HOW TO SET YOUR INDOOR TEMPERATURE TO SAVE COSTS
By Anber Rana and Piyaruwan Perera
PhD Students at UBC Okanagan
A recent report on changing climate states that temperatures in Canada are rising at twice the rate of the rest of the world (CCCR 2019). As a result, cooling loads and the associated energy use and costs will increase dramatically. The Wilden Living Lab research team measured the effects of changing the indoor temperature set points. Read about the energy and cost savings in both homes, the Home of Today – built to current BC building code – and the Home of Tomorrow.
Thermostats in residential buildings are important due to their ability to provide occupants a means to control their indoor thermal environment. Research indicates that North American residential buildings are typically designed for a temperature range of 21.5 – 24°C. The heating, ventilation and air conditioning (HVAC) system of a typical building offer one of the key contributions for household energy use. The thermostat can be used to change the operating configurations of the HVAC systems to achieve greater energy savings.
Measured Temperatures for Home of Today and Home of Tomorrow over the year
Temperature data for the Wilden Living Lab homes was collected through temperature sensors and real-time data logging systems. Figure 2 shows variation in the indoor temperatures for the Home of Today and the Home of Tomorrow over the past one year period.
Figure 2 Indoor temperatures for the Wilden Living Lab Homes for year 2018
During most of the year the Home of Tomorrow shows lower indoor temperatures, except in July and August when the Home of Today shows lower temperatures. The average temperature set-points for the two homes main floors and basements are shown in Figure 3.
Energy Simulations using Wilden Living Lab Temperature data
Two energy simulation models have been developed for Home of Today and Home of Tomorrow using HOT2000 (A free energy modelling software developed for low-rise residential buildings which was developed by Natural Resources Canada). The average temperatures shown in Figure 3 were used to calibrate developed energy models. Moreover, behavioural data collected from a questionnaire, such as hot water usage, thermal heat gain from the occupants and closing of blinds were also incorporated.
In order to assess the impact of temperature set-points on energy consumption and cost, the energy models were simulated with identical temperature set-points. The temperature set-points used and the corresponding energy consumptions are shown in Figure 4.
Based on the analysis, decreasing winter (heating) temperature set-points from 21.0 to 17.50C will result in up to 14% savings in Home of Today and up to 10.2% savings in Home of Tomorrow. However, cooling (air-conditioning) temperature set-point changes from 220C to 280C during the summer season results in a savings of less than 5%. Accordingly, the savings are more significant for both homes for the winter season as compared to the summer season. Table 1 shows a comparison of different temperature set-points on annual energy use and costs.
According to Table 1, if set-point temperatures for the homes are changed the energy consumption and energy cost change significantly in the Home of Tomorrow due to the use of expensive electricity for space heating and cooling. Moreover, the energy consumption and the environmental emissions for the Home of Today are significantly reduced with the changes in temperature set-points due to the use of high-emission natural gas for space heating. The Home of Today realizes a greater long-term environmental impact and energy use reduction based on temperature set-point adjustments compared to the Home of Tomorrow. The economic impacts of different temperature set-points for both homes are shown in Figure 5.
The temperature changes can help in reducing the energy of the dwellings, however, that needs to be balanced with the occupant’s thermal comfort.
Stay posted for more real-life data results in the future. In next month’s issue, we’ll talk about the cost-effectiveness of a geothermal heat source pump!
- Canada’s Changing Climate Report (CCCR).,https://changingclimate.ca/CCCR2019/chapter/headline-statements/. (2019)
- Hoyt, T., Lee, K.H., Zhang, H., Arens, E. and Webster, T. “Energy savings from extended air temperature setpoints and reductions in room air mixing”.(2005)
- Li, Danny HW, Liu Yang, and Joseph C. Lam. “Impact of climate change on energy use in the built environment in different climate zones–a review.” Energy 42, no. 1 (2012): 103-112.
- Moon, Jin Woo, and Seung-Hoon Han. “Thermostat strategies impact on energy consumption in residential buildings.” Energy and Buildings 43, no. 2-3 (2011): 338-346.
- Traylor, Caleb, Weihuan Zhao, and Yong X. Tao. “Utilizing modulating-temperature setpoints to save energy and maintain alliesthesia-based comfort.” Building Research & Information 47, no. 2 (2019): 190-201.
- Yang, Zheng. “How does building occupancy influence energy efficiency of HVAC Systems.” PowerPoint presentation. (2016)