Fully concreted crawlspaces... huh?

[xsports33]

This website has been phenomenal with helping me with information, hopefully you all can help me with a non-lubricant topic.

I just moved to the mid-west (Chicago suburbs) from the west coast (San Diego) and my new-to-me house has a fully concreted and insulated crawl space. It was a huge selling point that the seller and realtor kept pushing. I'm very new to the concept or crawl spaces and basements. So, my question is what is the advantage of a fully concreted and insulated crawl space compared to a "normal" one? Also, there is a dehumidifier in the crawl space that has been running 24/7 (probably because it's summer in the mid-west), does it really need to be on all the time if the crawlspace is concreted and insulated? There's only 1 "window/vent" in the crawlspace that is currently sealed. i've heard i need 2 to properly ventilate the crawlspace... again, is this necessary if its concreted and insulated? From the research i've done, fully concreted/insulated crawlspaces are "supposed" to be sealed... so does that mean i don't need the ventilation?

someone please shed some light on the subject?

Thanks in advance!!

 

[duaneb9729]

The crawl space should be open to the rest of the house some how, normally, the crawl space is open to the basement some how, and that is all the ventilation it requires.

 

[Mr Nice]

Why is a crawl space needed.....why not just build on a concrete slab ?

 

[LS2JSTS]

IMO, the crawl space should be ventilated well with vents on all four sides of the foundation.

Keep them open in the summer months and then close them off in the winter months.

Do you know if you are in a Radon gas area? Many times homes built in radon gas regions, they will crete the floor in order to prevent the gases from rising through the home.

Come winter, you'll appreciate the insulation. A crawl space that is uninsulated, especially around the floor joists and the bond is a leaking sieve, that will be very drafty. We used to put blue board up along the walls and backed fiberglass in the floor joist pockets as well.

Sounds like they built your new home well.

 

[mrsilv04]

IMHO, a concreted crawlspace is a waste of time, money, and concrete.


You need to get a hygrometer (humidity gauge) and get a reading of the humidity level in the crawlspace. They can be had at W-M for less than $10.

The humidity level in the crawlspace should be around 55-60%. If the dehumidifier is set too low, and is trying to get it down to 40%, then yes, it will be running a lot.


The dehumidifier might be set at a too low of humidity level and is running needlessly.

 

[eljefino]

There was probably a reason they concreted the crawlspace. Maybe after the fact. If there's cinder block construction they hauled the blocks in under the house otherwise they probably would have made molds and poured concrete.

I'm thinking the area is prone to flooding but the radon is a good excuse too.

My basement is half basement, half crawlspace due to a hill, house expansion, and laziness dealing with rock ledge. I don't think anyone "wants" a crawlspace; they could just do a slab or full basement, they are things that just sort of happen.

 

[river_rat]

Originally Posted By: LT4 Vette
Why is a crawl space needed.....why not just build on a concrete slab ?

Cold in winter and floods the lower walls in the spring when the snow melts, and then there is the monsoon rains of spring and summer. The water wicks up through the concrete.
Best to have the house elevated in the midwest.

 

[xsports33]

The house was originally built in the 1920's, but there has been significant upgrades and remodeling since then. The previous owner put in the concrete and insulation in the crawl space. I'm guessing it was just dirt before that.

We had a Radon gas inspection prior to buying (VA loan requirement) and we're good there. The dehumidifier is set to 60%, and it still runs non-stop. The only time it's not running is if i crank it down to 90% or just "off".

So... do i need ventilation if it's concreted and insulated?

 

[eljefino]

It may do you well to try and keep moisture out of your floor as it's bad for the wood. First idea off my head is 4x8 foam board.

 

[LS2JSTS]

The VA inspector should have REQUIRED venting on all four walls. Previously, before they gutted the whole VA/FHA appraisal/inspection process, it was required in any home in this market region.

Did you get a copy of the appraisal the VA did?

Was the house moved to this foundation?

 

[LS2JSTS]

Originally Posted By: xsports33


We had a Radon gas inspection prior to buying (VA loan requirement) and we're good there.


Good deal. When Radon first made headlines, many with sand/dirt floors in their crawl spaces did the testing and realized that they were getting radon in the house. That is why many of them went back and retro fitted concrete floor in the crawl. The concrete floor prevents the gas from rising.

If you inspect a home with a full basement and it has Radon remediation in place. You'll notice that they cap the sump crock and pump that air out of the basement. Thats because the radon doesnt come into the house through the concrete floor, it comes in through the hole in the concrete at the sump.

Not saying you have radon, only that they may have had it tested before, and then installed the floor to cap it.

