Finally have my AC working properly again, after 4 or 5 visits from the AC group that replaced the evap coil.

Got to thinking about it when reading in the elect bill thread in WYD:
https://sigforum.com/eve/forum...0601935/m/8950093205

Our house is roughly 1970 sq ft, single story, built in 1976 & nearly full-gut remodeled around 5 years ago, with a semi-converted garage.
1 main AC & 2 mini splits (1 in the garage, 1 in the tiny house in the back)
Pool & a couple fridges & a deep freezer.

With this overly hot summer, our power bills have been the highest we've ever had in nearly 13 years of home ownership.
We had lower summer bills in our nearly 4k sq ft 2-story former house, which also had a pool (but also had 4 ~2014 solar panels).

I spent some of the time in the attic with the AC guy on the last visit & it's stiflingly hot up there.
We have good soffit vents, but no ridge vent [that I've noticed, I need to get on the roof & blow off the pine needles, so I can give more attention to any attic vent sources then], so I'm guessing the heat really doesn't have a lot of method/path to escape.
Also, the area over the former garage has no blown-in insulation, something that stands to be remedied & could probably do with adding a bit more elsewhere.

Doing a bit of reading, the ridge vent doesn't seem like an overly daunting task
Alternatively, a powered vent fan is less roof destruction & a couple hundred $ cheaper
Adding radiant barrier seems fairly simple as well

Given all that, what would be the pros/cons of a ridge vent install over a powered fan
And, is DIY radiant barrier as simple as it seems?

Ridge vent is non mechanical

The fan, at some point is going to go "Pbhhht" on you. Thermostat, motor, switch, something...

And I'll tell you when it's going to go out on you: The second hottest day that year. You're gonna have to get up in the attic, which is about 7 degrees cooler than a pizza oven and fix it.
But the important thing to remember is, it's the SECOND hottest day, at least it's not the first!

Ask me how I know this.

That is something I had in mind with the powered fan over the ridge cap

RE: Ridge vent, full length of the roof, or is a partial vent [in the center?] sufficient? I have about 50ft of peak end-to-end of the roofline.

If you put a fan up there, consider a solar powered one. Ours has been trouble free for 12 years now.

Your utility company may have a program to have a free energy audit (Duke Energy here does, and I took advantage of it) and if so you may get a free expert opinion for your specific situation.

You might put on a small solar panel system, since that was what reduced your bills at the large home.

Have the vents installed by a pro roofer, one it gets done right, two you are not up there putting them in, and if it leaks, it's their problem...

You might want to have the existing insulation added to, or replaced since it's an older home. Some companies will vac out the old insulation, which is good if you have or the house had pests that left little droppings in the attic. Then blow in a greater R factor with new insulation.

As far as the garage, the guys doing our home said it probably won't make a difference in your power bill if the garage isn't on your central air. You did say you have a unit out there, so if you are running that unit, then it could help to insulate it.

I looked at the powered vents and the conclusion I found from several sources were similar in that they are not really a good idea.

Hard-Wired Powered Attic Vents

Example of a hard wired power attic vent, pictured from the exterior of a home.
Powered attic vents, also known as powered attic ventilators or attic power vents, are electric-propelled fans that help pull stale air out of an attic space. They work much like a box fan placed in a window on a hot summer day. They can effectively pull the hot air out, but come with a tradeoff of higher electricity costs.

Overall, one of the main reasons for attic ventilation is keeping your attic at a constant temperature when compared to the rest of your home. In the summer the space may be a little warmer and a little cooler in the winter, but what we are trying to avoid is extreme temperature fluctuations from season to season. This is important to note when discussing powered attic vents because their power can often be either detrimental to a ventilation strategy, or not powerful enough to make a difference at all…

According to Danny Parker and John Sherwin at the Florida Solar Energy Center, “vent fans have the potential to reduce measured peak summer attic air temperatures by over 20 degrees farenheit. However, the impact over the cooling season is fairly modest with well insulated attics.”

