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Not a green area, but seeking advice on HVAC issue, if someone has time.

davemax21 | Posted in GBA Pro Help on

Need help from Pros here on what to do.

Had an attached closed porch gutted a few years ago. Was never insulated, connected to the kitchen, with an entry door. Had the porch gutted, re-studded insulated, and had a half bath in one part put in, and the other open area just for storage.
They punched thru an old basement window under the porch (was a basement window on that side of house until the old porch was added on decades ago, but was boarded up). Under the porch is the ground, dirt. the siding does go down to the ground on the porch.
they cut a hole in a new piece of plywood they installed where the old basement window was to run ductwork under the porch, and put in 2 floor vents in the “new room”. one in the bathroom, one in the open area.

The original contractor ran duct from the furnace, then branched off 2 flex ducts and punched through the basement to the underside of the porch… was never a good seal at the plywood board (old window).

Then fabricated some boots to the underside to the vents above. Problem: always had air and of course bad underporch smell coming from the vents in the room. Both around the openings and from the center of the duct itself. Even with the furnace off, you could hold a piece of tissue paper in the duct and see it blow. He came back and spray foamed, better, but still there. He wasn’t a pro HVAC guy..

Anyways, we just finally had a professional HVAC company come in, rip out all his work, and start over, from the furnace, to the wall, under the porch, to the vents. They did a better job at the basement wall/window by having just one pipe/duct go through the board, easier to seal this, They told me they would air seal the ducts and we should smell nothing and feel no air coming in.. !!
Well, it’s worse, they used the flex ducts again underneath, and only used zip ties to hook this to the new boots underneath.Zip ties barely attached, no foil tape in sight, .. They caulked in the room at the vents to the subfloor and linoleum,… but there is more air and smell coming in . The room and now kitchen stinks.

What should they have done here ???
I have not paid them yet, have a bill for $500. I told them they made the condition worse, and actually did nothing new here?
any advice you can give me to ask the HVAC company or what I should be expecting from them? I have left them a message last week on their voicemail, telling them I have their invoice, but I am holding off on payment until I get this resolved.

PS: I have a friend’s house, that had an addition put on one entire side of his house.. a bedroom and family room added. All over an unconditioned crawl space with dirt floor.. He has shown me this area underneath, i have seen the duct work running just over this floor up to his rooms.. that dirt space stinks. but there is no odor whatsoever in his rooms at his vents.

I should be able to have ductwork run through my stale smelling crawlspace, and not smell it at the end.

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  1. GBA Editor
    Martin Holladay | | #1

    There are several issues here.

    1. The room you describe doesn't appear to have a real foundation. It sounds like it is supported by posts, with a leaky crawl space underneath. The best way to fix this problem would be to install continuous concrete foundation walls to support the room. The concrete walls should be connected to the floor joists in an airtight manner.

    2. The ducts are running through unconditioned space. That's bad.

    3. The crawl space has a dirt floor. The dirt should actually be covered with an airtight polyethylene vapor barrier with taped seams. Even better -- the poly should be covered by a rat slab.

    4. Your room may be depressurized by the stack effect; that would explain why crawl space odors are entering the room. The solution is to seal the air leaks in your floor and your ceiling.

    There's a lot of work to do to fix all these problems.

  2. davemax21 | | #2

    Thank you. Short of putting up any concrete foundation (i know that would be ideal), I can't go into that expense. Is the depressurization what is causing tissue paper to blow when you hold it down into the duct from the vent in the room? even when furnace is off?

    But shouldn't, or can't duct work be sealed enough where nothing can into these "pipes", in other words from point A (furnace) to point B (vents in floor), if sealed properly, it would almost be like a pvc pipe from A to B, you could run that pipe through a sewage plant and not smell anything at the other end. I know it's not apples to apples example here, due to the many areas for leakage in the ducts..
    but also, it's frustrating due to my comment above in the original posting about my friend's house.. has 3 ducts running through his unconditioned space and absolutely no odor at even his floor vent level.

  3. davemax21 | | #3

    Part of the problem is , where the crawl space siding, that goes down to the ground, butts agains the rock faced concrete block on 2 sides.. there are openings there, you can see daylight, it was never a tight fit, you can stick your hand in the space from outside in those areas. It sounds like any plastic would need to go all the way up all 3 or 4 sides of the crawl space underneath? So knowing that, i'm assuming that air is getting into the crawl space from outside, and that air is pushing the stale air into the ducts, or the depressurization is sucking in the air from the space and pumping it into the room above?

  4. davemax21 | | #4

    Final thought, if I wanted to eliminate all the problems above, can you recommend baseboard heating options or sizes?
    I can rip out all the duct work underneath in the crawl space, seal up the board/wall/window where they punched through from the basement, seal up the floor above (2 spots where the vents were), and have 2 small baseboard heaters put in.
    I had an electrician a year ago tell me there's room in my breaker box for this.

