Will half marathon training improve my 5K?

Yes. For a new runner who has done low mileage like yourself, training for a half should help lower your 5k time.

I have no idea by how much. And to truly reap the benefits you might need to do 4-6 weeks of 5k specific work sometime after the half.

Yes.

Long answer: maybe 30 sec? sub 18? I know when I bumped 10 mpw from 40 to 50 doing primarily longer distance workouts like that for a half, my 5k dropped about 45 seconds. Your mileage may vary, but my legs did feel very sluggish because I hadn't sharpened up in the week or two leading up the 5k.

5K is still 95%+ aerobic. Increased volume is bound to help especially if your only doing 30-40 mile weeks

Gotta make your long run longer. The Half should feel short if you're to run it well. 16-18 every Sunday.

longer run wrote:

Gotta make your long run longer. The Half should feel short if you're to run it well. 16-18 every Sunday.

I wouldn't jump straight from 10 mile long runs to 18 mile long runs, rather it would be advisable to increase by a few miles each week.

I have found that building up to a longest long run of 26km about two weeks out from a HM race works well for me, and then start tapering with a last big race specific workout 10-7 days out from the race.

If you spent as much time running as you do making threads then you'd be sub 14.

Just build up mileage.

I found that I got so used to running at half marathon pace, which was the idea, that I couldn't seem to run 5K pace. When I would run a 5K while in good half marathon shape my body would just gravitate to 6:00 mile pace. It felt like I had the physical capacities somewhere inside me to run 5:30 pace but it would fall back to the slower rhythm. It was sort of like when you flat spot a tire and it keeps wanting to skid more and more on that spot. Maybe it's just me, my body works that way, but I always found it easier to come up from say mile or 3200 shape. I can slow into a rhythm more easily and hang on than I can speed into a rhythm.