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Insulation Confusion


chrisssss's Avatar
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05-15-03, 07:46 AM   #1  
chrisssss
Insulation Confusion

HELLO,

I OWN A CONDO IN QUEENS NEW YORK. I HAVE AN ATTIC AROUND 450 SQUARE FEET THAT I AM CONVERTING INTO A ROOM. MY CEILING IN THE ATTIC IS PITCHED AND MADE OUT OF WOOD. THERE IS ONE SMALL WINDOW IN ONE OF THE CORNERS OF THE ATTIC, PROBABLY ONE FOOT BY ONE FOOT. I HAVE ASKED SEVERAL PEOPLE, INCLUDING MY CONTRACTOR ABOUT WHAT TYPE OF INSULATION TO USE AND NO ONE CAN TELL ME. I AM VERY CONCERNED ABOUT CONDENSATION AS SEVERAL PEOPLE IN MY CONDO COMPLEX HAVE MADE THE SAME CONVERSION AND NOW THEY ARE NOTICING THAT THE SHEET ROCK IS BECOMING DEFORMED. MORE IMPORTANTLY THEY ARE NOTICING WOOD ROT AND MOLD. ALMOST ALL OF THEM HAVE AN EXHAUST IN THE SMALL WINDOW AND THAT DOES NOT SEEM TO HELP. WE ARE NOT ALLOWED TO PUT ANY KIND OF HOLES IN THE ROOF SO THAT ELIMINATES ANY TYPE OF SKYLIGHT SITUATION. WHAT IS THE PROPER THING TO DO HERE?? SOME HAVE SUGGESTED THAT I BUY THESE PINK VAPOR BARRIER SHEETS THAT ARE SOLD AT HOME DEPOT STAPLE THOSE TO THE ROOF AND THEN PUT INSULATION.

 
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resercon's Avatar
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NJ

05-15-03, 08:57 AM   #2  
At the bottom of this message is a www icon, click on it and on that site scroll down on the topic for "VENTILATION". I strongly advise you give this site to your neighbors who are experiencing problems with these rooms and they should also read topic "SICK BUILDING SYNDROME & ENERGY CONSERVATION."

What attic ventilation does is ventilate the roof. Having a fan in the room on the other side of the insulation separating the roof from the fan is not attic ventilation. Condensation formed between the roof and the insulation because the roof is not ventilated. this WILL occur in both the heating and cooling seasons. This is because heat is generated from inside the home during the winter and outside the home during the summer. Since all heat has moisture in it, as the heat transfers through the roof and/or insulation you do not want to trap the heat. Not having adequate free venting trapped the heat between the insulation and roof causing the condensation. Result mold and wood rot. Your neighbors probably need a new roof and if they allow this to continue it WILL get worse. They have no choice at this point to remove both the sheet rock and insulation and then have the structual members of the roof inspected by a professional.

 
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05-16-03, 02:34 PM   #3  
You can only insulate this area if you can ventilate the roof. The same is true with installing sheet rock to the rafters. If you cannot install vents to your roofing system, then you have no other choice but to leave it the way it is, which means the rafters must be exposed and uncovered.

I understand that the association where you live limits you to what you can do to the exterior of the townhouse. There are ways that you can install adequate free venting under these circumstances where the vents are not noticable. You can contact a local contractor and he will evaluate the site and give you the options and costs. If you want, you could try giving me a better description of the area and I can give you some solutions. Example, does the roof overhang the outside wall or is it flush with it? How high is from the floor to the peak of the roof? etc.

 
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05-21-03, 07:01 PM   #4  
Reasons for their statements.

Slate roofs are water shedding systems and not water tight systems. Today the substrates of roofs are usually plywood. Years ago they used wood slats or planking. With slate, wood planking is more common. Both the wood slats and planking could not be described as an air-tight system.

Ventilation was found only to be needed when homes were being installed with insulation. Old homes that do not have insulation do not require ventilation and when they were built vents were not installed. If you take an old home and install insulation, then you have to install vents in the attic.

The reason older homes without insulation do not require attic ventilation is because of convection. One characteristic of convective heat transfer is the warmer the air is the faster it rises. Also air with a lower humidity level will extract humidity from air or an object that has a higher humidity and vice-versa (ErH%).

These are the reasons why the architect and contractor made those statements. The slate roof being a water shedding system, planking as a substrate making it not an air-tight system and no insulation installed. The difference between having insulation and not having insulation is the temperature of the air between the sheet rock and the slate roof. Without insulation the heat traveling through the sheet rock will heat up the air in this space. This will cause the temperature of this air to rise and it will escape through the roofing system taking moisture (ErH%) with it. It has been done this way for centuries. What insulation does in this application is that it prohibits or slows down the heat transfer, thereby lowering the temperature rise of the air inside this space. The probability of condensation occurring under these circumstances are very high. Attic ventilation reduces this probability dramatically.

The problem I have with this is things change and they rarely ever stay the same or use the same materials and methods that was used years ago. Going from wood planking to plywood or slates to asphalt shingles or adding insulation later will induce the condensation. Even applying a radiant paint could induce the condensation by reducing the temperature in this space and slowing down the air movement.

So do I recommend just installing sheet rock over the rafters? You can but you must understand the consequences if things change and have the decency to take the time to explain the same to the next owner of the home if and when you ever sell the home.

 
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