I believe you mean, @opaone, not opaline…?

You are correct my fault for not verifying spellchecker. @opaone

I would go 800 CFM w/ an 800 CFM MUA.

Regardless of how well sealed, or not, your house is you don't want to pull air in through leaks in wall cavities. That's not good for interior IAQ and can result in mold in the wall cavities. It also significantly reduces hood performance.

And it’s a fair assessment that a remote blower on the opposite side of a 2x4 wall would be fairly silly to do?

As far as MUA that’s what I was afraid of since there are very limited practical ways for us to accomplish this. It’s a first floor with no access to the attic from there and the basement is partly concrete foundation otherwise height is somewhat of an issue and serviceability goes out the window.

Based on reading your well documented experience, you still stand by not recommending a VAH?

Opaone and kaseki have a bias against VAH. A bunch of us on this forum, have had a VAH for years, and like them. Yeah, they’re not as easy to clean, as hoods with baffles. However, ours (almost 9 yo) does a great job of removing odors and effluents…and, is very quiet, even on high.

Oh that’s nice looking what cfm do you have and do you also have MUA?

You have to get a bigger duct installed than 6".

Yes, the plan is 8” or 10” depending on blower size we go with. And yes, cooking outside is certainly easier when taking into account all these guidances which are there for good reason but it seems like no one is familiar with them so you end up being your own HVAC.

I have a bias against VAH only because they do a poor job of removing effluent and are quite loud.

Let’s put the bias aside, if I were to get a 600cfm VAH liner that’s supposed to be as efficient as the 900cfm regular (still find this hard to conceptualize) would that be a mistake purely from a technical standpoint?

I’m finding out more and more, the venting and sizing will be the least of my issues. How would I deal with a potential wall obstruction where the hood would go? Is metal flex completely out of the question even for short portion?

@opaone and @kaseki in looking at the wolf 800cfm blower it seems the HVI rated sound is extremely low by comparion of the other blowers at high being only 5.5. Taking into account perfect conditions, any thoughts on how or why that is? Also - how come the 600cfm unit at high and .1sp runs at the full 600cfm potential whereas the 800 only runs at about 88% being 710cfm? All interesting observations in learning about.

Anything you do is going to be better than what you had, simply because of the increased capacity of the duct and a high CFM blower.

Headers exist in construction so that openings can be done in walls. Even load bearing walls. This is not that hard. Or that complicated. What goes out, has to come back in. To get it out, requires a duct that is big enough, and a fan that is big enough. Same for in. Roughly equal. Your house probably isn't all that tight either, and will have some leaks back into it already. If you are tightening that up, then you might need to get more into the exact details.

Thanks @minardi. It seems that no matter what I go with whether it be a 600cfm VAH or the 800 Wolf, the fact remains some MUA will be recommended and whether that 600 runs at full or the 800 runs at 600 it’s not going to change much in the way of MUA.

The VAH marketing is BS. Yes, theoretically, their design without baffles reduces static pressure drop and therefore reduces CFM needs. In practice, the squirrel-cage blower works quite poorly pulling against negative pressure. In any reasonably tight house they are useless without an open window or makeup air. The blower wheels, which are impossible to clean, get caked with grease and dust, further reducing their effectiveness over time. That said, if you with an external blower, then the VAH is a standard baffle design, and the hood is very well made and very nice-looking.

If your hood has lots of capture volume, you can run lower cfm than with a flat bottomed hood.

We are going with a 42” wolf liner so whatever that capture area is.

Looks like not much capture volume. Baffles are at a shallow angle. Typical for inserts, I think.

@John Liu Not to be pedantic, but the terms are containment volume and capture area.

So as I’m learning more here’s what I got so far - for custom canopy over liner will have a removable front panel for ease of serviceability and easier duct install. One thing I am now considering is rather than going 800cfm internal, to instead go with a 900cfm remote and run the duct cross the house which is 22’-23’ length and with all the calculations of equivalent lengths equates to about the same 20’ according to wolf spec. That’s still within their recommended 50’ total length. The duct would run between the floor joists and above my kitchen ceiling at just past 8’.

If we do this, I know some recommend for and against silencers but in my case since the silencer would not be accessible like it might be in an attic install, I’m thinking to just do away with it. Any thoughts on this plan? Is it crazy to run 20’ of duct instead of just going right out the back?

The driver for this is two fold, first limit blower noise level indoors and second, the side where this would be vented has bedrooms upstairs so there’s potential with open windows for air to waft in. Also, the neighbor’s house is just physically 12 or so feet away on the other side of fence (city living).