# About to insulate - things to watch for?



## precaud (Oct 19, 2006)

I've been turned down by every contractor who came to bid on installing isulation in the ceiling of this old place. The problem - not enough room between the roof and ceiling joists - only 15" max to 8" min. So I went to the non-licensed guys. The good new is - I found someone who will do the job. This guy has two kids and he says they are small enough to get around up there and have done this sort of thing for him before. The bad news is, he will only do fiberglass batts. I was wanting to do spray-in cellulose, but he won't do it.

So... besides the obvious precautions to take when working with fiberglass, does anyone have any words of wisdom to share? Things to look out for? I've never worked with fiberglass before on this scale. I'm planning on using R39 batts, I think they are kraft-faced.


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## Sandor (Oct 19, 2006)

Compressed glass insulation loses R value. R39 is about a foot thick, and some of your space is 8 inches. Cramming that insulation up there may ruin your ventilation, and you will not have R39 anymore. If it gets wet from condensation, you will end up with something approaching R0.

Improperly installed batts will cost you. Like gaps between the pieces.

Is there any insulation up there now? What does the framing look like up there, space on center.

Honestly, there really is not enough room to do the job properly for anybody. And before anybody chimes in about an unlicensed guy, he is desperately trying to make a living doing a crap job that nobody else wants to do.


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## precaud (Oct 19, 2006)

Sandor, there is NO insulation up there now, but there is plenty of room for it. The minimum 8" described is between the beams, and the beams themselves are 4" on the ceiling and 12" on the roof, both roughly on 15" centers. So we have the needed 12" even in the shallowest section.

I agree, installation is very important, no gaps is the goal. BTW, this guy is NOT desperate, he is quite busy, and does excellent plaster and stucco work as well. Yesterday I viewed a remodel he just finished and his work is superb. Let's just say that this guy's English is good enough to communicate details of the job...  The contractors were given their chance and noone wanted the job.


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## Rhone (Oct 19, 2006)

Fiberglass has it's pro's like it never loses it's fire resistance, doesn't settle, if it gets wet when it dries it goes back to normal (though if kept constantly in a wet situation mold/mildew will grow on it) it can be easily moved and put back, and its cons being that it must be installed to the book else it goes from around R3.2/inch to R1.8/inch.  No matter how "to the book" you install it, it will never insulate nor make you feel as comfortable as well as blown cellulose, fiberglass is also a painfully slow and far more costly in both material and labor.

Blown, is easy to install and goes in every nook & cranny but you have to prep ahead of time by surrounding recessed lights with fiberglass, your chimney as well, and if you have soffit & ridge ventilation you need to install ventilation jackets.  Blown is no fiberglass when it comes to fire resistance.  It only takes a 75 watt light bulb to fall on it for it to reach smoldering temperatures and what flame retardency it has deteriorates over time.  If it gets wet, it's damaged and likely the fire retardency reduced as well.  

To install fiberglass, it should be 2 seperate layers and each piece needs to be "fluffed" before laying down.  The first layer needs to be deep enough to bring it all to the same level as the tops of your ceiling joists.  In otherwords if you have 2x6 ceiling joists 16" o.c. and no insulation already then the first layer needs to be 5.5".  The next layer should be 24" wide to minimize seams and whatever thickness you want.  Lay it down perpendicular to the first layer to minimize gaps and it will cover the joists and prevent whats called short circuiting.  That's where the heat short circuits through the ceiling joist bypassing the insulation because wood only has an R1.5/inch.  

