Attic ventilation. Turbines or ridge vent?

Jim O'Dell

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2,783
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Between Aledo and Fort Worth, TX
I have been thinking for several months that I would add ridge vents to my shop building. It started out as a car port, that then was enclosed. No ventilation was installed at all. Not sure why it didn't rot and fall apart. A co-worker had a company come out and do a study on his house for energy efficiency and their comment was that it was good that he had turbines because they were better than ridge vents, and it was good that they were brown instead of silver. Does that statement make any sense to any of you? I'm not opposed to turbines since the house has 4 of them, but I thought the ridge vents were either equal or superior to them? I'm taking vacation time starting March 13 to fix my leaking valley at the shop. I'm planning to take off only the amount of roof I have to for the repair. But it will open up a perfect place to install one of two turbines that the shop would need, if they are in fact better.
If ridge vents are better, one Lowes has the model and color I'm interested in on close out for $6.29 per 8' section. The ridge vents would be cheaper because of this.
Thanks for any help you can offer! Jim.
 
Turbines are cool, we had them on several of our farm buildings...only problem is in time they start to squeak as the wind makes them revolve....so you have a maintenance isue you wouldn't have with the ridge vent.
 
Around here, everyone uses ridge vents. However, you have to deal with more consistent high temperatures.

Ask your salesman/contractor which system will move more air through your attic space.

With you being in TX, I would suspect that you would want as many air exchanges as possible in the attic due to the heat.
 
Jim, you do have other options available.

Gable Vents...sizes and styles vary. Installs into the gable ends of building.

Can Vents.....These require a hole of the correct size cut into your roof sheething and you shingle/seal these in.

Also remember to have eave ventilation (Duro-Vent) to move the air in your attic, and make sure nothing like insulation gets in the way (plugs them up) of these doing their job.
 
Thanks guys! I plan to do the soffit vents every bay to get good air flow, regardless of what type of roof vents I go with. I know you need as many square inches of soffit vents as you have in ridge or turbine vents. But is one type of roof vent not better than the other?
Joe, I'm the contractor, and I don't know jack :D. That's why I'm asking here. I don't trust the helpers at the home stores. I have a tool guy at HD I trust. I have talked to a couple plumbers, one at each of 2 HDs that were very knowledgeable and helpful. Watched one guy take about 25 minutes to explain to a couple how to install a faucet. Very patient and gave them the confidence that they could do the job. But most of the guys in the roofing section I've seen are lumber expediters.
Some information that may be helpful. The roof of the shop and the house have about 90% coverage in shade during the summer, which helps a lot. I'm a little unsure about cutting in a turbine when I'm not reroofing that section. Sounds like another leak to me. Keep the thoughts coming! Jim.
 
We lived in St Louis for five years and that is the only place that I have had turbins. Just like the guys are saying, they can make noise if not maintained. Also I had two of them blow off on two seperate occasions. I would stay away from them if possible. My neighbor here has ridge vents and he actually had ceiling water damage during a good blow from a thunderstorm. That is the only incident that I have heard of reguarding ridge vents but not many homes right here have them. My house, on the other hand, has neither ridge vents or turbins and my roof does not make noises, leak or have any rot and it is thirty years old with tons of humidity and heat. It does get hotter than the dickins up there though.

The system that I liked best is the power gable vent set up. If your roof line is such that they can be installed you might want to consider them. The ones that I have had did not leak, did not make any funny noises, required no maintenance and removed hot air at a high rate. I guess that the only downfall is that it does take electricity to run them. I do not know how many years that they will run before they fail.
 
But is one type of roof vent not better than the other?

Jim,

On the Canadian Ww'ing/DIY forums, discussions about roof turbines has been one of those hot button topics, almost like the Sawstop debate is on SMC. :eek:

Some folks think those whirly-bird unpowered turbines are great.
col442.jpg

Other folks maintain that they are no better than a non-turbine vent.
static-closeup.jpg

Some people rather ... aggressively disagree. :crash:

The main argument is that if the wind is blowing -- which is what you need for a turbine to spin -- then the wind will just blow through your roof vents anyway. One fellow actually kept track and and found that a whirlybird turbine was no better than a non-turbine vent.

Here is his findings. FYI. :thumb:

Personally, I had (officially) sufficient venting on my roof. It still gets darn hot in there! We put on a thermostatically controlled powered attic vent, it kicks in at 110F, if I recall, and we found that helped keep the upstairs bedrooms coller in the heat of the summer. Even with A/C in the house, we would get stratification because we have a large vaulted entryway for the cold air to "fall down" and we have kids that don't close their bedroom doors... :doh:
So this helps keep the heat out of the attic radiating down into the house. I wouldn't do it on a shop, but I think it is a good idea for a house.
 
