Insulating a crawl space, and frozen drain pipe
We recently had the kitchen redone in our 1840's Vermont farm house. The kitchen is over a crawl space. Before the remodel, insulation had been pushed up in between the floor joists and held into place with netting of some sort. Now, we know it's not enough insulation and want to add more. My contractor, who works exclusively on older homes (remodeling; not tearing down and rebuilding) suggests that we add more fiberglass to what's there, and then cover it all with foam board insulation. His reasoning for this is that the foam will seal everything in, making it airtight (if done correctly), and it will keep the mice out of the insulation.
I'm not sure this is the best approach to take. It seems like the foam board won't be providng much R-value, since it would be too far from the underside of the floor. Instead, it seems like it would be more of a support for the insulation, something that could be accomplished much more cheaply with some plywood or even plastic tarps, stapled in place. If I were doing it myself (which I never would), I would pull out all of the old insulation, put 1" foam board up against the floor, caulk it in place, cover that with batts of fiberglass, and then cover all of that with tarp or plywood.
Please give me your thoughts on this. The reason it's an issue right now is because our drain pipe has frozen and the water is stuck in our sink (it's been below 0F for a week or so). We never had this problem before the work was done, and so I think that the insulation that was in place before the remodel, has been disrupted and isn't keeping the pipes protected any longer.
We have heat tape against our water pipes, but not against the drain pipe. Thank goodness.
Thanks for any thoughts/wisdom/critiques you can offer.