New Roofs - Power Vent vs. Hip Roof Side Ridge Vents
 

Yes, I am getting a new roof. It's original from 2004.

My insurance company has suggested that I replace my large power vent with two hip roof side ridge vents. He said it would be more aesthetic, lower my electric bill and actually function better. I have found articles on the web that seem to support this. Has anyone done this?

Any thing you can do to remove any rotating powered equipment the better, less fire hazard, lower electric bills

Have you considered solar-powered fans? They are more effective than vents and, being low powered (not mains), are not a significant fire risk.

I have the vents and no fan. I have check the tempeture between outside, garage and attic. The differences ranges up to about 10 degrees. Now the garage is cooler than outdoors in the morning and the attic is a lot hotter in the evening so a fan running in the evening might be of some help but overall I don't think a fan is needed, epically during the afternoons. Turn off you fan and measure the temps and see what happens with your house.

Facts
 

Let's discuss facts rather than make generalized statements. My facts are based upon a electricity monitor which checks power consumption 10,000 a second. I know how much a fan costs to operate, time of day, hours and minutes a day, month and year

Powered fans come in three flavors, solar, big box store power fans and efficient fans, usually found on line.

I can state unequivocally that solar fans do not operate well into the evening that a thermostat controlled fans do. In other words it quits before the job is done. Readers may love, love their solar fans but that is the cold hard truth. Not enough? Our home inspection guru who posts here is in hundreds of attics here has posted that they make no difference in perceived temp.

That leaves powered fans. But wait exactly how long do fans run in a year? 213 hours.

A big how store fan uses 380 watts or 80.94 kwh a year. At SECO rates that is 9.46 a year.

An energy efficient fan consumes 22 to 120 watts (multiple speeds) or up to 2.99 a year. Quiet cool fans on amazon.

So, cost of operation is simply NOT a factor. You have been given bad advice based upon folklore. I would retain the power vent.

Thanks for that info but how do you figure only 213 hours a year?

The energy monitor tells me what is running for how long for which days and how much it costs.

You may think the fan comes on and stays on for hours, it isn't always so. It can come on, cool the attic shut off only to come on again . A rain storm almost immediately shuts off the fan as the roof cools.

Now certainly we can debate run time for a fan set to 130 degrees vice 125. But that is not the point.

If you like discover what is on in your home, what is driving the bill. Sense energy monitor, Sense: Track energy use in real time to make your home more energy efficient., Amazon $299.

Neighbour had them put in, waste of money.

If you are referring to powered attic ventilators (mounted in your roof), don't bother. This has been researched by the energy labs. Heat is primarily transferred from the hot underside of your roof sheathing to everything in your attic through radiative transfer. An attic ventilator will not address the radiative transfer issue. Powered ventilators may also suck conditioned air from your home if the ceiling penetrations are not sealed well. Save your money.

It has been researched for identical homes built in (wait for it)


1979

Air ducts and homes in general are much more airtight then they were 41 years ago. It is a rumor that refuses to die.

Homes may be better sealed than previously but the physics of radiative transfer hasn't changed since 1979. There is a reason why radiant barriers, if properly installed, work. Power ventilators are not worthwhile because they don't address the primary mechanism of heat transfer. Reread my post as I used the words "may also suck conditioned air if the ceiling penetrations aren't sealed well ".

Ah, the difference between us is I know exactly how much radiant barriers save and you do not. Bottom line is radiant barriers will not save enough in your grandchildrens lives to pay for themselves.

I also have toured under construction homes here and have seen the sealing of the ceiling penitrations. Now if I were doing the ceiling it would be better but they certainly are sealed 'well' also the duct connections are sealed.

I am more confused than ever researching this online. Georgia has apparently even banned them!

Georgia Pulls the Attic-Ventilator Plug

Attic ventilator fans have taken a whupping in the court of building science, played starring roles on useless-products lists, and gotten roughed up in the comments sections of blogs. Now they’re gadget non grata in Georgia’s supplement to the 2009 International Energy Conservation Code.

