How can I vent a heat pump water heater?
Hey all,
I’ve currently got a 7 year old natural gas water heater and I’m just planning for the future of replacing it.
I am on climate zone 5b Nebraska. Home built in 1918. Water heater is in a ~7 ft tall 800 sq ft basement with r10-20 walls and rim joists all air sealed. No slab insulation. Has a small 120 sq ft crawlspace below one room that is about 3 ft tall same wall and rim joists insulation. 15 mil vapor barrier on the dirt floor to the walls.
Minimal direct conditioning but hvac is down there as well. Basement has a bathroom minimally used, has laundry, workout and shop space. No “living” space.
my thoughts on ducting for the HPWH – I don’t have easy access getting to the unconditioned attic. But if I could duct it to take intake air from outside when it’s hot outside and then otherwise just from the basement during cold season. Exhaust I could go to the basement or 1st floor easily. If going to 1st floor, should I patch it into a supply duct for the first floor? Could I go to a return duct that spans a 1st floor joist in the basement? I didn’t know if ducting the HPWH exhaust to a return for the HVAC would cause issues. Or exhaust to the outside during the cold season too.
But I don’t know if I should worry about makeup air or not. It’s a 1918 house that all of the exterior walls on 1st and 2nd floor have a 1” straw type mat and that’s it. Attic has moderately well air sealed (best I could do without tearing up the whole attic) r60 blown in cellulose that I did last winter.
I know I could just do no ducting for intake or exhaust for the HPWH but being able to take heat from outside for intake during the hot season and ability to exhaust the cooler air to main living space during hot season or exhaust to the outside during the cold season could be nice for more efficiency/comfort.
Replies
Double check the HPWH specs before getting too carried away with plans for ducting.
If you just install , it will help dehumidify the space (and likely increase life of your other utility equipment.
I’ll definitely check the specs and make sure it can be ducted in those ways, just trying to see what my best options may be. I don’t have any glaring humidity issues in the basement prior to insulating and air sealing but I’m sure it’ll actually prob be a bit dryer after doing that at least during the cooling season since we tend to be fairly humid.
"Venting a heat pump water heater depends on whether you need to manage the cooled exhaust air. Here are some common approaches:
Unvented (Standard Setup) – Most heat pump water heaters operate efficiently in a well-ventilated indoor space without additional venting.
Ducted Exhaust – If you want to direct the cooled air outside or to another room, you can install an exhaust duct.
Ducted Intake & Exhaust – For confined spaces, you can fully duct both intake and exhaust to control airflow and prevent cooling of the surrounding area.
Consider Room Size & Climate – Ensure the space has enough air volume (typically at least 700-1,000 cubic feet) for efficient operation.
I’m aware of standard recommendations/options that they simply can be ducted for intake, exhaust, or both. I was checking specifically on people’s opinions on my above listed options. Seems very AI generated which isn’t particularly helpful.