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  1. #21
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    Default Re: Air Circulation In Summer Without A/C?

    Quote Originally Posted by keith3267 View Post
    Mastercarpentry makes a good point about the dust, but it is only valid if the window fan has an air filter on the outside of it. His point also applies to a whole house fan.

    There are low cost window fans, not box fans but window fans that fit into an opening only 10 inches or less in height. In fact I have one that uses a squirrel cage type fan that is only 5" tall, has a filter and can push or pull air. This one was a little pricier (about $30) than the typical twin 8" fans commonly sold for windows. It also has a built in thermostat so that also ran the price up a little.

    If one fan helps in either configuration but you need a little more, you could get two, one blowing in at the kitchen with a filter and one exhausting at the other end of the house. This would make a wind tunnel and with less vacuum, it would not draw in the dust as much.
    I tried a portable fan today at one end of the house pulling air from the outside. Didn't seem to help much. I dunno if it's a fair test... I mean, I'd need a BIG fan to make a noticeable difference, right?


    Quote Originally Posted by keith3267 View Post
    Honestly though, I would start with good gable vents at each end and see how that works. One recommendation though, get some good 1/4" hardware cloth to reinforce the screen. Birds will sometimes push in the screen or make a hole in it and then nest in your attic. The simplest solution is often the best.
    So it's your contention that gable vents... the lack of air circulation in the attic space... may be the primary cause of the afternoon heat? IOW: the heat from the attic as the day goes on, then heats up the house? If so, wouldn't I notice that the ceiling was warm?

  2. #22
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    Default Re: Air Circulation In Summer Without A/C?

    Quote Originally Posted by Mastercarpentry View Post
    I'll disagree with Keith as to the placement and airflow of the window fan, and here's why. Done as he suggests, you create a 'vacuum' towards the fan, and every leak in the envelope reduces that vacuum and the efficiency of the airflow. It also allows dust to be drawn inside from those leaks. By reversing the concept and pushing the cool air in, you still have the same envelope leaks but they have less effect on the efficiency of that airflow (positive pressure still exists) and you're pushing any dust out through the leaks. In any open-ended air-moving system pressure will be more effective than a vacuum.

    I keep a box fan on the truck for work, and there's a small rope tied to the top handle so I can figure out some way of hanging it in almost any window on the inside. If I want more effective ventilation from it I mask around it with cardboard and tape. "Window Fans" made with sheet-metal enclosures used to be made and don't look too bad for a 'permanent' installation; spray paint gives you whatever color you like to blend in with the decor. Alternately you can make something similar (even out of wood) which works with your box fan, again painting to match. With the fan inside the screen it will hardly be noticed outside of that room. The better the fan is sealed into the opening the better it will work. With your attic as small as it is I kind of doubt that it's building much heat but if you can ventilate and insulate it better do so- every little bit will help.

    Phil
    Thanks for replying.

    My question is: how big a fan do I need to make a difference? I tried a test today with a portable fan in the 'hot' far end of the house... trying to exhaust air -out- through an open window. Didn't notice much.

    I guess I'd like some way to test -whatever- solution before going crazy.

  3. #23
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    Default Re: Air Circulation In Summer Without A/C?

    It is true that the bigger the problem, the bigger the fan required. Your initial post indicated that the issue wasn't that big so a small fan seemed reasonable.

    Fans can only do so much though. If your afternoon temps outside are uncomfortably high, then a fan really won't do much, it can't cool the outside air down any. For that, AC is the only answer.

    You are right that if the hot attic is the source of the heat in the house, then the ceiling will be quite warm. But you have to understand that because of the large surface area of the ceiling radiating into the house space, it doesn't have to be that much warmer to transfer a lot of BTU's into the interior. It's not like a space heater that has to be intensely hot because of its small radiating surface area.

    To get an idea, you would have to compare a ribbon, coil or ceramic space heater to one of the oil filled radiator looking heaters. You would never touch the ribbon or coil or even ceramic surface of one of those heaters when on and if your dr_apes or other combustible were to come in contact, you would have a fire. But one of those radiator types get quite warm to the touch but will not burn you or start a fire, but provide just as much warmth. Your ceiling has a much larger radiating surface area than even the radiator type space heaters.

    But you also have to understand that warm air rises so the ceiling will always be a little warmer than the floor. So its a judgement call to some extent to determine if the ceiling is warmer due to convection currents in the house or from the heat of the attic. A heavy layer of insulation in the attic should retard the heat transfer. Venting the attic will reduce the amount of heat available to transfer through the ceiling.

    But it is possible that you could be getting heat gain through the windows or even the walls. Sunlight strikes the structure and every where the sunbeams hit, there is a transfer of heat. To find the sources of heat, you could hire someone who has an infrared camera. I think this is always money well spent because it accurately identifies the problem areas, no guessing. Normally these are used in winter to find heat losses, but it could be used in summer as well. Generally the heat losses in winter are also the heat gains in summer, fix one and you fix the other.

