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StephanieW
HVAC system in dirt basement

Hello!

We recently installed a new HVAC system in our 1890s folk victorian. We have a "Michigan basement" as we call them here - basically dirt floor, with stone walls with a wood retaining wall. The dirt is damp - not wet from leaking - just way underground damp. When we turn on our new system, the house smells like earth..... I don't think it is a mold issue. We put plastic down on the floor in the furnace room, which helped a little. Any other suggestions?

We have been in the house less than a year, and are about $120,000 into a remodel (new well, new HVAC, 4 rooms of carpet, 10 rooms of wallpaper removal, patch and paint, 3 bathroom updates - one of which was a gut, converted garage to kitchen, landscape and yard rehab, electric update, and a whole mess of decorating updates). We need a fairly easy cheap short term fix if one exists!

Thanks!

Stephanie

JLMCDANIEL
Re: HVAC system in dirt basement

I would suggest a heavy duty dehumidifier in the basement. Seal all duct work and enclose the HVAC unit is a small room fed with outside air.

Jack

dj1
Re: HVAC system in dirt basement

Right now your A/C unit gets air from the service room and the basement - so you can see why you have a problem.

If you move the return to the first floor and supply the air to the unit via a tunnel, you will eliminate your problem. The tunnel must be leak free.

Get your contractor back and see if he can figure out how to do it.

HoustonRemodeler
Re: HVAC system in dirt basement

What DJ said,

A dehumidifier in the basement would run 24 hours a day until the you sucked lake Michigan dry.

JLMCDANIEL
Re: HVAC system in dirt basement
dj1 wrote:

Right now your A/C unit gets air from the service room and the basement - so you can see why you have a problem.

If you move the return to the first floor and supply the air to the unit via a tunnel, you will eliminate your problem. The tunnel must be leak free.

Get your contractor back and see if he can figure out how to do it.

If it is picking up air from the service room instead of the air return from the house it was not installed properly.

Jack

ed21
Re: HVAC system in dirt basement

I think sealing the return air ducts in the basement, covering the dirt floor in the furnace room(a slab might be best) and bringing in air from outside to the room would help as JLM stated.
The reason for the sealed/floored room is to isolate the air handler from the basement. No matter how much you seal the R/A ducts, their is no way to keep the air handler from sucking in some air through various loose connections, service panel, holes, etc.

dj1
Re: HVAC system in dirt basement
JLMCDANIEL wrote:

If it is picking up air from the service room instead of the air return from the house it was not installed properly.

Jack

Exactly, I just didn't want to say it without seeing the unit. I also believe that the contractor should have a first chance to rectify the situation.

If the contractor doesn't respond in a timely manner, the homeowner has a right to contact the state contracting board for help. They keep a bond for this exact purpose of fixing malpractice mistakes.

StephanieW
Re: HVAC system in dirt basement

Good News!

The HVAC installers were back yesterday for the "final" step in installation. They checked everything closely, ran the AC for 24 hours to help dry out the humidity, and all is well. They did say if it becomes an ongoing problem, they can install some kind of vent in the basement itself (?) - but it will be cold down there if they do. I am sure the ductwork is not airtight - some is new, but some was installed when the previous owners added a fuel oil system 30 years ago. I think I am just going to have some old house funk that creeps up through the floor and seeps in cracks...... (As an aside, we live in a small town and used a very reputable HVAC company. I am confident that it was installed correctly.)

Thanks everyone!

Mastercarpentry
Re: HVAC system in dirt basement
JLMCDANIEL wrote:

If it is picking up air from the service room instead of the air return from the house it was not installed properly.

Jack

Agreed. Your system's return air intake is not coming completely from the house interior as it is supposed to, but at least partially is coming from the basement/crawl space so something here isn't sealed up correctly. It may have been part of the existing system which they reused, but that still does not excuse them from making it right unless the contract specifically indicated they would reuse it as is. If it happens again first call another HVAC company out for an inspection. Don't tell them the work was recently done (though they will be able to see that), just ask them to locate the problem and recommend a solution with their price in writing on their company letterhead. If it's cheap enough get two different companies to look at it. Once you have that go back to the original installers and tell them to make it right and repay what you spent on the inspection(s). If they balk, take them to small claims court- with the documentation you have (including our responses here) you will win.

Phil

cocteau3
Re: HVAC system in dirt basement

I agree, make them responsible. HVAC in a dirt basement should be done with sealed, insulated, flexible ducts for supply air and return trunks. Professional grade mastic should be applied on the duct joints of any metal ducts entering or attached to the furnace. Furnace should be sealed with gaskets rated for this location.

Always better to bring up the HVAC from the foundation when planning a reno. Better to run trunk lines into the attic and feed the upstairs from the ceiling, or bulkhead in the first floor, or use exposed ducts in some buildings. I've seen horrible shotgun foundations become abandoned and the house will stay fresh because the heating envelope is isolated from the foundation whether or not it is encapsulated... good luck with the contractor.

:confused:

Fencepost
Re: HVAC system in dirt basement

All current codes require ducts in new construction to be sealed. When reusing existing ducts, that might be a bit of a grey area, but some inspectors will consider it to be "disturbing existing construction" which requires bringing it up to current code... which means sealing the old ducts where possible.

Note that I didn't say "where easy" but "where possible." That means that if the duct is accessible, even in a hard-to-reach (but still reachable) crawl space, it must be sealed. If it's enclosed in a building chase (such as a drywalled box from the basement to the attic) then that's not accessible and sealant wouldn't be required -- unless you opened up that chase during other remodeling.

In a previous Ask TOH episode (I'm too lazy to look it up for you) they demonstrated a method of sealing ducts from the inside using a vaporous sealant blown through the ductwork. This will not only seal the accessible areas, but the inaccessible areas, too.

P.S. -- the rest of your basement dirt floor should have a vapor barrier applied.

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