Dan McDunn McDunn Construction thank you for your feedback on the guide. I wanted to follow up on your experience with heat pump water heaters. You mentioned you ended up removing some and I would like to learn more. Was this because of the noise, cooling effect, performance, or something else?
Thanks so much to the colleagues who joined me, Kaitlin Burton Beyond Efficiency
Thanks for the question. I will say that I have used them in single family, multi-family, and ADU projects. We used to use on demand gas water heaters, typically mounted on the exterior of buildings, low cost, space efficient, relatively quiet, quick.... During the last few years, as Berkeley was in its no gas phase, we switched to heat pump water heaters. None of my clients could afford the two part system with the condenser outside and the tank inside, so we were using the tanked heat pump with the condenser on top of the tank. Those take up a great deal of space, are noisy, and make cold air in the process of making hot water. Even those that we have created mechanical rooms with outside access have annoyed some of my clients to the point they run them in all electric resistance mode, or want them swapped, which we have done. If you don't want the ducts and the building penetrations, you need to have a place to dump cold air into the space, and if that happens to be a space accessible from the interior, you are dumping cold air into the interior of sometimes very small ADUs. We are doing one now that is so small we are using an on demand resistance water heater. It seems to me that a gas on demand would be better for the environment and for operational costs, but that was not an option. Is it now? Now that the City has been rebuffed by the District Court on appeal?
I will admit, part of this is new technology adoption and no experience in the marketplace for how to handle things. However, heat pump water heaters are not really ready for primetime in my opinion, and the alternative nat gas on demands solved so many issues. At $1200 a square foot to build super small ADUs, 10 square feet of space to accommodate a heat pump water heater gets very expensive and net net to the client it is only downside for the same result - hot water.
Dan, for the very small ADUs we sometimes recommend electrifying the main home water heater, and upsizing by one tank size (eg if 50 gallon HPWH would do for just main home, go up to a 65 gallon product) to also serve the ADU. This can work if the run is short enough and an on-demand recirc loop is added. Wondering if this scenario would be an option that could have worked in any of those problematic situations? That aside, would like to better understand which brands you've used and had the best and worst experiences with... if you go to the "expanded list view" of the HPWH product page here (https://buildinggeni.us/products/heat-pump-water-heaters-hpwh), info on space and clearances is included. We still need to add the extra small products that are only 20" diameter, although those also seem really tough to track down from suppliers...
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