I'll add a plug for the areas west of Leesburg, VA on Rt 7 in Loudoun County. We moved here this Summer to Round Hill, VA on the eastern flank of the Blue Ridge mtns (6 minutes and I'm on the Appalachian Trail). Vineyards, breweries, and horse farms at every turn with gorgeous scenery and only 30-35 minutes to the IAD employee lot. Prices are not "low", as you'll pay a minimum of $700k for a nice 3-4,000 sq ft home on 1-3 acres....however Houston is our only UAL domicile where you can get below that anywhere close to the airport in a desirable neighborhood with strong public schools. Taxes are moderate here and so are the politics. Schools are very strong.

If you want a more conservative area with nice homes on large lots in the $500-600k range you can go south to Facquier Co (Warrenton) or continue west on Rt 7 over into the Shenandoah Valley to Clarke Co or preferably Frederick Co for the schools (Winchester)...all of these commutes are in the 45-60 minute range.

IAD has a TON of UAL growth potential (reference Scott Kirby comments this week) as we are clearly the dominant air carrier in N.Va, especially for the premium and business traveler. Loudoun is the wealthiest county per capita in the entire country by a long shot with Amazon, Google, etc all building up rapidly here in the next 10 years. Don't buy off on the moaning about much of the initial IAD growth being RJs...it's called connecting traffic and will lead to notable domestic (MAX) and international (A321 & 787) mainline growth next five years so long as we keep taking on new used/mainline jets.
Good luck!