Plumbing Engineer February 2020/61
earlier 13-duplex building complex has been fully occupied since it opened. The solar thermal systems have operated very effectively and the 3/8" home run tubing has proved itself as a viable last mile for fast hot water delivery with low heat losses. Solara has been marketed as "Ecoluxury Living" with all utilities included in the monthly rental price. Four of the 24 apartments have two bedrooms and the upper two floors are served by an elevator. Heating and cooling for each apart- ment are provided by cold-climate air-to-air heat pumps. Energy Recovery Ventilation (ERV) air exchangers provide the ventilation. Energy Star appliances include heat pump clothes dryers. The overall building achieved less than 0.5 air changes per hour at negative 50 pascals. The Energy Use Index (EUI) is below 40 kBTU/ft2/yr! I think that it is safe to say that Solara defines the state of the art for high perfor- mance buildings. The very efficient hot water distribution and production system is one reason that the EUI values are so low. In order to estimate DHW demands for the production and distribution system design, I monitored the DHW use at netZero Village and other recently renovated multifamily buildings in upstate New York. Clearly, high-efficiency fix- tures and appliances have lowered per capita water use, often below 20 gallons per capita per day (gpcd). That demand depends, however, on the demographics, including age, num- showers. Quelle horreur! The showerhead spray was just too weak to satisfy renters. I checked the pressure at the showerhead spigot and found very low pressure - no wonder the spray was so flaccid. I reconfirmed my pres- sure drop bench testing numbers for the twigs - all was OK. Reluctantly, I had to conclude that the shower valve/ cartridge combo had stolen too much pressure. And, we couldn't test them in-situ - they were now buried in the walls. Some valve combos reputedly don't rob pressure, but not this model! We fixed the problem in the first four buildings without changing out the shower valve combos. But, not without a lot of consternation. Stay tuned for the next article in our series for the rest of the story. Almost a year, including half of the winter, have passed since Solara opened. The overall DHW system has worked very well - no complaints about the modified showers. The solar thermal systems provided the bulk of heat needed from late spring until early fall. After that, the electric elements and air-to-water (A-W) heat pumps have taken over progressively more of the thermal backup loads during periods of extended grey weather. Welcome to the real Solara The developer designed Solara as a logical extension of his earlier very successful netZero Village complex. That
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