Cool draft from HVAC registers......

[chrisexv6]

I have a two floor home with oil fired, forced hot air heating. When the heat is running, all is fine. However, once the heat is off for about 5 or 10 minutes, the cold air begins to prevail. There is a slight draft coming through all of the registers, and is evident by a "drafty" feeling near each register, as well as by touching the metal registers themselves (they are cold to the touch).

I dont know what the exact remedy would be for this or if there even is one. The returns are located one on each floor, the furnace is in an unfinished (uninsulated, probably an issue) side of my basement. I dont know if cold air is infiltrating the feeds to the rooms, the returns from the two floors, or both. Ive tried adding duct tape (the real stuff, shiny aluminum) to seal the ducts, but I havent noticed a difference yet (havent done EVERY duct, but most of them). The upstairs ducting is flexi-duct located in my attic (I live in the Northeast, so the attic is "untreated" space, just has insulation in the joist spaces). It has plastic around the ducting, I dont know if thats the duct itself, or some type of insulation.

Any ideas would be greatly appreciated.

Thanks!!!
-Chris

[Jay11J]

Is it just the vents upstairs that feeds from the attic?

There maybe not enough insulastion on the pipe. it shouldn't cool down that quick.

Where are the vents on the main floor? I know on older homes, they have it on the outside wall, not up from the floor. (like mine) there nothing between my vent and the outside wall, so I am getting some cooler air. but I run the fan on all times to help keep the air moving.

[chrisexv6]

It seems to be the vents on both floors, however the downstairs (main floor) doesnt seem as bad, because they are not the flat registers that are installed in the ceiling. Rather, they are older diffuser-type registers, so they dont seem to absorb/radiate the cold as much, but there is a definite draft coming from them.

As far as the location of the vents on main floor, they are located in the interior space, wherever there is an exterior wall. So, while they arent open to the exterior wall, they are still allowing a little draft thru them.

I was thinking the upstairs issue could be because of duct leakage in the attic space, might get ambitious and go up there tonight/tomorrow. The cold air return for the upstairs travels thru the attic as well, so Im wondering if perhaps cold air is leaking from the attic into the return, and flooding the system while everything is off.

Incidentally, should METAL duct be insulated? (i.e. the cold air return in the attic, the metal duct before the attic vents get fed off of flex, the plenum in my basement, etc). And if so, what should I use to do this? I have a feeling more efficient insulation of the duct work will do wonders.

Thanks!!!
-Chris

[notsohandy]

I have forced air heating and cooling; ductwork underneath the floor. When the furnace shuts off, the ductwork itself, as well as all the air inside it quickly cools down. When the furnace comes back on, all that cooled down air in the ducts is forced out first, via the registers. Sometimes, for a few minutes, usually two or three minutes, depending on how cold it is in the crawl space, cool air comes from the registers. (Especially the one in the back bedroom which is connected to the furnace by a long stretch of duct work.) That may be the cause in your case. Have you just noticed it? How long has it been doing that? Once, when I was poking around in the crawl space, I noticed that some of the ducts did not fit very tight where they link up to the registers, and some untreated air was coming in around the registers. (drafty.) If you have adequate crawl space, you might want to take a strong flashlight and slither around under there and inspect. My 2 cents.

[chrisexv6]

Ive actually always noticed the cold air coming out first. I figured thats just a drawback of forced air, figure the air stagnates inside the ducts and gets cold eventually. However, Ive just noticed the draft from the registers with the system completely off. It may have been there before, but this winter I can definitely notice it and its bothering me :)

Luckily the ductwork in 3/4 of the house is exposed. Only part not exposed is over the finished side of my basement (whcih is only half of it). The second floor ducting is in the attic, and half of my basement is unfinished so I can see those ducts too. I spent 20 minutes walking around the attic. The flex-lines running to each room are insulated, as well as having pink insulation piled around them. None of the flex lines are really very long, they ran the feed from the basement up to the attic and the length of the attic, via metal duct, with the flexi-lines coming off to each room. Where they come straight off, they are connected nicely. Where they "angle" off, the boot they used to tap into the main line seemed a little leaky, so I taped them up with foil duct tape. However, the return and the feed metal ducting is uninsulated (i.e. no insulation piled on top of or around them). That might be part of the issue right there, I just wouldnt know what to wrap the solid metal ducting in to insulate it if I needed to. Another thing Ive found is that some of the floor registers in the main floor have gaps around the "boots". I might try to fill those gaps, to prevent them from allowing in air from the unfinished/uninsulated side of the basement.

And one more place to insulate, I plan on building a box to cover the folding attic steps when they are folded/closed. I have a feeling Im losing some hot air around the "seal" (in quotes because there really isnt one) around the steps door when its closed.

Any other suggestions? I havent been able to find many other places leaking cold air, so now I think Ill have to tackle insulating/sealing the ducts.

Thanks!!!
-Chris

[Ed Imeduc]

notsohandy
You dont say if the crawl way is sealed up. It should be We put registers in the duct to Warm it up down there.

go check http://aboutsavingheat.com/crawlspace.html

might help to read it.

chrisexv6 You cant have any just metal duct up there in the attic. The best way now is get the fiberglass duct board and cut and fit it to go over the metal duct . For the flex duct up there to seal them .We have to band the inside on first then pull the insulation down over that and another band in it . Now no tape but seal it down with the mastic made for this. we feel that any loss in the basement is in the home and helps it. Do you have insulation down there in each joist space up there on the sill plate all around the home? It helps. they make a insulated box like ,that goes around the attic stairs. Think about that.

My .02 cents

ED ;)

[chrisexv6]

Thanks for the advice. In the interest of making the project quick (its cold up there in the attic!!), I piled up some regular pink insulation around the ducts, at least to hold some of the heat in (I assume this stuff wont catch fire, they have it piled up on the flex-duct as well). But I realize the correct way to fix it is the "duct board" fastened to the ducts themselves. Right now though, the pink stuff was quick and easy.

As far as the attic steps, I was going to build my own box, because I couldnt find any pre-built ones locally (i.e. HD/Lowes). Its not a hard project, so Im sure it will work out fine. Im holding off on it for now, because I want to see how (if any) much difference the pink stuff makes around the return/feed into/from the attic.

The flex duct actually seems well connected. Looks like they have band connectors where it meets the main supply line. They're all tight, and there are no visible tears in the flex duct itself.

As far as the unfinished side of the basement, there is no insulation in the joist spaces on the ceiling (which is the floor of the main floor of the house). Couple that with the fact that our kitchen has a tile floor above the unfinished space, and we get a lot of cold feet in the kitchen. The computer room is over unfinished space, but at least has carpet so it retains some heat. Maybe Ill get some insulation and put it in the joists on the unfinished side. I agree with *some* leaks being good though, otherwise its just gonna suck supply air through every little tiny gap, that you might not even be able to seal up. Its almost like you want a controlled amount of "looseness" in the house. For me, Id be thrilled to make it all in the basement, as long as it help keeps the rest of my house warm. (BTW, any idea how to insulate a bilco door opening? Not the Bilco door itself, but the door that opens up to the steps that the BIlco door covers. I have an awful lot of cold air coming in there, but have never seen anyone talk about insulating one, or even replacing the door itself if need be).

Thanks for the advice!!!
-Chris

[Ed Imeduc]

Didnt mean for insulation up in all the floor joist. Just up in the joist on the sill plate all around the homes belt board is all. We always put registers in the duct work down in the basement. Can you glue polystyrene sheets on the door.

ED :thinker: