i am going to post this message here in hopes that someone can offer some guidance. here’s the situation- i have built a timber frame house using SIPS. the full basemant foundation is daylighted to hte south(50 ft.) and on the s. east and s. west approx. 15 ‘. . below grade the foundation is sealed and insulated w/blue foam(2″) and the walls are 10″ thick. all walls are poured concrete. on the above grade portions of the foundation the walls are 6″ thick w/a 4″ brick ledge at grade. i was going to do a stone veneer using a combination of diamond mesh ,dove tail ties and mortar to hold the veneer fast to the walls. last winter while working inside w/the thermostat set @ 55(radiant in-floor heat) i noted that once the outside temp. went below 18 deg. the exposed walls frosted and condesated heavily. i have an HRV. (not yet installed.) how much will this help? i know that i can insulate the inside walls but that is exspensive and labor intensive as i am doing most of the work myself. i also know that i can insulate the outside walls but then how can i get my veneer to adhere? also w/ 2″ of foam my brickledge becomes 2″. no fake stone please. any ideas folks? i am open to any and all suggestions. also fyi – i am a logger not a tradesperson. thanks, jimbo
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How old is the concrete. New concrete can take a long time to lose all its free moisture.
Are there any sources of vapor in the basement?
SamT
the walls are 10 yrs old but the 6" slab was poured late last fall jim
The first time I read that through I thought you were saying you were getting condensation on your SIPS. We're actually talking about condensation on the inside of the exposed concrete basement walls right?
Is the floor sealed and insulated as well as the walls?
What sort of climate are you dealing with?
Is the condensation uniform on all of the walls or concentrated in specific areas?
Kevin Halliburton
And with that, the great emporer Oz gently floated away on a curtain of hot air, laughing at the unfortunate ignorance of little people beneath him. But under his breath he cursed that stupid little dog...
sorry for the confusion . yes ,i am talking about the concrete walls in the basement , more specifically , the wall where they are above grade. the 6" slab is insulated w/ 11" blue foam. radiant tubes in floor.beneath that is a vapor barrier and 1' of compacted sand. the slab is insulated from the wallw/bl. foam. the climate is westrn n.y . think buffalo ! cold winters! thanks, jim
How about adding a 5 1/2" steel ledger on top of the brick ledge? That would give you 1" insul + 1/2" weep space and still leave the majority of the bricks( 4"?) over the concrete ledge.
SamT
Interesting problem.
You conditions now are so much different that what they will be when living in it that it is hard to say.
You have moisture being given off by the concrete, by the framing, and maybe from DW/plaster that won't be given off after a year or two.
But you are not living in it and people's "exhaust" (breathing) give off lots of moisture along with bathing and cooking.
You are operating at cool tempature. When you have it at 70% the air can hold a lot more moisture and the wall will be warmer and you will have less condensation problems.
Also you are using radiant heat so that you don't have moving air and that allows the foundation wall to be colder.
" i have an HRV. (not yet installed.) how much will this help?"
If you are in a dry enough climate it will help, but don't know how much.
Where are you located? Some one with personal experience in your climate will have better ideas of how bad a problem this is.
Will the inside areas be accessible for addint insulalation later?
What about using 1" of poly iso foam on the outside? That is about R-6 if I remember and still leaves you 3" of your brick ledge.
A lot of people don't understand the relationship between moisture humidity and condensation.
Here is an online psychrometric calculator.
http://www.engineeringtoolbox.com/8_240qframed.html
When you have moisture (water vapor) in the air the amount stays the same as the air is heated or cooled until some action adds or removes moisture. It can be removed by the tempature going below the dew point and it condenses (that is what AC and dehumdifiers do) or added by evaportorating water (shower, plants, breathing). It can also be changed by mixing in outside air that has a different moisture level.
The amount of moisture that the air can hold varies by the tempature. The ratio between that amount and the current amount is the Relative humidity, given in percentage. The other term you need to know about is dewpoint. That is the tempature where the % relative humidty level reach 100% and the moisture condenses.
Now if we take a house with 70 degree air @ 30% RH we see that it has a dewpoint of 37 F.
Now if we have outside air of 30 F and 60% RH that it contains an absolute moisture level of 14.48 gr (of water)/lb (of air).
Now we bring some of that air in and warm it up to 70 and it has 13% RH and when fixed with the moister air helps reduce the humidity level.
The same action happen weather it is done by opening a window or an HRV is used. The advantage of the HRV is that it helps warm the income air by the heat of the exhausted air so that less energy is used.
I have posted this message.........
you have condensation.
Why be so neurotic?
Stop watching your walls!
I Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
Edited 10/7/2004 9:35 pm ET by firebird