As you can see, fiberglass and to install it properly is unlikely to happen in 8-15" of space and will be costly because of the cost of materials & labor.  You also need to air seal before you insulate up there.  The attic is the single most important place to air seal due to what's known as the stack effect, doing so will have the biggest impact on reducing cold drafts in your main levels & basement making them more comfortable.  Sort of like the statement, if your hands & feet are cold wear a hat.  Insulation is extremely poor at stopping or even slowing air leaks.  In summer the stack effect reverses and hot attic air gets pushed down any air leak into the living area causing your AC to work harder.  It doesn't sound like you have room to air seal, but blown is better at reducing air movement than fiberglass.  So, blown is certainly the way to go in that limited space.  Do you know what type of ventilation you have?  Old houses normally have gable end vents.  Is your house old enough to have knob & tube wiring in the attic?  That's a reason one can't insulate up there until it's replaced.  Otherwise, there isn't a big difference between adding blown cellulose to a wall or floor cavity or adding it to your situation.  But, regardless going from none to a good chance of improperly installed fiberglass at only R1.8/inch will still be a big impact.  At a minimum tell him to make it 2 layers, one 15" wide and deep enough to to level it with the ceiling joists, the next 24" wide and whatever remaining thickness can work and installed perpendicular to the first.  Also, you'd get faced kraft for the bottom layer, and have the paper face down right against the ceiling, any remaining layers shouldn't be faced.


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## wg_bent (Oct 19, 2006)

The think in your post that got me worried is "kids" and small enough to fit in a space that's only 15" High.  

Also, I believe you can get blown in fiberglass.  I've put cellulose into a house before.  Really great stuff.  But, if there is no insulation up there at all, consider how you will accomplish a vapor barrier.  If you blow in cellulose, just think about where the condensation point is inside the insulation...You'll figure out that it's going to get damp there and as Rhone said...once wet, cellulose takes forever to dry.  Also, I didn't realize that once wet it looses it's fire retardance properties.  

I dissagree that a light bulb will make it smoulder.   I tried to get it to smoulder with a blow tourch when I installed it...I couldn't make it do anything more interesting than the edge of the small peices getting red.  As soon as the flame was removed...nothing.  Simply back to it's original state.    I do still believe fiberglass is a  better material since it's well, glass.  

you've got a tricky situation...good luck with it.


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## precaud (Oct 19, 2006)

Rhonemas, thanks for your thoughts there. Some details on the house should answer some of your questions. It's adobe-style (flat roof, no overhangs or soffits), built in 1930. The walls are thick - double-wall pentile (like concrete block but same material as brick.) I only see one "vent" in the ceiling, on the north side. The roof joists are 2x12, the ceiling joists are 2x4. This is New Mexico, so moisture buildup is not a problem... Interior finish is lathe and plaster throughout, which provides a very good air seal. I have no draft problems at all (not counting the deteriorating caulking on a few of the windows   )

Yes, this house has the old K&T wiring, but only for the lights, so they don't carry much current. The outlets are all wired from the basement. Nevertheless, this is the reason why cellulose is out of the question in my mind. The contractors who inspected it said the same - they would only go with blown fiberglass, but they turned down the job because their boys wouldn't fit up there.

I agree with your ideal installation technique, but I don't think we can do it that way. The beams are roughly on 14-15" centers, the batts are 15.5" wide, so I figured there was enough overlap to give a gap-free installation.


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## Rhone (Oct 19, 2006)

Wow, deja vu.  If there was an New Mexico version of my wood framed house that would be it.  Same exact "feeling" looking at it.  

Sounds like you know more than you're leading about the insulation   You have it, go with the 15.5" insulation, kraft faced, notched in such a manner it fits tight and covers the top of each ceiling joist, and that's about it.  Now... are you in a heating dominated climate or cooling?  If heating the paper should be down against the ceiling and no paper on the joists.  If cooling the paper should be facing up.  I'm still curious how they're going to do it in such a little space, is it going to be installed by a 6 year old!?


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## precaud (Oct 19, 2006)

> Wow, deja vu.  If there was an New Mexico version of my wood framed house that would be it.  Same exact "feeling" looking at it.



Interesting... I hope yours came with less "deferred maintenance" than mine did...



> Sounds like you know more than you're leading about the insulation



Well I've read alot lately, but you know the difference between knowledge and experience... I'll take the latter any day.



> are you in a heating dominated climate or cooling?  If heating the paper should be down against the ceiling and no paper on the joists.  If cooling the paper should be facing up.



