Sizing Heat Pumps

We’ve been working with our project team to narrow down our HVAC strategy for the house. With upped insulation in the walls, high performance windows and air tightness (targeting 1.5 ACH), we should need significantly less energy (>70% less) to keep our house warm vs standard new builds. We are planning to install an electric heat pump + heat recovery ventilator.

Image credit @sarahlazarovic

How to get the sizing right on that combined system? We want to have enough heating / cooling power for North Vancouver’s current and future climate, but not oversize too much. Costs, duct sizing and system longevity (impacted by rapid on/off cycling occurs) all factor in.

In our climate, heat pumps are generally sized for winter needs versus summer. Our energy model finds that we will need a minimum of 5400 Watts of heating at -6.3°C (cold peak) and 3200 Watts cooling at 29.5°C (hot peak). As such, it recommends a minimum 2-Ton heat pump, able to provide 20,500 Btu heating output. This is based on standard Hot2000* assumptions for single family homes – 2 adults and 1 child living in the house 50% of the time.

It’s also based on typical (historical) meteorological data for the region, rather than extreme conditions or events i.e. our model assumes a July max temperature of 29.5°C, whereas during BC’s 2021 heat dome, we experienced closer to ~40°C.

Given this and other modeling uncertainties vs reality, it seems wise to bake in some extra capacity (x1.5) into our system. We’ve decided to go with a 3-Ton heat pump that can provide 36,000 BTU, with a variable speed drive to regulate output smoothly depending on need (versus on/off cycling).

Coming up - equipment selection and the complexities of make-up air!

#netzero #netzerohome #heatpump #hvac #electrification #energymodelling #HOT2000 #greenbuilding #sustainability

• HOT2000 is an energy simulation modeling software developed and maintained by Natural Resources Canada to support the EnerGuide Rating System.