Insulation survey

[John Raabe]

These are comments from builders about what types of insulation they are using. Dense pack cellulose seems to be more popular than fiberglass batts. I think the third guy has the best information.



Here's a link to This months Survey (may not work after Dec 09):

[rocking23nf]

I personally find the pink fiberglass insulation very easy to put up. Its easy to cut to shape, fairly cheap. I have not tried spray foam, but holmes on homes raves about it. But im the kinda guy who likes to do the work myself, and i havent seen any do it yourself spray foam kits at any stores or anything.

[MikeT]

This was advertised in Fine Homebuilding magazine as a spray foam option for DIYers:

http://www.rhhfoamsystems.com/index.php

Not checked into it other than looking at the web site....

[upa]

They exist but OMG they are pricey. I looked at DIY foam kit to do my kit ~640 square feet of roof to an R40 level and it was $500 for fiberglass and roughly $3000 for spray foam, you can guess which I picked.

[MountainDon]

Pretty much all the builders around here who are building better quality homes are using wet blown in cellulose. It is not a DIY proposition. The blower is similar to the dry blow-it-in-your-attic types, but there is also a water mist sprayer. It takes some experience to learn the proper amount of water. It also takes experience to be able to blow pack enough cellulose into the wall cavities to get the right density. That why it's called dense pack. Then it has to be allowed to dry. A quality installer measures the moisture content over a period of days - weeks maybe. It has to dry down to a certain point before he will allow the interior walls to be finished.

All the nooks and crannies get well packed with cellulose. There are no gaps anywhere. Spaces behind electrical boxes, behind pipes and wires are all nicely packed. It's actually beautiful to see. Even taking my time there is no way I could achieve the same well insulated wall using fiberglass batts. I did my best but I just know it is not as good as a professional cellulose installer could achieve. I would have had our cabin done with blown in wet cellulose but I could not find a contractor who would do the job without an exorbitant surcharge for driving up into the mountains. In fact two said "no, sorry, it's not worth my time."

I believe fiberglass batts were invented as a way contractors could cheaply insulate walls with minimally skilled labor. That was back when energy was cheap. Now it is more important to insulate supremely well and it is worth the extra expenditure to install cellulose. With more and more installers the price will likely become even more competitive and batts may end up being used by the DIY'er. At least that's my opinion.

[John Raabe]

My favorite insulation system has been BIBS, but it not available everywhere and is also a specialty contractor situation. Like dense pack cellulose, a good installer will get complete coverage and fill all the voids and little spots that a batt insulation system will miss.

I did a small study once (for my book, Superinsulated Design and Construction, p. 35) where I compared the total R-value of a 2x6 wall with R-19 insulation and 12% of the wall area in framing. If batts are used and miss 6% of the coverage in voids, the total R-value of the wall is 13.53 due to framing losses and voids.

If you eliminate the voids and use the same R-value insulation (R-19), the total composite value for the wall jumps to R-17.6 (you still have the same framing losses). That is a 30% increase in overall insulation effectiveness.

If you do install batts yourself, then a really great upgrade is to add one inch or more of foamboard sheathing to either the inside or the outside of the wall. That redundant layer insulates those voids and the framing and increases the overall effectiveness by about 1-1/2 times the R-value of the foamboard.

[rwanders]

I had a cathedral ceiling with 2x12 rafters and metal roof over sheathing to insulate-----seems to be very difficult to reach R48+ with fiberglass or other material and leave enough space for ventilation----11" of sprayed closed cell foam provided about R66+ and removed the need to ventilate the roof. It was expensive----a little over 3500 for a 24x24 12/12 roof but I think it was worth it. I would have liked to spray the walls and floor also but used R21 FG in DIY mode to manage my costs. If spray foam costs ever come down I think it will come to dominate the market.

[glenn kangiser]

Dirt.... a foot and a half of plain old dirt.....

[Mike 870]

I have an insulation question/theoretical problem.  If you are in a heating and cooling climate (like Ohio), lets say you frame and dry in your house with tyvec on the outside.  Could you build with double staggered 2 by 4 studs:
1) Insulate the outer wall with fiberglass,
2)then put a non pearmiable vapor barrier in the middle of the two 2 by 4 walls
3) and then insulate the inner wall with fiberglass

Would you have to worry about condensation problems in such a design?  Would the insulation prevent a temperature difference from causing condensation?  Just trying to brainstorm a DIY method of having a sealed envelope and aviod moisture problems.

[poppy]

Mike, you don't want a sealed envelope or non-permiable barriers in Ohio.  The walls have to breathe.

Remember that we have both heating days and cooling days so vapor needs to travel both ways through the walls.

