gas water heater in sealed attic

A new house inspected today had a gas tankless water heater in a sealed attic. Is there a proper way to do this without bringing in combustion air that would defeat the purpose of a sealed attic? I apologize if this question has already been addressed. I couldn’t find it in the forums. Thanks.

Age of Home…
Location (state , province , etc…)
A sealed attic would be wrong by many standards let alone having a water heater…

The home is in Texas. Sealed attics are common on new homes but this is the first one with a gas appliance in the attic.

Most are going to be direct vented (i.e., the vent will be concentric with the exhaust inside and intake duct wrapped around it). What is the vent setup of the unit that you are looking at? Brand/model info? These units will also require a condensate drain, assuming it is a condensing type water heater. They are frequently misconfigured, especially the ones with a neutralizer cannister.

Please post any pics that you have of the unit and vent assembly.

Thanks, I do believe that’s what it is.

All of the PVC vented units and all of the metal (stainless) direct vent kits that I am familiar with are zero clearance. They can spray foam right up to the vent where it penetrates the roof. When in doubt, download and reference the manufacturer’s installation manual (always capture the info necessary for you to be able to do that).

Just make sure you know what you are looking at. I’ve seen botched conversions where they tried that with 80 series furnaces.

What do you consider a sealed attic?
Was it gas or electric?
Any images?

If the attic is indeed completely sealed (as in full encapsulation), then I would think a gas water heater will need to have combustion air brought in from outside just as a gas furnace would. I would also think this would have a minimal effect on the efficiency of the system as a whole. It’s just not that much air.