Savannah Marsh home

[gcollins]

Thats my plan thanks.

Since you are an expert I believe your recommendations. BUT---With the fans out, crawl walls, rim plates and dirt floor are to be sealed and the floor sealed from the inside -- does the outside moisture go thru the concrete blocks?

[bluestone]

Outside moisture will definately move through a block foundation ,exterior asphalt damproofing slows it some, but it's just a band aid. You can use Drylock or similar coating on the inside and that will slow it further. 6mil poy vapor barrier on the crawl floor overlapped at least 1 foot, I highly recommend place a 2 inch rat slab of poured concrete over that even if access is limited. Make sure extirior drainage is adequate, footing drains, gutters and downspouts, and grading, you will never dry out a damp crawl unless these are addressed

[gcollins]

Thanks to all--we have a plan. Suprised I heard nothing from the Ga coast.
Guess they are making too much money installing fans

Oh, the attic. After reading the slate bible, I will not install a radiant barrier.

[gcollins]

Which is best; run the poly up the crawl space wall 12 inches or 4-6 inches to the top of the concrete block wall ??

[teddy bear]

Which is best; run the poly up the crawl space wall 12 inches or 4-6 inches to the top of the concrete block wall ??

Most prefer keeping the plastic 6" below the top of the block for termite tube inspection. TB

[gcollins]

Thanks, will do. Can always lower the plastic if I get too much condensation.

[gcollins]

I assume the poly should also go around the support concrete pillars interior to the walls---12'' up from ground

[bluestone]

Assume nothing, but yes

[gcollins]

Outside ground level dropped 12-18 inches and drains and gravel installed:
3 of 4 fans removed; one fan put on timer. (need advice on finding 120v -----------------humidistat to open circuit when outside RH--goes to 70%]
6 of 7 --15 ft sq vents sealed;
Floor poly installed and sealed; mimimum condensation under poly after 3 days
Ducts checked and sealed.
Floor joist h2o content 12%.
insulation vapor barrier slashed.

New findings--two of the main AC systems have humidifiers, one is moldy.
I plan on removing both of these systems. What think youall?

[cem-bsee]

clean 'em with 0.3 bleach + h2o -- let it sit for 45m -- then rinse

then let 'em sit -- you may need them next winter --

[pstu]

>>need advice on finding 120v humidistat to open circuit when outside RH--goes to 70%

There is something like that made by Honeywell. It works with 120V, one model will open circuit above setpoint, another model will close circuit.
http://customer.honeywell.com/honeyw....aspx/H46C1166

Search on "Honeywell H46" and you will find several variations and I think one will suit your purpose. If there is a competitor I sure would like to hear of it, as far as I know this is a unique product.

Hope this helps -- Pstu


.

[gcollins]

thanks for the Humidistat info--What is the general opinion of the SMARTVENT product. ? www.smartvent.com

[teddy bear]

Opening vents on %RH is an inaccurate method of measuring moisture levels in air. 40^F, +70%RH is dry. 80^F, +40%RH is wet. Dew point is best. Dew points less than 45^F is dry. Forget opening vents on a crawlspace in green grass climates. They never dry when you need it. It is not dependable. TB

[pstu]

I had a literal answer in mind when I pointed out the Honeywell dehumidistat. It very much is true that a dewpoint sensor would give much better results. Air at 51F and 100% RH for example, would be only 48% RH when warmed to 72F -- each is 51 dewpoint. If I am not mistaken, an *absolute* humidity sensor is used in the Smartvent.net product. It is very different from the smartvent.com product.

I would want to do all my homework and make sure of all my assumptions, before doing something that contradicts Teddy Bear's advice. Cannot remember when he has ever told us something in error and/or not wise. In particular when he says "they never dry when you need it", see if that doesn't appear to be true in your climate.

Best wishes -- Pstu

[gcollins]

TB and PSTU--thanks. I opened up my 40 year old Unit Operations textbook and refreshed my brain with the psychrometric tables. And did a few HVAC-talk searches on dew pt. TB, several of you posts on other threads were quite educational and quite clear on measuring absolute H2O content.

My original thought were to seal the crawl--but I have a Split 4ton AC with a humidifer and large gas furnace there(combustion air ). I could pump conditioned air to the crawl from other attic AC units or pump some attic air to the crawl

I also understand the temp delta between the crawl and the outside and its impact on moisture--probably 5 months of the year the fan should never come on

And the RH has stabilized at 50% after the poly floor install with just a timer on one fan. Feb has seen a majority of the days in the 40 to 60% RH range with temps between 50-70^. The crawl was between 70 and 80%RH before poly.
So, the fans seam to work in the cold/dry weather. When the humidity comes, I would close the last fan and if necessary install a dehumidifer in the crawl for the summer months.



So.... do I have to buy a smartvent or where do I find this due pt monitor or absolute humidity monitor to run the fan already installed? Or do I find another solution for the furnace air?

[teddy bear]

For furnace air, some codes suggest a 4" supply duct from the air handler to the crawlspace. When the fan/furnace operates 750-100 cfm of air is discharged into the crawlspace. This pressurizes the crawl, helping the draft of the chimeney. An equal negative pressure sucks in fresh air in the rest of the home. Combustion gases go up the chimeney. Not all bad. TB

[cem-bsee]

I had a friend making an enthalpy controller in 1980 -- $350
he was selling to beer warehouses!

search THERMASTOR.com --
he is into dew point -- sent me a psych slide rule --
I just glanced at his site --

[teddy bear]

Dew point controlers are expensive. Even if you make the investment, this not a solution. When the outdoor dew points are low, your crawlspce is dry because dry air is infiltrating your home. Opening a vent during dry weather is not needed. When your space is wet, the outside is wet. After sealing the earth, close the vents. If you have excess moisture in the crawlspace, dehumidify. This is the inevitable end of your search. TB

[gcollins]

O.K. I've read a dozen articles on sealing the crawl and am 100% back to sealing the crawl-the psychometric chart tells all.

1. Sealing - only one more fan.
2. I have two solutions for air for the furnace-if I have a code problem with my AC guy for the supply air to the crawl.
3. Install CO2 monitor
4. Install dehu--I am presently spending 10K$ to refinish my teak/walnut floors.

What did I miss?


TB thanks again.

[tuncos]

3. Install CO2 monitor

Do you mean CO

I have found this thread quite interesting. It really sounds like the construction industry needs to quit doing things the same way they did in the 1950's...