I just have a quick question about installing a second layer on insulation in an attic. Client has blown in insulation in his attic. He is moving and one of the home inspectors said he should have more.
My intention is to run R-30 batts perpendicular to the joists. Does anyone have a better suggestion or will this be sufficient? Since this will be the second layer I dont need batts with vapor barriers do I?
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Replies
How about blowing more cellulose in?
Never done it before. Its kind of a tight spot to get into I have to go in through a pantry. How big is the machine(or how long is the hose)? I guess its pretty easy to do but then do I need to install baffles? How hard is it to lay evenly? Do I need to drag a rake up with me? And finally is it messy? It seems like it would throw all kinds of dust and fibers through the house.
I guess i'll look into it. How does it compare price wise to batts?
Edited 1/4/2005 11:00 pm ET by MSA1
The problem with batts are that you cant install them tight to each other. The resulting gaps between the rolls really reduces their effectiveness, even a 1/16" is bad.
Blown in cellulose is easy to do. Yes its dusty, but only where you are filling the machine with the balles of insul. They give you a ton of hose, more if you request it. So depending on your situation you could maybe set up outside and snake the hose up the side of the house thru a window. BTW it takes two people to do, one to feed the machine and the other in the attic with the hose.
Stretch some masons line across the attic to give you a reference point on how deep to blow the cellulose. BTW the total amount of insul should add up to R49 in the attic or abought 12" deep for cellulose.
I have always wondered what the true R-value of a FG ceiling bat is.If I understand correctly R-values are tested by putting the material between to plates and meausring the heat flow between them.Of cousre that does not allow for any air moveing and is somewhat represenative of walls (assumign a good installation).But in an attic the top of the bat is exposed to the air and in fact the attic is ventalated such increase air flow across the surface of the bat.AND PLEASE, PLEASE, PLEASE, PLEASE DON'T UPLOAD URL'S.First it is extra work.And 2ndly it does not work correctly.Now if it was a true URL I could download it and then click on it. But that is extra work. And it does not work on my system because it is not an URL, but MicroCr*p shortcut.Please just copy and paste the URL into your message. It is faster for you and anyone can easily just click on it and so to the site.
As reinvent says, cellulose is the better choice, but you do need to add the vent baffles. Once they are installed, the rest of the project is faster than dragging batts up through an attic scuttle and laying them out.
F/G is cheaper than cellulose on a square foot comparison, but if you compare R value per inch of product, you get more bang for your buck with cellulose.
Since the HO is selling the house, they may want to make the decision on which product to use, based on installed cost, not performance.
BTW, I find that I can sub out blown in cheaper than I can do it myself. My insulation contractor has the equipment and experience to do it in half the time it would take me and a helper.
Dave
Thanks for all the advice. I checked out a machine and cellulose at depot today. The guy I talked to said the cellulose is cheaper.
It looks like I may go with the cellulose. I need to discuss it with the home owner first. I thought I would need the baffles but it sounds like even with installing those it shouldnt take much longer to do.
It's my understanding that cellulose is also opaque to infrared radiation, where fiberglass is more or less transparent. As such, cellulose provide a better barrier.
It might be a job that's cheaper to sub to an insulation contractor. A miserable task, but well worth the trouble and/or expense.
what about a third choice! Foam! Both cellulose and fiberglas are affected by moisture and offer several problems.. their effectiveness is always reduced in the real world compared to their stated values..
Foam on the other hand offers several advantages. first it's far more effective in sealing heat paths out of an attic, second water doesn't affect it, third it adds rigitity to what may be a marginal strength area. Forth it's "r' value isn't affect by tempurature. and finally it's just cool to watch that stuff swell up and fill an area!
the downside it needs to be done with someone with the equipment and training so you will have more cost involved than just spreading some fiberglas bats yourself.. You will quickly get a return on those higher costs though!
I'd love to see foam installed (looks cool) but they're selling this house and they're not going to pay that expense.
As Steveo suggested, why not just blow in more celluloise?
Have you not got removeable vents to get access, or any access door or hatch to this area?
i've found that getting an insul.company with the proper blower,etc, is almost the same price as me buying the stuff and doing all that work.
And, no ,you don't need another VB. Hopefully there is already one just above the ceiling material.