How do I figure out the right way of adding more supply and return registers?

Old 01-20-19, 07:56 AM
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How do I figure out the right way of adding more supply and return registers?

Hello everyone,

We're renovating our finished basement. It has a bedroom that has no HVAC registers so, needless to say, it's not the most comfortable room in the house in the summer or winter. (It has a small window but it's not enough). We want to add a register. The duct that's right above the bedroom supplies air to the kitchen and a living room upstairs on the main level, so it already has several registers. Can we simply cut another one there? Does it depend on the size of the duct and the number of existing registers? Does it depend on the specs of the HVAC unit? How do we figure out the right way to do it? And is it possible that we will need to drag a brand new duct to the downstairs bedroom from the HVAC unit (from the plenum chamber, right?)?

Also, the basement has no return registers so we want to add one for better air circulation. Do we need to do similar calculations for it?

Thank you!
Old 01-20-19, 08:26 AM
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It's best to bring in an HVAC pro to assist you, there's actually a lot of science involved in balancing a system (and figuring out whether you have the right system in the first place).
Old 01-20-19, 10:18 AM
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Granted there is some science but I've added both supply and return ducts to past basement jobs without any ill effect.

As an example, if I close all my current basement ducts does it throw the entire house into kaos? Nope!

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