As a home inspector I will way into to this. I have never inspected a home that had attic problems because of ventilation problems. I think every time I have found a problem it has been related to leaking roofing or flashing problems. Even here in the deep south where 75% humidity is common in the summer. As I understand it, the main purpose of ventilation is not cooling, but keep the moisture levels down which leads to rot. Cooling is really secondary issue and I am sure it does help keep cooling bills down.

Based on what I have read eve and ridge vents are the best because they encourage a natural air flow or air from the bottom to the top of the attic. They don't typically leave dead spots in the attic. So that is what I install in my houses I have built.

On my current house I couldn't because of the style. We have exposed rafter tails and vents would have been UGLY! So I just have large gable vents that fit the style of the house.

The only homes I have ever heard of having problem were with cathedral ceilings where there was on cavity left for air flow. Moisture would get trapped in there and rot the rood decking and sometimes the joists. I have not seen one yet, but I have heard the stories.

My 2 cents worth
Jeff
 
Even here in the deep south where 75% humidity is common in the summer. As I understand it, the main purpose of ventilation is not cooling, but keep the moisture levels down which leads to rot. Cooling is really secondary issue and I am sure it does help keep cooling bills down.

Jeff,

Careful... This is a regional thing.

In northern climates, cooling an attic is important -- even in winter. Proper venting keeps the roof cold, which is important. If the roof gets warm, then the snow melts and run downs, and when it gets to the eaves it freezes. This creates large (and impressive) icicles at the eaves. But more so, it causes the melting water to back-up under the shingles. All this wrecks shingles, wrecks eavestroughs, and wrecks roof decking.

But, venting to keep moisture down is also a problem, as you described. In the summer it is warm moist air, but in the winter, you also have moisture problems, as when the warmth migrates through the insulation, it can cause condensation if the attic is not properly vented.
 
Down here in Fl they are starting to go against "conventional wisdom" and eliminating all venting -- foaming the underside of the roof deck, including sealing the soffits. No venting what so ever. The idea is to keep the heat out of the attic entirely. It seems it is a feature of many high end houses.

here is a link

http://www.sprayfoam.com/spps/ahpg.cfm?spgid=66


We thought about retro installation but our house has scissor trusses and they couldn't get someone up there to do it -- best done before the drywall is installed

Jay
 
Interesting article Jay. It has some good points but I am a bit skeptical. And there are some big holes in there breathing wood logic there. Many new ideas have proved to be major problems so I wouldn't want to try this on my house till it had a few years to prove it worked in the field.

Things that come to mind are "Masonite" paper siding that deteriorates and has to be replaced. Synthetic Stucco that sealed the house and also sealed in the water and rotted homes from the inside out. Trocal roofing, that was a commercial product used on flat roofs. All seemed like great ideas but ultimately proved to be major headaches for the home owners and the manufacturers.

My first question is what happens to that sealed wood when your roof springs a leak? Once water gets in there there is no way out and no way to see you have a problem. By the time you find it the roof is rotten. Thats exactly what happen with the Synthetic Stucco.

It may be a great thing and it does sound like could be a great energy saver. I just don't want to be guinea pig. I know the conventional methods work. Maybe this will prove it's worth too. I've just seem to much over the years.

Jeff
 
Yes Jay, If you can use the expanding spray foam, there is no need for ventilation for heat in an attic. The barrier is such that it probably does ok for moisture also.
Using a simple dehumidifier with that set up would be ideal. Same thing with roof structures made with SIPs.
And Art is correct that regional requirements are different. I remember seeing that when I started doing some research on this subject a year or so ago. And I remember some This Old House episodes on roofs where they use a very sticky rubber membrain for the first 36" or so of the roof to help insure against the ice dams. And almost all of their projects are in the northern quarter of the US. Luckily that's one thing I don't have to plan much for here in Ft. Worth!
Jeff, thanks for the info. That is what I had understood in my research, but thought the energy guys comments were contradictory, and wanted some other opinions. Question, do you know if there is a difference in how the roof line is pointed compass wise that this works best? My main shop roof runs north-south. The finish room would then be east west. Most of our spring storms are from the southwest.
Allen, when I was redoing the exterior of the shop walls, I wanted to use gable vents for ease of installation, but the roof structure and the south gable were built in a way that I had 2X12 material stacked up in the way. In fact, the garage door was on that wall and didn't even have a header! That was acceptable for this type of structure, but it got one installed anyway when I redid that wall!! Thought about a powered gable fan for the north gable, then started investigating the ridge vents. This structure is really weird. The main shop building was here first as a carport (20 X 24). It was then enclosed. Then a slab was poured (12 X 24) next to it, but it was shifted 10' to the north, and a 12 X 14 covered patio created. When they added the roof on, they didn't cut the old roof off. Didn't even take the shingles off of it. (It is one of those valleys that is now leaking.) This basically created two attic spaces to deal with. There is a 2' X 4' section cut out right below the ridge at that wall, but it would still trap a lot of heat in the side addition. I imagine when I studded the walls for the finishing room, I tweaked something and created the leak. But that was almost 2 years ago, and this is the first time I've notieced it leaking.
Thanks again guys! If they are at minimum equal types of ventilation, I'll go with the easier to install ridge vents. Jim.
 
