Quote:
Originally Posted by sa226
Last thing is that if you're increasing the CFM's by a lot , you need a "make up air" unit. In the winter with the house all sealed up, if you're sending a bunch of air out of the house without allowing any in, you can create a negative pressure. I think its a building code thing. In our house there is a little white box mounted below the electrical panel, I think it senses the negative pressure and kicks on the furnace fan if required.
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This is true. Our house (10 years old) has a switch that turns on the whole house ventilation fan when the hood fan is turned on. No idea what the rating is on our fan, but the builder said it was strong enough that he building code said we needed to have the two linked.