‍

Most Canadian homes have hot water heaters but residents don’t pay much attention to them because they run quietly in the background. Still, as the home’s heating and cooling systems become more energy-efficient, the cost of hot water becomes more evident. Conventional hot water heaters have been getting more efficient, but there are now alternatives and add-on technologies on the market that builders and homeowners should learn about.

In this video, Building Knowledge Canada Vice President Andrew Oding visits a high-performance Net Zero Home and discusses some alternative ways to increase the efficiency of hot water systems. 

Andy: In a high-performance Net Zero Home like this, one aspect of the mechanical systems that often gets overlooked is the water heating. When you look at the entire load of a Net Zero Home, the energy that it takes to maintain hot water for the occupants is almost equal to the energy it takes to heat the home for the entire winter. So, hot water becomes a really big deal when we try to optimize the energy for these new homes. The natural gas hot water heating most frequently used in NZR Homes is tankless condensing. It's highly efficient, with a uniform energy factor of about 0.97 to 0.99. The nice thing about some of these tankless units is that they can provide gallons per minute in hot water flow, to keep up with the demand of large families while operating at nearly 100% efficiency. As we move beyond fossil fuel-based heating systems—for decarbonization, to integrate with solar panels or all-electric homes—you can move into electric hot water systems, such as electric tanks or air-source heat pump hot water tanks.  

Air-source heat pump hot water heaters (ASHWT) come in two distinct types. Type 1, are packaged ASHWTs, these units are highly insulated hot water tanks wherein the heat pump condenser sits atop the hot water tank. This system uses the energy in the room and the space to heat the hot water in the tank, efficiencies of 300+% are possible (COP 3.8+ for some units). Type 2, are split heating systems. In this scenario, the heat pump sits outside the residence, takes the energy from the outdoor air, and moves it into an indoor storage tank. More information is available on air source hot water heating in our Not All Heat Pumps Are Created Equal: Right-Sizing, Right Selection of ASHP (and Dual Fuel Systems) webinar slides and recap. 

The other part of hot water efficiency isn't just the efficiency of the heating system, it's also about the design of the plumbing system. There are three specific ways to increase the efficiency of hot water use in a home through distribution changes. Option 1 is to utilize drain water recovery. This technology takes the waste heat out of the main wastewater stack and puts it back into the water service line. Studies show anywhere from 20-40% increase in efficiency on hot water heating systems. Option 2 is to right size the hot water delivery pipe by optimizing or reducing the size of the hot water delivery pipe the amount of standing water in the pipe is reduced substantially. The result is less energy loss and better/quick hot water delivery to the sink or shower. Option 3 is the use of recirculation pumps on hot water lines. Hot water efficiency is increased by ensuring hot water is available at the tap or shower immediately. 

The right water heating system for your building depends on the residents’ water use, the available utilities, and of course your budget. Through our Builder 360° program, builders can learn which of these systems will work best in their designs and how they can best work together.

Connect with us anytime, and let us know what outstanding questions you might have on this subject.