Full Face Helmet + Windshield?

I'm buying my first motorcycle soon. I'm going to wear a full-face helmet. My question is, will a windshield on the bike do anything for me? The majority of my riding will be at 45 mph or less. Occasional highway at 60-65 mph, but only for 3-4 miles at a time. Thanks!

Of course a windshield will aid in your riding comfort.
I ride two different motorcycles.
2003 Kawasaki KLR 650 Dual-Sport and a 2001 Honda Goldwing.
Majority of my riding is to and from work. That fits the 45 mph or less criteria. I always wear a full face helmet.
My comments below are in regard to your question.
Hands down I prefer to ride my Goldwing. The comfort from the windshield and fairing just can't be beat. Much more comfortable to ride. I can ride all summer with the face shield up. I for one do not enjoy the naked bike wind in your hair style of riding.
When I ride the 650, I have to keep the face shield down. Why you ask? Well no matter which helmet I wear I have to put up with a whistling noise from the air hitting the bottom of the open shield. As soon as the shield is down, whistling goes away.
I always wear hearing protection while on the 650. Hearing protection is only needed on longer trips with the Goldwing.
I have to wear warmer riding gear when riding the 650.
I will be looking for a different cycle to use in place of the 650 mostly due to the lack of windshield. But I continue to ride the 650 for the following reasons.
Gas mileage: 53 mpg vs. 36 mpg
Tires: Rear 650 tire that I can change myself around $85 vs $180 plus around $30 for mounting and balancing for the Wing.
Fun: Around town the 650 is a lot of fun. Long travel suspension is great for the beat up roads I ride on each day.
Costs: I bought 650 for about $3,000. It is easy to work on and cheap to plate and insure.
Do yourself and buy a bike with a windshield. If anything it will keep the bugs off your riding gear.
Good Luck

A windshield won't do much below 45 MPH.

It will help block some wind at highway speed, but is not necessary.

Personally, I prefer to not have a windshield or a fairing. I like the feel of the wind on my body.

I always wear a full face helmet though. In the past, I wrecked enough times on the track to really appreciate their value.

Nobody here has ever been on a bike apparently.

Of course a windshield will have an effect at 45 m.p.h.

Yes it is cool and all that to feel the wind on you going down the road, but riding a bike with a windshield for an extended period of time is much less fatiguing than riding one without...

a windshield will not help anything if you have a full face helmet, especially at that speed...

go without...

also it will make the "vents" built into the helmet much less effective (less air going to the helmet=less air going through the vents)

I wear a full face on a cruiser with no shield most of the time. Above 65 MPH I do feel a lot of wind in the chest and it is easier riding at that speed with a windshield, I just don't like them myself.

A windshield diverts the wind around your person.

With a full face on there is a good chance the wind will buffet over the top of the helmet, and you will be like a bobble head.

You will know pretty soon if the wind is wearing on You. Even a small shield can take a lot of strain off Your arms and upper body.