My heating system: just fine or time bomb?

September 20, 2007 1:12 PM

My forced hot air system has no return ducts. Instead, cool air falls directly into the basement, where there's a filtered intake on the side of the furnace. Are my life, health, and or selling prospects at severe risk?

You should also know that the hot water heater is right beside the furnace, though on the opposite side as the intake. Both are oil burning. Also, I live in Massachusetts, and plan to sell my home in about a year. The place is about 1200 square feet, and I've lived in it off and (mostly) on my whole life... so I've made it this long!

Will no return ducts cause my home to fail an inspection, or cause complications with the sale? In the mean time, how great are the risks from combustion fumes, dust, mold etc. from my basement?

The highly reputable firm who I am confident will do a first rate job installing the return ducting, has given me a rather expensive estimate. If I put it off, or opt for second or third rate, am I really just postponing the inevitable?

posted by a22lamia to home & garden (9 comments total)

The only problem with no return ducts is distribution efficiency. The hot water heater has nothing to do with it. If you have something crappy in the air down there like mold, or radon, or whatever, then it might help spread that into the rest of the dwelling better than a furnace with returns. If that is the problem then it is certainly bigger than a lack of return ducts.
posted by caddis at 1:29 PM on September 20, 2007

oh, and all the combustion fumes go up the chimney. if they didn't you would have died from CO poisoning long ago, even with return ducts.
posted by caddis at 1:30 PM on September 20, 2007

Most homes that I've been in (and I used to work in residential construction, so that's quite a few) do not have return ducts, just a large return register in the side of the closet that they're located in. And those were generally houses much larger than 1200SF. caddis is correct about the water heater, so you should be okay.
posted by LionIndex at 2:20 PM on September 20, 2007

Carbon monoxide and radon detectors, as well as a GOOD allergen filter (changed regularly) on the intake may give you peace-of-mind.
posted by trevyn at 4:20 PM on September 20, 2007

Radon detector? That's a new one on me. ;) Just do a charcoal-can screening. Radon problems don't just pop out of nowhere.
posted by Myself at 4:52 PM on September 20, 2007

Older houses weren't nearly as air tight as modern houses. Until sometime in the early '80s, it wasn't common practice to even fully wrap a house under construction in plastic wind barrier, and it only became common practice to put moisture foil or plastic moisture barriers on the warm side of insulation in the '60s. So if your house is that old or older, putting a cold air return on your oil furnace may be putting lip stick on a pig. Your "cold air return" maybe a big space under your basement door, and various oversized holes around plumbing stubs coming up through your floors, from the basement. As long as they have enough square footage to prevent your furnace from creating negative pressure in your basement while it operates, you'll gain very little by installing a dedicated cold air return. In other words, if you can easily open your basement door when your furnace is running, and not notice additional heat suddenly pouring out your warm air ducts, or notice "whistling" noises suddenly abate, you have enough open area for air to be circulating.

Were I you, before I spent money on a dedicated cold air return, I'd look into reducing air intrusion in other areas, like windows, and improving thermal efficiency with additional insulation, attic vents, replacement windows, etc.
posted by paulsc at 6:09 PM on September 20, 2007

Carbon monoxide and radon detectors, as well as a GOOD allergen filter (changed regularly) on the intake may give you peace-of-mind.

Perhaps, but they have nothing to do with a lack of return ducts. If you have these problems return ducts will not make them go away. Let's put this into perspective. The lack of return ducts IS NOT A HEALTH ISSUE, AT ALL, NOT EVEN ONE TINY LITTLE BIT! ok, sorry for shouting. however, if you have bad air in your basement you have bad air in your living space, regardless of your HVAC system. We are talking 10 cigarettes a day versus 15, well, both are pretty awful for you.
posted by caddis at 6:14 PM on September 20, 2007

Issues at hand: 1. moisture and mildew/spores in the crawlspace, 2. extremely cold nature of return air, and 3. questions about whether you're actually able to get ENOUGH air for an efficient process.

1. Legitimate issue if you have an unfinished, but probably vented (or not, depends on where you are) crawlspace, especially over dirt, especially if you have any mineral accretion on the block, or water/moisture down there. It'll probably be vaporized in the combustion process, but...meh.

2. "Cold air returns" are sort of a misnomer, they're really the "least warm air", and depending on where they're located they're often not even that. This air has to either...infiltrate through the crawlspace, which is easy w/ the venting it probably has, or get cold enough and bypass enough to actually come through your floor, at which point I GUARANTEE it's a LOT colder than the 60-65 degrees it should be. In this case, you're potentially trying to heat air that's as little as 5-10 degrees warmer than the outside air, whatever the outside air IS (could be 10 degrees all together!) instead of re-heating 60/65 degree air to 70 degrees. Rate of rise shouldn't have to exceed about 5-10 degrees, but having to heat 25 degree air to 70 obviously takes a LOT more energy!

3. Depending on whether your crawlspace is vented and how big it is, you might actually (and likely) be starving your furnace of air. It's got to be able to suck in enough to get warm air at capacity and offgas the combustion air. An amazing amount of people have undersized returns, which basically destroys your efficiency rating.

We work with this sort of thing all the time at work. Call an HVAC company or 2 and request a visit, your ROI on energy bills might come w/i a season or 2.
posted by TomMelee at 6:35 PM on September 20, 2007

Oops...add on to number 1:
If the air down there is moist, and it probably IS, that does NOT mean that your living space air is moist. If you are force-blowing humid air into your living space, you might have a lot more issues....such as rot, mold, condensation w/i the walls...nasty stuff.
posted by TomMelee at 6:37 PM on September 20, 2007