Replacing attic insulation with a whole house fan

Hi, I've recently bought a 1930's house with a whole house fan that discharges directly into my attic. The attic has gable vents, so plenty of discharge space is available. The attic floor joists are 2x6's and the fiberglass in sulation is ancient... it's matted down to about 2" high. I'd like to repl ace the insulation. It's covered in a heavy layer of dust, probably most o f which was deposited over the years by the whole house fan.
Is it ok to replace the fiberglass insulation and just let the dust settle on it over time? I have little interest in spending money to cover the att ic floor with plywood or OSB just to keep the fiberglass relatively dust fr ee. Should I worry about this sort of thing?
All comments appreciated. Regards, Theodore
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On Thu, 20 Mar 2014 17:18:49 -0700 (PDT), snipped-for-privacy@yahoo.com wrote:

Yes, the more insulation the better, at least 6 inches. Keep the heat of the attic from entering the house, and vice versa in the winter.

If you make an attic floor, will dust settle on that instead?
Despite that, I put 3/8" plywood in much of my attic, which is made with trusses and I later learned wasn't meant to have a floor at all. 3/8" because anything thicker was hard to carry upstairs, anything thinner would break when I stepped on it. I have double layers in the most used places, and for some of the least used places, I'm lying down anythow, because the pitched roof is too close to the floor. Because I only have a small trap door, I cut each sheet in 3rds lengthwise, 16".
Nonetheless, it helps store lightweight things up there, heavier things if it was meant to hold them as your attic might be.
And it kept me from stepping through the ceiling for the first 28 years. don't know how to put more than 6" of insulation in when the joists are 6" high.
We had a whole house fan in JHS and HS. House had no AC and probably didn't have much insulation in attic, I can't remember. But the problems with the fan were: It did nothing during the daytime to keep the house from getting hot. When the sun went down, turning the fan on would pull outside air into the bedrooms etc while pulling the hot inside air out of the bedrooms to the attic and out the vents if there were enough vents. But if the air outside was still hot -- and often it was 80 or 90 out until 11PM -- and the air inside wasn't so hot, that would replace the not so hot inside air with hot outside air. What good is that. Plus it would bring in all the dust from outside (something I don't care about but others do.)
In addition, it's hard to insulate the house from the attic where the whole house fan is. The shutter vanes aren't enough. I think there is a way to do it, however.
I'm a big believer in roof fans or gable fans, (which also need adequate outside vents from the attic) though others tell me if my attic floor were well-enough insulated I wouldn't need one. maybe they're right, but given my current level of insulation, I like the fan because it turns on automatically between 9 and 12 in the morning, depending on how hot the sun makes the attic, and turns off between 7 and 10 (except a few days when it is so hot out that sucking in outside air does't cool off the attic enough and the fan would run all night. But even when it doesn't do that, it can run 8, 10, 12 hours a day. I don't know how much that costs. For the most part, it's not running when I'm sleeping.
I have a manual switch on the second floor to turn it off when the thermostat would turn it on, and I turn the fan off during early spring and late fall so that the sun will heat the attic and the attic will heat the house, another thing people tell me wouldn't happen if I had enough insulataion. I also put on tan shingles instead of dark brown. Some people say that should make no difference (I guess that also depends on their being enough attic floor insulatoin) but it seems to make a difference to me.

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On Thursday, March 20, 2014 7:18:49 PM UTC-5, snipped-for-privacy@yahoo.com wrote:

s directly into my attic. The attic has gable vents, so plenty of discharg e space is available. The attic floor joists are 2x6's and the fiberglass insulation is ancient... it's matted down to about 2" high. I'd like to re place the insulation. It's covered in a heavy layer of dust, probably most of which was deposited over the years by the whole house fan.

e on it over time? I have little interest in spending money to cover the a ttic floor with plywood or OSB just to keep the fiberglass relatively dust free. Should I worry about this sort of thing?

