I live in CT and would like to add more insulation to my attic. The house was built in 1964 (Colonial)and has blown in cellulose fill to the level of the rafter 8". However there is no vapor barrier! I have been informed that increasing my insulation will cause a moisture problem without a vapor barrier. Is there any way to increase my insulation level without having to remove the cellulose and install the vapor barrier? If this is not possible what would be the best course of action?
If you add UNFACED fiberglass roll insulation over the cellulose, it will not make your problem any worse. The insulation will still be able to vent through the attic.
I think the person who "informed" you assumed you would be using roll insulation with a vapor retarder as part of it, and in that case the "informer" was correct.
Architect (NY) and Home Designer (PA)
Posts: 2477 | Location: Tobyhanna, PA | Registered: 24 October 2005
Although not using a vapor barrier is NEVER a good idea, you can create one by using a ceiling paint with a low permeability rating. As mentioned, adding unfaced insulation is the way to go, since the insulation values are accumulative, and you do not wind up with a mis-placed vapor barrier, which is worse than having none at all.
Posts: 105 | Location: West Haven, Conn. | Registered: 15 November 2005
Blown in cellulose is good, it will act like a vapor barrier as its permeability is very low. You could use more insulation, however, just add the blown cellulose to get the desired R-value, I would guess 6-8". The cellulose is much better than fiberglas at reducing moisture migration into the attic, however you need to be sure the attic is still ventilated properly. No exhaust fans dumping int the attic and ideally continuos soffit(not blocked by insulation) and ridge vents.
Posts: 7 | Location: Ohio | Registered: 01 March 2006
Although not using a vapor barrier is NEVER a good idea, you can create one by using a ceiling paint with a low permeability rating. As mentioned, adding unfaced insulation is the way to go, since the insulation values are accumulative, and you do not wind up with a mis-placed vapor barrier, which is worse than having none at all.
It is NOT true that having no vapor barrier isn't a good idea.
In fact, it is a CODE requirement to not use a vapor barrier in wall, floor and ceiling assemblies in many locations.
Also, vapor barriers are not required in ceilings or floors when they are in common with vented underfloor spaces or vented attics.
So no, a vapor barrier is not required at all times and in many instances will actually cause problems when installed and therefore should not be.
And no vapor barrier is required in this attic provided it is vented.
This message has been edited. Last edited by: homebild,
Blown in cellulose is good, it will act like a vapor barrier as its permeability is very low
This is not true.
Cellulose insulation is NOT a vapor barrier.
A vapor barrier is defined as any material that has a perm rating of 1 or less.
While cellulose insulation has a low air permeability, it should not be confused that cellulose has a low water vapor permeability because it does not.
A vapor diffusion retarder on the warm-in-winter side is required by code for all blown in types of insulation including cellulose where the geographical region dictates the need for a vapor retarder.
The reason a vapor diffusion retarder may not be needed with cellulose insulation is that it abosrbs upward of 20% of it's weight in water, and does not readily allow for water vapor to condense.
It is condensed vapor that is the enemy and vapor diffusion retarders are designed to help alleviate condensation by controlling vapor flow into frame cavities.
It is cellulose's water vapor absorption ability that may allow for it to be used without a vapor diffusion retarder.
But it is also this very ability to retain water that lower's it's R-value and causes it to compact further lessening it's ability to insulate.
But cellulose is not a vapor barrier and doesn't act as one.
Cellulose is very permeable to water vapor and retains water vapor readily.
This message has been edited. Last edited by: homebild,
Homebild: I will not pretend to know what the code requirements are where you live, but Higgenles, who created the original posting, lives in Connecticut, where I live. Here, it is standard practice to install a vapor barrier, or a vapor retarder, on walls and ceilings which are insulated, for all the reasons mentioned in previous postings of mine. They may do it differently where you live, but this is Connecticut.
All states must adhere to the latest version of the National Building Code, be it BOCA, CABO, or the Unified, as a minimum standard for construction. Beyond that, every state modifies the national standard to suit it's own unique needs, and publishes it's own version of the building code, recognizing that climatic conditions vary all over the country. As an example, living in a coastal area potentially exposes the structure to hurricane-force winds, requiring construction methods which are otherwise not needed inland of the coasts, even within the same state. Likewise, the details for vapor barriers in Florida, or along the Gulf Coast, are exactly opposite of those required in the areas of the country having heating degree-days of 5500, or more, per year.
Additionally, municipalities within the same state are free to require more stringent practices than might be required in adjacent communities within that state. Try tremodeling a structure within New York City in the same fashion as within Westchester County, or Nassau County, in New York, and you will quickly see this to be true.
