Replies

1. 
   Guest_ | May 31, 2000 08:18am | #1

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   Chris,

   Probably not by themselves. It would also depend upon what type of venting you have in the main basement. The UBC requires 1 sq ft of vent area for every 150 sq ft of footprint for an underfloor area. If the new basement is unheated, the moisture which will ultimately develop in the masonry can promote dry rot in the floor joists. If you put an 8x8 vent on opposite walls, you would allow for cross ventilation with about the right amount of venting for your 132 sq ft footprint.

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   Guest_ | May 31, 2000 07:42pm | #2

   *How many times do people need to be told that venting a basement or a crawl space is a bad idea??????Rule of thumb - basement (particularly this one) is colder than outside (at least in summer)Fact of physics - Warmer air holds more moistureFact of Physics - Warm moist air condenses on a cold surfaceFact of Physics - Warm moist air will increase in relative humidity when cooledCan someone please explain how they think they can dry out a basement or crawl by bringing in outdoor air?Granted - it will work in the winter time, but it will also freeze everything in there!Chris - where is this house? It may make no difference - but you may actually live somewhere where the air gets warmer and drier in the summer - I will move to this place if that happens!-Rob

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   Chris_Barritt | Jun 05, 2000 12:38am | #3

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   Rob, our house is in mid MD where it can get very humid in the summer. As I said we've had no sign of moisture as of yet, so we just open the door to the addition on days when it's nice a dry. I understand what you're saying, it's just that I get a different answer depending who I'm asking. I don't want to be repairing something a few years from now when I should have taken some precautions earlier.

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   John_Dawson | Jun 06, 2000 04:14pm | #4

   *The advice you just recieved and the physics lesson were both spot on. I live in PA and have the same weather. I simply cut down on NON atmospheric borne moisture (transmission thru block / concrete) with a siloxane sealer - this is not silicon but old fashioned water soluble "water gel" which sets up in the concrete surface. To combat the chilly / damp effect of atmospheric H20 you have two options. The first is the same as you use on the main floor (air conditioner) and the second is a dehumidifier. Either will remove moisture by condensation on cool coils. the ac dumps excess heat outside the dehumidifier inside. Two other options come to mind but are more complex. THe first is a Canadian style air exchanger. This exhausts house air over a radiator, cooling (or heating in the winter) the incoming air. The now cooled and denser incoming air dumps some of its moisture via condensation and this can be drained away (with a pump). The last method you already found. It was automated in the sixties and you might still be able to find a copy of "a differential temperature basement ventilator" on Popular Electronics microfiche. What it was, was a motorized plywood shuter and a fan bolted to a window or outside air source. Internal and external thermistors sensed temperture and if it was cooler outside it drew in some good air and blew out the bad. The same thing could be done with humidistats. All of these solutions cost money in the form of electricity / heat. You may want to try one last expensive technique: check your Radon level. If it's up, for about $250 you can justify sub slab suction. This will draw air from the basement and rooms above and throw it away outside. If you are drawing conditioned air the moisture level will be lower. Of course you will have to have a vent somewher to bring in moisture laden outside replacement air which you them have to spend more money cooling and drying out -- you get the idea. By the way , just moved up from Georgia. Garage basement combo stayed at 100% humidity 9 months of the year. My total cost for tool and furniture protection ran to about $10 for WD-40 and J&J paste wax.Never vented, never cooled, never dehumidified. Sometimes I'd cheat and open the upstairs door and let some cool air drift down so the beer would not warm up as quickly, but generally adapted a so what ? approach. good luck

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   Chris_Barritt | Jun 06, 2000 04:14pm | #5

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   I recently put on an addition that resulted in a separate basement area 6' x. 22' with it's own outside entrance,block walls & concrete slab. There are no windows & one end is below grade. The insulation is between the floor joists with the vapor barrier against the subflooring. We've no signs of moisture as of yet, but an ounce of prevention is worth of cure. Would a few holes through the common wall into the main basement be enough ventilation via natural convection? We live in Maryland