To enable our society’s transition to a low-carbon economy, we need to change the way we design our buildings and our communities. The proposed changes to the Ontario Building Code outlined by the Ministry of Municipal Affairs are a good first step. They address the efficiency of buildings and through recommissioning requirements being considered, aim to improve the long-term performance of buildings; however, more is needed to achieve Ontario’s climate change action goals. In Ontario, heating systems are the primary source of greenhouse gas (GHG) emissions from buildings. To achieve Ontario’s GHG targets for 2030 and 2050, we need to act now to accelerate the use of low-carbon heating sources.
We recommend the following additional changes to the building code to remove barriers to, increase adoption of, and future-proof buildings for low-carbon heating sources:
1.Encourage low-temperature heating in building design
2.Require in-suite heat pumps to be compatible with low-carbon heat sources
3.Treat district energy on the same terms as in-house plants to allow for low-carbon heating to be developed at economies of scale
Today, the air in most large buildings is heated by hot water circulated throughout the building, and that hot water is produced by a boiler fueled by natural gas. Typically, these buildings are designed to use hot water at temperatures between 160°F to 180°F, but lower temperatures can be sufficient to maintain the space at a comfortable room temperature of 68°F to 72°F. Lowering hot water design temperatures for space heating will both improve the efficiency of buildings that choose to use conventional boilers and will future-proof buildings by enabling them use low-carbon heat sources.
At temperatures of 160°F to 180°F, even a condensing boiler rated at 90% efficiency will operate with an efficiency closer to 80%, because it is not able to condense properly. In addition, requiring water to be heated to temperatures of 160°F to 180°F prevents the use of low-carbon heat sources such as geothermal energy and waste heat recovered from sewers, data centres, refrigeration plants, and other such sources. Heat pumps are used to extract the heat from these low-carbon sources and boost it to the desired temperature. Heat pumps operate much more efficiently at low temperatures and many types of heat pumps produce hot water at a maximum temperature 120°F. Decreasing hot water design temperatures for space heating to 120°F will open the door to a broader range of heat pump technologies and improve the business case for using low-carbon heat sources. Under the existing building code, when buildings are modeled to ensure they comply with energy efficiency requirements set out in SB-10, the reference building against which they are compared is modeled with a hot water supply temperature from the boiler plant of 180°F. We recommend that the reference building be modeled with a hot water supply temperature of 120°F to promote lower temperature heating in building design, future-proof buildings, and accelerate the adoption of low-carbon energy systems.
In-Suite Heat Pumps:
In recent years, we have seen a trend toward large, multi-unit residential buildings being designed with in-suite heat pumps that extract heat from a hot water loop supplied by a boiler fueled by natural gas. The in-suite heat pumps typically selected for these buildings are only able to operate with a water loop temperature that ranges from 60⁰F to 90⁰F. Limiting the operating range to these temperatures means that the building cannot be directly connected to low-carbon heat sources such as geothermal energy and renewable heat recovered from low-temperature sources.
It is critical to select heat pumps that facilitate technical and economic integration of low-carbon energy sources. This can be achieved by selecting heat pumps that can operate within a larger temperature range. We recommend requiring that water-loop heat pumps for large, multi-residential buildings be specified with extended range operation, allowing them to work with a water loop ranging from 40⁰F to 100⁰F. In addition to encouraging adoption of low-carbon heat sources now, this change will allow buildings to be more easily retrofit in the future to connect to low-carbon sources as our economy shifts further in that direction.
District energy has the potential to drive transformative step changes in GHG emissions from the building sector. Embracing district energy in our communities has the power to
•Reduce energy consumption through energy sharing;
•Improve the feasibility of developing low-carbon, carbon neutral, and net positive communities by leveraging economies of scale;
•Convert waste heat into a resource; and
•Enhance energy resiliency to help our communities adapt to climate change impacts.
District energy should be considered on the same terms as in-house plants to allow for a fair comparison of environmental benefits. Based on energy modeling practices used under the existing building code, if a building is planning to connect to district energy, the district energy system efficiency is not considered in determining if the building is compliant with energy efficiency standards in the building code. Both the reference building and the proposed building are assumed to have the same efficiency during the modeling process. This means that if a proposed building plans to connect to a district geothermal system with a heating efficiency of 400%, the proposed design will be modeled as no more efficient than the reference building. If, however, the same building plans to install a condensing boiler within the building that is rated at 95% efficiency, it will be modeled as about 13% more efficient in heating than the reference building. Particularly considering the potential district energy has to facilitate our society’s transition to a low-carbon economy, at minimum, buildings should not be discouraged from connecting to a low-carbon district energy system.
[Original Comment ID: 211008]
Submitted February 12, 2018 3:43 PM