As part of the design process, we’ve also begun working with an energy consultant who will help us define the HVAC system for the new house.

The first step in defining the system is determining what the heating and cooling requirements will be. To determine this, a data model is created that takes into account the house dimensions, density, amount (and type) of windows and doors, R-values for walls, roof and foundation, plus a variety of other inputs.

The output is then used to determine the HVAC sizing, layout and design. This includes what types of mechanical systems we will use, plus how the ductwork will be run. Our original intention was to use a high-efficiency furnace and A/C unit, but our consultant presented a few additional options for us to consider. We discussed at length the merits of a geothermal setup, but the costs are quite significant. The government does offer up to $7,000 in rebates, but it’ll still be hard to stomach the difference. If we don’t go geothermal, he suggested a high efficiency furnace and a heat pump instead of a traditional A/C unit.

A heat pump is basically an air conditioner in that it will extract the heat from your home in the summer, but will also pull heat from outside air in the winter. In many climates, this setup is enough to cool and warm the house year round, but in Canada we would still require an additional furnace. The beauty of this dual-fuel setup is that the two systems share the heating load, each system operating when it is most cost effective. The heat pump does most of the work, but the furnace takes over when the temperature drops below the heat pump’s ability to operate efficiently.

Regardless, our consultant will be providing a detailed cost/benefit analysis of the various options so we can make an informed decision. He’s also made some recommendations regarding the building envelope.

From an insulation standpoint, he’s recommending we take a “20/40/60” approach. This means we’d have a R-20 foundation, R-40 walls and R-60 roof. This is well above code and while I completely agree with the approach, cost will be the deciding factor. At the moment, we’ve only budgeted for 12/20/30, and I fear the price will outweigh the diminishing returns. We’ll still get it priced as I’m curious what the delta will be.

Photo by Flickr user jtuason