building a new house got bids 2 seperate insulation contractors
one says blown attic insulation is better than batt & the other
one say’s just the opposite ??? which is more efficient
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
Learn how to plan, fabricate, and install a chute to conveniently send your dirty clothes from an upstairs bathroom or hallway to your laundry room below.
Featured Video
SawStop's Portable Tablesaw is Bigger and Better Than BeforeHighlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
This answer will serve to "bump" your question up near the top of the heap again, as I'm not sure, but would say that blown insulation may seal around penetrations into the attic (pipes and so on) better than batt. Batt, IMO, sometimes just filters the warm air out and cold air in, doesn't really stop it. Also depends on what kind of blwn-in (cellulose or fiberglass?).
Blown-in is my choice whenever the owner will pay for it. If batts, I would lay one layer in between the ceiling joists and another layer ACROSS the top of that.
one says blown attic insulation is better than batt & the other
one say's just the opposite ?
Depending on your attic, either might be right, or both.
If framing doesn't allow much room you'll get more R-value with batts since it is more dense, at a slightly higher price.
If the attic space is open then blown in will provide the best R-value per $.
If some places are tight and some open, it often makes sense to insulate the tight areas with bats and blow the open areas.
If the insulating contractor's blower is down for repairs, is tied up on other jobs, or he just doesn't own one, then he will claim that batts are better regardless.
If the contractor is short handed it often requires fewer man hours to blow it, so that's what gets recommended regardless of what makes sense with regards to R-value.
We recently had an insulation contractor say there was no way to blow an area, which we later learned was based mostly on the size of the guy he usually uses to blow fiberglass. He found a skinny kid and like a miracle the attic in question can now be blown.
It's funny how the world works. :-)
"If framing doesn't allow much room you'll get more R-value with batts since it is more dense, at a slightly higher price."Beg pardon, but it's exactly the opposite. Either Cellulose or BIBBS can be blown denser than batts in a contained space and will disallow the convection currents that FG Batts are famous for
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Beg pardon, but it's exactly the opposite. Either Cellulose or BIBBS can be blown denser than batts in a contained space and will disallow the convection currents that FG Batts are famous for
As usual I agree with you...
...sort of.
Owens Corning high density FG bats have an R-value of 3.8 per inch, which is hard to beat in moderate climates, even with blown in cellulose. Of course that's assuming it's installed 100% correct, which isn't usually the case unless the installer is maticulous.
Where I do agree is with FG's loss of R-value in real world situations that have a wide temperature differential, and the generally better overall value of cellulose.
While I'm not really a big fan of FG over cellulose in attics, by far the best insulation contractor we've used only installs fiberglass so unless we have the time to do it in-house we go with fiberglass. If insulation space is really tight we'll go with a foam. :-)
Where I do agree is with FG's loss of R-value in real world situations that have a wide temperature differential, and the generally better overall value of cellulose.
Trout:
I have only been able to find research (from ORNL) about the R value loss as temps drop in horizontally applied low density or overfluffed (insulator fraud- you have the inches but not the density) loosefill fiberglass. I have never found research about this happening in properly installed batts in a regular wall cavity. The R value of batts will drop if you don't know how to do a properly installed building wrap/sheathing membrane since exterior air will blow through them. Do you have or know of any research on this fiberglass batt supposed flaw?
Another issue I see on these threads is that radiant heat passes right through batts. Any research info on this? Never heard that before except from lying promoters of "high R" foil faced products such as P2000. Their product has 1" foil faced expanded beadboard foam rated at R27.....even better is 2" at R48!!!!!!
Edited 7/28/2006 3:24 pm ET by experienced
I have never found research about this happening in properly installed batts in a regular wall cavity.
Unfortunately, it's true. Within each stud cavity an air circulation pattern will develop as the warmer portions on the interior cause air to migrate up and the cooler exterior causes air on that side of the cavity to sink. The basic problem is related to how easily air can freely pass through the insulation and thus react to the temperature extreames.
The documentation on this is usually in the form of test walls from this agency or that, which shows the effective R-value of fiberglass goes down as the temp. difference grows.
Keep in mind a little ridgid foam on the exterior can greatly reduce the temp extremes so the fiberglass works better.
Another issue I see on these threads is that radiant heat passes right through batts. Any research info on this? Never heard that before except from lying promoters of "high R" foil faced products such as P2000. Their product has 1" foil faced expanded beadboard foam rated at R27.....even better is 2" at R48!!!!!!
That's true...sort of. There just isn't normally a huge amount of radiant heat coming through the walls.
