The mesh of the vent would not allow anything larger than an ant to pass through it.

If the vents are installed correctly they will work.

Whether a ridge vent is the best design for you depends on the design of your roof/attic, the insulation location and your climate. It is usually the best because it reduces the required vent area by half when installed with eave vents.

There is nothing to love or hate about a ridge vent IMHO.

The only thing that I can say is, on the family room addition I can see that I get now get snow melting along the ridge vent and refreezing on the gutter (producing a large ice dam) which was not much of a problem before with the 2 pot vents. I don't know why this would be, except probably the pot vent allowed warm air to exit above the snow so it didn't melt.

I do know that you have to be sure that the soffit/eave vents are not blocked by attic insulation and there is good air flow up to the ridge vent. Also don't put in a power vent as well (as my roofer sold to me) since then neither one will work correctly.

If you are on the roof and can feel air flowing out the ridge vent, you know it is working.

Raee - did you put roof venting along the entire ridge line?

What do you mean by a power vent? We have two attic vent fans right now. They discharge from the gables. They make so much noise, I hate to use them.

A continous ridgevent coupled with continous run soffit/eave venting will be interrupted by any other venting type such as gable vents with or without the fans. If you go ridge/soffit venting, you'll want to block off the gable vents. You dont have to remove them, block them off from the inside or outside if not accessible from inside the attic.

The purpose of ridge and soffit vents is to allow excess moisture to escape from the attic space rather than to cool the attic. The use of mechanical fans would also do that but their primary purpose would be to cool an uninsulated attic in very hot weather.

In order for someone to properly design the attic ventilation system they would need to know the climate, the orientation, the shading, the shading, and insulation. As with most building design systems, there are few simple rules that apply to all conditions.

I am so confused. The first roofer I saw today said that he puts in ridge vents for all his installations. The second roofer I saw said that it is a big waste of money and to just put in a couple of $35 domed vents.

We are in Southern California - - there is no shade near the house or garage - no trees - - we added insulation the last time we re-roofed back in 1996.

Presently, we have gable vents and the two power fans that sound like jet motors. They have to be manually turned on with a light switch. We use them during hot days in the summer. My husband thinks it helps the house to cool down. I can't say I have ever noticed a difference.

Our house is a single story.

Plumeriavine, Do you use evaporative coolers,(aka swamp coolers)? If so I might be able to advise you with the use of up-ducting coinciding with your gable vents as well as strategically placed dormer roof venting. Continous run ridgeventing along with continous run soffit/eave venting is mandatory up where we are building in nor cal, but is rarely used in so cal. Here in the mojave desert I installed ridgeventing on a roof replacement project, but up ducting working with the attic ventilation is what gives you a cooler attic when using evaporative cooling units.

The mention of radiant barrier in your other post, it can be installed to work together with a ridgevent/eave vent system by stapling it to the underside of the rafters in the attic. You hold it up 3" from the eave vents and is then overlapped up to the ridge and overlapped there. Some use foil tape for the seams. The hot air is trapped in the rafter spaces and is carried out through the ridgeventing by way of air coming in at the eave vents. If you have existing open rafter tails with occasional eave vents every four to six feet, you would want to make every rafter block a vent for a continous run eave venting.

The two separate issues of moisture ventilation and cooling the attic are very confusing to most people.

Part of the problem is a misunderstanding about how heat enters the house from above. The sun heats the roof surface and the underside of the roof becomes hot. That surface (if not insulated or there is no radiant barrier) radiates infrared heat to the floor of the attic. This form of energy does not heat the air but the hot floor does. A radiant barrier at any location in this energy transfer path is very effective however blowing the hot air out of the attic is not very effective in reducing the heat gain in the shingles and the ceiling of the room below and it often brings in hot humid air from outside not to mention the cost of running a fan all day.

Ridge and soffit vents along with sufficient insulation (and a radiant barrier if the climate is hot enough) are much more effective than the old method of blowing air through the attic. Yet many builders and manufacturers still hang on to the "intuitive" concept that fans save energy and increase the longevity of the roofing materials.

Would most homes in Southern California be good candidates for radiant barriers (excluding coastal areas)?

It would seem to me to be a good thing to be able to choose the roofing material you want (aesthetics) and put it over a radiant barrier.

Are radiant barriers expensive or heavy?

Would it go on top of the plywood?

Anyone ever do cost/benefit ratios for radiant barriers?

Thank you all for your input. Sierraeast - I do think we could staple the radiant barrier to the underside of the roof at the rafters in the full attic for our main house.

In our guest house area, there are no attics to speak of.

The guest house does not have plywood down, so we are adding plywood on the reroofing.
I don't think we could use a radiant barrier there because there is no air space/attic. Am I right?

"Would most homes in Southern California be good candidates for radiant barriers (excluding coastal areas)"? Yes

"Are radiant barriers expensive or heavy"? No. Radiant barrier comes in rolls typically 50" wide x 1000'. It is a foil faced one side with fiber mesh inbetween kraft paper on the back side. You can get it foil faced both sides as well.