Good question. From the charts I've seen, we're in the grey area. The southern part of the state is definitely cooling-dominated. 100 miles north of here is like Colorado and definitely heating-dominated. I don't tend to worry about cooling, as the house has a full basement which keeps things pretty cool except on the worst days in July. So I'm not sure it matters. My personal leaning in this situation is to have the kraft face up, to reduce air currents in the batts, and should make it a little easier to install with the non-consistent joist spacing.



> I'm still curious how they're going to do it in such a little space, is it going to be installed by a 6 year old!?



No, they are 12 and 15... the guy's sons. He's bringing them over this afternoon to make sure they fit up there! Would I ever ask my son to do something like this? Not on your life. He told me, this will be an easier job than the last one he gave them, insulating an under-house crawl space. I guess this is proof that cultural differences are quite real... (is that stated PC-enough?)


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## Rhone (Oct 19, 2006)

Well I purchased a condemned house, you and I may be in a similar situation.  It was the only way I could financially provide a house for my family.  But, I'd probaby been better off destroying what was there and building up from scratch   The people before me lived with a broken sewer pipe for 30 years, no working bathrooms, and someone snuck in while they lived there and lit the place on fire.  Over the course of 3 years I've spent 20-30 hours/week fixing it carefully monitoring finances.  You're like me, one of the first financial decisions that made sense was to add insulation.  Having a house like that, if you're new at it, one piece of advice.  I'm not certain you're married or have a family, but with a house in disrepair your first priority needs to be to save the marriage.   I know a lot of seperations come about purchasing a fix-r-upper.  My wife spent the first several months crying after we moved into our place and depression took her, then she got very sick and my parents had to take care of her.  I thought we'd both be fixing it up, she lost all her energy.  It's easy to get lost in the priorities with a place that needs fixing, I even told my wife pulling out her box of pictures since I'm doing all the work not to hang any up because it'll just be more work for me to patch.  I was fixing rafters, leaky plumbing, insulating, and replacing all the lower walls in my basement from the sewage damage none of which were things to make my wife feel like she had friends or a home.  It was when she got very sick I realized she was probably suffering from serious depression from the house and I had to be a man.  The heck with the leaks in the roof I need to save the marriage!  I put buckets under the leaks and got the bedroom, living room, hallway, and trim done, the things that would help her feel like it was a house.  I came home one day she was there, feeling better, and had hung up three pictures of friends & family and was staring at them.  That's all she needed.  She improved rapidly, and then came the curtains, and the flowers, and cute pot holders, and all that crap woman usually like to have out but what a lesson learned in life to make you realize where your priorities need to be.  It's easy to get caught up in the house and after living through the experience your priority needs to be to the marriage first.  Best of luck to ya!


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## precaud (Oct 19, 2006)

Wow, Rhonemas, what a story. This gives new meaning to 'environmental sensitivity." Fortunately I'm not married so I don't have to deal with anyone's tolerance to chaos but my own.

I have nothing but respect for you taking on such a huge project house. And I'm VERY glad that you're both feeling comfortable in it now!

The guy just came with his oldest kid. Amazingly, he fit up there just fine. So it looks like we'll go ahead with it. Tomorrow he comes back and we decide where to make the access holes. Yeah!


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## GVA (Oct 19, 2006)

precaud said:
			
		

> Rhonemas, thanks for your thoughts there. Some details on the house should answer some of your questions. It's adobe-style (flat roof, no overhangs or soffits), built in 1930. The walls are thick - double-wall pentile (like concrete block but same material as brick.) I only see one "vent" in the ceiling, on the north side. The roof joists are 2x12, the ceiling joists are 2x4. This is New Mexico, so moisture buildup is not a problem... Interior finish is lathe and plaster throughout, which provides a very good air seal. I have no draft problems at all (not counting the deteriorating caulking on a few of the windows   )
> 
> Yes, this house has the old K&T wiring, but only for the lights, so they don't carry much current. The outlets are all wired from the basement. Nevertheless, this is the reason why cellulose is out of the question in my mind. The contractors who inspected it said the same - they would only go with blown fiberglass, but they turned down the job because their boys wouldn't fit up there.
> 
> I agree with your ideal installation technique, but I don't think we can do it that way. The beams are roughly on 14-15" centers, the batts are 15.5" wide, so I figured there was enough overlap to give a gap-free installation.



