SPG's Research Committee Presents: EndoTherm case study

EndoTherm is an additive for hydronic based heating systems. It improves the thermal properties of water, producing natural gas savings of up to 15%. In 2019, SPG recommended the installation of EndoTherm at three Multi-unit residential buildings (MURBs) in northern Alberta. This technical case study showcases that the annual energy savings realized after one heating season post the EndoTherm installation of the three buildings were of 6.98%, 10.25%, and 13.01% respectively. However, when only the heating annual baseload is considered the savings correspond to 12.14%, 16.59% and 19.88% respectively. Due to the variability in the savings, it is speculated that there are many external factors which can hide the savings realized by the heating additive such as building orientation, changes to building occupancy, adjustments to operational set points, and tenant behavior. These speculations are neither confirmed nor denied in the analysis and opens the door for further studies. Consequently, energy savings are guaranteed with EndoTherm, but the savings percentage in MURB type facilities are likely to vary widely depending on a variety of external factors.

Problem Statement

The addition of central heating additives into hydronic heating systems is an ever-increasing practice to improve the energy efficiency of the system to achieve natural gas savings and lower greenhouse gas (GHG) emissions. These types of additives produce savings of up to 15% in heating gas by reducing the surface tension of boiler water, which increases the effective surface area between the circulating water and the inner surface of the heating pipe which increases the rate of heat transfer. The result is a substantial reduction in energy required to achieve the same room temperature setpoint. The typical useful lifetime of central heating additives is eight (8) years from the installation date.

Figure 0‑1: Heating system without heating additive (left) and with heating additive (right)

This case study demonstrates the actual energy savings realized by EndoTherm, a central heating additive, that was installed in the hydronic heating systems of three MURBs in Slave Lake Alberta, Canada, and compares them to the maximum percentage reduction in natural gas consumption that can be achieved (i.e. 15%) with EndoTherm.


Global warming is an issue that needs to be addressed from every possible angle there is demand to find new ways to reduce carbon footprints. SPG aims to “simplify sustainability” for our clients by providing high impact Energy Conservation Measures (ECMs) that can be implemented to improve the efficiency of a facility while reducing GHG emissions and saving money on utilities. 

In November 2019, SPG conducted ASHRAE Level II Energy Audits on three multi-residential facilities in Slave Lake, Alberta, Canada, at which time,  Energy Auditors identified that the hydronic heating systems of these sites were not equipped with heat transfer enhancing additives. This finding was recognized, by SPG’s Energy Analysts, as an opportunity to improve the efficiency of the heating systems by adding EndoTherm into the hydronic heating systems to reduce the natural gas consumption and hence decrease GHG emissions.

To calculate the energy savings that were achieved, a statistical analysis of the Heating Degree Days (HDD) for the region and the historical total natural gas consumption prior to the installation of EndoTherm was completed for each site. A corresponding line of best fit was determined from the data and was used to estimate the monthly gas consumption of the following months if EndoTherm had not been installed. A net difference between the estimate in gas consumption if EndoTherm had not been installed along with the actual consumption values post-installation corresponds to the energy savings realized by the heating additive.

 For the purpose of this case study the multi-residential facilities have been kept confidential and are referred to as Buildings A, B, and C respectively. Buildings A and B are of squared shape, perpendicular to each other, have identical heating systems, and have the same building size. Building C is an L-shaped building and is located less than one kilometer away NE from buildings A and B. 

Figure 0‑2: Buildings A and B (left) and Building C (right) (Google Maps, 2020)


The gas consumption data post-installation of EndoTherm for each building was compared to the previous 18 months of utility data by analyzing gas consumption to HDD from the closest onsite weather station. Efficiency performance was determined following guidelines of the International Protocol for Measurement & Verification of Performance (IPMVP).

It is worth mentioning that two consumption data points were removed from the analysis for Buildings A and C as these were found to be outliers in the data. 

The post EndoTherm analysis of the three buildings indicates that the installation of the heating additive had a positive impact in the hydronic heating systems as energy savings were realized in all three facilities. Actual total natural gas savings yielded a fair degree of variability across the sites as they ranged from approximately 7% to 13%. From a financial point of view, these savings correspond to simple payback periods of approximately 2 years with return on investments (ROIs) between 253-322%.

When the estimated natural gas consumption by the domestic hot water (DHW) systems in the facilities is removed from the average annual gas consumption, it is possible to get a close approximation of the percent savings related to the heating baseload alone. This is possible to do as the DHW systems in all buildings are completely independent from the gas HVAC systems, and there are no other process loads that use natural gas at the sites.

Based on the estimated annual gas consumption heating baseload and the savings realized by EndoTherm, the percent savings on the HVAC equipment alone correspond to 16.59%, 19.88%, and 12.14% for Buildings A, B, and C, respectively.

The variation in savings between the identical Buildings A and B suggests that there are many factors at play that can affect the realized savings. Some of the obvious factors could include changes to the building occupancy, adjustments to operational setpoints of the heating boilers, and variations in thermostat setpoints across the tenant suites. Other not so obvious factors could consist of building orientation or wind exposure levels as either building may be shielding the other building from the wind, thus reducing its heat loss levels that consequently reduce its heat load requirements. This analysis does not explore if any of these factors contributed to the discrepancy in savings between Buildings A and B.

Another important factor to consider that can hide energy savings from EndoTherm in MURBS is tenant behavior. For example, if tenants leave windows open during the winter and the request for heat inside the tenant units is always on, this can cause the heating boiler to be running unnecessarily. 


The energy savings realized by the installation of EndoTherm in three MURBs in Slave Lake, AB were calculated using IPMVP protocols. The analysis showed that all sites benefitted from EndoTherm by reducing energy consumption. None of the sites achieved an annual reduction of 15% when compared to the total annual fuel consumption. However, when only the heating baseload is considered it is evident that savings can be beyond the marketed ‘up to 15%’ that is claimed by EndoTherm. Building B was the facility that had the greatest energy savings followed by Building A and then Building C. 

The savings varied significantly from sitetosite suggesting that there are many factors at play that can mask savings related to the installation of EndoTherm in MURB facilities. This study suggest that these factors can include changes to building occupancy, changes to the building’s operational parameters, building orientation, and tenant behavior. These factors are not further explored in this study to either confirm them or deny their effects.


EndoTherm. (2020) EndoTherm – Energy & Gas Saving Central Heating Additive. Retrieved October 2020 from https://www.EndoTherm.com/


Marcelo Martinez EIT, EMIT, MSc