"Would it go on top of the plywood"? The mention of radiant barrier in your other post, it can be installed to work together with a ridgevent/eave vent system by stapling it to the underside of the rafters in the attic. You hold it up 3" from the eave vents and is then overlapped up to the ridge and overlapped there. Some use foil tape for the seams. The hot air is trapped in the rafter spaces and is carried out through the ridgeventing by way of air coming in at the eave vents. If you have existing open rafter tails with occasional eave vents every four to six feet, you would want to make every rafter block a vent for a continous run eave venting.

I'll ask again, if you have evaporative cooling, up ducting with your present gable venting,(without the use of the fans), and dormer vents offer an inexpensive and reliable way to not only cool your attic, but keeps the power and water bills down by your cooler not having to work as hard or come on as often. In many cases on installs that I have done using up ducting, the homeowners never needed to flip the cooler on high cool whereas before the install, high cool was necessary in the warmest part of summer. You can install the up ducts yourself, or if hired out, would be an inexpensive "hire".

Yes, the venting is along the entire ridge. The roofer did this when I replaced the roof--I had talked to him about how hot the upstairs was in summer in spite of the pot vents, and he suggested a power vent--which he installed in addition to the ridge vent. Mine is not in the old eave vents, but is through the roof. He did not block the eave vents or tell me I needed to (but they were pretty well blocked by the replacement siding already).

It also was/is very noisy--enough to awaken us when it came on at night. He replaced it, saying it was a faulty unit. Still noisy, and as we got into autumn it was coming on in the middle of the night when temps fell to around 40F. He couldn't explain why. I was worried that it would be pulling heat out of the house when I wanted to keep it!
So I called the company that makes the vents. They told me that one reason it was so noisy was that it was designed for a much larger attic than mine (which is only about 500sf), and very likely was not getting enough airflow. That is also when I learned that mixing venting systems causes neither to work effectively. They told me some things to do to the stat to keep it from coming on at inapprop. times too.

The radiant barrier insulation is very light, it comes in big rolls and looked like foil-coated bubble wrap (at least the type I've seen). It is stretched across and stapled to the bottom of the rafters--the plywood is laid on the top of the rafters--this leaves a channel for airflow between, from the soffit to the ridge vent. So if you have rafters you can add the barrier.

I remember how hot it can get in SOCal and how expensive utilities are--I would add the barrier if I had the coin to do so. Don't see why coastal rea would be an exclusion though.

Regarding the guest house, Are you pulling up the existing roof boards and replacing it with plywood over? If that's the case, you could run strips of radiant barrier down on the backside of the ceiling material, then run insulation that isn't as thick as the rafter width leaving an air space, then do the ridgevent/eave vent thing. They have a sheathing, ( osb ), that has foil on the underside called tech sheild. I dont know it's effectiveness layed down over the rafters and there are opinions that shingle life is shortened due to reflectivity of the heat transfering from the ply to the shingles with the heat having nowhere else to go. If you are running plywood over the existing roof boards, you might consider running furring strips on top of the existing roof boards running the same as the rafters,(over them) which would leave you an air space. Then lay down the tech sheild or drape radiant barrier over the strips and then plywood using a ridgevent and a ventilated drip edge at the leading edge of the roof.

Here is a link that might be useful: vented drip edge

Hi again!

Everyone is so helpful!

No, we don't have evaporative cooling. Honestly, I didn't think anyone did anymore. That's the old swamp cooler that you put water or ice into? Maybe I don't understand the term.

We do have air conditioning.

We have gable vents.

We have some "attic fans" that were put in back in the 90's by our last roofers.

I've never been in the attic, so I don't know if there is any up-ducting, but I tend to doubt it. I'll try to find out, though.

The ways to do the radiant barrier for the guest house sound intriguing. I wonder if it would be better to do the radiant barrier only with a less expnsive shingle if the life of the roof might be shortened by having the heat reflecting back up under it. A more expensive decorative shingle may be a waste in that situation. I have to explore this.

Clearly, re-roofing is not simply throwing on new shingles. You could possibly make the houses more pleasant by making some smart choices with ventilation and barriers and proper insulation.

It gives me pause to ponder the conundrum that more ventilation doesn't create pleasant redundancies but instead can be counter-productive.

My poor roofer! He's going to hate me when I ask him to help me figure this out!

You wont have any up ducting with a/c. It's only beneficial with evaporative coolers.

If your roofer likes the idea of furring strips on the guest house, you could lay down the radiant over the existing roof boards, then the strips, then the plywood which would have the airspace needed between the old roof boards and new sheathing. Couple that with ridgeventing and ventilated drip edging and you should notice a big difference in the guest house.

I was reading about evaporative coolers - - those are pretty modernized now. I was thinking of the old swamp cooler my grandmother used to use. Evaporative coolers have come a long way, but aren't good for humid areas. It would probably work for us, but our air conditioning is still going great. Might be something to consider for the guest house.

The radiant barrier won't cause the shingle life to be reduced; even radiant barrier sheathing is allowed in most warranties now. Your roofer will probably think otherwise if he's never read an independent study on the subject.

I would like to replace my roof shingles (tear out 2 layers of shingles and replace), but I am also interested in siding and windows. When I do the siding, I am going to have the old cedar shakes removed first. Is there a problem with doing the roof before the siding? My house is a split level, so the lower half of the roof butts up against the siding on the upper half.

Is there a rule of thumb when installing a roof and siding at the same time?