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I have a condensation problem with a 100 year old two story house with a walk up attic. The attic was insulated about 5 years ago with cellulose insulation. This past summer the wood fascia and soffits were replaced and covered with aluminum fascia and vented soffit. The north wall of the house had cellulose insulation blown-in, the rest of the house had already been insulated. Vinyl siding was installed over a 1/4″ fanfold insulation.
There was never a condensation problem until this winter. It is severe enough that the floor boards are cupping with visible signs of moisture in the grooves.
Any suggestions as to why this problem has just now showed up and what can be done to fix it.
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There's a pretty fair chance the fanfold and vinyl have reduced the number of air exchanges so that moisture generated in the house isn't escaping as quickly, so it's finding its way into the cooler attic and condensing.
You need to find the source of the moisture and correct it.
Possible culprits:
Furnace/boiler/water heater not properly venting out of the house. This isn't likely, but can be deadly, so be sure to keep it in mind.
Humidifier on a forced air system set too high.
Excessive moisture in the basement or crawl space. (A very common cause of condensation in attics!)
Clothes dryer not vented out doors.
Teenagers taking long showers
Plumbing leaks.
Where are you located?
*I agree with some of the suggestions already made. You have to eliminate the source of moisture. Air seal all openings that allow warm moist air into the attic. This can be accomplished with a smoke gun and PU foam gun. Weatherseall doors to attic, etc.I think what probably occured is that in venting the attic, you are creating a draft and/or lower pressure than the finished spaces which is now siphoning the warm air out of the living space. What did you hope to accomplish with the ventilation?When we reside/reroof older houses, I explain that unless they are willing to properly insulate and weatherize the house there could be potential problems from adding ventilation. In short, if there are no symptoms from non ventilation, if it aint broke, don't fix it. If this is your customer's house, its your baby now. If its your house, try stuffing insulation along the eaves and ridge vents. In other words, close the vents. Your problem will go away. Do all the airseal stuff that you can anyway.There used to be alot of good discussion on this topic many years ago. But it has all but disappeared. The vent/ nonvent debate is really common sense.
*Wait a minute Tommy -- Are you suggesting that venting an attic can cause problems? Andy
*Andy,I actually enjoyed those old threads. Maybe we can lure Fred back into the fold.
*Tommy, I loved those threads. But Fred and I remain friends, and I'm pretty sure he's not coming back. We had several conversations that revolved on why people got so hot on the topic. That alone was fascinating; add to it the physics of building and I'm hooked.Andy
*Greg, you mention vented soffit, but you don't say anything about ridge vent or other vents near the peak of the roof. If you have vented soffits, but nowhere for the warm air to escape, you have no ventilation at all. Even if you have ridge vents, is there a path for the air to travel through to reach the peak of the house ? Or does some of the insulation block off the path ?
*Yes there are roof vents. In fact prior to all of this work being done the rafter cavities at the exterior walls were stuffed full of fiberglass insulation to keep birds out of the attic. The roof shuld have better ventilation than it ever had, but it doesn't seem that way
*The attic may have better ventilation, but with the addition of the cellulose and the siding you've cut off a lot of the old paths that that the moisture had to escape. So now it leaves via the path of least resistance--the attic--which happens to be cold and leads to condensation.If you do a better job of air-sealing the attic you could probably cut down on the condensation problems in the attic, but then you'll have more moisture problems inside the house. Moisture that used to escape in a fairly diffuse manner will be bottled up inside the house, and could lead to mildew and condensation and such.I think the key to the problem is to get amount of moisture generated within the thermal envelope under control and to ventilate that moisture out of the house in a predictable and non-destructive manner via controlled passive or active mechanical means.Steve
*I'm typing from northern Michigan so my perspective from that geographic area: Those large, old, and sometimes unvented, attics underwent many air exchanges which dispersed the moisture in many directions. We side the homes with products that don't breathe (compare to us putting on a raincoat) and then are surprised that new set of problems are created. In a perfect world where all moisture from within a home is properly vented and not driven into the attic and there is no heat loss into the attic (relatively impossible to attain given depth constraints) then we would not need attics that are vented - woe to those who plug attic vents when heat loss/moisture is present and home is wearing a "raincoat" - in this country we get ice dams, water backup and infiltration into the home, mold and mildew. Talk of sealing all those locations where heat/moisture can enter attic is well and good and certainly a worthy goal. Most folks though are content to do a pretty good job sealing (on new construction) and perhaps no sealing at all on a retrofit, and heat loss is a fact of life. These result in making proper attic venting a necessity. Admittedly attic venting is addressing symptoms rather than cause but alas perfection is elusive with technology now in common use. Must be on a roll as am preachy today.
*i'm a little confused, because you mention "floorboards", but then refer to a vented attic... so i'm assuming it's not a living space.if your current venting is inadequate, i would be recommending attic fans installed behind attic vents at each end of the attic (one drawing air in at one end and one at the other moving air out). will reduce your energy bill in the summer too (some ROI).
*Location climate is the first question. I did not see location, but am blind sometimes.Next, the moisture is out of control bigtime, and needs local eyes. Call Fred Lugano or Joe L.near the stream,ajFor Joe... http://www.buildingscience.com/For a google on Fred...http://www.google.com/search?hl=en&q=Fred+Lugano&btnG=Google+Search
*Great article... with pictures and diagrams which I like being a very visual person.Fred is the author...http://www.homeenergy.org/archive/hem.dis.anl.gov/eehem/98/980508.html
*Steve Zurby... one our boys...Good article Steve... You better hook up with Mike Smith to golf at a future Fest get together...http://www.oldhousechronicle.com/archives/vol01/issue03/technical/priorities1.htmlnear the google stream,aj