Re-insulating a botched 4 season room

Mark asks:

I'm reinsulating between 2x8 floor joists of a 4 season room that wasn't done properly. 

It is almost at grade level, no access to underside of joists. Am putting full 1" x 1" strips on each side of joist flush with bottomm of joists. Then I am putting 1/2 inch wolmanized lumber down on top of these rails with screws. Then I want to put r19 kraft faced insulation, faced side up to floor. 

Am I doing this in the right way and do I need to be concerned about trapping any moisture? Ventilation needed? I will be adding a cold air return, another hot air vent too for a total of 2. The other existing vent was not run back to main plenum. Also adding a gas pipe for a gas fireplace. 

Thank you, 

Mark

Jake's answer:

Mark,

The way you are installing the insulation sounds like it will work.  

All "crawl spaces" must be ventilated to help control moisture.  The crawl space should have some sort of covering over the soil as well, like a 6 mil plastic sheeting.  I know this could be hard to do if there is no access.  You might be able to do it when you are installing the wood to hold the insulation in place. This will help contain the moisture and minimize the amount of moisture that can rise from the moisture in the soil.  

Is there anyway you can add some ventilation, at least one on each corner?  If you can accomplish these two items, you should be in pretty good shape.