For Resercon (and anyone else)


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Old 03-22-03, 04:02 AM
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For Resercon (and anyone else)

I was very interested ion your response to C Grover in the thread about moisture, mold and Dricore. My house here in Minnesota is about 50 years old and over the next 3 or 4 years (money permitting) I intend to re-side my house with fiber cement siding and install new windows. I should also say that I am an architect, so I know the basics of what you said and what was said on the website you referenced, but I do strictly commercial and industrial design, so I don't get into the real details of residential design.

My concern with the work I am planning is that I am going to really tighten up the house. Right now its pretty loose and I don't have any mold or indoor air quality problems that I know of. I've already done what I can so far: dump A-coil drain and dehumidifier drain into a floor drain; taped kitchen, bath, and dryer exhaust piping joints; and so on.

I'm thinking I will install an air exchanger so I can still get air changes that my leaky windows now provide. Any other measures that you think would be adviseable?

To complicate my plans, this winter my wife and mother in law (who lives with us) decided they wanted a humidifier. I was able to talk them out of it for the remainder of this winter, but don't know about next winter. At the very least, it seems to me that the air exchanger and humidifier would battle each other.

My final concern is that, here in Minnesota, the energy code requires an air infiltration barrier on the exterior. I was going to use Tyvek until I started hearing about problems with it shrinking over time and tearing at the nails, thus, no waterproof membrane. Don't think I want to use #15 felt with sealed joints because of perm rating and possibility of creating a double vapor barrier. Have thought about installing felt over Tyvek without sealed felt joints; will probably drive the building inspector crazy, though . Any thoughts on this?

Wow, that was really long winded and rambling! Hope you get the idea of my concerns.

Bruce
 
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Old 03-22-03, 09:11 AM
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Minnesota's building code for residential structures exceeds the vast majority of building codes throughout the U.S. In the air sealing industry the Minneapolis Blower Door is considered the standard throughout the country. Minnesota is considered the inline skating capital of the world, which reflects their attitude towards the outdoors. The codes and the public behavior indicate overall public awareness of energy efficient living and healthy indoor environments. Many of us in this industry, if not all, look towards Minnesota as the prominent innovator in producing energy efficient living (behavior) and healthy indoor environments. It is good to note that these go hand and hand. Healthy indoor environments are influenced more by behavior than method application. This infers what may apply in Minnesota will probably not apply elsewhere in the U.S. With this caution stated, I will answer your questions.

The first concern is with the air barrier required such as Tyvec. Manufactured and some wood siding products can contain "LIGNIN". This is a naturally occurring substance found in these products and is a detergent. As with any detergent, it reduces surface tension. When this type of siding is applied over these air barriers, the Lignin degrades the air barrier ability to repel water. Installing a light building felt over the air barrier to meet code, which will not allow the Lignin contact with the air barrier, is the most acceptable method. Since this application is installed by overlapping, it will not be airtight and could be described as a drainage plane. Though the perm ratings of the two materials combined might violate the five times rule concerning vapor barriers, the method of application reduces the probability of it causing a moisture problem.

Lack of air exchange increases humidity levels and increased air exchange reduces humidity levels inside the structure. The need for humidifiers is usually a direct result of the increased air exchange. When homes are built or modified that reduce air exchange, humidifiers are rarely needed. If an air-to-air exchanger is utilized, then it is only a matter of adjusting the amount of exchange to achieve adequate air exchange and humidity levels. Adjusting the timer usually does this. This is more or less trail and error depending on the occupants needs. This will eliminate the need for a humidifier in house or on the furnace.

Design methods used for duct sizing, such as "Equal Friction or Static Regain" do not minimize life-cycle costs on air-to-air exchangers. This is a particular concern for residential energy efficiency. The pressure balancing at elbows, take-offs and the like are not as concise for residential than commercial applications. In most cases the adjustments are done on-site and never calculated.
 

Last edited by resercon; 03-22-03 at 09:34 AM.
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Old 03-22-03, 10:03 AM
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Resercon:
Thanks so much for your reply. I feel a lot better about my upcoming projects now. Now all I have to do is save a few thousand more dollars!

