Crawlspace insulation questions


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Old 07-08-10, 12:06 PM
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Crawlspace insulation questions

I've been searching and reading posts about crawlspace insulating tips, but I still have some questions. My crawlspace has a concrete floor, with vents on three sides.
I've come to the conclusion that all the insulation should be removed from between the floor joists, and those vents should be sealed off. I've also read about 6 MIL plastic on the floors, and two or three inches of insulation on the walls. My questions are: What type of insulation for the walls? The pink rigid type? If so, can I just glue them to the walls with liquid nails? Also, whats the best way of sealing the vents? Thanks. John
 
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Old 07-09-10, 09:53 AM
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There has been a lot of information on the web concerning new applications to conserve energy. Most of these come from Build Science Organizations (BSO's). From someone who has been in the energy conservation industry for decades, I refer to these proposals as “New School”. Which clearly infers that I am “Old School”. An example of the difference between the two schools is New School believes that basements/crawl spaces are partially conditioned. Old School position on this subject is there is no such thing as a partially conditioned space in a structure. You either want to heat/cool an area or you do not to.

I oppose the application you intend to do not just because I am “Old School” but because of the 3 major types of moisture transfer inside a structure. Which are Equilibrium, Capillary Suction and Gravity. Equilibrium follows the second Law of Thermal Dynamics, “High to Low”. Simply put an object of lower humidity, such as the air outside, that comes in contact with air of higher humidity, such as the air inside your crawl space, will absorb humidity from the higher humidity air until the two are equal in humidity. Your crawl space vents allow this process to occur.

For New School to support their position they supposedly address Capillary Suction. Simply put if you ever dipped a tissue's corner in water, the water would rise up the tissue that is not submerged in the water. There is no argument that this is a major source for moisture inside basements/crawl spaces. Putting a moisture barrier on a dirt floor and insulation the walls that has a vapor barrier would reduce the amount of moisture transfer from the ground to the basement/crawl space. It is good to note that the prohibition of moisture transfer works in BOTH directions. In other words a moisture barrier prohibits moisture coming into the basement/crawl space also prohibits moisture inside the basement/crawl space from leaving.

The last one is gravity. Simply put if you ever hanged a wet towel outside after several minutes if you felt the towel from top to bottom, it would be drier at the top and wetter as your hand moved down the towel. Though all 3 moisture transfer mechanisms apply upstairs from the basement/crawl space, gravity is an important factor involving basement/crawl spaces. In fact it is an essential part of a drainage plane for the water shedding properties that architects design into their structures.

In New School defense, they do recommend controlling the amount of moisture generated inside the structure. Such as making sure the dryer, bathroom and kitchen exhausts vent to the outside properly. Monitor your plumbing and address leaks mediately. Unfortunately most people don't read that far into these papers or the paper refers to other guidelines, which no-one reads. This is a problem, in fact they even have named it, “Sick Building Syndrome”. They don't mention variables like humans give of 2 pounds of humidity a day and dogs 5 pounds from breathing alone. How many people and pets are you allowed to have in your home to “Sustain a Healthy Indoor Environment” under their proposed applications? Do you limit the number of times one can wash their hands and use the bathroom? How about installing a waterless urinal? All kidding aside, what is usually recommended is a Heat Recovery Ventilator (HRV). Unfortunately there are few places on this earth where one is cost effective. Alaska would be one place. In other words the costs of the HRV wipes out and savings you may achieve by sealing your crawl space.

I apologize for the long post and I hope my position on this application is clear.
 
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Old 07-09-10, 10:58 AM
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So, should I just replace the insulation between the floor joists above the crawl space?
 
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Old 07-09-10, 12:41 PM
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If the insulation is in good shape, I see no need to replace it. If in some areas it is bad, then just address those areas. Air sealing is a good thing in your situation. Just follow the wires, cables, pipes and/or ducts to the point where it penetrates the conditioned space upstairs and seal around the penetration with foam, caulk or even scrape pipe insulation if you have.
 
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Old 07-22-10, 08:06 AM
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Sick Home syndrome is not caused by conditioned crawls! You mention airsealing in other posts and just recommended sealing all the floor penetrations from the vented crawl. Tight homes need proper controled ventilation.

Have you read the research on Conditioned Crawls. It makes a lot of sense to follow the "New School" methods when you understand the science and read research they have done. I live in a humid climate zone and have converted my vented crawl to a sealed and conditioned crawl.

I have seen first hand the moisture issues caused by vented crawls and how well conditioned crawls work at keeping humidity levels low.
 

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Old 07-22-10, 10:17 PM
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Research papers state a position.. For those of us who seek new approaches in our field read such papers. It is common place for us to look for other research papers that both support and dispute that position before implementing it. As professionals we refer to this as “Due Diligence”. This explicitly implies that research papers are not fact.

Sick Building Syndrome (SBS)was originally for inadequately ventilated “High-Rise”structures. This stems from research papers that held the position that less air exchange would result in lower energy costs for the building. Guess who wrote those papers? As an energy conservationist, I am ashamed of that fact. Some years later residential homes were being condemned because of mold. It was found that in the vast majority of these homes had one thing in common, energy conservation measures. This along with the High-Rise incidents led to an Architects of America conference lead speaker starting his speech saying, An architect never did anything to a structure that led to the condemning of that structure. This speech effectively extended the phrase SBS to residential because people were getting sick in these homes and was specifically aimed at energy conservationists. An apology followed shortly after for the finger pointing. But it did make me and others think of what we are doing and how we should proceed.

I do not expect you to understand the reasoning behind my position nor can you expect me to understand your reasoning behind your position. However, it is my desire that your position isn't based solely on this research paper.
 
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Old 07-26-10, 10:49 PM
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Is your HVAC unit and ducting down there? http://www.advancedenergy.org/buildi...l%20Spaces.pdf

Are you in a radon high risk area that you require vented? Geologic Radon Potential of the U.S.

You may need to cover the foam board: http://www.icc-es.org/reports/pdf_files/NES/Ner699.pdf

Will your LOCAL B.D. allow changing from a vented to aclosed crawl?

Where are you located? http://www.eere.energy.gov/buildings...s/db/35379.pdf http://www.energy.wsu.edu/documents/...awl_Spaces.pdf

Things to do for the change: http://www2.iccsafe.org/cs/committee...E_06_64_07.pdf

Be safe, Gary
 
 

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