Four Reasons to Turn Down Your Building Temperature
Turning down the thermostat will make the payer of the energy bill happy and decrease building carbon emissions if the fuel is petroleum based.
Image courtesy of Building4Health
As IAQ management priorities expand from controlling exposure to airborne SARS-CoV-2 to building decarbonization with clear deadlines, recommendations for HVAC settings may seem contradictory. Should a building manager increase outdoor air ventilation to promote a safe indoor environment for occupants or decrease energy consumption to reduce the carbon footprint? How do building managers straddle this line?
There actually is a starting point that addresses both sides of the coin. This is to simply turn down the thermostat a little bit. Now, the question becomes, what is “a little bit,” and what are the tangible outcomes that define improvement? In addition, if occupants complain about feeling slightly chilly, how do you justify telling them to put on a sweater?
Let’s look at four ways that decreasing the thermostat during the heating season can be beneficial.
First, lowering the thermostat will decrease the energy needed to heat a building when the outdoor temperature is cold. This is an obvious and direct outcome that will make the payer of the energy bill happy and decrease building carbon emissions if the fuel is petroleum based.
Second, lowering the temperature will automatically raise the indoor relative humidity (RH) toward the healthy zone of 40%-60%, which is beneficial in several ways. Moderate levels of water vapor decrease harmful drying of skin, airway mucus membranes, and insensible fluid losses. Furthermore, if RH 40%-60% is achieved, the respiratory immune system will be optimized.
The third benefit, and one which is less obvious, is that a lower temperature with the consequent increase in RH decreases the air concentration of many harmful gases emitted from indoor furnishings and surface materials.
Chemicals widely used in fabrics and surface building materials release semi-volatile organic compounds (SVOCs). SVOCs are released from solid materials into the air, onto airborne particles, and into dust on floors. These compounds move between environmental reservoirs, called partitioning, in response to thermodynamic forces largely driven by temperature and relative humidity.
An office study compared changes in airborne concentrations of six Semi-Volatile Organic Compounds (SVOCs) in response to lowering the indoor temperature versus increasing ventilation rates. Airborne concentrations of the SVOCs quickly decreased five-fold in response to lowering the indoor temperature. In contrast, increasing the ventilation rate by up to 500% for several hours at a constant temperature had no measurable influence on the SVOC concentrations. SVOCs redistribute from initial sources to air and surface materials that function as reservoirs to buffer the air concentrations of chemicals, reducing the short-term effectiveness of controls by ventilation or filtration, compared to long-term effectiveness. Partitioning of indoor chemicals to aerosols increases inhalation exposure, while partitioning to surfaces increases ingestion exposure through contact and ingestion. These compounds can be quite toxic to the occupant nervous and endocrine systems.
Fourth, and not a benefit to everyone, a lower temperature burns more calories. For people trying to lose weight, the most personal consequence of reducing the indoor temperature is an increased metabolic rate.
Adults exposed to cooler temperatures at night for one month decreased their stores of harmful white fat, the type of fat found in obese people and associated with type II diabetes and cardiovascular diseases. Conversely, the amounts of beneficial brown fat increased. Specifically, after a month of exposure to mild cold, the study participants had a 42% increase in brown fat, a 10% increase in fat metabolism, and improved insulin sensitivity following a meal. Not surprisingly, humans acclimate to cool temperatures by increasing brown fat, which leads to improvements in glucose metabolism.
In summary, turning the thermostat down by a few degrees can:
- Save building energy;
- Improve human immunity;
- Reduce harmful gases and particles in the airborne environment; and
- Help people on a weight-loss diet achieve their goals.
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