Georgia allows solar-powered attic ventilators, but attic ventilators designed to use grid power “shall not be connected to the electric grid.” In other words, you can have one, as long as it’s not plugged in.

Dealing with the heat. Despite the compromise, the rap on attic ventilators is now anchored in code. Promoters of these machines say the devices help cool attics by exhausting hot air to the outside. However, attic-fan critics say the fans often draw makeup air from a home’s interior. During the summer, there’s obviously a major energy penalty if your attic fan is pulling air-conditioned indoor air from the living space into the attic through leaks in the ceiling.

Frequently cited research results from a study conducted in 1993 and one conducted by the Florida Solar Energy Center show that attic exhaust fans also can depressurize the living area to the extent they create potentially hazardous backdrafting conditions, particularly in homes with atmospherically vented gas appliances.

You have no idea what I know or don't know. Once again, the physics of heat transfer in the attic is dominated by radiative transfer. Attic ventilators will not address that issue. Continued rambling about ceiling penetration sealing doesn't change the physics. Got it?

Yes, that is part of it. However, people have assumed that you can save energy by trying to reduce attic air temperature with a powered ventilator. In reality, conduction of heat is less important that radiative transfer from the underside of the roof sheathing so they aren't effective.

The most effective technique is spray foam insulation on the underside of the roof sheathing with the attic sealed from the outside air. This insulates the roof sheathing so that you don't have a large hot radiator. This technique will keep your attic at about 10 degrees warmer than the air conditioned part of your house and really makes sense if your HVAC ductwork is in the attic. I speced this in my previous custom home (outside The Villages) and it is very effective. Unfortunately, it is an expensive retrofit - best done during the construction of the house.

I thought all the homes in TV were built with ridge vents. My CYV has them, I think that's really all you need. If you want more air, crack open the attic access steps in your garage. I use to do that, then I realized two things. The fire block to the house from garage is gone. Also termites don't live above 120 degrees, so those wooden trusses are about the only worry I have in a masonry home, so i don't mind a hot attic. My electric bill is never more than $85 with SECO anyway.

https://i.pinimg.com/474x/43/75/bd/4...3cd834907f.jpg

I know a tremendous amount on attic cooling in TV. In fact I have 631 billion* data points on this. I will never understand why posters here can not appreciate it when someone is helping with facts supported by reams of data.

*10,000 a second for two years

I tend to believe the scientists who have done real research on building science. Being a scientist myself, I go with the facts. You don't seem to understand basic physics. Whatever, feel free to carry on.

Then you will appreciate that the actual savings from radiant barriers are 3 to 5 percent of cooling costs as measured by users. Or one to two percent of actual electric bills

Your best guide is the real world. But if you want a scientific study here you go National Renewable Energy Laboratory (NREL) Home Page | NREL › docsPDF
Internal Roof and Attic Thermal Radiation Control Retrofit Strategies for ... - NREL. It found 2.4 degrees Celsius cooler attics in those with radiant barriers. While 4.32 degrees is great a attic fan that can lower the temp ten to 20 degrees is better.

Guess what? That study found. Wait for it


Three percent savings in COOLING costs. So here we go scientific proof.

But feel free to carry on. Better yet do your own study as I have.

Instead of worrying about saving money, worry about making money, IMHO, most people would be way ahead if they invested the money they spent on energy saving devices & other things related to their domicile in the companies selling the technology and other related items.

The reason that I HAVE money to invest is BECAUSE I save money in a myriad of ways.

I guess you can look at this two ways.

1 - It doesn't cost much to operate since it only runs 213 hours a year.

2 - It doesn't do much since it only runs for 213 hours a year.

3. I have the thermostat set too high.

4. It is so effective than it only needs 213 hours to cool the attic.

Or something else.

But here again the OP got 16 years out of a roof that was power vented. Above average life expectancy?

