Thanks for your replies and useful information. The typical box fans available locally are rounded ones, so I would have to had padded/filled in around them too. And I came across some more information about air stratification which got me to thinking about air flow, humidity and venting- some people have vents opening in the roof to release the hot air. This is a discussion where some one talks about horizontal air flow removing 'good' air with hot air staying up the top- though if you had the exhaust fan up at the highest point you would get more of the hotter air being removed I think: http://209.85.173.132/search?q=cache:AsuB1xJiPZYJ:www.orchidsafari.org/ghse/ghse1.html+greenhouse+exhaust+%22high+velocity+fan%22&hl=en&ct=clnk&cd=1&gl=au This is interesting in that I read about someone who installed a the exhaust fan on the opposite end wall to an evaporative cooler or wet wall which worked well to remove heat but also removed a fair bit of humidity. In contradiction I've read turbine ventilators do remove humidity and are installed and used to not only remove heat in summer but to remove moisture from under the roof/ceiling or in attics. I know some one who uses whirly birds/turbine ventilators though they have said height is really important for them to be effective. So I ended up not going with fans for exhausting air on the opposite end wall to the cooler and instead got a 30cm turbine ventilator whirly gig thing. I also found a few more exhaust fans [for bathrooms, etc] and got one [25cm AUS $49.00. that will fit under the whirly, extracting air keeping the turbine spinning. The exhaust fan is not on a thermostat but I figure I could just turn it off and maybe cover it in winter to stop heat escaping. I will be placing it in/on on the roof nearer towards the highest point where hot air should rise to. I don't know how effective it will be but with misting under the benches, the evaporative cooler and trickling water down the shadecloth/matting against the fence I'd be happy if it only reduced temps just a few degrees. Where my masies, dracs, pleuros, oncids, miltonias etc are at the moment is a mucher small potting shed, which I kept totally closed up last summer but I did set up a hose in there to release a small spray of mist [slightly dripping] and have the evaporate cooler in there [+ fan inside circulating air around]. Despite some days with temps going past 35 degrees celcius I didn't lose or have any plants visibly suffer or have masie leaf drop except for one plant that was a newbie. I think it was keeping the humidity up around 80-90% [+ shading] that helped. My main concern really has been about ondontoglossums and hybrids with the cooler/cold ones like crispum, I have been told and read too that they do better if temps can be kept lower in Summer. I will post back later on how it works out and put some pics of my turbine/exhaust fan up in my Pleurothallidinae and Oncidiinae Grow House photobucket folder. Damian. Here is a link that might be useful: My http://s21.photobucket.com/albums/b253/daemondamian/Orchids/Pleurothallidinae and Oncidiinae Grow House/

I have no clue about our duct work, we vent at 90 degrees to exit house, about 8 feet. Our "quiet" 600 CFM sounds like a locomotive when on high, and our smoke detectors always go off when I cook steaks inside. I have the wolf df range, and I also suggest your hood be at least 6" wider than your cooktop so that it works on your outside burners. Working within the confines of HOA will probably determine your appliance choices. At least you have some existing hood/duct work, rather than a recirculating filter system. Huge plus!

Hollysprings - Ventilation price is not the issue. The issue is the cutting and moving of cabinets. My kitchen is a kosher kitchen which has a lot of complications when doing a layout. My kitchen is spacious to accommodate the need for doubles of everything, yet it is very utilitarian. Its design is superb and meets my needs. I have had professionals chef cook in my kitchen and praise the functionality as well as the beauty of my kitchen. In fact, one asked to come back and use my kitchen again. Ventilation only becomes an issue if I install a grill or a CC or BS. We have finally concluded we cannot install a CC or BS range because cutting and moving cabinets will cause other issues and will not look well. We are contemplating your suggestion of protecting a deck area. Also under consideration is a 30 inch BS char broiler which can be placed where a breakfast bar is currently located. The breakfast bar can be removed and a new counter top and 3 cabinets can be installed. If we do this, we will ventilate with a 900 CFM unit (although only 600 is necessary, I believe). I understand your feelings about the lack of ventilation with my electrolux - I was concerned. But the engineers at electrolux assured me it was not necessary - and it hasn't been!!! I cook constantly and many people use my kitchen. No one has felt the ventilation to be inadequate - perhaps cathedral ceilings and a ceiling fan help odors to disappear. I have wallpaper in my kitchen and there are no smoke marks or oil splotches on it, nor are there any on my ceilings. Sidpost - thanks for the interesting suggestion, Sandra, I called solaire and firemagic. Both did not recommend the usage of their portables indoors. I had thought of putting a grill on a moveable cart and placing the cart right outside my french doors so I could stay inside and grill outside. But they did not think that was a good idea. I try to think outside of the box - but safety is a paramount concern. If you find a way to achieve our aim - let me know.

