Attic ventilation in Phoenix area homes ? (rentals, houses, water heater)

[Farmer Larry]

Originally Posted by veritased

Thanks Farmer Larry. That is a good data point.

When people in AZ have to replace their roofs due to heat, what specifically is failing ?

The most common problem I have seen is the monsoon storms ripping off shingles, that happens when the adhesive edge fails and if the storms don't cause the failure the blazing heat will cause old shingles to start curling up and then it is much easier for the wind to tear them off.

[Potential_Landlord]

It seems to me anything besides blown-in insulation has a dubious ROI for Phoenix attics. Speaking of it - do you guys have an idea what it costs to have insulation blown in for a 2-storey 2000ish sf home? -Thanks.

[veritased]

From watching the videos and several other sources, seems like soffit vents around the perimeter to presumably some sort of ridge vent to allow air inside to rise and move out is a good move, especially if the ceiling is as sealed from the attic space as possible.
Which sounds like a good idea to keep pests out of your house, such as what I keep reading are scorpions falling through such leaky openings. So kill two birds with one stone.

If that's all true, then I still think a solar powered attic fan would still be helpful to reduce the afternoon temp rise in the attic closer to ambient outside shade air temps ? Solar powered moves less CFM than a powered fan, but then I see arguments in favor of just using that juice to run the A/C vs less efficient net cooling effect of an attic fan. I suppose $/BTU favors active cooling via HVAC, but solar comes for free.

[veritased]

Originally Posted by Farmer Larry

The most common problem I have seen is the monsoon storms ripping off shingles, that happens when the adhesive edge fails and if the storms don't cause the failure the blazing heat will cause old shingles to start curling up and then it is much easier for the wind to tear them off.

I see. In my upcoming home, we have what I was told to be cement tiles.
Maybe also the underneath layers can also fail after some amount of scorching heat.

[DougStark]

veritased, forget wasting your $$ on a solar operated attic fan. You'll NEVER recoup your investment.

Like I and others have said, just add a ton of blown in insulation in the attic and make sure your ducts don't leak air.

[Farmer Larry]

Originally Posted by veritased

I see. In my upcoming home, we have what I was told to be cement tiles.
Maybe also the underneath layers can also fail after some amount of scorching heat.

I really like tile roofs and they last a long time but you are right about the roof paper needing to be replaced every 15 or 20 years. My brother recently bought a house with a tile roof and he will soon need to have the paper replaced.

[Farmer Larry]

Originally Posted by Potential_Landlord

It seems to me anything besides blown-in insulation has a dubious ROI for Phoenix attics. Speaking of it - do you guys have an idea what it costs to have insulation blown in for a 2-storey 2000ish sf home? -Thanks.

I did my own with a friends help, bought my own blow in insulation and they loan you the machine for free if you buy enough insulation. It was rather easy to do, hopefully your attic is tall enough to move around in. I rigged up a long stick attached to the hose to reach the outer edges. My next door neighbor has the same floorplan as me but his attic has less than 3 feet at the peak and mine has about 5 feet, I would not even attempt it if I had his short attic. I did mine over 10 years ago and do not remember what it cost.

[Zippyman]

Originally Posted by Farmer Larry

I did my own with a friends help, bought my own blow in insulation and they loan you the machine for free if you buy enough insulation. It was rather easy to do, hopefully your attic is tall enough to move around in. I rigged up a long stick attached to the hose to reach the outer edges. My next door neighbor has the same floorplan as me but his attic has less than 3 feet at the peak and mine has about 5 feet, I would not even attempt it if I had his short attic. I did mine over 10 years ago and do not remember what it cost.

I had mine done with blown cellulose by King insulation around 2010, around 1900 sq feet with the garage & 10 inches of insulation.. We went from r-19 ish to r-50-ish. Cost then was ~$1500-ish (installed) There was a three man crew & a box-truck of insulation & they did it in just a few hours. The change was literally noticeable the next day - I remember it being the start of the cooling season & my a/c started kicking on a couple hours later in the morning after it was installed. We had a noticeable reduction in a/c bills immediately - but the biggest unexpected benefit was just comfort. The living room with vaulted ceilings didn't have "hot spots" anymore. Definitely worthwhile.

[DougStark]

Originally Posted by Zippyman

I had mine done with blown cellulose by King insulation around 2010, around 1900 sq feet with the garage & 10 inches of insulation.. We went from r-19 ish to r-50-ish. Cost then was ~$1500-ish (installed) There was a three man crew & a box-truck of insulation & they did it in just a few hours. The change was literally noticeable the next day - I remember it being the start of the cooling season & my a/c started kicking on a couple hours later in the morning after it was installed. We had a noticeable reduction in a/c bills immediately - but the biggest unexpected benefit was just comfort. The living room with vaulted ceilings didn't have "hot spots" anymore. Definitely worthwhile.

With many vaulted ceilings (my house included), you can't add additional insulation to the attic because there is no attic. Some vaulted ceilings follow the roofline, with about 4" of insulation between the studs.

[Hal Roach]

I would want an air-gap in the cathedral ceiling so air could escape the ridge vent.