Yes. Ridge vents are a must and are very efficient

Agree. Ridge vents are the only thing you need. They don’t wear out, stop working, or need replacing.

Agreed. Also, houses are designed with sufficient vented soffit area to match the ridge vents and the round passive vents at the top of the roof with respect to airflow. I believe the reason for this ventilation is to prevent any moisture buildup.

My oh my ….. we have some folks with their knickers on fire.

I am taking care of a friend's home. I knew he wanted to install a radiant barrier while he was gone, so I placed a remote temperature sensor in his attic. Before the barrier was installed, it read, on average, about 129 deg F during the afternoon. After the radiant barrier was installed, the attic's average temp was 113 deg F during the afternoon. The heat load on the ceiling is significantly reduced.

Why are you two getting so intense about a minor issue. It all sounds like a waste of money. Life is too short and I'm sure you both can find something better to do with your time than fight about who knows more about heat transference.

Yes, Foam is the absolute best. I have begged for two years to have foam sprayed in my new house, during build, but The Villages would not do it. But times are changing, and I’m hearing rumors that it might start happening.

I have no idea what the others here know or don’t know either. I do know solar powered fans have done little to no good on our Ivy. We have two but see no difference. I would suggest you get the advice of “real” experts and research actual facts and make your decision based on that. There are a lot of opinions on this forum, but they are just that.

I think you're saying that either method saves about the same amount? Neither seems like a lot of savings for the investment. 1 - 2% of my electric bill comes to around $20 a year. Not enough to pay for radiant. With a fan, a net of about $10 a year. That will take a while to pay off also. Not worth my trouble I think.

Hip vents are passive and will offer limited ventilation. Prefer Power Vent with humidistat.

You have a humidity problem in your attic? How do you know?

Yes, we specified spray foam for a new house construction and the builder took care of it. It works well and keeps the attic relatively cool. The attic is completely sealed to the outside. The only downside is that it is pretty expensive so there may be a long payback period. You do save some cost by being able to go with a smaller HVAC system because of reduced heat loading on the house. I did the heat load calculation myself (manual j) and got it correct - I specified a Carrier system with a 2 speed compressor and the system ran nearly continuously at half-speed during the summer with essentially no cycling - this is what you want. The installers must be careful to make sure their mixing guns are working properly otherwise you could wind up with an uninhabitable house. The spray foam is the mixture of two different chemicals. There are two types of spray foam; open and close cell. Each has their pros and cons. I specified closed cell. The attic, in south GA, never got above 85 degrees. The air handler and all duct work was in the attic.

If you get a chance, go visit Green Key Village just outside The Villages. They are building with spray foam insulation and some other proven energy efficient techniques.

Having been in the ventilation business in another life the only ridge vent that is any good is made by Airvent. But keep in mind that the wind has to be blowing to create a vacuum effect. The most effective method is solar power fans placed at the peak of the roof without any ridge caps thus preventing negative air flow, but you must have enough properly installed eave vents, i.e., with the vents facing out for any method to work properly. By the way, there is a 26% Federal Solar Tax credit on the labor and material costs of those fans.

Unfortunately, doing my research on the web leads to the same results. Totally different opinions from the "experts" too.

If your house is properly insulated, the venting that is there is sufficient. People try to sale items you don't need. Sorta like those houses with lighting rods. Cooling the attic by 10 deg will make no difference to your electric bill.

Who cares about the 10 degrees in the attic. Measure the ceiling inside the house and you won't see any difference. Measure a wall at the 6 foot level where your body spends most of your time. There will be no change. These vents are just a shell game by the sellers

Really
 

It's not 3% of your electric bill. The cooling of the house is only part of the bill. $100 electric bill, $30 of it for AC, so 3% of $30 is less than a dollar a month. Do get suckered in by a snake oil salesman

I also researched this. Those power vents are not nearly as effective as additional roof venting. Do you mind sharing who is your insurance company. First I've heard of an insurance company being that proactive with good info.