Another point mentioned in Parker and Sherwin’s abstract is that the study took place in an area where homes are heavily air conditioned. This suggests that the powered vents could actually be pulling cooler air up through the main floors of the home and out of the attic, thereby increasing energy costs and forcing the air conditioning unit work harder. If you wouldn’t place a box fan in a window when there’s air conditioning cooling that same room, then it may not make sense to use a powered attic vent if you are utilizing air conditioning to cool the entire home.

Finally, Parker and Sherwin note that the existing homes in the study did not originally have a exhaust ventilation, like a ridge vent. This is a major point because the addition of any exhaust to a system lacking one would be beneficial, whether that vent is powered or non-powered.

Weaker powered vent units can be just as damaging to your home’s ventilation strategy as the strong ones mentioned above. According to other homeowner reports, weaker power vents have a tendency to circulate air rather than expel air. While a consistent air flow is important for avoiding mildew buildup, what’s needed most is the discharge of hot air from the attic. And weak powered vents just don’t cut it.

On top of the apparently complex downsides mentioned above, you have the electricity costs. Hard-wired power attic vents need to be plugged into your home’s power source, inevitably increasing your energy bills. Though the added costs may be small over days or weeks, the increases start to add up over the course of months and years. Higher operational costs is a substantial reason why traditional hard-wired systems have transitioned to solar power over the last few years.

Solar Powered Attic Vents

Solar powered attic vent, pictured from the exterior of a home along the roof line.
Solar-powered attic ventilation removes almost 100% of the electricity costs associated with older hard-wired vents but does not eliminate the negatives that come with powered attic vents in general.

Simply removing electricity costs does not change the way the unit operates. The fans are often either too powerful, or not powerful enough. There’s unfortunately no way to guarantee you get it just right. And when added on top of a proper vertical ventilation strategy (like a ridge vent exhaust and soffit vent intake), powered vents can actually have damaging effects that wouldn’t have otherwise existed. More is not always better!

For these reasons, it is best to use more natural, time-tested methods of exhaust for your roof. If you already have proper venting in your attic, then you are better off without the addition of a powered fan, even if it is run on solar panels.

Link

Solar is likely more than we want to spend. It was already there on the old house, so I don't really know how much it affected our monthly elec bills.

RE: Garage
We do have a mini-split there, but it also has 1 register tied to the central AC, but it's the farthest register from the unit, so it's about like an asthmatic blowing through a straw.
The garage also has an attic access that could probably stand to be sealed a bit better, but it's never uncomfortably hot in there. We don't run the split in there 100% of the time. Long-term, it'll be my home office & it's where our Peloton bike is located.

Thanks for the attic fan info. The idea of a smaller cut into the roof is appealing.
I'll need to really look around next time I'm up there, or in the attic, to see if there is an existing path for the heat to escape, but I don't recall there being a ridge vent or anything, but I haven't actively looked for it.

I would close off the AC vent from the house to the garage, no way it can be efficient and doing that will force more air back into the insulated dwelling, In fact probably smart to close that off permanently.

You should see some kind of roof vent, typically on the back of the house if you don't have a ridge vent system either box vents or off ridge vents, if not then you should have gable vents at the ends of the roof. There has to be some kind of venting, the roof/attic has to breath in fresh air and out old stale air.

A ridge vent is superior to a powered vent.

The problem with powered vents, aside from the fact they're electro-mechanical devices, so they will eventually fail, is they can lead to sub-optimal attic air exchange. This is because they can cause the air exchange to be limited in coverage, resulting in air stagnation in some areas. Air stagnation leads to mold, mildew, and rot.

Thanks gents.
Will try to get up there [roof & attic] after work & take a look at what's preset right now.

I put a gable vent in my last house bought from lowes. Came with a switch that was temperature sensitive, all I had to do was Mount it to the interior gable vent and plug it in. IIRC I set it for 100° and let it run. It did reduce the hot air in the attic and with it being automatic I didn’t have to do anything

I had to Mount mine like in the photo as there was no stud that fell within the mounting bracket. Behind the plywood I closed in the gaps so the air would go out the gable vent and not back into the attic

I didn’t hard wire it in, just ran an extension cord from a nearby outlet and clipped the female end off and wired it into the box on the fan.