Ahh. Knob and tube is the scariest stuff out there other than un insulated conductors. :shut: 
Get all of it out of there or as much as you can please.........  Especially while you have access to it...  You say it is only for the lights but old school wiring such as yours.... houses used to have a 60 amp service before all the modern (somewhat) appliances came and one circuit was usually dedicated to lighting,ie: all of it the whole house light circuit was on one fuse......  If you have wall sconces in some areas and there is an outlet below it chances are this is also on the same circuit......  It is also important to remember that K&T is an ungrouded conductor.  BX is a bit better but the metal sheath would come unconnected from the box causing you to lose the ground also, BX is now called MC the main difference is that there is a ground wire inside the sheath in addition to the hot and neutral...  Everything has been changed in the electrical industry to have redundancy but for good reason.  And im sure that after 70 plus years in the heat down there the mineral insulation on the K&T is a bit fragile................ Do yourself a favor and please replace that old wiring.... :roll: thanks for reading my rant.....
And one last thing I believe the moisture that rhone was talking about is not from rain but from condesation..........  Such as the pounding sun on one side of the roof and the cooler air on the other creating well....... a moisture problem.


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## precaud (Oct 20, 2006)

"Thanks" for the rant, GVA, but it ain't gonna happen. I've inspected the wiring in four locations and the insulation is in great condition. The electric service is not as old as the house, and was upgraded at some point; the lights are on three separate circuits, and as I noted, the outlets are all wired from below. So the K&T will stay. It's fine for the lights which don't pull much current. We decided to install the kraft face down and just cut it away where it contacts the wiring.


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## DriftWood (Oct 20, 2006)

When its time to replace the roof install a covering of 4/8 sheets of plywood with 6 inches of closed cell foam sandwiched between two sheets of plywood, this a one piece product sheet that is installed over your existing roof, screwed down and the new membrane is applied over everything.


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## precaud (Oct 21, 2006)

Well the guy gave me a ridiculous quote ($1500 labor for just over 1000 sq ft). That's quite a chunk of change for two kids crawling around a ceiling and one adult (plus me) cutting and feeding them batts for a day.

EDITED... negotiating...


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## RoosterBoy (Oct 22, 2006)

also one thing to worry about is un licenced people doing work in your house make sure your insurance company will cover you if they get hurt working for you. in this day and age they could very well sue you for lots of money. so relay check that out

thanks
Jason


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## precaud (Oct 24, 2006)

This is a two-part post. The first is titled, Isn't the Internet Wonderful? I met with the guy again today, showed him the GreenFiber website (this guy doesn't own a computer and has never been on the internet!) so he could see how easy it was to blow in cellulose compared to cutting and placing fiberglass. Once he saw the pictures, he was sold. He cut his labor charge by 1/3 and we shook hands. So on Wednesday morning his crew will be here to do it.

The second part is, A Little Customer Service Goes a Long Way. I needed to buy 60 bags of Cocoon insulation tonight and reserve the machine for the Wednesday morning install. Called Home Depot, they had it in stock, but said they don't reserve machines for rent - everything is 1st come, 1st serve. I explained my situation, with a crew coming Wednesday. Too bad, they said. Too bad is right, you lose my business. So I called Lowes, whose store just recently opened here and I hadn't even been there yet. Their phoneperson told me the same thing but suggested I come in and talk to the manager. So I did. He was more than sympathetic. He said "Why not take the machine home with you tonight, that way you're sure to have it when you need it?" I didn't expect this and was floored. What a different attitude. Actual service! Needless to say, they got my business.

Not only that, but then, the employees who loaded up my truck don't know these machines from Adam. There were two of them sitting there. They thought it was all one system. So they loaded both blowers and both hoses in the truck. I didn't complain.

