Do power attic fans help?

[Joe Mascitti]

IF those are 5 PAV's...the clothes would get sucked off your back while walking down the hallway...

[adrianf]

The House Is A System
•Research at the Advanced Energy Corporation showed that 40%of the air exhausted by a PAV is conditioned inside air!

The House Is A System
•Convection loops move only 20% of the heat from the roof deck to the attic floor!
•Radiant heat transfer is responsible for 80%+ of the heat transfer.
•So, you could create Hurricane Katrina in your attic and only affect 20% of the heat transfer.

The House Is A System The House Is A System
•Lessons:
3.“Improve”attic ventilation and run the risk of making the house more humid, more likely to grow mold, cause the electric bills to go up and possibly cause a fire or CO poisoning!

[Shophound]

If "The House Is A System" was more widely understood, we'd be well on our way to seeing not only greater energy savings, but higher comfort level satisfaction within our homes. We've been trained to seek active (read: energy consuming) solutions for problems caused by passive sources that have been inadequately considered. Concurrently we'll always need some level of mechanical climate control due to the design of most homes and the various climates we all live in. It just makes sense to place focus on the dwelling structure itself to do more of what it is supposed to do...give us shelter. Shelter not only from rain and sun, heat and cold, but the vagaries of climate that we all must live with.

[adrianf]

If "The House Is A System" was more widely understood, we'd be well on our way to seeing not only greater energy savings, but higher comfort level satisfaction within our homes. We've been trained to seek active (read: energy consuming) solutions for problems caused by passive sources that have been inadequately considered. Concurrently we'll always need some level of mechanical climate control due to the design of most homes and the various climates we all live in. It just makes sense to place focus on the dwelling structure itself to do more of what it is supposed to do...give us shelter. Shelter not only from rain and sun, heat and cold, but the vagaries of climate that we all must live with.

I have personnaly invited and paid for GCs to attend building envelop seminars. Of the ones that I have invited very few have accepted.

[mark beiser]

I passed by a house last week that had 8 PAVs visible from where I was. I didn't have time to turn around to go take a picture, but I'll try to remember to get one soon.
It was a large 6000+ sq ft home.
They were large PAVs too, probably rated for 1200+ CFM each...

The House Is A System

Amen to that!

[printmanjackson]

Saw this driving by.
If these are PAVs as they appear from the distace i'd like to be there when they fire them off.

looks like someone will be greasing the meter

I wonder how loud they are. I bet you can heard them from the street!

[steve3871m]

Some info:
http://www.energystar.gov/index.cfm?...ic_ventilation

http://www.eere.energy.gov/buildings...pdfs/26450.pdf

http://search.nrel.gov/query.html?qp...ic+ventilation

[texasmax]

Thanks all for the excellent information and discussion

[energy_rater_La]

I think it would be a wonderful thing if more people would understand the
house as a system.
One hvac owner I deal with has an ongoing argument with me about pav's.
Until I 'prove' to him that they don't work he will keep installing them.
Unfortunately..any 'proof' is by quote college educated idiots' therefore
not to be believed.
I avoid the topic as much as possible with folks with that mindset, they will
never chabge their minds.

good discussion folks. Long..but good!

[adrianf]

Two quick qualifing questions.

Is the earth flat or round?

Is smoking 2 packs of unfiltered cigarettes a day unhealthy?

But for the record the college educated idiots can be just as dense. My example: Measured air flow through a 5 ton system was 1260 in and 1260 out the recommendation was to clean the coil. The degreed individual didn't think there was anything wrong because you were getting out of the unit what went in

"In my experience, logic did not convince anybody at any point of time. As I read in a book the other day, only when the spoken word appeals to the other person’s self-interest, will or thought process, will logic be of any use. Logic primarily is to be used for rational beings, or inanimate objects, say with computers. Logic works perfectly in such a system because they are devoid of their own thought process and neither do they possess a sense of individuality and hence self-interest. Human beings are primarily emotional creatures. In an emotional atmosphere, there is no place for logic." Kiran

[Brian GC]

One hvac owner I deal with has an ongoing argument with me about pav's.
Until I 'prove' to him that they don't work he will keep installing them.


good discussion folks. Long..but good!

Hasn’t it been determined here that not all PAVs are bad…only the ones used with inadequate soffet and gable vents? In less than ideal situations, reducing motor rpm to 200 – 300cfm would make for a perfectly operating PAV. Low power with low cfms. Disconnecting a PAV should never be the first choice, it’s illogical.

Logic keep us out of trouble, emotions get us into it. Look at the animal kingdom, they’re 90% logic and do very well.

Brian

[mark beiser]

Hasn’t it been determined here that not all PAVs are bad…only the ones used with inadequate soffet and gable vents? In less than ideal situations, reducing motor rpm to 200 – 300cfm would make for a perfectly operating PAV. Low power with low cfms. Disconnecting a PAV should never be the first choice, it’s illogical.

Logic keep us out of trouble, emotions get us into it. Look at the animal kingdom, they’re 90% logic and do very well.

Brian

I disconnect them every chance I get, but I have the training and test instruments demonstrate and quantify the negative impact they have on a particular house.

At least in my area, the cost to fix the average existing home in my area, so that a PAV doesn't negatively impact the building envelope, would be far higher than any alleged potential savings/benefit from having it running.
It would not be economically feasible, if even physically possible, to seal many of the homes I see every day to a level that would prevent a PAV from causing unintended negative consequences.

Then there is the issue that virtually all of the homes in my area with gas furnaces and water heaters draw their combustion air from a ventilated attic, most of the time the appliance is physically located in the attic.
You can bet your a** I'm disconnecting any PAVs I find in those homes.

If you are building a new house, I'm a big fan of moving the the insulation to the roof line, and sealing the attic. It makes one hell of a lot more sense than having to deal with super heated air in an unconditioned attic.
Ventilated unconditioned attics in cooling dominated climates, with the air handling equipment and ductwork in the attic, are a pretty dumb idea, but it has been the norm for decades.

[Brian GC]

I disconnect them every chance I get, but I have the training and test instruments demonstrate and quantify the negative impact they have on a particular house.

At least in my area, the cost to fix the average existing home in my area, so that a PAV doesn't negatively impact the building envelope, would be far higher than any alleged potential savings/benefit from having it running.

Though my post was quoted you did not respond to it.

I'll pose the question again. Isn't reducing the PAV motor speed better in most cases than disconnecting it?

Brian