of the heating system, and configuration issues. Minor repairs and configuration changes can often be completed along with the inspection, but upgrades and major modifications require planning and more investment. Heating system retrofits can be completed with less disruption during summer, when the equipment is not being used.

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