The next 3 days are going to be hectic, tomorrow prepping the space and making holes in the ceiling, Wednesday is install day, and Thursday will likely be spent cleaning up the incredible mess I expect this job will leave. Will report back in when it's done.


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## precaud (Oct 26, 2006)

Wow! Insulation rocks! What an amazing difference in comfort level.

Today they blew 80 bags of Cocoon into just under 1200 sq ft for an average of R-49. Because the roof has a slight pitch, and I told them to just fill it to the bottom of the roof joists, it actually tapers from R-60 on the east side to R-38 on the west. Took a crew of three 7 hours to do, in a workspace as much as 15 inches to as little as 8.

A word about the crew. These guys know how to work. Yes, they were from south of the border, one is the brother of the head guy. They were incredible. Focussed yet relaxed, always singing (often in unison) and joking, but it never interefered with what they were doing. And an absolute joy to be around.

I kept thinking of the anglos that came and inspected the job, and refused to bid it.

I'd hire these guys again in a flash for anything within their skillset.


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## Rhone (Oct 26, 2006)

I hate to say this, I read these too late.  It's against code to have blown cellulose in contact with knob & tube, around here seeing old houses with the attic burned out was likely from that reason.  By code only fiberglass or rock wool, blown or otherwise is allowed contact with it or, you don't fill in around it.  It becomes brittle over time and may have been damaged/broken in the process.  If it's now covered in cellulose that's a lot of insulation for it to build up heat.  

R49 is monstrous.  You've cut your heat loss/gain by around 98% through your attic, please as financials become available do something about the knob & tube up there because as the fire resistant chemicals in the cellulose breaks down your risk of fire increases.  If it's not a time bomb now, as time goes on your risk becomes higher & higher.  You should replace it regardless of the insulation or not, I'd move it up your priority list now that it's there though.


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## precaud (Oct 26, 2006)

Rhonemas said:
			
		

> It's against code to have blown cellulose in contact with knob & tube, around here seeing old houses with the attic burned out was likely from that reason.



I appreciate your concern, but that's only true in some states. There's nothing in NM code about it. And there is NO case evidence of fire caused by K&T covered by insulation. And many states who initially barred it have backed off that position and now require it to be approved by inspection before being covered. Approval rate is over 95%, the denials being mostly due to splices added to the wiring and not the original wiring itself.

See, for example:  http://homeenergy.org/archive/hem.dis.anl.gov/eehem/91/910504.html

MA, NE, and PA have done similarly, probably others too.

As I wrote earlier, the wiring is not as old as the house. I was able to inspect the wiring in four places. The condition of the insulation was fine. As someone who works with electricity and electronics every day, I feel qualified to make that determination, and wouldn't do anything to knowingly put myself at risk.

The other fact is, except in one bedroom, the K&T only carries current to the lighting fixtures. Most of the outlets were added later and wired up through the basement with romex. 



> If it's now covered in cellulose that's a lot of insulation for it to build up heat.



All the incandescent lights in my house have been changed to compact florescent bulbs, reducing current draw by a factor of 5. So current draw on a particular branch will rarely exceed 100 watts thru the K&T. That is not going to generate any heat.



> R49 is monstrous.  You've cut your heat loss/gain by around 98% through your attic


Yes, it is huge. And R60 in the living room is even more so (morso?). I'm experiencing for the first time what I've read; that heat loss/exchange is primarily (not exclusively) a vertical event. And... we all mostly think of insulation as reducing heat loss. And we love our stoves as a radiated heat source. Well, as I walk from room to room, it's obvious that I've just eliminated a 1200 sq ft radiated _cold_ source! Huge!


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## precaud (Nov 13, 2006)

Thought I'd post a follow up, now that I've lived with this for a few weeks. All I can say is WOW, what a huge difference this has made, clearly the single best improvement I've made to countering heat loss in this house. The central steam heat thermostat is set to 63, it's mid-November, evening temps going down to the mid-20's every night, and it has yet to come on. So far I burn the stove for 4 hours in the evening and that's it. Finally the thermal mass of the house is working for me. (edit: except I burned this morning - I'm experimenting with wood geometry and placement!)

