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Question DetailsAsked on 7/5/2014

1949 house-how to disconnect/discard oils furnace in crawl space and remove unneeded ducts

1949 house with huge old oil furnace in crawl space, large, inefficient ductwork and above ground oil tank (full). I am plumbed for gas and HVAC inspector advised removing/replacing ductwork. I am going ductless. First, is the old oil furnace providing heat to the crawl space that could be protecting the pipes from freezing? (Uninsulated vented crawl space on dirt with no vapor barrier or floor insulation). If so, what is the best, greenest, most economical way to resolve that? 2nd, how do I safely disengage, seal off the old oil furnace to abandoned under house, seal off opening to house, remove/seal all the ductwork, including the bottom load bearing stack to roof and sell oil tank/fuel? I am going ductless and don't want the old, faulty ducts allowing contaminants, pests and leaks. I also need the space occupied by the huge round duct leading to roof, for the new, above floor system. Is sealing the ducts w/plastic foam better/cheaper than removing & closing off the vent

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1) if you ever get below significantly (more than a couple of degrees) below freezing for more than a few hours a night then yes you have to consider pipe (water AND sewer) protection - can be done in areas with very rare freezing conditions with wrap-around pipe insulation, in cooler areas with full fiberglass insulation batting in the floor joists with housewrap tyvek across the bottom of the joists to hold the batting in and limit air circulation, to putting in thermostatically controlled heat tapes and insulation in colder winter areas. Get some advice from plumber on that regarding what is normal in your area - if you have an open crawlspace unlikely they were counting on the furnace to keep it all warm, so you might not have to do anything about the pipes, or at most wrap-around insulation.


2) For resale purposes, I would not abandon the furnace or ductwork in place - I would remove it. First, get it tested for asbestos (likely yes) then get it removed appropriately - by licensed certified asbestos removal contractor if yes, otherwise cut into handleable pieces with sawzall or abrasive bladed saw and have hauled to dump - or get a dumpster to your place to put it in. Warning - if DIY removal,, HEAVY double-layer leather gloves like welding gloves for handling cut pieces, and tough long-sleeved shirt and heavy pants like Carhartts to avoid slicing yourself to ribbons - and keep an elestic bandage in your pocket just in case, because if you slip you can get a real serious gash real quick, and it is tough to slither out of a crawlspace holding one arm with the other hand. For removal of ducting - cut and drop, then use rope to pull pieces out - many of the injuries occur when people try to drag cut pieces out with them as they crawl.


3) Duct removal is not tough if exposed in floor joists or under them - succumbs to a sawzall in quick order - one or two mandays work typically to remove entire house worth, plus another one or two to plywood plug the holes in floors. Of course, if doing 2-story house then you may choose to leave a few pieces in the walls rather than cut into them to remoe the ducting, though commonly you can just use an impact puller to yank it out of the walls from the bottom - beingcarefulnot to tear out plumbing or elecrrical in the process. A sandbag or couple of concrete building blocks tied to a cable (no stretch) to a custom-cut piece of 2x4 across the top of the ducting works well for this - drop weight a few feet and it will rip ducting (that has been cut free top and bottom and any visible hangers) out pretty well.


4) Hah Hah - selling the oil and tank - that is a good one. Unless you have a friend who wants to buy the oil and hand pump it into drums to take to his tank, likely to cost you from $0.20-1.00/gallon to dispose of waste oil, as in most jurisdictions it cannot legally be sold as heating oil because they do not know what contaminants are in it (water, rust, etc) - so has to be taken to a refinery for reprocessing, or to some industrial user as area heating or asphalt plant or kiln firing oil. In large cities there are a few companies that filter and reprocess it for heating oil or mix it with refinery bottom-end product to make bunker oil for sale, so in that case possible you might be paid a bit for it - but normally nothing near the $3-4/gallon you paid for it. Guess you could Craigslist it, but risk spillage on your property by person buying it from you - might not be worth the risk.


Tank and piping removal can cost typically $500-2000 depending on tank size and type of foundation that has to be removed, and has to be done by a certified tank removal company, and the removal and oil spillage cleanup inspected and certified. Hang onto the certificate, and in most areas recordable at county recorders office, as proof the tank was properly removed and cleanup up. Also, if was listed on state storage tank registry (usuallynot if under 500 gallons) be sure they remove it and show it as properly removed.


Of course, contaminated soil cleanup can run from a few hundred $ for the normal minor spillage from filling (a drum of soil or so), to tens of thousands if it leaked substantial amounts for many years, especially if into groundwater or under foundation. Total AST (above-ground storage tank) removal and cleanup typically runs in the couple thousand to five thousand range, not often over ten thousand. My recommendation - do NOT abandon the pipes in the ground - because a full removal and decontamination certificate cannot be issued in that case, so could impact future sale. Spend the couplehundred extra and remove them and patch the foundation hole, if any.


5) Sealing ducts is cheaper than removal - but I would not use foam - assuming typical rectangular metal ducts, just galvanized metal end caps put in with seam sealer and sheetmetal screws should do the job fine.



6) You say "load bearing stack" - not clear what load it is bearing - but if truly load bearing then obviously will need to be supported. I can't imagine it is load bearing - usually just a cast iron pipe (if very old) or single or double-wall galvanized (old) or stainless double wall duct (modern) that can be ripped out, or is more commonly removed up to just below the new furnace ceiling level, then left in place fromthereto roof as an outer liner for the new flue for the new furnace, which would most likely be smaller and sleeve into the old liner using centralizers. in many code areas, leaving in place can eliminate need to open up walls and ceilings to put in new firestops like you would have to do if ripping out and putting new furnace ducting in. Might need adapter flange at top where the old and new come into the roof vent, though commonly the roof stack itself can be left intact too - just a new cap put on, or penetrated with the new pipe if uses PVC pipe (condensing furnace).

Answered 5 years ago by LCD




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