My In-Laws have something similar, but also have a ridge vent. Their house is similar in age, maybe early 80s if I had to guess.
I'd have to see if there is a suitable place to put something like that. With how our attic is, I think a roof mounted powered fan would work better, if I went that route.

IN San Diego; we put in a whole house fan (Quiet Cool) which is quiet (unlike Whisper Quiet) and vents the attic.

Down side: it pulls air through the house then through the attic before venting outside.

Being close to the ocean, humidity is rarely an issue

Class A contractor with over 3 decades of experience and now a consultant for homeowners in dealing with their contractors…

First I’m assuming you’re dealing with a shingled roof. If that’s the case AND your roofing deck has a 4” gap at the peak (2” on each side) then the installation of a ridge vent is THE way to go. Nothing mechanical to break down and will last the life of the roof. I would recommend hiring a qualified roofer as while it’s not rocket science there are some tricks that will lead to a better install. They can also cut the deck for the gap if necessary.

I would recommend using something like this..

https://www.gaf.com/en-us/roof...vents?Action=GetGrid

As a side note one of my current clients had the same issue with a black standing seam metal roof (Before I got involved) I found out that the roofer didn’t install a ridge vent so the owner had the builder get his roofer to come over and “fix” it. Well it was still hot as hell and when I went over to look at the install (at 0700 hrs) I found out that the roofer didn’t cut the underlayment out of the ridge…

You can imagine the conversation between the builder and contractor that ensued…;-).

It has been my experience that power roof vents typically don’t last… Try the ridge vent first.

This message has been edited. Last edited by: smlsig,

I chose powered vents. Spaced at roughly 1/3 distance from each gable. Set thermostats to reasonable level. Work very well. Reduced temperature in attic about 20 degrees. Yes, people say you are pulling ac air to the attic. Not evident by my electric bill.

Had wind driven turbines. Have to be lubricated from time to time. Ridge vents installed by a pro is the way to go.

Cool ply for the deck panels produced an attic temp much cooler than similar houses in my neighborhood. This was for a previous house that the builder allowed me to modify. I had installed cool ply (Looks like aluminum foil glued to bottom of roof decking), full length ridge vents as well as brick vents about 6 in up from foundation. No soffit vents.

Iunderstand a cool ply-like material or paint can be retrofit or painted on.

This is called “vent skinning”. Instead of drawing air in through the soffits, air is drawn in through the near ground level vents carrying hot air upwards through the outside wall space into the attic to go out through the ridge vents. The backs of the bricks heat up and radiate against the outside surface of the inside wall material thereby heating the interior walls.

The upward airflow carries this heat into the attic reducing the wall heating.

There’s also a paint additive available for inside walls that helps reflect heat back towards the brick space kinda like cool ply but I know little about it.

Update
I've been on the roof half a dozen times in the last year, never noticed the 3 ridge vents that are there.
So, I've got ridge vents.

On to other methods to bring down summertime heat up there:
Radiant barrier on the underside of the roof?
Add insulation to the existing & over the converted garage?

Both seem viable DIY projects

This message has been edited. Last edited by: P250UA5,

Make sure that the holes cut for your soffit vents are cut to size. My house was built in 2000 and the holes were about half as big as they needed to be. During my last roof repair i had ridge vents installed. Being a data nerd I bought some cheap wireless thermometers that measure temp and humidity to make sure the flow was moving heat and humidity. The brand is Mocreo. They have a phone app.


ETA. The Mocreo thermometers are rechargeable. The charge last about 2 years.

Good luck
-TVz

Am a believer in ridge venting as well as adding at least one turbin fan depending on the attic size as well a shape of the roof causing dead air and unmoving air spaces.. .............................. drill sgt.

One of the best things I ever had, house wise, was a whole house fan. It was mounted in a hallway ceiling and vented into the attic. When it was on, it did a great job of cooling the house and the attic. It was quite powerful and on full blast, sounded a C-130 taking off. I would own another on in a second.