Having followed this forum for several months, it seems to me that some of those who regularly post here are less interested in helping those who ask questions of the so-called "experts", than in igniting controversy, and in engaging in self-aggrandizement. Certainly, an open forum is likely to produce differences and disagreements, but the tone and tenor of the responses should be geared around those who are searching for answers, not focused on generating conflict, which helps no one.
Posts: 105 | Location: West Haven, Conn. | Registered: 15 November 2005
homebild, Thank you for the information, I did confuse the issues. In my area we do not normally use vapor barriers in ceilings. I use cellulose due to its low air permeability which i am convinced results in less heat loss-the main objective of insulation. When combined with a well ventilated attic, the results are quite good for my circumstances. If a vapor barrier is needed in a retrofit situation, as stated in the original post, I would suggest the paint route to keep the moisture from penetrating the drywall/plaster where damage can occur.
Posts: 7 | Location: Ohio | Registered: 01 March 2006
Originally posted by W. J. Parker: Homebild: I will not pretend to know what the code requirements are where you live, but Higgenles, who created the original posting, lives in Connecticut, where I live. Here, it is standard practice to install a vapor barrier, or a vapor retarder, on walls and ceilings which are insulated, for all the reasons mentioned in previous postings of mine. They may do it differently where you live, but this is Connecticut.
All states must adhere to the latest version of the National Building Code, be it BOCA, CABO, or the Unified, as a minimum standard for construction. Beyond that, every state modifies the national standard to suit it's own unique needs, and publishes it's own version of the building code, recognizing that climatic conditions vary all over the country. As an example, living in a coastal area potentially exposes the structure to hurricane-force winds, requiring construction methods which are otherwise not needed inland of the coasts, even within the same state. Likewise, the details for vapor barriers in Florida, or along the Gulf Coast, are exactly opposite of those required in the areas of the country having heating degree-days of 5500, or more, per year.
Additionally, municipalities within the same state are free to require more stringent practices than might be required in adjacent communities within that state. Try tremodeling a structure within New York City in the same fashion as within Westchester County, or Nassau County, in New York, and you will quickly see this to be true.
Having followed this forum for several months, it seems to me that some of those who regularly post here are less interested in helping those who ask questions of the so-called "experts", than in igniting controversy, and in engaging in self-aggrandizement. Certainly, an open forum is likely to produce differences and disagreements, but the tone and tenor of the responses should be geared around those who are searching for answers, not focused on generating conflict, which helps no one.
Connecticut statewide uses the International Residential Code 2003.
The IRC 2003 does not require a vapor retarder on walls, ceilings, or floors when the spaces are ventilated.
There is no requirement for a vapor retarder at all for the ceiling insulation for the original poster's home in Connecticut.
Section R318.1 of Connecticut's Building Code states:
"In all framed walls, floors and roof/ceilings compromising elements of the building thermal envelope, a vapor retarder shall be installed on the warm-in-winter side of the insulation.
EXCEPTIONS:
1. In construction where moisture or freezing will not damage the materials.
2.Where the framed cavity or space is ventilated to allow moisture to escape.
3.In counties identified with footnote a in Table N1001.2
I believe what I have offered has been a helpful, non controversial contribution to the forum and the poster, especially when others have given erroneous information regarding Connecticut Code and vapor retarders which can actually damage the original poster's home, don't you?
Thank you all for your input and discourse. I also followed up with some local insulation companies who were very helpful and said many of the some things that were posted. My plan is to;
1.) Vent my bathroom vents to the outside.
2.) Re paint my ceilings with water retardant paint. (Painting is on the 2-do list anyway).
3.) Add unfaced fiber glass or cellulose (I hate the mess though).
However I am now concerned about adding flooring for storage given the concerns for adequate ventilation.
Perhaps using strips of plywood instead of sheets would allow for enough ventilation.
The first thing you need to do is air seealing work in the attic. Fibrous insulations such as fiberglass or cellulose will not stop air from flowing through them, they'll only slow it down if anything.
Air sealing requires crawling through your attic and sealing any penetrations in your attic floor with an air impermable material (foam, caulk, etc.) Areas to watch for include but are not limited to: recessed can lights (may need to build box around them to leave airspace between light and insulation so light doesn't overheat), wire penetrations, duct penetrations, soil stack penetrations, and basically any other spot where air can leak from the living space into the attic space). Then more insulation can be blown on top or rolled on top of what you have now. It's also important to note that the best way to prevent any type of attic moisture problems is to have an airtight ceiling line, but then also to control the relative humidity inside the house with some type of exhaust fans to pull the moisture out.