Think of radiant heat as the heat coming off a campfire. If you're sitting a distance from the fire, most of the heat is radiant. Put anything inbetween you and the fire and the amount of heat getting to you goes way down. In that situation a simple piece of aluminum foil by itself will have a relatively high R-value.
If the foil/foam products are tested near high heat sources, such as directly under siding or roofing that reaches pretty high temps, then the obverved R-value is high. Put the same material under a slab of concrete and the R-value goes way down to about that of normal foam.
The documentation on this is usually in the form of test walls from this agency or that, which shows the effective R-value of fiberglass goes down as the temp. difference grows.
Why can't I find any of this documentation? Or others that say this stuff provide it?
If you're sitting a distance from the fire, most of the heat is radiant.
and unless the fire is huge, you won't feel it since the strength of radiation decreases inversely with the square of the distance from the source. In the temps, we work at in houses of say up to 120-130 deg F, the foil won't have much R value and loses much of that to dust after a period of time. The Florida Solar Energy Center study on retrofit in an attic found a payback of 30 years on contractor installed foil under the rafters. A DIY on a retrofit or contractor installed on a new house may make some sense.
Edited 8/2/2006 11:44 pm ET by experienced
Here's a little info from a government source:
http://www.ftc.gov/bcp/rulemaking/rvalue/comments/04.htm
"Either Cellulose or BIBBS ..."
OK, so I know that you're not speaking of overalls, but I know not of BIBBS. I going to venture the first two parts are "blown-in", but what's the rest?
Tim
http://www.getbibs.com/
You're wrong, though... all installers are required to wear overalls, and a bib if they eat lobster for lunch at the jobsite.
Go with blown cellulose. Slightly higher R value than batts and no gaps!!! It is crazy in these days to being considering anything but blown cellulose (re-cycled paper) in regular flat attics.
Experienced, we are also beefing up our insulation this fall and considering having it blown in - can you define what you mean by 'regular flat attics'?
Thanks!
For example in a bungalow or full 2 storey house where the attic is simply flat ceilings with no cathedral or sloping ceilings. These can be done also with blown cellulose but may present some difficulties that can be done better by professionals rather than a homeowner working with blowing equipment for the first time (assuming you're a DIY type).
Before you do any attic blown work, learn about airsealing and do that prior to the insulation. A couple of good booklets on this are "Keeping the Heat In" and "Caulking, Sealing and Weatherstripping" found on the following websites http://www.nrcan.ca and http://www.gov.ns.ca/energy (I particpated in writing many of the booklets at the second site).
Ok, I live in a ranch-style home with vaulted ceilings in the living room, which is in the middle of the house. Everything on either side of the living room is flat-ceilinged. So cellulose would be the optimal (optimum?) choice for me in those areas?
I'll check out the websites; that's great info.
Thanks!
No doubt about it - blown in, properly installed is far better than batts. FG batt insulation is the least effective insulation you can choose.
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
Hi,
After doing quite a bit of looking around, I settled on blown in cellulose for my place -- based on this stuff:
loose fill FG R2.8/inch
loose fill Cellulose R3.2/inch
FG bats R 3.1 / inch
http://www.builditsolar.com/References/InsulationTypesEEM-01454.pdf
Not a whole lot of difference, but the cellulose is better at filling gaps and is tighter for sealing up air leaks from the living space.
FG is more susceptable to degraded performance from moisture than cellulose is -- important if you don't have a very good vapor barrier.
FG has a problem in cold weather with convection currents forming in the FG that transfer heat from the warm ceiling to the cold air above. Under cold conditions, this can cut the effective R value in half per this ORNL test.
http://www.homeenergy.org/archive/hem.dis.anl.gov/eehem/92/920510.html
Per the test, cellulose does not have this problem.
Cellulose also has a lower embedded energy content.
As someone mentioned, doing some sealing of electrical and plumbing penetrations, and sealing up duct joints with duct mastic before adding insulation would be a very good idea -- a good guide on doing this here:
http://www.builditsolar.com/Projects/Conservation/conservation.htm#Insulating
(the EStar one).
Gary
loose fill Cellulose R3.2/inch
Cellulose that is manufactured by "fiberizer" equipment (just a different way of shredding the paper) is rated at 3.8 per inch by ASTM consensus approved testing. Another advantage is that the weight per unit volume is reduced significantly but still gets a better R value- less paper; more R!!
By just blowing cellulose in the walls of a couple of 2 storey homes and measuring air leakage before and after by blower door, I found reductions of 34 and 39%. No formal airsealing by foam/caulking/etc. was done for this test.
Edited 7/17/2006 2:16 pm ET by experienced
The one real advantage of batt over blown is that any future work up there will be much easier and cleaner with batts. You just pick them up and put them aside rather than scooping and vacuuming.
-- J.S.