We had a kick-off
meeting with our MEP consultant Benjamin Klein and I will try to summarize (before I forget everything which was discussed!):
- Heating / Cooling: Each apartment has its own ducted air handler (12,000BTU Mitsubishi), but we might have a combined 6 ton condensing unit on the roof. Here the link.
- Each apartment can have its own temperature setting, but we’ll have one shared bill which we’ll have to subdivide by apartment size (judged by square footage). The main reason for this solution is that one big condenser is a great deal more efficient at low temperatures, which translates into an even lower heating bill. It’s also simpler to maintain one unit vs 7 or 8 units. We would probably be fine with less than 12k BTU, but that’s as small as they get. Additionally, the pump runs with variable speeds so it is able to scale down it’s heating/cooling output without losing efficiency.
- Fresh air:Each apartment will get its own Energy Recovery Ventilator (Zehnder ComfoAir200), which will be independent from the ducted air handler to keep things simple and to avoid negative interaction between the individual fans. One simple solution for avoiding double ducts would be to have the air handler supply in the living area and the ERV supply in the bedroom. ERV return in the bathroom, and AH return just outside the bathroom. The supply air out of the ERV is a couple of degrees colder than the design temperature, but this might even be welcome because it’s a bedroom. Both units are hidden in the ceiling above the bathroom but accessible.
- Fresh air UPDATE: We will have two ComfoAirs550 in the unconditioned basement supplying the apartments with fresh air. There are some advantages to this simpler approach: it’s less expensive, the filters are accessible from a common area and can be serviced by 1 person, there is less room for human error due to the wrong settings of the HRV (download the user manual here to see that they are quite complex to operate) and we have almost no duct losses.
If you like to see more about our Haus here is the link…