My advice to anyone considering doing it is... DO IT, and go for as much R value as you can afford - especially if you are hiring someone to install it, as the labor cost will exceed the materials cost. And do learn about the insulating material you plan to use before you install it. Think twice about using fiberglass; it's insulating value drops dramatically as the temperature drops, which is precisely when you need it.


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## wg_bent (Nov 13, 2006)

precaud said:
			
		

> Thought I'd post a follow up, now that I've lived with this for a few weeks. All I can say is WOW, what a huge difference this has made, clearly the single best improvement I've made to countering heat loss in this house. The central steam heat thermostat is set to 63, it's mid-November, evening temps going down to the mid-20's every night, and it has yet to come on. So far I burn the stove for 4 hours in the evening and that's it. Finally the thermal mass of the house is working for me. (edit: except I burned this morning - I'm experimenting with wood geometry and placement!)
> 
> My advice to anyone considering doing it is... DO IT, and go for as much R value as you can afford - especially if you are hiring someone to install it, as the labor cost will exceed the materials cost. And do learn about the insulating material you plan to use before you install it. Think twice about using fiberglass; it's insulating value drops dramatically as the temperature drops, which is precisely when you need it.



Why does the insulating value of fiberglass drop as temp drops?  First I heard that one.  Reference?  Also, I have to voutch for insulation also.  In my basement, the temp has yet to drop below 70, and I still have the back wall of the basement to insulate.  Just tore the sheetrock down on that yesterday, since the rest is done, floor is mostly in too.  Man was that 2x4 on the bottom of the old framing skanky, rotted and nasty.  Stunk up the whole house when I opened it up.  Tomorrow the drylock goes on!!


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## precaud (Nov 13, 2006)

Warren said:
			
		

> Why does the insulating value of fiberglass drop as temp drops?  First I heard that one.  Reference?


Warren, good explanations of "R-value drift" are:
http://www.monolithic.com/plan_design/rfairy/index.html
http://www.foam-tech.com/theory/rvaluedrift.htm



> Also, I have to voutch for insulation also.  In my basement, the temp has yet to drop below 70, and I still have the back wall of the basement to insulate.


Wow, very nice. How does it stay at 70 - do you have a heat source down there? What insulation are you using - polystyrene boards?

I also have a full basement, but I work there and am crowded already. I can't imagine giving up floor space to frame in perimiter walls.

Are the interior walls of the basement framed or masonry?


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## begreen (Nov 13, 2006)

RE: knob and tube - although there is no evidence of fires caused by knob and tube correctly installed and used, it is often misused. The problem occurs when someone splices into a knob & tube system (common) and either dramatically increases the load or does a poor mechanical splice - or both. All splices I ever did were western union splices then soldered and double taped, but it's sad to say that it is rare for electricians to take the time to do this, epecially in an itchy, dusty attic that is like 120 degrees.  

RE: Insulation. Yes, it's magic. Our "unheated" crawlspace/basement has yet to go below 60 degrees since I insulated it. I was working down there today and it was almost too warm.


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## wg_bent (Nov 13, 2006)

precaud said:
			
		

> Warren said:
> 
> 
> 
> ...



The furnace is down there in it's own small room.  I used r10 Insulpink boards against the cinderblock, then a framed wall with r13 bats followed by drywall.  My BIL thought I was nuts doing anymore than the Insulpink...but I'm convinced the extra was worth it.


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## wg_bent (Nov 13, 2006)

o.k.  I just read those two articles...now I'm depressed.


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## Rhone (Nov 13, 2006)

Well, I'm not really sure about the loss of R-Value or that it only applies to fiberglass if true.  The examples, one comes from a foam company the other from a quick look talks about loose-fill fiberglass which... loose fill fiberglass is just the junk of the industry, very little in common with fiberglass batts.  Don't worry Precaud, you're on the right track and don't Warren about your walls, the issues of fiberglass batts don't apply much when they're installed vertically.  In my energy books, fiberglass gets mentioned repeatedly as a bad choice for attics and floors for one reason or another, but those same authors say the problems that plague them don't apply much when they're used in walls, and they use it there themselves.  

