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I just bought an Opportunity Home - a totally refurbished house that is "green." However, the bathroom exhaust fans - in three bathrooms - all have motion detector nightlights and run 24/7. There are two switches in each bath, one for the vanity light and one for the ceiling light. There are no switches to turn off the fans.

My home inspection missed this, I'm assuming, because this could not be considered green by any measure, could it? Not to mention my electricity bill!

What can I do? I have basic wiring skills from the local community college and tools. Or should I contact the warranty people?

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Try to talk to whoever is responsible for the design of the house retrofit/refurbishment. Why houses (at least new or programmtically refurbished ones) don't come with an owner's manual is a constant bafflement - here's this extremely expensive, complex machine - figure it out yourself...?

What you may well have is a very tight (limited air exchange) refitting of the house, and the fans in question being the method used to ensure adequate air exchange for a healthy indoor environment. In a particularly good implementation of this, there may even be an air to air heat exchanger, warming (or cooling, in season) outside fresh air with the exhausted house air. That is more common in more extreme heating locales; it may not be cost-effective elsewhere (the heat exchangers themselves are not cheap.)

A fairly clear explanation of ventilating tight houses.

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+1. You have excellent points about ventilation of well-sealed houses and the possibility of a heat exchanger. (Of course, until the original poster finds out more about her house we can only speculate what "green" features it may have.) – Henry Jackson Jan 13 '14 at 19:15

I don't see why it would be illegal to have an exhaust fan running 24/7, but you could call your local building inspector to ask them. Obviously the answer to that legal question depends entirely on your local laws and building codes, so there is no blanket answer.

As for "green", which is a very vague term, I agree it seems a little wasteful but it depends on how much electricity the fans and lights are using and how much of your conditioned air is being vented outside.

To calculate how much an appliance is going to cost to run, you can use this formula:

Monthly cost = (Appliance watts) X (hours per day) X (days per month) X (price of electricity in $/kWh) / (1000 watts / kW)

So in my area to run a single 30 watt exhaust fan 24/7 for a month would be:

(30 watts) X (24 hrs) X (30 days) X ($0.20 /kWh) / (1000) = $4.30

If these fans are running all the time they may be a lower wattage, or you may have lower electricity rates than I do, so should do your best to find out what your actual numbers are if you're concerned about the electricity cost.

If you have the heat or AC on, there's also a cost associated with losing the conditioned air. Any air that vents out of the house will be replaced by outside air that is drawn into the house through cracks, and will add additional load to your furnace or AC. The numbers are harder to calculate, though.

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Thank you, I had thought about the heat loss. I'll collect those figures and calculate the cost. It just seems so wasteful; they're not small fans... – JANICE Jan 11 '14 at 17:51

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