My hot attic - conclusion

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First off - thanks to all for the comments and suggestions. I finally found my papers from when we bought the house and got ahold of the man who did the inspection. He's very knowledgable about this stuff and he assures me that if I do what I planned on doing - the attic will drop in temperature. This will in turn will allow the heat pump to work better since it's ductwork is in the attic. The end result will be a more comfortable bonus room, a heat pump that does not run as much, and if I'm lucky, an attic that's cool enough so I can use it to store more then just 'hardy' stuff. His reasoning is the R-factor of the ductwork insulation, and the differential between the outside air temp and the attic air temp. He went off on a bunch of stuff about BTUs, and such, which I didn't understand, but since he was helping me for free, I was polite and let him go.
to recap - I have 8 or so static vents on a tall peaked roof, that offer little help in moving the HOT air out of my attic, so I'm planning on replacing 2 of them with powered vents. there is a small heat pump in the attic which serves the ajoining bonus room, which is over the garage. Right now, the bonus room is always warm and the heat pump comes on very frequently, runs for 5 minutes, cools the bonus room down somewhat, then shuts off, only to come back on again in another 10 minutes or so.
His only cautions were: a) make sure the soffitt vents are clear (easy to tell by turning out the attic light and look for daylight). b) cover up all the remaining static vents except for one or two - the furthest away from the power vents I install.
I have a contractor coming next week to do the work and will report back the results - hopfully GOOD results. Yesterday the temp reached 112 degrees F in the attic.
thanks again, steve
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Steve Kulpa wrote:

112 degrees in a properly ventilated attic is not unusual at all. I don't know what your expectations are, but you may be disappointed.
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That may be true, and would be fine with me, if: a) it wasn't ajacent to the bonus room, which it heats up b) there wasn't a heat pump in there, with all the duct work c) I didn't need some storage place.
I'm disappointed now, so hopfully it won't get worse! :-)
steve
snipped-for-privacy@optonline.net wrote:

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Does the heat pump use attic air for its cooling air? If so, exhausting its output air though a gable vent, or using a vent for its input air might solve your problem, and increase its efficiency.
Bob
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Powered vents, 2? Unless you know how the house is built and how to run the numbers you could Increase the load on the AC by sucking house cooled air through the attic. With 2 units and your inspectors [ calculations ] you probably will. Your attic is not that hot, a properly designed and operating AC does this for millions of people. Get your AC checked first.
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Steve Kulpa wrote:.

For what it is worth the unbiased studies on powered vents all say that for homes with adequate ceiling insulation the power ventilator will use more electricity than it will save in reduced cooling costs. OTOH you can cool the attic somewhat which may have other benefits.
http://www.factsfacts.com/MyHomeRepair/ventilation.htm
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If it makes the heat pump run less - that's a good trade off imho!
also, there is no insulation under the roof, just above the ceiling
steve
Travis Jordan wrote:

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Steve Kulpa wrote:

I think he has a EXCELLENT plan. Inside attic temp is largely dependent on outside temp. I was told a properly vented attic shouldnt be more than 15 degrees above outside temp, that from a home inspector...
keeping the heat pump cooler is certinally a excellent idea
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Thanks! That's pretty much what the inspector I talked to said too.
steve
snipped-for-privacy@aol.com wrote:

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Temp difference is exactly what you need to look at to see if you are successful, the actual temp is obviously dependent on the weather and time of day.
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PipeDown wrote:

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snipped-for-privacy@aol.com wrote:

With a white tile roof and a radiant heat barrier, maybe.
http://www.fsec.ucf.edu/Bldg/pubs/pf337/index.htm
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Travis Jordan wrote:

Nice reference.
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snipped-for-privacy@aol.com wrote: ..

15 degrees difference is very little in some areas. A lot of what really is needed and what works and what is normal is area specific.
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Steve Kulpa wrote:

And keep it that way. Insulating under the roof will raise the temperature of the roof to the point it may become damaged. At least that is true for many areas and roofing types.

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Joseph Meehan wrote:

Do you have a credible cite for that? I suspect it's an urban myth.

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CJT wrote:

Well if I said it would start a fire, I would call it an urban legend. I may have miss worded it. How about "Insulating under the roof may raise the temperature of the roof to the point it may reduce its life" :-)

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Joseph Meehan wrote:

What little actual information I've been able to find suggests any temperature rise is on the order of a few degrees -- far less than the difference between shady and exposed areas.
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Steve Kulpa wrote:

Sorry I missed the first statement. It may not be a good payoff if the cost of running the fans is greater than that of running the heat pump.
Extra note about the heat pump. Since it runs for, I believe you said five minutes and then shuts off and you are not getting sufficient cooling in the room(s) it services, it sounds like you have an unrelated problem with the heat pump or the controls for it.
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Joseph Meehan wrote:

Certainly true. For the OP: is the heat pump (I mean, air conditioner) shutting off before the thermostat set point is reached? If so, you've got some other problem.
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