HIGH EFFICIENCY HOMES AND WATER HEATING
Sept 18, 2019
By: Daniel Beauchemin
Did you know that for every $100 spent on energy, nearly $20 will go to heating water? Now imagine building a high-efficiency home only to find out that out of $100 of energy costs, the cost for heating water is now $50? What went wrong?
Drain water heat recovery (DWHR) should be strongly considered to address the cost of heating water in high efficiency homes
Sadly and ironically, that $50 of hot water in a new high-efficiency home drains out and with it, the heat energy. So who in their right minds would design a high efficiency home and leave a giant hole in the wall to allow air to flow freely in and out of the home? The open hole in the wall analogy is the simplest way to describe the current high-efficiency home design when it comes to hot water and water heating efficiency.
Table credit: extracted from the Net Zero Energy and Net Zero Energy Ready Housing. Lessons learned and key findings from the ecoEII Net-Zero Demonstration and the R-2000 Net-Zero Energy Pilot. Natural Resources Canada.
Download complete report here
Some ingenious individuals have come across a solution to patch this “open hole in the wall” problem and recover this wasted heat instead of trying to address it with expensive and high maintenance/complicated water heating systems. The solution is quite simple, use a heat exchanger (drain water heat recovery DWHR) to capture that wasted heat and use it to preheat the incoming cold water. The technology is relatively affordable and straightforward. Best of all, it requires no maintenance and has a 50+ year life expectancy. It is also 100% recyclable because it is 100% copper. The longer, more efficient drain water heat recovery units will capture 59% of the wasted energy. That means incoming cold water at 50 °F (10 °C) is preheated using the waste energy from outgoing hot water from a shower to 80 °F (27 °C).
The cost with installation of a high-efficiency ThermoDrain unit is under $1000. ThermoDrain requires no maintenance and will outlast everything found in your mechanical room. Compared this cost to an Energy Star HRV, a high-efficiency furnace or any other high maintenance required items in the home – ThermoDrain is a no brainer as one high-efficiency home builder put it.