Early Results Show SuperGreen Duplex Even More Efficient Than Expected

The owners of the SuperGreen duplex have been kind enough to share with us their energy bills from first five months of occupancy of the home.  These early results show that the building is preforming more efficiently than expected, with over 20% less energy used than the energy model predicted.    The graph below shows predicted energy usage (shown as bars) versus the actual total energy usage in the duplex (shown as a green line) for the months of February through June, 2011.  The red line show is the energy usage of a similarly sized conventional new home in Whitehorse.

Month (2011)	Predicted Energy Usage		Actual Energy Usage
	kWh	$	kWh	$
February	1,698	$  201.71	1,699	$  206.51
March	1,516	$  177.92	1,309	$  143.47
April	1,186	$  134.77	909	$  104.32
May	1,119	$  125.99	686	$    82.48
June	1,070	$  119.66	551	$    71.62
Total	6,588	$  760.05	5,154	$  608.40

Actual Energy Usage Versus Modelled:
A widely used residential energy modelling software called HOT2000 was used at the time of design and construction to predict the building’s energy usage.  HOT2000 is NRCan’s software for determining a building’s EnerGuide rating.  It has been validated through years of use on hundreds of thousands (if not millions?) of homes across Canada.

A key observation here is actual energy usage is very close or better than predicted.  There have been critics who have suggested that the predicted energy usage will not be achieved.  As can be clearly seen here, the energy efficiency has been achieved, and surpassed!  The criticism of energy modelling of residential buildings is simply unfounded, and may stem from the problems commercial/institutional buildings are having with energy performance.  A good summary of the problems large, new buildings are having with energy efficiency is summarized Joseph Lstiburek’s article “BSI-007: Prioritizing Green—It's the Energy Stupid*”.  However, residential buildings are a different kettle of fish: they are much simpler and energy modelling and analysis is well established and results are predictable.

This model has some “default” assumption regarding energy usage in the home for lighting, appliances and other plug loads.  My experience, and as shown here at the SuperGreen duplex, is that these default “baseloads” are much higher than what a typical energy-conscious person uses.  As we can see in the month of June, where there is almost no heating required, baseloads in the SuperGreen duplex is almost half of that predicted.  Way to go guys on being energy-conscious homeowners!

I’ve also had the privilege of seeing over two years of actual energy monitoring data from Yukon Housing’s first two SuperGreen homes, located in Watson Lake.  These two homes show similar performance, with their actual energy usage being within 20% of the predicted energy consumption.

SuperGreen Energy Usage Versus a Conventional Home
For comparison purpose (and to help illustrated the predicted versus actual energy performance of the building) the energy usage of a similarly sized, new home in Whitehorse is shown on the graph as the red line.  This represents an electrically heated new home built in compliance with the City of Whitehorse’s energy efficiency bylaw.  By way of comparison, over these 5 months, total energy costs for the conventional home would have been $1570.  The actual energy costs over the same period for the SuperGreen duplex have only been $608.  That is less than half the energy cost – a savings of $965 in just five months!  Over a year, that might amount to savings almost equivelent to two whole mortgage payments.