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Proper Insulation for Crawl Space with Oil Furnace

I'm moving into a 75 yr. old house in the beginning of december and the inspection report said that I should have insulation installed in the crawlspace under my hardwood first level floors. The crawl space is split into two sections, the first being where the furnace is and is approximately 484 sqft. The second is 154 sqft and is separated by the first via the original foundation wall, which had some blocks removed for access/piping.

The main section has an existing vapor guard and I plan on installing one in the rear section, however the entirety of the crawlspace is uninsulated. There is uninsulated metal ducting from the oil furnace and two pipes (will be replaced by one run of PVC or PEX) running from the water main at the front corner to opposite, back corner (all plumbing is at back of house). Both existing pipes (one copper, one galvanized) are not insulated and poorly supported, below the joists (an entirely different story). The crawl space isn't very tall beyond what was excavated for the furnace, the front of the house has maybe three feet of space below the joists, with the back having two or less.

My question is what is the best route to go about insulating the space. The inspectors report suggested insulating the floor, but a lot of what I've read for crawlspaces with furnaces suggested insulating from the mudsill down and leaving the joist area alone. I live in Maryland and it is definitely an inbetween climate. Judging from the lack of insulation on existing plumbing there seemed to be no concern with freezing (or ignorance thereof judging by how it has been run), but wasn't sure if the wall insulation would be enough to make it worthwhile.

Any suggestions would be appreciated!


Re: Proper Insulation for Crawl Space with Oil Furnace

If the crawlspace is not currently ventilated, then insulate at the outer walls. If it is ventilated then insulate at the floor joists. Remember that insulation is used to thermally isolate an area from the exterior or other unconditioned space, which makes it's proper placement easy to determine. You also have to keep in mind that having heat-producing equipment in the crawlspace may require that you cover any added combustible materials you add such as foam insulation with an approved fire-resistant product. Check with your local building codes department on that. Replace all galvanized plumbing. Also you may need to re-route, insulate, or use heat tape to protect any plumbing which will not be covered with the new insulation to prevent freeze-up.


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