Bruce
 
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Old 03-22-03, 09:28 PM
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Bruce H,

That's why I am glad I am a Minnesota Boy!!!!

When I was building spec houses a long time ago in Minnesota, air exchangers became a real issue as the homes became much tighter but this wasn't addressed as IMPORTANT until issues of mold and mildew became more prevelant. Now when you construct a home or even renovate and upgrade, all areas must be balanced to work with each other. Doing one thing that you think is an improvement may effect another.

Problem is that unless all issues are addressed, the one thing that always gets effected is the "original budget of the project"!

Just some thoughts!
 
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Old 03-23-03, 03:05 AM
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Just one more thing(promise!)

One other thing I have thought about (and decided not to do) is insulate the exterior walls while the old siding is off. Wall construction is 1/2" gyp bd, 2x4 studs, about 1" of some type of celluose insulation wrapped with a foil/paper composite on the exterior side of the studs, 25/32" built-rite, #15 felt, and siding.

I had thought about blowing in insulation, but I am concerned about moving the dew point to an area between the gyp bd and the existing insulation. After 50 years of painting I'm sure I have a vapor barrier there and there is probably a vapor barrier at the insulation. Therefore, it seems to me I could get condensation between the 2 vapor barriers, with nowhere to go.

The house has about 2,800 sf of heated space and my gas bill is actually lower than some of the other houses of friends with similar size homes. I guess my other thought was "If it works, don't fix it!".

Resercon or Doug, do you think I am out in left field with this thinking? I will change my mind in a second if you think I am; I have always been a believer in doing something right the first time so I don't have to deal with it again. I have a very thick skin, so don't be afraid of asking me if I've lost my mind!

Again, thanks for the replies.

Bruce
 
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Old 03-23-03, 07:25 AM
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Slow-Fast-Slow

R-Value with insulation is Resistence or the slowing down of heat flow. SP-rating with vapor barriers is the reduction of moisture within heat flow or the slowing down of moisture flow. When heat with a percentage of moisture reaches the other side of insulation, it accellerates because their isn't anything to impede its flow.

If we look at your situation the paint on the walls act as a vapor barrier and the plaster or sheet rock which has a thermal value slows down the heat flow. Shortly afterwards the plastic slows down the moisture flow and the insulation slows down the heat flow. When the heat with a percentage of moisture gets to the other side of the insulation it accellerates both the heat and moisture flow. If a vapor barrier was put on this side of the insulation, it would slow down the moisture flow as the heat flow accellerated. Condensation is highly probable even though the percentage of moisture has been dramatically dropped because of the vapor barriers. This is because the vapor barrier applied to the wrong side of the insualtion and the accelleration of the heat flow allows moisture to accumulate. The whole purpose of a vapor barrier is to decrease the flow of moisture as you decrease the flow of heat. If you slow down the flow of heat and not the flow of moisture, condensation is highly probable. If you slow down the flow of moisture and not slow down the flow of heat, again condensation is highly probable.

This was considered the most common cause for moisture related problems with insulation until research found that most structures that were experiencing moisture problems did not have a vapor barrier applied to the wrong side of insulation. What baffled many researchers was the vast majority of structures investigated actually followed recommended applications. To make a long story short, it was found that the cause for all the moisture problems were related to air transported moisture than heat transported moisture. Hence the formation of the air sealing industry and the introduction of the Minneapolis Blower Door. Yes, they were the first to be used on a very broad scale.

Further research revealed that other applications within the structure affected the performance of moisture related problems concerning energy conservation. A phrase that is widely frown upon throughout the industry came about known as "Whole house being a system of energy use." Today the phrase that is commonly used and accepted is "Energy Efficient Living." This is what separates Minnesota from the rest of the country. An example of this is many years ago Minnesota mandated in their building codes that fresh air supplies must be installed in homes where combustion appliances were present. This was an important step because it changed the thinking of the entire energy conservation industry. What I find a little humorous is that many in this industry want to change the term energy conservation to energy efficiency.
 
 

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