I can only speak from experience and observation with my present home. It was built by a very energy-efficient savvy guy. Our utilities bills are so low as to be the envy of friends. I believe part of that is because the vents on our roof are the square type (similar to what is shown in Art's post) but are powered vents and thermostatically controlled. In hot weather, if we are outside, they can be heard but are not annoying. They are painted to blend with the roof and are hardly noticeable. I'm pleased with the results and if I were building today, that's what I would install. House or shop.
 
After Hurricane Charlie at least 95 percent of the homes here had roof underlayment and tiles replaced. 80 percent of these homes were 20 years old or older with no attic ventilation other than some soffet vents and there was no rot unless there was a roof leak. To me that says just one thing, keep the mosisture out and you will not have rot. A roof leak is another story of course, vented or not.

The rule around here to avoid problems is to keep the moisture out. Keep your doors and windows closed and/or run your airconditioner. Same inside a boat. After living here for sixteen years I am a beliver. Do not bring in any new air filled with moisture. If you do dry it out right away.

I realize that this may not apply to other regions but for anywhere that there is not an ice and snow problem it seems logical to me. Jim, that lives near Ft. Worth and started this thread, does not have the humidity problem that we do nor an ice and snow problem so what does it hurt not to have great ventilation if you keep the moisture out and have good insulation? Personally I would do nothing in his case, except fix the leak, unless heat in his work area is a problem.
 
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Allen, I believe heat is the problem he is trying to eliminate. I have lived in houses that did not have good attic ventilation. Heat gets bottled up in them something fierce and can be felt radiating down through the ceiling into the rooms below. It is essential to get that heat out as best as possible.
 
Question, do you know if there is a difference in how the roof line is pointed compass wise that this works best? My main shop roof runs north-south. The finish room would then be east west. Most of our spring storms are from the southwest.

Jim, if your talking about just ventilation I would guess it wouldn't matter much. As it a gravity system basically. Hot air being lighter and rising to the top where the vents and draws in cooler outside air in lower vents. In the summer you can feel a breeze coming out of the vents sometimes.

If your just concerned about ventilation, me, I would just install a ridge vent. If your wanting to try to cool it off some more I would look at a powered vent of some kind high in the attic that would move more air through. I have been in a lot of attics and I think the ones with power vents are sometimes a little cooler, but there still hot as an oven in the summer. I think that you have to move a lot of air to really cool them down very much. I installed fans in mine but I have my doubts they are really effective.

Only measured the temp in one attic just out of curiosity. 130+ degrees. It was unreal hot in that attic and I happened to have my meter handy. Needless to say I got in and out as quickly as I could.
 
Hi Jim.

I think you are on target with the ridge vents. I had them in Ohio thirty years ago, and had them installed when we built in 2002. I can add little if anything to the above discussion, other than in the winter, regardless of where you live, you need ventilation in the attic to keep the ceiling insulation dry. Damp/wet insulation amounts to NO insulation. I have seen the borg selling plugs for the turbine vents, and people tying garbage bags over the turbines in winter. Those people might as will put a sign on the front of their house proclaiming 'I am one stupid &^%#$.'

I had the option to have a sealed attic when we built, but it didn't sound like a sound idea to me at the time, and I am still not convinced that it is. Show me an R-60 or better on the underside of the roof decking, and I might start to agree with you.(heavy on the might.)

My real opinion is available for a small fee.;)
 
Jim,

The Florida Solar Energy Center has done a lot of research on ventilation and energy efficiency in cooperation with Florida Universities. I have not been able to locate the report that I have seen on comparison of ridge vents vs turbines vs powered vents. However, as I recall, the study found the most efficient combination is ridge vents with equal air intake from soffit vents. I recall that the ridge vent system gives much more ventilation area compared to the turbines as used in typical installations. The link below does not directly address your question, but is an interesting read on energy efficiency in residences:

http://www.fsec.ucf.edu/en/publications/html/fsec-cr-1231-01/


Personally, I think you would be ahead maintenance and efficiency wise to go with the ridge/soffit vents.

Hope this helps,

Jerry
 
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