    You could also get an IR non contact thermometer from places like Harbor Freight tools. You can catch them on sale for as little as $29. I have one and I use it for a lot of things. You can go around the house looking for hot spots. To see if the ceiling is the source of the problem, you would hang a conventional thermometer a few inches below the ceiling and then measure the ceilings surface temperature. If the difference is really significant, then its the ceiling, it it is not, say only 1 or 2 degrees, then the ceiling and attic are not the source of the heat.

    BTW, there is an option for AC that you may not have considered. A floor standing portable AC unit that has a hose that goes to the window.

    http://www.lowes.com/Heating-Cooling..._-10682062_2_#!

    I have the DeLonghi at the bottom of that page, but I got mine at Costco for about half that price. It is a heat pump but I do not use that feature in the winter as it gets too cold around here and the bedroom I use it in is on the north side. It only uses about 5" of window. The issue with one of these is if you use it in the living room and you are trying to watch TV, its a bit noisy, but I use mine in the bedroom and the noise is not loud enough to keep me awake. I did have to put a cardboard cover over the display because it is so bright. I sent them a response to their web site informing them about that, their sleep mode should shut off the backlight of the display.
    Last edited by keith3267; 08-10-2014 at 02:53 PM. Reason: You have to underscore dr_apes or it gets **** out.

  4. #24
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    Default Re: Air Circulation In Summer Without A/C?

    Thanks again for replying. I do have a laser thermometer gizmo. I will do some experimenting and report back.

    In the meantime, a couple of things:

    1. It's not a 'big' problem... except when it is. IOW: 10-1/2 months a year it's NO problem. But there is a 3 month hot/dry season in the Pacific NW and during 1/2 of that the temperatures are in the 80's and then it's a -big- issue. When it's 80+ it's like a switch flips and the house gets HOTTER than the outside. It's 9:30PM. It's 72 outside. It's 82 inside. About 3PM every day, the inside catches up with the outside and then stays that hot until 10pm. And then as if by magic, the inside drops 10 degrees and all is well until 3PM next day.

    2. Another thing I forgot to mention: we have a 'fan only mode' on the forced air furnace, which we've been told 'really helps'. Well, it doesn't help at all. And I wonder why. I mean, it's pulling air from the outside so isn't that like a 'whole house fan'?


    I do want to think about the gable vent idea.

  5. #25
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    Default Re: Air Circulation In Summer Without A/C?

    " 2. Another thing I forgot to mention: we have a 'fan only mode' on the forced air furnace, which we've been told 'really helps'. Well, it doesn't help at all. And I wonder why. I mean, it's pulling air from the outside so isn't that like a 'whole house fan'? "

    If set correctly, the furnace sucks air from inside the house, not outside.
    If the inside air is 82 F, then the heater fan will push air at that temp (when the furnace is off).

    To lower the temp inside the home you have to bring in cooler air from the outside or have an air conditioner.

    Air conditioners are not cheap and they require maintenance.

    Having to endure a few hot days or invest in an a/c system: that's your choice.

  6. #26
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    Default Re: Air Circulation In Summer Without A/C?

    Quote Originally Posted by suntower View Post
    Maybe the house cooling was OK when it was built, but when they added the super-insulation (when they built the airport) they neglected to add better venting.
    I was going back over this whole thread and this caught my eye. I'm not sure how to interpret this but if this means you didn't have as much of a problem before the super insulation was added, then it is very possible that the attic insulation that was added was blown in, and with your very limited attic height, the insulation now blocks the soffit vents.

    Of course this may mean that you didn't own the house before so you don't know if it was a problem. Adding insulation should reduce this issue, not aggravate it.

    The soffit vents could be blocked either by the insulation being blown right over the top of the vents or by filling the void completely where the roof intersects with the ceiling along the length of the house.

    During the cool of the morning, open the attic access panel and see if you can see a gap between the edge of the ceiling and the roof immediately above. Probably the only way to check the soffits is to pull down one of the soffit boards and see if insulation falls all over your face, You should wear a full face shield for this along with goggles, especially if the insulation is blown fiberglass.

    If this is a problem, then the best way to solve it will be to pull down all the soffit boards and remove the insulation. Then you should be able to access the attic insulation along the edge so that you can move some of the insulation and make a proper gap.

    You may want to actually get some batt insulation that will not block the gap and cut it into one foot lengths. Then push all the blown insulation in a foot, don't let it dam up to the underside of the roof, and then lay down the batts. That should keep the blown insulation from shifting and blocking the vents in the future.

    Another option is to use baffles that made for this application. They install to the underside of the roof where it goes over the edge of the ceiling and keeps the blown insulation from blocking air flow.

