# Intake vents in livingroom ceiling?



## jeremy (Aug 18, 2012)

I am working on a roof in Maui. My client has had several roofers attempt to solve blistering over the years and fail because they never addressed ventilation. The roof has a pitched portion (4 sided pyramid) with a flat roof extending beyond on all 4 sides. The pitched roof attic is closed off from the soffit vents so it has no intake. It does have a solar fan roughly two-thirds up the roof but obviously is doing very little if anything without the intakes. My plan is to vent the ridge and disconnect and cap the solar fan, and install static intake vents on the lowest part of the pitched roof right above the flat roof portion.

What got me thinking was when I opened up the attic door the fan was running and it created so much air flow in the house that it felt like AC. My client loved it, so now I am thinking instead of intakes on the roof why not put the intake vents in the living room ceiling and install some nice covers over them. The windows are always open in the house so air flow should be good. I am going to insulate the attic floor as well with R39 so I am planning to run ducts from the vents though the insulation so the air can flow. Would this design reduce the effectiveness of the insulation? Or be a problem for any other reason? Thanks in advance for any ideas, I appreciate the help.


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## Grumpy (Oct 29, 2008)

If you never ever use air conditioning it's not a bad idea. There was a roofer (or owner, I forget now) who had a house in some Caribbean island and he had a similar situation, but he had a gable fan. 

Around here I would be laughed out of a job, but we are in different climates with different architectural techniques. 

Just keep in mind that you will be introducing moisture into what little attic space there is. Also keep in mind you might not actually be doing anything to air in the roof ventilation. Though your customer may feel better indoors, it might not do anything to ventilate that little bit of space between the roof and ceiling thus placing him in the same boat he is in now. 

What power is the attic fan? Most around here are 550 CFM, the strongest I know of are 880. That's not alot compared to most traditional hard wired whole house fans. The point I am trying to make is I am surprised a little 500 cfm fan was enough to make a difference in a whole house.


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## shazapple (Dec 3, 2010)

sounds like you're basically changing it from an attic fan to a whole house fan
http://en.wikipedia.org/wiki/Whole-house_fan


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## jeremy (Aug 18, 2012)

Grumpy said:


> If you never ever use air conditioning it's not a bad idea. There was a roofer (or owner, I forget now) who had a house in some Caribbean island and he had a similar situation, but he had a gable fan.
> 
> Around here I would be laughed out of a job, but we are in different climates with different architectural techniques.
> 
> ...


Thanks for your insights Grumpy, I appreciate it. I think I have decided to not put the vents in the ceiling. If it were my own home I would go ahead and make an experiment of it, as it does seem like a interesting idea, however I just can't mess with someone else's home without some empirical data. 

If you don't mind I am a little unclear on why the vents will not do anything to air in the roof ventilation? I am planning to vent the roof with Air Vent's the 'Edge'. Wouldn't that theoretically have the same effect as putting the vents in the ceiling? I have 128 linear feet of perimeter available to install the Edge vent, so 1152 sq. in. of intake. I have 8 feet of ridge to work with so if I vent that it should give me 144 sq. in. The fan is 550 as you correctly guessed, it is also closer to the ridge than I originally thought. Its center is a little less than 2 feet from the ridge, so the edge of its hole will probably be 12" from the ridge vent opening. I am wondering if I should just leave it running along with the ridge vent? The temperature of the attic is 115 degrees with 85% humidity. Thanks again for any advice.


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## jeremy (Aug 18, 2012)

Grumpy said:


> If you never ever use air conditioning it's not a bad idea. There was a roofer (or owner, I forget now) who had a house in some Caribbean island and he had a similar situation, but he had a gable fan.
> 
> Around here I would be laughed out of a job, but we are in different climates with different architectural techniques.
> 
> ...


Yeah I am not sure why opening the attic door had such a significant impact on air flow in the home because it is just an attic fan and not a whole house fan. Could it be just an initial movement of air due to the temperature difference between the attic and in the house? At least a 30 degree difference. I didn't have the hatch open long enough to see to if the air flow would stabilize.


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## Grumpy (Oct 29, 2008)

Oh I missed the part about the edge vent. I tend to ADD when reading lots of text  


I'm not a fluid dynamics engineer, and I don't even play one on TV, so I can't answer why the air movement is as it is. Certainly creating the opening can make a difference I am just as surprised as you it made the difference that it did. I was going to basically do the same thing in my garage, I have a solar fan in the roof over the garage, and put a large vent in the ceiling. My cousin who is a mechanical engineer pointed out the fan is rated at much less CFM than it would actually be drawing. So I placed that idea on hold, but now it might not be a bad idea at least to try and if it doesn't work, I didn't really lose anything. Pshhhh what do engineers know anyways?!


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## jeremy (Aug 18, 2012)

Grumpy said:


> Oh I missed the part about the edge vent. I tend to ADD when reading lots of text
> 
> 
> I'm not a fluid dynamics engineer, and I don't even play one on TV, so I can't answer why the air movement is as it is. Certainly creating the opening can make a difference I am just as surprised as you it made the difference that it did. I was going to basically do the same thing in my garage, I have a solar fan in the roof over the garage, and put a large vent in the ceiling. My cousin who is a mechanical engineer pointed out the fan is rated at much less CFM than it would actually be drawing. So I placed that idea on hold, but now it might not be a bad idea at least to try and if it doesn't work, I didn't really lose anything. Pshhhh what do engineers know anyways?!


Yeah I totally agree. Even if it does not help I don't see how it can hurt. 

With an attic floor of 700 square feet what do think would have a greater cooling effect on living space, a 1600 CFM whole house fan or R39 Attic floor insulation? again with respect to Hawaii's climate. For that amount of square footage the cost of install is about the same and we have solar power here year round so electric cost is negligible.


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## brianshaw (Jan 21, 2013)

I have rarely seen intake vents for the roofing.


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