HRV and bathroom fan
Paulmcgee
| Posted in General Questions on
HRV and bathroom fan?
Our property will not have AC, in the summer it does not make sense to use the HRV and bring warm moist air in (only on summer bypass at night) especially when using a boost switch in the bathrooms. Therefor would it be best to also have bathroom fans?
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Replies
So where are you getting fresh air from during the hot/moist summer days? The ventilation requirements don't go away. If you're thinking the bathroom fans are going to pull in air through leaks in the house, then that air will be just as humid as the air the HRV would bring in. It sounds like an ERV might be a better bet than an HRV.
I favor the KISS principle most of the time, which in this case means get two simpler systems that perform different jobs, rather than a more complicated system that tries to do everything. Get purpose built bathroom fans for the bathrooms. And then decide what is required for fresh air ventilation for the whole house. As Trevor says, the requirements for ventilation don't go away seasonally.
An ERV with a boost option would be the better choice. As Trevor wrote, your exhaust fan will depressurize the house and therefore would pull unconditioned air in through leaks. It's better to let the ERV do the job.
If the plan is to leave the windows open, then it doesn't matter. But often better to close them, so in a humid climate, the ERV is much better. And you will still need a dehumidifier.
A properly sized and ducted HRV/ERV would have the capacity to do a good job of clearing one bathroom, two at most. This is because there should always be a largish pickup in the kitchen area as it is typically the source of most indoor air pollution.
This generally means bathrooms need fans. There is also nothing wrong with having both a bath fan and a stale air pickup in the bathroom (my home has this).
As for ERV and HRV and humidity. You have to be realistic about the moisture transfer capability of most unit. Whether you run an ERV or an HRV, you will still be bringing humidity into the home.
If the house has no AC, this doesn't matter as the indoor air's dew point (the amount of water vapor in the air) will generally be a bit above outdoor air. Houses have humidity sources (people, plants, showers, cooking), without active dehumidification, there is no way to get this bellow outdoor mean. The ERV/HRV would not be bringing "moist air" into the house. It would be bringing in fresh air, which is what counts.
In a house with AC, you would want an ERV. The AC would be dehumidifying the indoor air, thus there is moisture difference, an ERV would help dry the fresh air coming in and reduce the latent load on the AC unit.