    Installing gable end vents should not be hard either. You only have to remove the siding where the vents go. They should come with flashing. I would avoid the round vents as they have a tendency to leak even when fully flashed. There are square ones that work good and are universal but the best are the triangular ones, but the triangular ones have to match the roof pitch so they may have to be custom ordered.

    This link should help, its a dot gov link from the energy department.

    http://www.energystar.gov/index.cfm?...ic_ventilation
    Last edited by keith3267; 08-11-2014 at 12:20 PM. Reason: add link

  7. #27
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    Default Re: Air Circulation In Summer Without A/C?

    The houses were build in 1970. In 198x... a court ordered the local airport to compensate all the homeowners for all the racket by retro-fitting with these amazing 3-4 pane windows and adding sound proofing insulation... which is MUCH more dense than the usual 'pink' stuff. It's almost as thick/dense as styrofoam. I think it's called '705'. It's specifically for sound-dampening. The houses are so tight that they put these little vents in the lower corner of rooms you're supposed to open from time to time to let the house -breathe-.

    BUT no new venting was added in the attic. So my half-assed theory is that the attic probably should've had extra vents to compensate for the added heat build-up. None of the houses had gable vents probably because they weren't needed until the new insulation was added.

    Anyhoo, I tried my laser thermometer today and FWIW... after noon, the ceiling is always at -least 4 degrees hotter than the walls which face the exterior or the floors.

    Thanks for your explanation of the furnace 'fan mode'. Yeah it doesn't help.

    I dunno if gable vents would make a difference, but it seems like the attic should have better ventilation. I just keep wondering why no one else in my neighbourhood has done this.

    HOWEVER, the 10 months of the year when it's not hot, I don't want to mess things up. The heating bills are SUPER low.

    OTOH, this global warming thing is certainly apparent now. It's getting progressively hotter/drier pretty much every year here now. The whole Seattle/Rain thing is a myth. Gray? Yes. But 'rainy'? Not so much.

  8. #28
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    Default Re: Air Circulation In Summer Without A/C?

    Proper ventilation of the attic will not "mess things up" for the rest of the year, in fact it will insure that it maintains maximum thermal efficiency. You probably have Rock-wool insulation or maybe a particular type of cellulose. Rock-wool is particularly good at noise abatement, but I saw a type of cellulose at a home show once that was also made for this purpose.

    If the moisture content of the insulation increases, its thermal efficiency decreases. A high relative humidity (RH) can drop the R-value in half. With proper ventilation and a vapor barrier, you can actually have a lower RH in the insulation than you have in the outside air.

    Checking your soffits should be your very first step. You can probably check them easier by pulling off a fascia board rather than trying to drop the soffit board, it depends on how your house was built. If there is any issues with the soffits being blocked, clearing this up will improve the insulation year round. Then look at the gable vents. For this you may want to consult with someone on selecting the proper size so that you don't over/under do it.

    You can google for attic vent calculators, here is one:

    http://www.gaf.com/Roofing/Residenti...ion_Calculator

    The general rule is one square foot of free vent space per 150-300 sq ft of attic floor space. Local zoning laws may require more or less.

    Making a guess (and I will not ask for more information from you, you can figure this out for yourself) but since you say the attic is about 2.5' tall at the peak, I will assume a roof pitch of 2/12 (2 in 12 or 2" rise for every foot of length). This would fit for a house that is around 24 to 28' wide on the gable ends. A one foot tall louvered triangular gable vent at each end of the house would provide a total of 6 sq ft {[(1'x6')/2]x2** vents of free vent space which is enough to vent 900 to 1800 sq ft of attic space.

    In some areas that would be enough even if you did not have soffit vents or they were plugged up by excessive insulation, but I'd still want the soffit vents.

    The closer to the source that you fix the problem with the minimum disturbance of what is working, the better you will be overall.

  9. #29
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    Default Re: Air Circulation In Summer Without A/C?

    A 4 degree difference is not much, so my guess is that the insulation in the attic is adequate but it's worth checking the ventilation up there anyway. Sometimes the baffles that are supposed to retain the insulation fail and soffits get clogged for many feel either side with loose insulation.

    On the fan, simply placing one near the window won't do much good. That will draw air from inside the house just as much as from outside. It needs to be in the window opening, preferably sealed to it reasonably well so that all the air into it comes from outside only. Cardboard will work temporarily sealed with blue painter's tape. If it then does well enough then create a nicer mounting system. It's the sealing that makes the thing work, not just moving air around but getting only the cooler outside air moving through.

    Phil

  10. #30
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    Default Re: Air Circulation In Summer Without A/C?

    4 degrees is a lot because it is a huge surface area. If it was 4 degrees over a couple of square feet, then it would not be a big deal, but 4 degrees over the area the size of the ceiling can pump a lot of BTU's in the space below.

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