We need to raise our floor by about 4 inches. Underneath is a dirt floor crawlspace and little to no insulation. Planning to just build up over existing floor which is original pine. Hate to cover that up, but need to get the rooms level and this seems to be the most cost efficient. What can I put between the layer to get the right amount of insulation? Do I need to do anything underneath the original floor? Access to the crawlspace is very limited.