Yii Dropdown Validation constantly empty

So I'm a Yii Newbie, and I'm putting together a website with a friend. I've got the basics down, but I'm running into an error. I want to have a page with two drop-down menus. The second drop down menu's data is based on information from the first drop down menu. I want to be able to verify that both of these drop down menu's have selected viable data, and herein lies the problem.

Whenever I try to verify the drop down menus, it always says that they are empty, whether they have selected viable options or not. I assume it's a small thing I'm not seeing, but I'd love some help. Thanks in advance!

Controller File

public function actionResTest()
{
    $model = new Room;

        if(isset($_POST['yt0']))
        {
            echo($model->validate());
        }
        $this->render('resTest',array('model'=>$model));

    if(!isset($_POST['Room']['building_id']))
        {print_r($_POST); $_POST['Room']['building_id'] = '';}
    $data = Room::model()->findAll('building_id=:building_id',
        array(':building_id'=>(int) $_POST['Room']['building_id']));

    $data = CHtml::listData($data,'room_id','room_number');
    echo CHtml::tag('option', array('value'=>''), 'Choose a room', true);
    foreach($data as $value=>$name)
    {
        echo CHtml::tag('option',
            array('value'=>$value),CHtml::encode($name),true);
    }
}

View File

 <div class="form">

<?php
$build = $this -> getBuildings();
$buildList = CHtml::listData($build, 'building_id', 'name');
?>

<?php $form=$this->beginWidget('CActiveForm', array(
    'id'=>'room-resTest-form',
    'enableAjaxValidation'=>false,
)); ?>

    <p class="note">Fields with <span class="required">*</span> are required.</p>

    <?php echo $form->errorSummary($model); ?>

    <div class="row">
    <?php echo $form -> labelEx($model, 'building_id');
        echo $form -> dropDownList($model, 'building_id',$buildList,
    array(
    'empty'=> 'Choose a building',
    'ajax' => array(
    'type' => 'POST',
    'url'=> CController::createUrl('room/resTest'),
    'update'=>'#' . CHtml::activeId($model, 'room_number'),
    )));
     echo $form -> error($model, 'building_id'); ?>
    </div>
    <div class="row">
    <?php

    echo $form -> labelEx($model, 'room_number');
    echo $form -> dropDownList($model,'room_number',array('empty'=>'select a building'));
    echo $form -> error($model, 'room_number');
?>
    </div>


    <div class="row buttons">
        <?php echo CHtml::submitButton('Submit'); ?>
    </div>

<?php $this->endWidget(); ?>

</div><!-- form -->

Model (Rules Method)

public function rules()
{
    // NOTE: you should only define rules for those attributes that
    // will receive user inputs.
    return array(
        array('room_number, building_id', 'required'),
        array('room_number, building_id', 'numerical', 'integerOnly'=>true),
        array('description', 'length', 'max'=>200),
        array('image_url', 'length', 'max'=>150),
        // The following rule is used by search().
        // Please remove those attributes that should not be searched.
        array('room_id, room_number, building_id, description, image_url', 'safe', 'on'=>'search'),
    );
}

I think it you should add this code:
$model->attributes=$_POST['Room'];
before
echo($model->validate());

Hope it works, correct me if i'm wrong.. :)