HVAC design

My house design calls for a ductless heat pump that will provide the main cooling and heating with a backup heating via standard forced air furnace. The reason for the need for a backup heating source is that most air-to-air heat pump will stop working by -15°C. Now in Toronto, there are not many days (nor that many hours during the day) in the winter where temperature will fall below -15°C. However, a backup heating source is still necessary to ensure that we are not in the cold when the heat pump had to be turned off. I’ve also called for separate ducts for a Heat Recover Ventilation because that’s the right way to bring fresh air into a relative air tight house.

For the HVAC design we have contracted Haibo Chen from Fulford Supply. Mr Chen told me that in Toronto the design temperature is -20°C. Because the air-to-air heat pump will no longer be working at -15°C, so even though I consider the furnace as the back source, during the design stage for building permit, it is probably better to just have the furnace as the main source of heat. Then once I have all the heat loss information, I can simply choose the heat pump to match the heat loss numbers. The total charge is $750 for the furnace duct design and heat loss calculation, and $200 for HRV calculation and design. Mr Chen is very prompt with the work. We started the work on April 11 and he provided his preliminary drawings on April 19, one week after the work started.

Here’s the furnace duct design.

Basement:

First floor:

First floor:

Second floor:

Third floor:

And here is the HRV duct design.

Basement:

First floor:

Second floor

My house, being designed without a lot of interior walls, will definitely have some difficulty in getting all that ducts in. I will have to review it with my architect to make sure all the ducts can fit in the joist space. But thank you Mr Chen for promptly turning out the HVAC design. It really wasn’t a very productive week for me having waited over a week for contracts from K. H. Davis Consulting for the structural engineering work. At least we’ve got some work completed.