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Posted by RP on July 19, 2005, 11:04 pm
ron wrote:
>
> TURTLE wrote:
>
>>
>>>Lots of post recently about attic venting. One of my HVAC units is in the
>>>attic. Would an attic fan help with the HVAC? It gets pretty hot up there,
>>>even with a ridge vent and undereave venting.
>>>Thanks.
>>>
>>
>>This is Turtle.
>>
>>this is the hottest time of the year and you need to check the temperature up
>>there at about 3:00 P.M. . Any temperature of 120ºF or more up there is hurting
>>in the form of heat being transmitted into yoiur duct work to be brought into
>>your house.
>>
>>First Ridge venting in my opinion is trash because i have seen attic i would
>>have to go into with temp.s of 140ºF and have ridge roof vent system on them.
>>Now also here it is nothing to see 100ºF+ all the time and hot sun on the
roofs.
>>
>>Second Even with a Ridge vent. You can add a motorized attic vent and if the
>>ridge vent holds the temperature down . The Motorized vent will never come on
>>because of it being run by a thermostat to come on at set temperatures.
>>
>>TURTLE
>
>
> This is Ron,
>
> The real issue at hand is heat oppression and I agree with Turtle,
> Ridgevents are for the most part a waste of time. But i would go a step
> further and offer that electric fans as their presently offered are are
> an even bigger waste of money and energy. The issue is understanding
> the dynamics of heat. At dawn the roof gets hot, the air in the attic
> begins to warm, expand and then rise. Conventional thinking is that as
> hot air rises, it will draft through either passive ventilation or
> ridgevents, and replacement air will be replaced through your soffit
> ventilation. The bonus with a "ridgevent" is that any breeze might
> create venturi, and can be that much more efficient. It simply doesn't
> work, Heat pressurizes the attic and your soffit vents prove it every
> afternoon. Hold up a feather duster to your soffit and you'll see
> heated air streaming from them.
If you have air exhausting from the soffit vents then you either have
ductwork problems (leakage into the attic) or attic air exhaust
problems. This isn't normal. You could have a light breeze hitting the
opposite some other side of the house or a lateral breeze across the
side you're on causing a venturi effect. Normally there is a net rise of
air through the soffit. Heat doesn't generate extra air molecules. If
there is air leaving the roof vents then it had to enter somewhere
first. If its exiting everywhere through every opening then you should
probably call ghost busters or get the ductwork repaired.
hvacrmedic
> That pressure literally impregnates
> everything in your attic, including the ceiling itself. Heat gain
> compounds, once it's allowed to begin it cannot be stopped short of
> dusk. 110 volt fans are thermostatically controlled, they start out
> behind and never can catch up. In addition over 80% of all fires in
> attics are attributable to electric fans shorting out. I seriously
> recommend solar powered attic ventilation. It's proactive, It's on at
> dawn, before the heat of the day. A properly sized unit (1100 CFM+) can
> actually keep heat gain from happening all day long.
>
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