I'm having my house re roofed. My house only has gable vents. No vent's on the roof. The roofer wants to install vents on the roof.?

put a ridge roof vent in and be done with it

They are not necessary but a good idea. If you can afford them yeh fine , if money is tight no.

it gets HOT in the attic and it is best that you install '' whirly-bird '' roof ventilators == this does help reduce that heat source and lower your electric bill .... get the vents .... the roofer is just doing his job by advising you ............

providing both gables has vents there is no reason the roofer cant install ridge vents ..i note you say you have batts between the rafters ..there should be a minimum of an inch air gap between the batts and the roof and a gap top and bottom ..you must ventilate

vents are usually louvered pitched downward to stop rain & snow from getting in there,w wire mesh to keep animals out,the vents ventilate so stale damp air gets a bit of constant air current preventing wood rot & mold from damage to interior supports,small wood slats are tacked on the glass edge tucked under the clamps, on each side where the roof guy cuts the square hole one small sq cut at the opposite roofline edges does no harm,they are quite necessary

The more ventilation, the better off, or so is the modern thinking. If that insulation is right up agaisnt the roof, then there may be an issue, If they want ridge vents and you are in a snow heavy area, there may be an issue. If you do not have proper supple venting for air movement, there may be an issue.

Have you had condensation issues, mold issues up in that area? Things like that would be an indicator that your current system is not working properly. Ask them to show you why you need to change it.

Attic walls, or the attic roof? Walls go straight up and down, let's be clear about terminology.

Are you saying there is insulation in your roof, between the rafters? If there is that's very good, but if it's tight up against the underside of the roof, there's not much point to adding vents. It would vent heat out of the attic but you already have the gable vents for that; the ridge vent won't improve the performance any.

Ridge vents are best for venting heat out of the roof itself, from an airspace between the insulation and the underside of the roof decking. If your insulation is tight against the underside of the deck, the ridge vent won't improve matters much.

I suppose the roofer wants to get a few extra dollars from you, as I think the gable vents are enough. This is all I ever had.

The question to ask is, why are the existing vents not enough?

Also, they subtract from the appearance, add a new opportunity for leaks, and add cost and labor to the project.

Why are you asking us and not your roofer?