Whole house ventilation, (WHV) was once a very effective way to cool north Texas dwellings. It pains me to see these wonderful large blade fans dumped on the curb for bulky trash pick-up all around east, west and south Dallas in the older neighborhoods.
WHV coupled with ceiling fans will allow the thermostadt to be set 5-7 deg. cooler. My personal experience has been that the outdoor average temperature needs to be in the 90's before we need to resort to mechancially assisted cooling. Of course high humidity can distrupt this.
Attention has to be paid to insulation, thermal envelope break and weatherproofing when installing the fans to be sure they don't compromise its function or cause problems with the introduction of water.
The only reason not to install WHV is if someone doesn't have the interest or inclination to open and close windows to make it work effectively.
The savings in overall energy consumption, air quailty and comfort make this a very sound strategy for keeping cool for very little cost during the dog days of summer. I find the soft fan rumble a comforting and restful sound at bedtime.
Glad to see your participation on the forum.
My wife, who grew up in a house with one, has been after me to investigate a WHV fan. We have a small house, 2000 feet, with a high ceiling and a dormer window in the center of the living room. Seems to me that it would be a good spot for one. Do you do the design work for this small a job?
I just had a vapor barrier installed, attic ventilation adjusted and attic insulation added. The house is 2x6 construction, passive solar orientation, with low e windows.
What about humidity? Do I use the fan at night when the temp is 70-75 but then suffer during the day trying to pull out the humidity with the AC? I haven't checked the web yet, is there a site you could recommend to help me understand a WHV system?
I second Tony M's welcome. I am also interested in reading more on this subject. I am a bit confused by the terminology though. Is what you call a WHV the same or similar to what is more commonly called an attic fan? Having been in a house (Grandparent's) with such a fan, I know that this fan is only part of the equation. You also need good attic ventilation to make this truly effective. It is my understanding that houses such as my own with only 2 turbines covering 3000 + sq (including attached garage) are not prepared to benefit from this arrangement.
Can you tell us a) how you determine the proper placement of the fan b) how much (and what type) ventilation you recommend for the attic space.
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The whole house ventilation is essetially the same as an attic fan but it is different in some ways. In older houses the attic fan sucked air out of the house and blew it out the attic - "attic fan". Today we have homes that have attic fans installed in them simply for the purpose of ventilating the attic but they do not ventilate the house.
A WHV can be added to a high window in a tall space but you must have some way to insulate the back or inside of the opening during the hot and cold months. Insulated shutters work well for example.
I don't know of a site devoted to just WHV. You might check out A&M's website and snoop around or the Florida Solar Energy site. While I've read articles here and there most of what I know to be true about the subject comes from hands on experience as it is such a simple technology.
The point about humidity is accurate. You have to feel the quality of the inside air to know when to use it or install a very expensive control system. We design control systems for the commercial buidlings but the cost is restrictive for residential buildings. Normally, you don't want the interior relative humidity to exceed 45% or it can cause a lot of problems. If it is humid outside, then you do have to rely on the A/C to get it out.
Personally, I just sense when the humidity inside is high and we start to feel sticky. When that happens the cooling effect of the fan isn't working anyway so we shut if off. As with most of the simple things, they require a handson approach to managing the interior comfort of you home.
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