[ya_think] I did a search ... and it came up empty. Perhaps the thread has dropped off the archive. I did a search on clinresga, and another ventilation thread came up, but I didn't not see anything posted in that thread, either by clinresga or kaseki that contradicts any of my statements. That being said, the setup is comparing a VAH internal blower to a Fantech inline blower. Convoluted ducting or not, you can always use a significantly more powerful inline or external blower and get the same capacity as any internal blower, and it will (from a motor noise point of view) be significantly quieter as long as the blower is sufficiently far away. The key here is that the original poster is already on an external wall - so my assumption is that the external blower would not be that far away from the hood itself. You are absolutely right about a tonne of variables impacting the actual characteristics (efficiency and noise). I really wish HVI certification were required for all fans (with filters) - that would give everybody a true relative assessment between products. But unfortunately, we don't have that now. All we can say is what we have personally experienced, and how some aspects of physics plays into things. [antss] I am pretty sure all blower manufacturers provide CFM ratings at the inlet of the motor with zero ducting. In my research, I have not seen any indication otherwise. As far as I know, HVI testing doesn't using ducting either. Maybe my statement should be: "for the exact same blower, a longer duct will reduce the air moving capacity at the same effort level, or will increase the power required for the same air movement." And, actually, an SPL meter is NOT more accurate than my ear - perception is everything. The SPL, which gives you a single dB measurement, actually weighs all the various frequency components into one number (there are actually a number of different weightings that are defined, including a flat distribution, none of which match the frequency response of my ear). My point is that, the SPL could detect a peak in a frequency that nobody can hear. If nobody can hear it, why does it matter? Given that one has to live with their range hood in operation every time they cook, I would say perception is king. Put it this way: if blower X has a minimal SPL rating, but in my kitchen it drives me crazy vs. Y that has a higher SPL rating in identical test conditions, which blower does it make sense to buy? I will concede that I don't know whether grease really gets into VAH motors or not. VAH cleaning instructions include the housing (easily removable) and the blower wheel (clean in place, or remove with a hex wrench). The warranty is five years for the motor, so I assume that not enough grease gets in to mess up the motor within five years. Given that the motors are enclosed in a different housing, it shouldn't be that difficult to proof most of it against grease - the trickiest part would be the motor shaft enters the housing, but most of that ought to be protected by the blower wheel itself. Grease is sneaky though. I never claims that fan size / rpm / cfm follow a linear relationship, but you can make general claims about them with the proper assumptions. For example, for the same blade design and RPM, a bigger fan will move more air than a smaller fan. But the very fact that there are many complex variables and that they do not hold to a linear relationship means that you can very well have a smaller fan that is both quieter and moves more air than a bigger (poorly designed) fan. Just saying it's plausible, and shouldn't automagically be dismissed as 'smoke and mirrors'. (And I've never read or owned a fluid dynamics tome.) Once more, I reiterate that I only compared internal blowers to internal blowers in the show room (the exception being a Viking external blower I saw at the distributor - different location altogether) - which happens to be a reasonable simulation of my particular environment. The majority of them [external blowers] are... what? Easier or harder? Harder, if the blower is going somewhere other than the first floor (second floor, or roof application). But the original poster asked about 4' of ducting, so I assumed first floor - in which case, just mount the thing onto the brick veneer (more annoying) or siding (less annoying). Running the electricity 4' out isn't all that difficult either. I agree you can't compare against a 1500 CFM external powerpak (unless it was specifically installed in a similar config - pretty unlikely), but a would also say that 1500 CFM (or external blowers) are not typical installations. The original poster did not specify the capacity they were looking at, so I made an assumption that it would be in the 900-1200 CFM range. VAH maxes out at 1200 CFM (or 1800 "equivalent" CFM). Regarding the fire starting inside the hood, I don't have that concern, I didn't even say that, I was merely correcting the misinterpretation of a VAH claim. On the other hand, why say no to a bonus safety feature? I realize that all companies, including VAH, will stretch the truth, massage the message, spin the numbers, in their favour. No problem. But I have yet to hear anyone point out anything really wrong with VAH performance claims (grease in the motors notwithstanding). They've been in business for 75 years - if there was something really wrong with their claims, I'm sure they would have a much worse reputation at this point (or been sued all to hell). One thing I do like about some of the VAH models is that the halogen versions often have a heat sensor that automatically maxes out the fans when it gets too hot. The downsides is that the lights only have two settings (instead of being dimmable), and the fans have discrete settings (which is common, but I think I might like the flexibility of analog dials). Also, they don't have a delay timer stop feature. Anyway, I would agree with your (antss) first post - it does depend on the specifics. I am in a similar situation as the original poster, and I decided against the external blower in favour of an internal blower, based on the assumption that good quality motors and blade/wheel designs are a lesser noise component compared to air movement, and I specifically went with VAH because a filterless design is, in general, quieter than a filtered design (backed up by my "anecdotes". Sigh. I talk too much.