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Vent Bathroom onto Mechanical Room to feed HPHW?

emma_vt | Posted in General Questions on

We are currently building a new house and will have a HPWH in the basement mechanical room. The mechanical room shares a wall with the basement 3/4 bath. We’re putting a shower in there for the occasional house guest and dog bath, but it will be used very sparingly. Would it make sense to vent that bathroom into the mechanical room rather than up and outside – thinking that if someone was showering the HPHW would be calling for heat and could make use of the limited warm/moist air and save an exterior penetration.

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  1. charlie_sullivan | | #1

    That's a clever idea. I think it would work best if it used the HPWH fan with a duct to draw the air directly from the bathroom. In theory, the amount of sensible and latent heat it needs to draw from that air is more than the amount produced, because much more goes down the drain. So I wouldn't be worried about excess humidity not captured by it, but on the other hand, the efficiency boost you'd get might not be as much as you'd hope.

    Other issues: Would it meet code? Probably not but maybe you aren't constrained by that in VT? Would it be harmful to performance when the showers are taking place elsewhere? Maybe not, the duct would probably mean you are circulating air around more of the basement.

    I'd suggest you try it and monitor humidity to make sure it works OK.

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