High Velocity A/C with Ventilation
dennis_vab
| Posted in General Questions on
My home is under construction right now. It’s 2,800 square feet, 2 levels, with a great room open to the second floor. I’m leaning towards a high velocity A/C and wanted to use Zehnder for Ventilation. My quote from them is just over $10k. In an attempt to do a more cost effective system I would like to incorporate an ERV into the ducting that will be used to cool the house. That means the air handler will need to run with the ERV.
Can anyone give me some pointers on how to best incorporate the ERV. Should I tie the bathroom to the exhaust side? I don’t see many units available that will put out as much cfm as Zehnder does.
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Replies
High velocity is great for retrofit where you have to fish ducts through existing walls. For a new build there is no point in spending the money on it. Standard air handler and ducting works just as well, cheaper to buy and cheaper to operate.
Generally the best ERV setup is fully ducted with separate ducting.
If this is out of the budget, the next best thing is a hybrid ducted setup where the stale air pickups are ducted and the fresh air is supplied to the return duct of the air handler.
In this case you run the stale air pickups to the bathrooms, kitchen and laundry room. A small pickup in the main bedroom is a good idea to guarantee air changes there no matter how much the air handler runs. Another small pickup in a the entrance shoe closet is a great option to keep funk at bay.
For this setup to work best, you want a low loss return ducting and spec an autobalance ERV. This will keep the flow in the ERV balanced as the air handler ramps up and down. Zehnder Q series, Panasonic Intellibalance or Broan/Vanee AI are good options.
I’ve read comments suggesting that high velocity system are much noisier than standard ducts.
That’s true, especially if you have a lot of fittings in the duct runs. Whistling sounds are a common complaint. Higher velocity air tends to be noisier, and it’s due to physics so you can’t really do much about it. I agree with other posters here that high velocity systems should generally be considered to be for retrofit applications where your ability to install ductwork is limited by the existing structure. For new builds, conventional systems have some significant cost advantages, they’re quieter, and contractors tend to be more familiar with their installation and operation.
Bill
The reason I am entertaining a high velocity is because of the layout of the house. I will still talk to the installer about his thoughts on a traditional system. I have some constraints that I will have to see if I can work around.