Roof ventilation

[CEPenworks]

We built our house 20 years ago and they installed ridge vents. Since the beginning the second floor would get warm in the late afternoon early evening during the summer. Doing some research I realized it was from the attic insulation becoming superheated and radiating into the house. That research also said the attic should be close to the temperature outside if properly ventilated, mine has always been significantly hotter. Now 20 years later I had a roofing contractor out specifically to look at the wind damaged barn roof and he also surveyed my house roof. The house has three large dormers whose ridges are below the main house ridge. He is claiming the ventilation is shunting from these ridges to the main ridge and we are getting no circulation from the soffit vents. Some of his evidence is moss and fungus growing on the roof at the base of the dormer ridge vents. He claims getting rid of the ridge vents on the dormers will significantly improve the attic ventilation and keep it cooler. Dose this make sense or is he blowing smoke to get more work? He wants to replace the whole house roof not just fix the ridge vents since it has a couple lifted shingles.

[Willyou]

It sounds to me like you have a very inventive contractor (don't blame him too much. He may believe it). What difference could it possibly make what path the air travels to be vented as long as it gets vented? If any difference, the shorter path would be better.
My logic tells me that it is unlikely that you can get the attic temperature equal to the outside temperature using only convection. I could be wrong, but I think power ventilation is required for that to happen. However, I also wonder if your ridge vents and soffit vents are all working properly. At the very least, you might have them checked to see if they are both large enough and fully open. I know there is a ratio of how big the vents should be as compared to the size of the house. I have to ask, Is there a large slot in the sheathing at the ridge under the vent cover?

[Snipe Hunter]

1st... moss will grow in the shade. Tree shade, dormer shade and north facing areas. It has nothing to do with insulation or ventilation. It has to do with moisture on the roofing material and not enough direct sunlight. No different than moss growing anywhere else.

I climb through attics all summer long. No matter how they are vented or insulated, they're always a lot hotter than outside the attic. As much as 40 degrees hotter. 20 years ago, attic insulation standards were a lot more lax than today. I see R-19 to R-30 in 20 year old homes. In my zone, R-38-R-60 is the norm today.

The ridge vent draw from the soffit vents. The only way to really cool it down is to draw air faster from the soffit vents. A lot of times, the ridge vent i cut way to narrow. They need to be widened. Also, soffit vents can be inadequate. Not enough vents, too small of vents, vents plugged with paint etc. The wider the ridge vent and the more soffit vent the merrier. Sometimes they didn't install baffles for the soffit vents and the insulation is blocking air flow. In humid environments, the old style cardboard baffles have flattened and no longer draw air. Some contractors only installed vented vinyl soffir every few feet. That's not enough.

You can check and fix these things. But it's still going to be hotter in the attic than outside. Attics have a lot of air volume that needs to continuously flow through relatively small openings. You could add a couple powered roof vents (not powered gable vents) and that will move a lot more air but yur soffit vents will need to be sufficient in order to draw all that moving air.

But again... moss ain't caused by lack of attic ventilation and has nothing to do with insulation. Mold inside the attic is.

[bobotex]

1st... moss will grow in the shade. Tree shade, dormer shade and north facing areas. It has nothing to do with insulation or ventilation. It has to do with moisture on the roofing material and not enough direct sunlight. No different than moss growing anywhere else.

I climb through attics all summer long. No matter how they are vented or insulated, they're always a lot hotter than outside the attic. As much as 40 degrees hotter. 20 years ago, attic insulation standards were a lot more lax than today. I see R-19 to R-30 in 20 year old homes. In my zone, R-38-R-60 is the norm today.

The ridge vent draw from the soffit vents. The only way to really cool it down is to draw air faster from the soffit vents. A lot of times, the ridge vent i cut way to narrow. They need to be widened. Also, soffit vents can be inadequate. Not enough vents, too small of vents, vents plugged with paint etc. The wider the ridge vent and the more soffit vent the merrier. Sometimes they didn't install baffles for the soffit vents and the insulation is blocking air flow. In humid environments, the old style cardboard baffles have flattened and no longer draw air. Some contractors only installed vented vinyl soffir every few feet. That's not enough.

You can check and fix these things. But it's still going to be hotter in the attic than outside. Attics have a lot of air volume that needs to continuously flow through relatively small openings. You could add a couple powered roof vents (not powered gable vents) and that will move a lot more air but yur soffit vents will need to be sufficient in order to draw all that moving air.

But again... moss ain't caused by lack of attic ventilation and has nothing to do with insulation. Mold inside the attic is.

Remember you have to balance your intake to your exhaust venting. Its about 300 sq ft of upstairs floor area per 1 sq ft of vent. GAF and Owens Corning have free calculators on their websites. I don't think the dormers would matter either way. Yes he is pretty creative. Soffit vents are the best because they are so low, just make sure they don't have any obstructions such as insulation baffles running too high.
Good luck, Haven't been on here in Years. Good to see some old names.
Robert

[Snipe Hunter]

If you want to get rid of the moss... carefully scrape it off. Apply Spray and Forget which is dissolved iron and zinc (iirc )and install zinc strips and/or zinc flashing to control it.

[EatenByLimestone]

On your new roof, have the ridge vent be either cobra vent or a metal variety. Make sure they put the end caps in the metal ridge. Don’t assume they did. Plastic ridge makes me lots of money when animals enter through it.

[Gary G™]

Consider a whole house attic fan.

[CEPenworks]

Thanks for the responses. I have another roofing guy coming on Monday I thought I would run it by him also.

[CEPenworks]

I had another roofing contractor look at the roof and comment on the ridge vents. He also suggested to remove the ridge vents on the dormers and possibly add a powered fan since the main ridge was not long enough.