    -- I know this will cause the room to be totally sealed off from below, no odors, air, etc..good thing.
    -- Plus, the room itself is so small, total porch size is about 72 square feet, broken into one 25-30 square foot 1/2 bath, and the other 40 square foot room.
    -- Also, the house is in one of those low municipal electric areas, 3-4 cents per kilowatt hour..

    Anything you can suggest or let me know what to look out for if I decide this, and if you feel this may be a better way to go for this small addition?

    Thank you.

  5. GBA Editor
    Martin Holladay | | #5

    In theory, perfect air sealing can solve your problem. The work can be tricky, however.

    If you want to solve this problem by attempting a perfect air sealing job, here are the steps you need to take:

    1. You need to seal all of your duct seams. The usual material for this work is duct mastic. Here is a link to an article with more information: Sealing Ducts: What’s Better, Tape or Mastic?

    2. You need to seal the leaks at the edges of the plywood used to fill in your basement window.

    3. You need to seal the leaks between the duct and the plywood.

    4. You need to seal all of the leaks in the floor of your room. This may be the trickiest step of all. The best approach would be to use a theatrical fog machine to pinpoint the leaks. Here is an article with more information on this topic: Pinpointing Leaks With a Fog Machine.

    5. You need to seal all of the leaks in the ceiling of your room, in order to reduce the stack effect.

    One more point: every room in a house with a forced-air heating and cooling system needs a return air path back to the return-air plenum of the furnace. This is best achieved by installing a return air duct from every conditioned room. If the room in question doesn't have a return-air duct, you will need to leave the door to the room open, or install a transfer grille of some kind. For more information on this issue, see Return-Air Problems.

    Good luck!

  6. GBA Editor
    Martin Holladay | | #6

    If you decide to install electric baseboard heaters, you need to:

    1. Perform a heat-loss calculation to determine your design heat loss.

    2. Hire an electrician to install the electric baseboard.

    Here are links to two articles on heat-loss calculations:

    How to Perform a Heat-Loss Calculation — Part 1

    How to Perform a Heat-Loss Calculation — Part 2

  7. davemax21 | | #7

    Thank you for all the time you put in responding. Very good advice.
    As for the ducts; the plywood is sealed quite well with caulk where the duct goes through. Under the porch, they start with round "pipe", then branches off to 2 flex ducts. These are attached with zip ties. I think these need to be at least taped, foil tape.
    At the boot end, the flex duct is connected to the pipe of the boot again with a zip tie, no tape. At the floor opening, from inside, it looks like they did a good job with caulking around and even under the linoleum.. and i don't see any cuts or gaps in the boot itself looking down.

    All this odor and air that used to come from both the duct itself and around the boot /vent sides , now only comes in from the duct itself.

    I see under the porch where the flex duct can be better sealed to the pipes on both ends. Other than that, most of the duct work is the flex duct, about 6-7 feet of it per vent. (which i'm assuming is air tight).
    The room does not have a return, however, the room connects to the kitchen, and there is no door anymore, you walk right thru. the house only has one return, in the living room floor, 2 rooms away.

    As for electric; I would hire an electrician to do the work. Thoughts are if only one baseboard heater would be sufficient, perhaps in the bathroom, door is always open, and could warm that room and the other room, seeing the other room is off the kitchen, and the kitchen has it's own duct. But I can let the electrician make that call.

    I have not heard back from the HVAC company after calling them and leaving them a voicemail about my concern. Still have a $480 bill.

    PS: I see in your article on tape vs mastic, at the bottom steps for sealing flex duct to pipe, it looks like the conctractor did not insert the pipe far enough into the flex duct sleeve, and did not fasten the sleeve properly, no screws, only that flimsy zip tie I mentioned, and definitely no foil tape.

  8. davemax21 | | #8

    Hey Martin,
    The building contractor that was out to the house this past weekend, called me to tell me he had some thoughts as well. He told me to tell them they should have at least replaced the old flex duct, from what he saw, it didn't look new. But better yet, stated they should have put in hard pipe, not flex. Taped the pipe at all seams, the double wrapped with insulation. Told me there should not be any odor or airflow if done correctly.

  9. charlie_sullivan | | #9

    I'm surprised that the contractor though they should tape the seams, rather than using mastic. See the article Martin already linked to.

  10. davemax21 | | #10

    It is tight in the crawl space, maybe thought it would be easier to use the foil tape, then use the double wrap insulation. I did see the mastic vs tape article.. I think the tape is an option of course. I think it also stated that the mastic can come apart at seems at times?? I think the mastic is the preferred, but after what I have been going through, I think his main point was to at least not use the flex duct,and use hard pipe for starters.

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