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/

C&R - I believe you live in Texas? Well, Chicago doesn't have the same climate as Houston (thank god). Exhaust fans in the laundry are not required in my burb. And I have to say, I've never noticed that the washing machine raises the humidity measurably. My washer is a front loading HE washer and uses very little water. Never have I ever felt the need for an exhaust in my current laundry. Plus, my new laundry has an operable window. Anyway, it seems to me an odd requirement - don't most dryers essentially act as exhaust fans when they run because they take air from the room and exhaust it (through the dryer) outside? kudzu9 - my husband agrees with you that a 5 foot long duct does not impact a fan negatively. But most of the time this fan is not running, and during extremely cold weather the duct's air temperature (being essentially open to outside) drops to be freezing cold, and of course the longer the duct, the further that cold air reaches underneath our master bath floor, which is why he'd like to keep the duct as short as possible: we like warm toes :-)

Hi guys, I just had central AC installed a few weeks ago. I have a 2 floor home, main floor, upper floor ( bedrooms ) and the basement. I'm quickly seeing that the upper level never gets as cold as the main floor, and the basement is always extremely cold. I have closed ALL vents in the basement, and this helps to equalize the temp in the house, however, it seems that you really need to keep the furnace fan in "ON" mode, instead of auto, where it will shut off after the central AC has stopped cooling the house. However, what happens if you do NOT want the furnace fan running all night long ? I'm guessing new furnaces most probably have the option of a timed mode for the furnace fan... so to clarify.... you could have it going for a hour then turn it off for an hour, etc..... a real timed mode. Perhaps that doesn't exist, but I was thinking of that today...... I am just worried that constantly running my furnace fan will drastically increase my electric bill, and put a lot more undue stress on the fan. Running the furnace fan for even a week 24/7 is probably more than it would run for a full winter season when I'm heating. Anyway, thought it was a good topic, I'd love to hear your opinions. Thank you.

Electric heaters are prone to this due to dust settling on the heater coils of the unit during the off season of using the heating part of the system. This dust typically burns off after a few uses depending on how much dust build up is on the heater coils. If this is a ceiling mount heater / exhaust I doubt a smell would be much of a concern for long. The key thing when installing an exhaust fan is that the vent is installed nowhere near a sewer vent stack on the outside of the structure. (Like down wind and so on.)