My new energy book this year went extensively into fiberglass batts, studies, and results and says fiberglass batts in most cases is acting around 50% but can be *worse*.  Here's a brief synopsis (when installed horizontally).  First, to get the full R-Value it needs to be installed to the book, and I've seen reports say when fiberglass is installed too the book it has the same air penetration properties as blown.  But, we need to define what's too the book?  Ready for this?  Each piece/roll has to be "fluffed" to the height it's supposed to be. Then, each piece is supposed to be fit with surgical precision, absolutely no gaps and tight but not too tight.  The corners can't be bent up/down or rounded, if going between studs/joists the sides need to be pushed down with a putty knife and pulled back out to ensure the sides are "square".  All pieces must be fit tight together, any obstructions need to be cut around the obstacle to maintain a 0% gap (so that it fits like a glove), and can't be compressed.  The penalty of failing to do such, is astronomical.  My books show just a 1% gap around fiberglass batts will reduce its effective R-Value almost 50%, but it depends on the starting R-Value.  The higher the R-Value of insulation the worse the effect.  That is, a 1% air space around an R38 batt will reduce its total performance to act more like R20 whereas a 1% air gap around R13 batt will reduce it's performance to be more like around R9-R10.  Tomorrow I'll take a picture of the page in my book that shows the chart of just how much R-Value you lose with fiberglass batts with how much air space.  Since joists aren't a perfect 16" or 25" O.C., since it's not possible to make glove-tight cuts around obstacles, fiberglass will never reduce airflow or insulate as well as blown cellulose and probably most homes with fiberglass batts in the attic are almost all acting more like 50%-60% what they think it's doing (which the book says also).  On the contrary to fiberglass which is nearly impossible to install it correctly to get the full R-Value, blown it's nearly impossible to improperly install it to not get the full benefit.  Aren't you glad you went with the blown?  

I just finished installing insulation in my attic, I picked fiberglass batts because I'm not done remodelling and wanted the ability to move it out of the way and put it back.  So, I methodically fluffed, carefully placed each piece checking repeatedly no spaces, any obstacle I went around (instead of trying to cut the shape out of the batts) and afterward filled the hole with blown cellulose by hand.  There's no way I'd picked fiberglass batts again, it cost me probably 3x more, took me 10x longer, and I probably have about 80% of the R-Value since I was so careful.  I'd been better off to walk and destroy the cellulose when it came time for remodelling, and simply fill in the damaged area again with more by hand.  

There is what I call a useful insulation  limit.  Everytime you double the R-Value you cut your heat loss in half.  R1 cuts your heat loss by 50%.  R2 cuts it down to 25%.  R4 cuts it down to 12.5%.  R8 cuts it down to 6.25%, R16 to 3.13% as you can see each time you double your R-Value you cut down your heat loss by 50% each time.  But by the time you hit R38 you've cut it down to 1%.  Bringing it up to R98 you're still at 1%.  For example R60 cuts your heat loss by 0.48% over R38.  You have to figure out, is it really worth paying for almost twice the material to reduce your heat loss by 0.48%?  In my case (house & environment), with Electricity it certainly is.  Heating with wood, after 9-10 years it'll save me a cord, I didn't do it.


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## precaud (Nov 14, 2006)

As usual, Rhonemas, I find your reasoning pretty impeccable. I think the reason that the problems don't arise when batts are used in walls is because the top space in the wall is not a ventilated space, and these convection currents are vertical events. There's plenty of flow resistance in a vertically disposed batt.

Yes, installing batts properly is tedious work and requires great care. I hope your effort is paying off. The one thing I like about fiberglass is it's relative immunity from damage by moisture. If my aging roof starts to leak, the cellulose is going to drink up alot of water and take forever to dry out, probably with impaired insulation value. But I realized that batts would not have been installed properly by inexperienced workers, so I feel the cellulose was the best decision.

