Placement of ceiling fans

tinanApril 2, 2012

We're buying a townhouse with no A/C, the climate here is temperate but it does get hot some summer days. It is a 2 level home and has clay tile roof which is a good insulator but I'd like to add ceiling fans to help move air and keep things cool and more efficient. We will probably have a portable A/C for the bedroom for those really hot days.

I dislike having air actually blowing on me while sleeping so I don't think I want one in the bedroom. Would it be useful/effective to have a fan in the hallway over the top of the stairs, to push air down in summer and pull up warm air in winter (we keep doors open)? Or is it necessary to have them in each room?

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Having the fan in the hallway is not going to help the comfort level in the bedroom. Fans increase comfort through the wind chill effect by moving air past your skin. There are fans which rotate very slowly which may work for you.

Can you install an AC unit in the bedroom window. I think this would be more effective than a fan. It will also help lower the humidity.

    Bookmark   April 3, 2012 at 12:55PM
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"Fans increase comfort through the wind chill effect by moving air past your skin."

Begs the question as to why bother to make ceiling fans reversible?

    Bookmark   April 3, 2012 at 1:50PM
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The common practice is to reverse the fan in the winter. The idea is to pull the cooler air from the floor and force down the warm air sitting at the ceiling. The air is being pushed downward indirectly off the ceiling so you don't feel a direct air stream. This works well if you have a high ceiling in a 2-story entry.

    Bookmark   April 3, 2012 at 2:00PM
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Fan direction will depend not only on season, but .also on where in the room you are sitting.

    Bookmark   April 3, 2012 at 2:28PM
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You don't need a fan to "pull up warm air", btw. It does that naturally.

What do you mean by "portable A/C"? Those units that roll around are very inefficient. The ones that have one hose are much worse than the ones that have two. Be careful about that.

Is it humid where you live? Have you considered installing a couple of mini splits?

    Bookmark   April 3, 2012 at 2:34PM
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California - it's dry we don't have to worry about humidity thankfully, the heat is quite bearable in shade with a fan! I lived here without A/C for many years, happen to have central A/C now but new place will not have it, just want to maximize air flow.

Would it be more efficient to just turn on the furnace fan to move the air?

The furnace is a really old Whirlpool gas, we may replace it down the road but again temperate climate barely need the heat... so it's not at the top of our list for improvement. When we do we will get one with A/C if we can (it's in an interior closet).

By portable A/C yes I mean the type on wheels with a hose that connects to the window. I had one for several years a Sharp Plasmacluster it worked VERY well for our little cottage. I sold it when we moved to our current home with central air, but I was planning to get something like that again. The bedroom windows are sliding glass doors, not amenable to the in-window types and there are HOA restrictions on exterior appliances (such as split system or big ugly in window A/C).

THanks for the advice, sounds like a ceiling fan in the hallway would be a waste of money, I'll either put them in the rooms or just save towards a furnace replacement.

    Bookmark   April 4, 2012 at 12:57AM
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Just remember that the single hose portables suck a lot of conditioned air out of your home. That depressurizes the room and the air to replace it is sucked in through random leaks. In addition to being inefficient, It can even cause backdrafting in combustion appliances which is really bad. Buy one with two hoses.

    Bookmark   April 4, 2012 at 12:13PM
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ionized, I doubt the place is airtight enough to cause any kind of depressurization. Homes built before the 90's in California are not built the way homes in the rest of the country are built, people built like it never gets at all hot or cold here (no insulation, drafty not well sealed). That's OK with me because I have windows open almost year around anyway, I prefer fresh air.

A two hose system means heating air from outside which is less efficient, better to recirculate the inside air! The gas water heater is separately vented and the cabinet it's in is relatively airtight - furnace is in there too and of course would never be on when A/C is on. Having an A/C in the upstairs bedroom is never going to cause a serious enough vacuum downstairs where those items are to make any difference.

    Bookmark   April 4, 2012 at 9:55PM
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One hose means that you are constantly sucking your precious, chilled, indoor air past the hot coil and outdoors. Two hoses means that you are using outside air to cool that coil. The latter is much more efficient.

As far as "depressurization" goes, if you are sucking air out of a room, you are depressurizing it. The make-up air has to come from somewhere.

    Bookmark   April 5, 2012 at 2:25PM
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ionized, the cold air doesn't go near the hose, it comes out the front. The hose expels the heated air, which contains the heat removed from the room air - it's an exhaust only.

I am a scientist, and understand physics quite well. You can't actually depressurize a room that is not airtight - as you say the air comes from somewhere and it will enter as quickly as air is removed, thus never resulting in any pressure drop inside the home. The less airtight the room, the faster and easier replacement air can enter and the less negative pressure could be created.

There is no way a portable A/C unit in a room upstairs has the power to create any measurable negative pressure in the entire house - I am most certainly not worried about that especially after having used one for many years with no problems.

    Bookmark   April 5, 2012 at 7:29PM
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Tinan, you are dead wrong about his. You don't need anything more than kindergarden physics to understand it. The pressure differentials are very small, but enough to move air. Think cm of water, not cm of mercury. A structure that is not airtight can be partially depressurized if the rate of air removal is fast enough. It happens every day.

The single hose portable AC models remove conditioned air from the living space that must be replaced by outside, unconditioned air. The dual hose models cool the condensing coil by circulating outside air in and out the window through two tubes. Draw yourself a picture if you don't follow me.

    Bookmark   April 6, 2012 at 2:31PM
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Your argument makes no sense - the failing is not on my end. I don't really care for your insult about "kindergarten physics" if that even existed.

You see warm air is less dense than cool air so as it is heated it expands and takes up more space. So you can't talk about "air" as if it is always the same volume. It expands after it is heated and exhausted by the A/C. Yes of course the replacement air always comes from somewhere - if it comes from a gap under the door from the rest of the house, the air is cooler and therefore it takes less energy to further cool than if you bring in outside air from a hose on the unshaded side of the house. THe air that comes from under the door gap eventually could perhaps be traced on the molecular level to air that comes from outside, but it's not all coming from the sunny hot side of the house so do the the averaging effect it will ALWAYS be cooler and take less energy to cool than the hot air brought in by a hose.

And, since the air that becomes the exhaust will expand to a larger volume, it doesn't require the same volume of air to replace it. So I reiterate that the effect on the pressure in another room in the house (fear of "backdrafting combustion appliances" is a ridiculous fear and completely unrealistic the amount of pressure differential and air movement is negligible compared to just opening and closing a door.

I have no idea why I just wasted my time explaining this to you when I came here for practical advice on positioning ceiling fans, don't think I will bother coming back to this forum again.

    Bookmark   April 6, 2012 at 7:10PM
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You tried.

I don't think he'll last long at another forum of "scientists" that "actually understand physics" well (and don't have the need to announce that they do. lol

    Bookmark   April 6, 2012 at 8:56PM
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I hate that "believe me, I am a scientist" attitude. As a lab scientist myself, I feel like someone is dragging me through the mud every time I see or hear it. It is particularly embarrassing when followed by a big pile of steaming whatever.

    Bookmark   April 7, 2012 at 10:55AM
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