In any case, glad you got the "all clear".

And yes, FTR, install the vents on each wall of the foundation. Like I said above, open in the summer and closed off in the Winter. If you dont ventilate the crawl somehow, you will get mold/mildew. One vent is not sufficient.

 

[pcoxe]

With a sealed crawl space, you could install a downflow furnace anywhere in the house and use the crawlspace as a giant plenum. All you would have to do to ventilate a room is cut a hole in the floor and drop in a register grill. The concrete slab, especially if insulated underneath, could provide thermal mass to keep the temperature more stable. Any modifications, repairs, or additions to plumbing or wiring would be easy with an auto creeper. I'd like the concept if it was implemented correctly.

 

[LS2JSTS]

In Northern climates introducing the warm/humid air from the living environment into the crawl would be a recipe for disaster. Unless you wanted to go whole hog and heat/cool that crawl space to the same conditions as the living area. That would get real expensive real quick.

 

[xsports33]

We did get the appraisal, and the venting for the crawl space was not required. At least, not from what i see.

Probably next season, after the winter, i'll get another vent installed on the opposite wall of the existing vent. The crawl space will have to do with just 2 since the other walls end underneath a front porch deck and a back deck overlooking the a lake.

There is PLENTY of ductwork in the crawlspace for both the A/C and the furnance. But, i don't want to run the A/C or the furnance just to dehumidify the crawlspace.

 

[xsports33]

Originally Posted By: LS2JSTS
In Northern climates introducing the warm/humid air from the living environment into the crawl would be a recipe for disaster. Unless you wanted to go whole hog and heat/cool that crawl space to the same conditions as the living area. That would get real expensive real quick.



Agreed!! there's 4,000 sq ft. of house that i refuse to run the A/C for when it's just me. My wife is currently deployed and i'm running 2-3 week long missions almost monthly, so no one is ever really home. Hence the reason i HATE having that dehumidifier going 24/7 and skyrocketing my electic bill when no one is home.

 

[duaneb9729]

most of the time, as a heating contractor we do install a small register on the duct work in crawl spaces to help warm the floors and keep the humidity level down, it adds nothing to operating costs at all.

 

[LS2JSTS]

How does introducing warm humid air into the crawl space keep humidity down?

The cold winter air is already less humid than the air coming out of the air handler isn't it?

 

[JustinH]

Originally Posted By: LS2JSTS
How does introducing warm humid air into the crawl space keep humidity down?

The cold winter air is already less humid than the air coming out of the air handler isn't it?



Hot air coming out of a forced air furnace is very dry. It would lower the humidity in the sealed crawlspace.

I have a house from the 1930's with a full cinder block basement. We have a "wine cellar" area that has vents in the concrete right to the outside. The "living" area of the basement had wood framed sealed glass windows when the house was built.

When I bought it, it was a SWAMP in the basement during the spring and summer. Replacing 8 windows with vented glass block windows made the basement as dry as a bone, and you do not need to even use a dehumidifier down there.

Good airflow is important.

 

[jorton]

Seal off the vent fall, winter and spring. Add the small register. The furnace should be on so pipes don't freeze.

 

[LS2JSTS]

He has an Insulated crawl, NOT a Conditioned crawl. There is a huge difference.

Venting warm air into the crawl space in a cold climate is no different than venting warm air into a cold attic. All kinds of problems will follow.

Warm Air into Cold Air equals Condensation equals Moisture equals Bad News.

People from Texas and SC have completely different issues than in the North.

A properly vented and insulated crawl space in a Northern climate. Will treat that air space precisely as the air space is treated in the attic. That is the insulation is wrapped around the living spaces while the air directly above and below the insulation is allowed to follow the ambient temperature. If you try to heat or vent moist air in your attic in the Winter you'll get ice dams, insulation damage and loss of effectiveness or at the very least moisture problems. The exact same issues apply to the crawl space in the Winter months...and that does NOT included conditioned crawl spaces. They are a completely different thing.

In a conditioned crawl space the entire crawl is managed and either heated or cooled depending on season.

To the OP, there are regions of the country that have no bearing on where YOU live. If this question were posted from SC, Ca or Hawaii the answer would be different.

Look into smart vents with built in hydrometers, or possibly air to air interchagers if you have moisture problems. But one thing is constant, sealing off the crawl is not the way to go unless you want to condition that air. If you dont want to pay to heat and cool that air and remain an insulated crawl then air circulation and proper venting is your friend.....I agree with JustinH, good air flow is important, BUT never add heated air to a cold crawl space in the Winter months.

http://www.smartvent.net/crawlspacevent.htm