Mechanical Design

image cred @sarahlazarovic

We have been thinking about heating, cooling, set points and fans while on vacation in 90 degree temps + humidity 🥵

With an insulated and airtight home, we’ll use less energy to heat and cool our space. We’ll also have less fresh air seeping into the house (through gaps and cracks) – so will need to add mechanical ventilation, beyond standard kitchen/bathroom fans.

The plan is to install an air source heat pump paired with a heat recovery ventilator (HRV). Heat pumps regulate indoor temperature, while HRVs circulate fresh air ensuring that no heat is wasted in the process.

Our heat pump will replace our natural gas furnace, provide heating and cooling, and run on clean electricity :) Heat pumps use the same technology as fridges and AC units, except that they work both ways, pulling heat from outdoor air to indoors on cold days and vice versa on hot days. Heat pumps are incredibly efficient, producing >3 units of heating/cooling energy for every unit of electricity consumed (coefficiency of performance-COP 300% versus 90-95% for a standard condensing boiler!)

HRVs are ventilation systems that help optimize the efficiency of heat pumps. They exhaust stale indoor air and moisture, capturing outgoing heat in the process (~70-95% recovered) and using it to pre-heat incoming fresh air so the heat pump has less work to do.

We’ve been wondering whether to size our heat pump system for heating or cooling needs. The answer is, it’s a balance. It depends on how much solar heat is entering our house in the first place (See 6/19 post on windows), and whether we’re designing for average BC temps or extremes. Also thinking about what setpoints to use for heating and cooling? And how to best zone?

More to come on this topic as we refine the design. In the meantime, a plug: if you haven’t discovered @sarahlazarovic’s incredible climate drawings + minimum viable planet newsletter head to her site immediately to be inspired about heat pumps, electrification and fitting climate action into everyday life!

#netzero #netzerohome #renovation #greenbuilding #sustainability #heatpumps