Increasing your post-retrofit savings in one easy step

by ‐ Tags: case study, measurement and verification

Measurement and verification is the practice of quantifying utility savings after a water or energy conservation measure has been installed. This process is important for a few reasons:

  1. It helps build the case for and against certain types of retrofits;
  2. It allows corrections to be made when a project isn't performing as expected;
  3. It provides a way to address variations in weather and make sure savings are true and not due to milder weather conditions.

In this post I'll address the second value: using this process to find and correct performance issues.

Retrofits that do not perform as expected happen more often than we would like. Why? Poor design, mistakes by installation teams, faulty equipment, lack of control calibration, miscommunication, shoddy work and poorly drafted specs and contracts are some of the problems that our partner New Ecology, Inc. has seen. Just one of these issues can result in unrealized savings. An easy and efficient way to identify these errors is to monitor post-retrofit usage and compare it to previous usage and expected savings.

Let's look at an example from our database:

The building in question is a 17-unit mid-rise located in Boston. It was constructed in 1980 and has a single gas boiler with an attached indirect tank for hot water. In November 2012, the owner did a boiler replacement, switching from an older atmospheric boiler and indirect storage tank for hot water to a new modulating condensing boiler with new indirect storage tank. They expected to see a 26% reduction in gas usage from this work. New Ecology monitored the building's gas use over the first winter and was surprised to see that usage was similar to the pre-retrofit usage and very, very far off from the expect savings: once the usage was controlled for weather, actual savings were just 11%.

Post-retrofit savings

In the spring the team returned to the building with a representative from the boiler manufacturer and the installing contractor. New Ecology's Adam Meier explains, "The boiler settings were adjusted based on findings from the visit. Specifically, the team limited the boiler's modulation to ensure longer runtimes, lowered the boiler's domestic hot water target temperature and optimized the boiler for domestic hot water. They also lowered water temperatures in the heating loop, ensuring that the water was not hotter than needed and that the boiler was more likely to be in condensing mode." These are all too common issues with combined heat and hot water systems. Then they watched the data.

 

Post-Retrofit SavingsSince this follow-up work, the retrofit's performance has greatly improved. The summer usage (the base load which goes to hot water) is 20% less than it was last summer, and the heating usage in September and October has been 37% and 42% lower than last year, respectively. I'm curious to see how savings continue to play out over this winter.

Situations like this one are common, and largely unavoidable. Therefore, it's essential to monitor your usage – through bills or an energy management tool – so that you can respond when things aren't going as planned. If your project is functioning like it's supposed to, you can use your savings data to impress your colleagues.