Replacing shingles, have radiant barrier and... questions

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Old 04-17-17, 08:59 PM
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Replacing shingles, have radiant barrier and... questions

Live in DFW area (so north Texas). 4 bedroom single story 2600 sqf home, pretty large footprint. Steep roof (to the point where I'd never go up there).

About 4 years ago, I had radiant barrier installed. As a part of the deal, additional soffit vents were installed, powered fan from Home Depot went up and two whirlybirds were blocked up (but left in place). Ever since hen, we have kind of hated the powered fan as it is pretty noisy, but it keeps things cooler up there so we suffered it but no love for it all.

Fast forward to 10 days ago... got significant hail. The shingles need to go.

So I'm thinking as to what to do now.

I figure whirlybirds do not actually need to be replaced but they can close up those holes while replacing shingles.

But I'd like to do something about the noisy fan; sigh... what can I do? I found a page that claims to sell very quiet fans, here. It would need to be combined with something like this to protect the opening from rain.

Is this a fool's errand? Is there hope that we'll have powered ventilation without a lot of noise / vibration going into the rafters? Am I correct that I don't need to replace whirlybirds?
 
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Old 04-18-17, 03:46 AM
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Anything under power in an attic approaching 150 degrees will have a short life and will become noisy. My recommendation is a continuous ridge vent. It is passive and allows ALL the hot air to be evacuated as opposed to keeping a cap of hot air above the whirlybirds or forced air fan. I am certain you have contacted your insurance company with regards to the hail damage. Most will cover replacement less your deductible. Your roofer should recommend the ridge vent and close up all the other holes in the roof at the same time. If not, make sure he does.
 
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Old 04-18-17, 07:10 AM
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I agree 100%, just do not let them use any form of roll vent!
Roll vent is just that, it comes in a roll.
Also do not let them cheap out and use color mating 3 tab shingles for the cap!!
Use real hip and ridge caps.
 
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Old 04-18-17, 09:14 PM
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Thank you!

I am not sure that ridge vents are great option for me; the roof line is not a single continuous line like on the ranch home but yeah - they had to be creative with it all.

See attached for the sketch that the adjuster made; some of them different lines are at different heights too. (the line parallel to the bottom of the "U" is the tallest point)

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Last edited by bigboy; 04-18-17 at 11:16 PM.
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Old 04-19-17, 03:46 AM
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Aieee!! Creative is a word. I am only guessing at the tops of the ridges, but ridge vents are still your best option. Heat will rise to the highest point and sit there, so having a good ridge vent will allow that collected hot air to evacuate. I don't guess you have an aerial view of this roofline, do you?

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Old 04-19-17, 11:26 AM
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You, Sir, are correct in your assumptions. I do not have the side view similar to what I posted, but I indicated the sloping lines on the attached modified graphics.

I take it there is some math I can apply to this problem as in - size of my attic vs. the length of those specific horizontally running ridges and see if this would work? I have about a bajillion of soffits so on the intake side, I think I'm good (when installing the radiant barrier, the contractor added extra soffits to make sure that the powered fan will not be trying to suck cool air from the house).

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Old 04-19-17, 11:31 AM
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Now that the silliness has left me, of course I have the aerial image; Bing / Google etc...

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Old 04-19-17, 03:01 PM
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Resembles an SR71 Blackbird I still say, even with the limited horizontal peaks, you would be better off with ridge vents as opposed to powered or wind turbines, since the hottest air needs evacuation and it will settle in those peaks.
 
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Old 04-19-17, 03:37 PM
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Just to mention, they do have shingles with a high level of radiant reflection. The advantage is, it will reflect the heat before your attic has to deal with it. The RB you have still gets very hot and convective air flow adds that heat to the attic.

Although attic fans will help to keep the attic cooler it is very important that all leaks from house to attic are sealed along with lots of insulation. If not you end up cooling your attic with the your air conditioner.

Also, make sure you have as much as possible for low venting. With natural or powered venting there has to be lots of low vent area.

They also make hip-ridge vents. Local roofers will know if tornado or other weather is a concern.

Do you have mechanical equipment up there, like an ac unit?

Bud
 
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Old 04-19-17, 08:13 PM
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Thank you! That's what I was looking for (hip ridge term) - somehow I just did not find the right words. I'll ask.

Yup. Typical TX shenanigans going on in the attic: tank water heater (gas) and two AC units w. gas heat. I mean that's the way to do it; stick the AC units into the hottest part!

In related news, I really want to buy a thermal camera; I'm sure I'll find all kinds of leaks up there. Even once the units go (they are 15 years old now) - it seems to be a great thing to have around here.
 
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Old 04-19-17, 09:31 PM
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LOL, I was going to say that roof looked like TX but there are other places that get carried away also. It certainly would be a problem with our snow here in Maine.

Some of the air sealing is relatively easy and if you are on a slab there is far less because no crawlspace or basement involved. Attic access needs a perimeter box with air sealed cover. Recessed lights should be air tight and IC rated. Plumbing and electrical penetrations are easy to find. Inspect all duct to house connections and make the insulation continuous with ceiling insulation, no gaps.

Check the NFA (net free area) rating for your soffit vents and use one ft² for every 300 ft² of attic floor. That's a ballpark method for determining the total ventilation area you need. Then divide that half high and half low. Of course that is a natural air flow calculation which goes out the window with an exhaust fan. With the fan running I suspect all of the vent area will be intake, which can sometimes be an issue with pulling rain in the ridge vents. Always hard to predict and with your roof there will be no prior examples.

Bud
 
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