Welcome to the DoItYourself Forums!

To post questions, help other DIYers and reduce advertising (like the one on your left), join our DIY community. It's free!

Blow-in Insulation


Bruce H's Avatar
Member

Join Date: Oct 2001
Posts: 866
MN

10-25-01, 07:10 AM   #1  
I am planning on re-siding my home and thought that would be a good time to blow in celluose since there is no insulation in the walls. A post by Insulman indicated that the machines Home Depot loans is not adequate. Why? Can't get the required density? Would drilling more holes per cavity help? Any way to know if a rental store machine is adequate? Etc?

Also, what are pros & cons to using celluose vs. fiberglass?

Bruce H

 
Sponsored Links
Accurate Drywall's Avatar
Visiting Guest

Posts: n/a

11-05-01, 02:11 PM   #2  
Accurate Drywall
Would highly recommend cellulose, if you are removing old siding you could remove piece of ext sheathing (approx. 3"x8" piece of exterior sheathing at top of wall between each stud cavity to acess to blow in and fill to top. Replace piece by nailing back to top plate. Can do same thing below windows to acess below window cavities. May sound complicated but if you cut holes first, insulate, then replace sheathing, should move fairly quickly. If you used batt insulation, you would have to acess entire cavity. Good Luck! -- Have used the machines from Lowes in an attic and they worked fine for me.

 
Bruce H's Avatar
Member

Join Date: Oct 2001
Posts: 866
MN

11-06-01, 12:59 AM   #3  
Dew Point

Thanks for the info! A question that occurred to me after this post that I am trying to find an answer to: Right now there is no insulation in the walls and no vapor barrier of any kind. It occurred to me that if I insulate the walls, the dew point will be moved into the stud cavity. With no vapor barrier, I am concerned that I may be creating a serious problem for myself. I spoke to a couple paint manufacturer's reps about vapor barrier paint, but they were something less than enthusiastic about it and did not want to commit. Do you (or anyone) have any thoughts on this?

Bruce

 
Accurate Drywall's Avatar
Visiting Guest

Posts: n/a

11-06-01, 01:11 AM   #4  
Accurate Drywall
You can install a house wrap (Tyvek is a name brand) on the exterior after you have insulated and before you install new siding. This house wrap allows your house to breath but also serves as a barrier. Look TYVEK up on computer, sure you can find more info on it. Simple to install - just staple to exterior sheathing. Cost about $70.00 for 1 roll which normally does good size home, can probably find off brands for less. Comes in roll about 9'tall.

 
Bruce H's Avatar
Member

Join Date: Oct 2001
Posts: 866
MN

11-06-01, 07:03 AM   #5  
I live in Minnesota, so a vapor barrier is normally needed on the inside (warm side). The Tyvek you refer to is a wind wash barrier and will allow the house to breath, but without a vapor barrier to limit how much water vapor gets into the stud space, it seems to me that the vapor that condenses at the dew point may be too great to get out to the outside in a short amount of time. That may lead eventually to dry rot?? I know that walls are blown full of insulation all the time, and maybe I'm trying to analyze this too much, but I am also a firm believer in Murphy's Law. Have you heard of any problems associated with adding insulation without a vapor barrier in the northern climates?

Bruce

 
rbisys's Avatar
Visiting Guest

Posts: n/a

11-08-01, 05:38 PM   #6  
rbisys
Greetings, Bruce

If your going to side the house then you can super insulate from the outside without moisture problems either.
When I side homes having no wall insulation, I do the following.
Install 2x2 on the stud lines and install two layers of radiant barrier material. The material to use is type 2, perforated, foil both sides. Do not use bubble foil, it is too thick and expensivbe. This will exceed the performance of a 6" batt and you will not have condesation problems or mold/mildew problems. If you are careful around windows and doors you will eliminate most of the air infiltration. You should also have better humidity levels in the house because you will not have the condensated moisture in the bulk type insulations to penetrate the walls. If you have lap siding you can install the first layer over the laps and then the 2x2. This would be faster. DO NOT install the radiant barrier over the top of the 2x2. They need to breathe.

For more info on radiant barriers enter your search engine. "radiant barriers" or "reflactive insulations".

You can also install a radiant barrier over you attic insulation and greatly reduce your a/c costs.

Thank you for considering my opinion.

 
resercon's Avatar
Member

Join Date: Nov 2001
Posts: 1,873
NJ

11-11-01, 04:54 PM   #7  
My collegues have argued this issue for years, no decades. One school of thought stands on dew point is achieved in all types of insulation, to which there is no arguement. The other school stands on the fact that other types of insulation like fiberglass use trapped air for the thermal effect, celluose does not. Both schools agree that a vapor barrier paint with a SP-15 rating makes this arguement moot. Yet we still argue. Your concern is therefore warranted because even the foremost experts in this country cannot agree on this issue.