I don't remember now where the link is, but there is a reference somewhere on this forum about vapor retarder requirements for various climates.

Don't put your house in a plastic bag.

[poppy]

John

If you do install batts yourself, then a really great upgrade is to add one inch or more of foamboard sheathing to either the inside or the outside of the wall.

That's what my research has confirmed.  A continuous layer of foamboard goes a long way in providing added R value.

Even before I lucked into the free Polysio sheets, I was planning on using foam board of some type on the walls and roof.

Now I have enough Polysio to do everything including the floor.  I may add loose fill cellulose or something under the Polysio in the floor.

I'm trying to avoid fiberglass even though that seems to be the insulation of choice around me.

[MountainDon]

Building Science has several great articles on vapor barriers, insulation, etc.

Their designs are specialized for various climates. You would need the vapor barrier on the inside surface.


vapor barrier

[pagan]

When I was doing insulation contracting work, mostly retrofitting old houses, we would dense pack cello in the walls then we'd do an open blow in the attic space which was generally at least two feet deep when done. If we were lucky and had exposed rafters and wall studs we'd use strapping and screw one inch Hi-R foam boards to the studs and rafters and tape the seams. Then we'd dense pack cello in the cavities. The Hi-R cuts down on the thermal bridging and also adds about R-7 to the insulation.

My preference is for high expansion extruded foam, but the cost is prohibitive for most people, including me. I've been considering building a double 2X4 wall with the studs offset for each wall. The cavities would be filled with 4 inches of Hi-R giving a total of R 56 with no thermal bridging.

Air sealing is very important as you can have an incredible amount of good insulation but several thousand CFM air movement rendering the insulation worthless.

[John Raabe]

Actually the system Mike 870 proposes would work since the vapor barrier is buried between two sets of insulated framing and will never reach the dewpoint from either side. Such a double wall system has been built in many climates and was shown (w/ slight variations) in our Superinsulation book (p. 97). It has fallen out of favor in recent years not because it doesn't work, but because it tends to be more expensive for the added R-value than things like foam sheathing and it takes up quite a bit of interior floor area.

[Dave Sparks]

Agree John,
For the survey... 1" foam sheathed to a r19 wall. R60  blown glass on top. Really wish the windows were better when I built.

[John Raabe]

Me too!

Windows have improved a LOT! (Especially since we built in 1983!)

[rdzone]

Guess I will chime in, since we are currently in the insulation stage.  We have used R21 in the walls, and a layer of R38 with a layer of R21 in the roof trusses.  I took my time and carefully fitted every piece.  I am sure there are still gaps, but I bet I did a better job than if I had someone come in to do batt insulation.  We have been foaming all the gaps as we go along.

I would have liked blown in or expanding foam, but due to our location no one was willing without a huge cost, if they could even reach our cabin.

[MarkAndDebbie]

Cotton Batts - easy for me to install and I hate fiberglass.

[John_M]

I looked at cotton batts (recycled denim) and I would bet the cost is close to spray foam!

[Mike 870]

Thanks for the info.  I have read almost everything I could find online about insulation, vapor retarders, barriers etc. and it's still pretty confusing.  Insulation is something I'm willing to bend the return on investment rules on.  I consider it a wise hedge against fuel costs and wood chopping.  If I ever get to build I'm going to do some form of advanced framing technique.   There is a recent issue of fine homebuilding that covers 3 types of walls that are DIY able.  It's worth checking out.

[Beavers]

If you do install batts yourself, then a really great upgrade is to add one inch or more of foamboard sheathing to either the inside or the outside of the wall. That redundant layer insulates those voids and the framing and increases the overall effectiveness by about 1-1/2 times the R-value of the foamboard.

Just wanted to make sure I'm reading this right. 

I used paper faced fiberglass in my house, and it's ok to add a layer of foamboard (the pink stuff) on the inside before I drywall?

[MountainDon]

Yes, you could add a layer of that inside. Seal the seams well with tape.

[considerations]

I used Roxul R22 batts on the 2x6 walls and then got R30 high density fiberglass batts for the 2x10 cathedral ceiling. 

That is as far as I've gotten. 

I would hate to give up another cubic inch on the inside.  They are getting precious. 

So this rigid foam board is a vapor retarder?

[Beavers]

Thanks Don.  Is duct tape OK, or do I need the stuff that you use with Tyvek?

[MountainDon]

3M sells a Builders Sealing Tape that will work... I've seen a builder friend here using it on foam.

You could also caulk the seams with a foam compatible caulk.

Not sure about duct tape... it always seems to dry out after a few years for me.

That aluminum foil sealing tape should work too. Slower to work with as yoy have to remove the backing paper.