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Hood fan & water heater

arnoldk | Posted in General Questions on

Hi,

I have a two part questions I am looking for general consent since I keep going back and forth on both matters, hood fan and water heater.
The house is going to be a two story Pretty Good House, 30’x40′ slab on grade with approximately 2000 sq. ft. of living space in Zone 6. Currently we’re leaning toward 2×6 with foam on the outside. We plan on going 100% electric (grid tied) and hoping to also install at least a 2kw solar array (net metering) and expend in the future.

Hood vent:
I initially thought we would build the house with a recirculating hood vent and have the HRV exhaust place several feet from the stove deal with the smells but mostly the steam.  Because my wife and I do a lot of cooking and baking and I’m starting to lean towards having a vented hood fan with a damp of some type to minimise air leakage.
What are people thought and personal experience?

Water Heater:
Originally we were going with a hydride heat pump water heater but with it’s high initial cost and the fact it take the warm air you just heated I am rethinking thing. Now I’m wondering if there’s a better long term payback going with a standard heating element water heater.
Any thought or personal experience people would like to share?

Thank you,
Arnold

Replies

  1. Expert Member
    Dana Dorsett | | #1

    >"Originally we were going with a hydride heat pump water heater but with it’s high initial cost and the fact it take the warm air you just heated I am rethinking thing. "

    So, what is your intended heating source? If heating the house with a cold climate mini-split the heat drawn from the air is still being leveraged by the COP efficiency of the space heating heat pump, which most of the time would be at least twice as efficient as an electric element in the water heater. Sized correctly the seasonal average performance of a cold climate mini-split would be at least 3x as efficient.

    If you're heating the place by burning stacks of $20 bills in a small woodstove the heat pump water heater would be more expensive to run than a plain old tank. :-)

    If you're heating the place with cheaper fuel in a wood stove it's almost always a net win with the heat pump water heater.

    If you're heating the place with electric baseboards the cost of the heat drawn from the room is pretty similar to that of a plain old electric tank, but only during the heating season.

    In the summer the heat pump water heater will provide a decent amount of dehumidification, perhaps more relevant in zone 6A than 6B.

    There is no such thing as "payback" on a plain-old electric water heater. Whether the present value of the cost difference is favorable for the heat pump water heater over it's lifecycle has a lot of variables. Do you shower daily, or only on Sundays? How many people? What are the local electric rates? Any state/local subsidies for heat pump water heaters?

    1. arnoldk | | #3

      Thanks for the response Dana.

      The plan is to heat the house with mini-split (likely one each for each floor) and the wood stove is going to be used as a secondary/backup source with 23 aces to supply the wood.
      There will be 2 adults and 2 kids (currently 3-5 years old) living in the house and showering on average is every other day.
      Current winter electric rate in Canadian dollar are as followed:
      Off-Peak: $0.065/kWh -- 7 pm to 7 am and weekdays/holidays
      Mid-Peak: $0.094/kWh -- 11 am to 5 pm
      On-Peak: $0.132/kWh -- 7 am to 11 am and 5 pm to 7 pm

      Just to make sure I understood you correctly, getting a Hybrid Electric Heat Pump Water Heater such as the GSW or Rheem is normally worth the initial investment in the long run compared to standard electric resistance water heater?

      Do you have any experience or thought on the hood fan/range hood?

      Thank you,
      Arnold

      1. Trevor_Lambert | | #5

        Given that you are in Canada, you're in the same situation I was in a year or two ago. I crunched all the numbers, and based on financial considerations alone you probably cannot justify the hybrid water heater. It's hard to find one to actually buy, so if you plan to DIY you get to contend with that as well. If you get a plumber to install it, you're looking at about $3500. Compare that to $500 for a straight electric. $3000 buys a lot of kWh (about 270,000). You have one extra body, so your numbers would come out a little better than mine. I think my simple payback came to around 12 years. Considering there's a good possibility the water heater wouldn't last that long, it didn't seem like a good risk. The way I tried to justify it was the free cooling it would deliver in the summer. But it's pretty minimal, and if you have a heat pump as your main heating/cooling then it's almost pointless. I ended up buying a used one for $500, but not surprisingly it only worked in electric mode.

  2. BrianPontolilo | | #2

    While I was at FHB, we published a few houses designed by Zero Energy Designs (https://zeroenergy.com/), a very smart firm focused on energy efficiency and home owner health. Until working with them, I had always been told by designers and builders that range hoods needed to be vented outside and that recirculating hoods were a waste of money. It turns out that ZED uses recirculating hoods in their work, which makes me more comfortable with the idea, particularly in an otherwise appropriately vented home. I know they used a recirculating hood from Best (http://www.bestrangehoods.com/home.aspx) in at least one of the homes we published: https://www.finehomebuilding.com/2016/07/06/better-than-average.

    Maybe these articles will be helpful with your water heater question:

    https://www.greenbuildingadvisor.com/article/domestic-hot-water-no-perfect-solution

    https://www.finehomebuilding.com/2013/05/16/the-water-heater-payoff

    1. arnoldk | | #4

      I read the GBA article already but thanks for those others link. The location of my property we have no natural gas so it's pretty much electric or propane. My wife wants an all electric house with net-metering.

      My concern with the hood fan is more regarding the additional moisture all the cooking/baking will add to the house which is why I have started to think about a vented hood fan. A recirculating hood fan doesn't address that issue but the HRV would over time.

      1. Trevor_Lambert | | #6

        My wife does a lot of baking and cooking. We're in a super tight (0.22ACH50) house, with a recirculating hood. So far this fall/winter, we haven't had any humidity problems. It's been between 35-50% all the time, usually between 40-45%. High humidity could be more of a problem in the summer. However, if you're cooling your house, you can probably manage that with the mini splits. Our strategy in the summer is going to be to do a lot of cooking/baking outside.

  3. STEPHEN SHEEHY | | #7

    Our house is pretty tight. We have a recirculating hood that we literally never use. We cook a lot, but rarely do anything that generates lots of smoke. If we seared a lot of steak indoors, we'd have opted for a vented hood. As it is, if we had it to do over, we'd skip the hood entirely. The HRV on boost mode does a decent job keeping the air clean.

    As for water heating, we rejected a hpwh due to noise, since the house is small and we don't have a basement. We just use a resistance wh. They are simple and cheap and with plenty of solar generation, a decent option. Your cheap electricity makes the numbers even more reasonable.

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