But let us consider your situation with facts. It is a fact that it is more likely a condensation problem will occur in a wall with batt insulation than with blown in insulation. Reason, not all wall cavities are 16 inches on center. It is a fact that you have more wall surface area than attic floor or basement floor area. And greater the surface area the greater the heating or cooling loss. It is a fact that any vapor barrier with a rating of SP-15 would reduce the moisture content of the heat traveling through the insulation to a point where there isn't enough moisture in the heat to condense.

I'll let you decide.

 
rbisys's Avatar
Visiting Guest

Posts: n/a

11-12-01, 12:19 AM   #8  
rbisys
Greetings,

It doesn't matter if you have blown or batts. The problem is that you reach a dew point in the material and water vapor condensates. Short of encassing a wall in metal and welding the seams I know of no way of stopping this process.

Plastic films are for the most part worthless. Also, if you are not pulling moisture from the inside you are pulling it from the out side. It takes over a 1,000BTUs/# of water to convert from vapor to liquid.

The Nat'l Br Stnds released a report years ago on moisture in FG and cellulose in a house they bought and set up for testing. No occupants, the FG had 9.6% moisture and cellulose 14.4%. Appling the %5 increase heat flow for every 1% moisture you have about 48% and 72% increase.

I have seen in this area (ST. Louis) severe mold/mildew and dryrot in walls with 4 mil vapor barrier. I have seen moisture saturated in insulation in the summer during a prolong drought. The moisture buildup is so severe that the weight causes it to drain to the bottom thereby increasing the wood's moisture contaent to the point where rotting occurs.

You will not get moisture with the radiant barrier as long as it is installed right. Even if you did , it would probably be limited in amount, Since the film cannot absorb any moisture there would be no buildup or residual heat loss effects. The reason there is no condensation is because the film atains (approx) the interior temp. Warm moisture needs a cold surface to form on and it doesn't exist with RBs.

Because the high mass material and the stored FG/cellulose moisture, heat energy is released slowly. This is one reason why these materials are slow to respond to temp changes and a/c's run all day and long into the evening without stopping.

Please name your experts. Who do they represent?

Thank you for considering my opinion.

 
resercon's Avatar
Member

Join Date: Nov 2001
Posts: 1,873
NJ

11-12-01, 05:23 AM   #9  
Energy conservationist and Building Specialist of America (Architects). The following are facts.
1. The U.S. Dept. of Energy has mapped out geographical areas of the U.S. where vapor barriers should be applied, on the inside for areas that experience 8,000 degree days or more, no vapor barrier for areas where the climate is dry and on the outside for areas that are hot and humid.
2. Condensation is attracted to cooler surfaces.
3. More structures are destroyed by energy conservationist than by architects. (moisture related)
4. I am an energy conservationist.
5. The dominant heat tranfer mechanism for cooling is radiant.
6. The dominant heat transfer mechanism for heating are diffusion (capillary) and air movement.

I have been avoiding this issue for years because the facts are undisputable. In fact I joined this forum in the hope that that this issue would not come up. However I did post a reply that provoked a response, my mistake. In any industry, there are those who do a disservice to that industry by improperly applying techniques used in that industry. If I looked at 10 companies involved in energy conservation, what percentage of those companies would misapply techniques used in energy conservation? And yet the debate still goes on.

rbisys statements are correct. If you are to respond to this post, please forgive me that I don't.


 
rbisys's Avatar
Visiting Guest

Posts: n/a

11-14-01, 03:13 PM   #10  
rbisys
Greetings, Resercom

Welcome to the club. Your knowledge will earn you caustic comments and you will be the recipient of the knowlege of experts that know all there is is to know about something they know nothing about. This is not top judge them, but merely observing the process. I is unfortunate but living in a free society means that you can have products manufactured and sold through deceptive marking and political processes that is is diffinitly not in the best interst of the consumer. It doesn't help when you have your own government helping the black hat guys either.

I have been in this business for 30 years and still learning. I find it amazing how little value given to hard earned knowledge and experience. It seems that instant gratification and I know better because I saw it on TV is the way to go today.

This is not to discourage you from commenting on subjects. You sounded almost as if you thought you had made a mistake. Not so, more enlightend souls are needed, so, welcome to the club.

Thank you for considering my opinion.

 
Search this Thread