New Twiddle

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName:'Ember Twiddle'
});

application.template.hbs

{{#sticky-header}}
 sticky content
{{/sticky-header}}

sticky-header.component.js

import Ember from 'ember';
const { $, run, computed } = Ember;

export default Ember.Component.extend({
  classNames:['sticky-header-container'],
  classNameBindings: ['isSticky'],
  topPos: 0,
  isSticky: false,
  
  onWindowScroll(e) {
		let scroll = $(e.currentTarget).scrollTop();
    let topPos = this.get('topPos');
    if (scroll > topPos) {
    	this.set('isSticky', true);
    } else {
    	this.set('isSticky', false);
    }
  },
  
  didInsertElement() {
    this._super(...arguments);
    this._windowScroll = run.bind(this, 'onWindowScroll');
    $(window).on('scroll', this._windowScroll);
    this.set('topPos', this.$('.sticky-header').offset().top);
  },
  
  willRemoveElement() {
 		$(window).off('scroll', this._windowScroll);
  	this._super(...arguments);
  }
  
});

sticky-header.template.hbs

<div class='sticky-header'>
{{yield}}
</div>

styles.app.css

html, body {
  margin: 0;
  padding: 0;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}

body {
  height: 2000px;
  padding-top: 200px;
}

.sticky-header-container {
  height: 100px;
  width: 100%;
  text-align: center;
}

.sticky-header-container .sticky-header {
  height: 100px;
  width: 100%;
	background: green;
}

.sticky-header-container.is-sticky .sticky-header {
  position: fixed;
  top: 0;
}

twiddle.json

{
  "version": "0.5.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.2.0/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember-template-compiler.js"
  }
}