T...I found heaps of info on this very situation on "This Ole House" on You Tube recently. I believe you will be able to sort it all out when you get more info. There is just too much to tell you in this way, but they go up into the attic and show you the "what" and "why" and I personally felt rath er well informed after watching (I looked at several different ones). For instances, there is some discussion on the age and safety of the older fiberglass...and putting sheet fiberglass (thick) (with a moisture barrier) perpendicular to the joist when one already has blown-in cellulose, etc... But Oren may be right! The simplest way is often the best. Some pre-airconditioned houses were cleverly built with higher than eight f oot ceilings--like ten to twelve feet instead--and windows were heavily dra ped (think -the velvet of the old West or deep South movies) to keep the h eat outside. But...if the inside does not cool down at night when it is ex tra hot, then you may need to use some fans in the rooms you use often. Th ey make one feel cooler without lowering the actual temperature, use a smal l amount of energy to run, and the sound can be a really pleasant white noi se that will help you sleep peacefully.
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wrote:

Well this is so true.
I live alone but the table fan in the kitchen, atop the tv, probably blows air that would make everyone happy. The table fan in the office, atop the file cabinet, is aimed at the desk chair. The table fan in the living room would hit 2 or 3 people because the distance is greater, but could be set to oscillate. All of these are about 10 inches. I even have a table fan in the basement, about 6 inches, which is always cool or almost coo but manages to get sort of hot in the middle of the summer, and it's pointed at my work bench. Floor fans take up too much space. Window fans don't do much.
And on the window sill above the bed, I had a 4" fan blowing straight at me. that burned up so now I have a 3 inch fan that goes on the window sill or on whatever is to my left in the bed.
The bigger fans have light dimmers or motor speed controllers controlling their speed, so I can get them slow enough that I can't hear them. Light dimmers work for 3 out of 4 fans, but if the fan stops spinning the dimmer is set dangerously slow or you can't use a light dimmer at all with that fan.
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On Thursday, March 20, 2014 8:18:49 PM UTC-4, snipped-for-privacy@yahoo.com wrote:

s directly into my attic. The attic has gable vents, so plenty of discharg e space is available. The attic floor joists are 2x6's and the fiberglass insulation is ancient... it's matted down to about 2" high. I'd like to re place the insulation. It's covered in a heavy layer of dust, probably most of which was deposited over the years by the whole house fan.

e on it over time? I have little interest in spending money to cover the a ttic floor with plywood or OSB just to keep the fiberglass relatively dust free. Should I worry about this sort of thing?

It worked that way for many years, so I guess if you start over with more fiberglass insulation on top, no reason you can't do it again. Since it's going over existing insulation, the new insulation should not have a vapor barrier.
Also, DIK where you live, but in most climates the whole house fan is only effective and practical for some limited days, eg early Summer. It doesn't remove humidity and if it's hot outside, it only draws hot air in. It's most effective if you have cool nights and can draw in cool dry air. But if it's humid out, it doesn't work well then either. You may find that you don't use it that much anyway.
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On 3/20/2014 8:18 PM, snipped-for-privacy@yahoo.com wrote:

I did this in a house I once owned. It was trussed construction and there was about 3-4" of blown in fiberglass. I has a removable exhaust fan mounted in the scuttle hole ... it was designed for that purpose. Later I decided to add more insulation and had about a foot of cellulose blown in. But before doing so, I build a 2' wide walkway. Actually, it was a 2' wide crawl way; the peek was only 4' high right along the crawl way. First I put 2" thick of foam board down with the final layer of plywood for walking ... I mean crawling. Knowing the blown in insulation would be all over the crawl way, I put vertical pieces of cardboard along each side. Never had a problem with the fan messing with the cellulose insulation. When 1st done, it was very thick and if you touched it, you would propagate waves in it. But, that quick stopped as the air eventually left and it settled to a less thick coverage. After using the crawl way to store many things, like Christmas and Halloween decorations, I only wish I had made it 4' wide instead of 2'. BTW, I was able to get the 2' x 8' pieces of plywood and foam up there because I had the front of the house opened for a remodel/fix up. So, I cut a 2' wide hole in the sheathing and slid in the 8' long panels. And then covered the hole in the sheathing and put new siding over the entire wall.
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I have a whole house fan and use it mostly in the spring and fall when the nights are cool. To use the fan you must have windows open to draw in the c ool air. If you are thinking of using it with the AC I am not sure that wou ld work. I have gas heat and hot water and the pilot lights on those units are blown out if the windows are not open for the attic fan. I use circulat ing room fans to move air around our bedrooms at night. It helps make the r oom feel cooler.
I also agree insulation and good tight windows will help. You might conside r having an energy audit done on your house to see where you may have issue s. For more information http://www.epdmcoatings.com/liquid-rubber.html
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