What does it mean to be NET ZERO?


Time for an update on our Net Zero Ready, Devon Road project another Oakville luxury home in progress. and an opportunity to talk about Net Zero building. As we have commented before Net Zero not only provides a responsible approach to saving energy and being environmentally conscious it’s simply a great way to build. It really breaks down to 1) insulate well 2)  Efficient windows  3) Seal up the shell 4) super efficient HVAC 5) Solar panels ( to remove the “ready” label)

Net Zero, under the Canadian Home Builders Association’s program is a guarantee of optimum energy efficiency. Each home has to be third party verified to be 1/3 better than code in its energy consumption and must be capable of generating as much energy as it consumes measured over a year. What about the questions of Net Zero emissions? and is Net Zero emissions possible? Well the short answer is…. yes! Homes are now being built, here in Ontario, that are actually carbon neutral! So over the life span of their use ( say 50 or 100 years) they are built to absorb more carbon than they produce. But that’s beyond our IN Progress discussion right now, so lets move on to today’s discussion. you can read more about CHBA Net Zero program at NET ZERO HOME

Probably the first answer to What does it mean to be NET ZERO? is arguably first priority.

In the list above, for 1  “insulate well” we chose Zip Panels for the exterior sheathing. Zip panels are a  sandwich panel of insulation and plywood, providing structural rigidity and a continuous layer of insulation outside the wall studs. This reduces thermal bridging ( heat loss through the wood studs) and increases the effective R value of the wall assembly. Zip Panels come with tape which is used on the panel joints to form a continuous air barrier. Zip panels are available up to 2-1/2″ thick, providing over R12. Using the 1-1/2′ gave us a full R6.6 outside the wall studs!

Exterior insulated sheathing is a key compnent of what it means to be Net Zero

For number 2 above ” Efficient windows” we look at the numbers on the window label. First off the U or R value. The building Code allows a maximum of 1.6. Most double glazed windows can get, at best, just above 1. Our window is 1.42, this number goes into the calculation of heat loss and heat gain. Windows can be the “weakest link” in a building envelope so deserve particular attention. If the budget allows, triple glazed windows are an attractive option with U values usually closer to 1 and sometimes below depending on the characteristics of the individual window. The solar heat gain coefficient ( 0.27)  is an indicator of how much heat will pass thru the window (27%) , causing overheating in the summer. Our goal is somewhere between 0.2 and 0.3. The final number on the list is “condensation resistance”. This  gives an indication of when the window will begin to condense or “sweat”. A number of 48  indicates that, at design winter conditions  in Toronto, the window will sweat at an indoor relative humidity around   25%. The higher this number is the better for indoor air quality ( IAQ). Beyond our discussion today is the health benefits of maintaining between 35-60% relative humidity through the dry months. This is only feasible wicheck Window labelling for a Net Zero home is crucialth good windows and a tight building envelope.

As drywall is now complete and the cold months are upon us we keep careful track of the indoor humidity, maintaining it as high as possible to keep all the woodwork, millwork and wood floors happy. Allow the humidity to go too low and cracking will result from winter dry air sucking all the moisture from the woodwork and shrinking it. We look forward to showing you the interior woodwork progressing in full swing in the next In Progress but for now here’s a teaser of the crown mould in the great room. Amazing how a Net Zero home doesn’t have to compromise style and aesthetic to be energy efficient!