I agree with you on the math of heat loss/R value. But anecdotal evidence I got from people who should know suggested there's more at play than the math. One builder I talked to about it says he recently did a house at R60 in the ceiling and was astounded at the difference it made. He plans on doing R60 to his own house.

In my own case, I didn't decide on a particular R value. With the crew I had, language differences, etc. I realized it was unrealistic to expect them to put, say, 12 inches in consistently. The easist thing was to tell them to fill it to the bottom of the roof beams. At least then I would know there no dead spots.

BeGreen, yes, you seem to have found the same info I did on K&T. I examined my wiring, especially junction points, carefully before going ahead. Plus, as stated earlier, in all but one bedroom, the ceiling wiring only carries juice to the light fixtures. There's no way that a maximum 100W draw is going to cause any heat buildup. The problem would come in running 15-20 amps consistently for hours.

Warren, it sounds like you're doing a great job, and with the humidity you have down there, glass was probably a good choice.

PS - I said yesterday that my central heat hadn't kicked on yet... today was overcast all day and the heater kicked mid-morning... thumbing it's nose at me...


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## wg_bent (Nov 14, 2006)

What's depressing is that I know what I did in the 1 room in the basement is right, and since I know there is no drafts, the insulation combo of bats and polystyrene is a winner.  I sealed the heck out of the sil plate with great stuff also, so it's all nice and tight...but the rest of the house?  Who knows.  I know the plugs all leak.   I feel like tearing all the sheetrock off the walls and pumping in the expanding foam stuff.  My friend who insulated that way plus 2 inches of the aluminum backed foam board R15 heats the whole house with 1 cord of wood and a Defiant CAT stove.


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## Rhone (Nov 14, 2006)

Well Precaud, I owe you an apology because you were right!  I dug around in my energy books and low and behold there's a tiny blurb that states the temperature difference also affects it (see picture).  That's all I could find anything about the rated R-Value of batts decreasing with temp difference, doesn't mention how much or to what degree, but something I passed over.  I'm assuming it happens to all insulation, nonething I have mentions it happening to cellulose but I feel the higher the temperature difference the more force but I have to assume fiberglass batts is most susceptible.  

Here's the pictures of what this years energy book says, along with the chart explaining how devastating the smallest gaps have on fiberglass batts.  Oh well, the book recommends if I have fiberglass to blow cellulose over it saying the cellulose will fill any gaps/cracks I missed so I get full R-Value of the fiberglass batts and add it's own R-Value.  Maybe after I'm done remodelling   Enjoy


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## precaud (Nov 14, 2006)

A local energy conservation specialist told me that, if I have cold air coming out of the electrical fixtures, I should seal the opening that allows the cold air to penetrate down the walls in the first place. His point was that no attic air should find it's way downward into the living space or walls at all. Made sense to me. I found two openings over doorway arches that were wide open, and sealed them with styrene and gooey I mean great stuff.


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## begreen (Nov 14, 2006)

How did you locate these openings precaud?


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## begreen (Nov 14, 2006)

Rhonemas said:
			
		

> Well Precaud, I owe you an apology because you were right!  I dug around in my energy books and low and behold there's a tiny blurb that states the temperature difference also affects it (see picture).  That's all I could find anything about the rated R-Value of batts decreasing with temp difference, doesn't mention how much or to what degree, but something I passed over.  I'm assuming it happens to all insulation, nonething I have mentions it happening to cellulose but I feel the higher the temperature difference the more force but I have to assume fiberglass batts is most susceptible.
> 
> Here's the pictures of what this years energy book says, along with the chart explaining how devastating the smallest gaps have on fiberglass batts.  Oh well, the book recommends if I have fiberglass to blow cellulose over it saying the cellulose will fill any gaps/cracks I missed so I get full R-Value of the fiberglass batts and add it's own R-Value.  Maybe after I'm done remodelling   Enjoy



I believe it's recommended that fiberglass batts be layered in the attic at right angles to each other for this reason. First layer between the ceiling beams, then the next layers put down at right angles to the joists.


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## precaud (Nov 14, 2006)

BeGreen said:
			
		

> How did you locate these openings precaud?


By getting up there with a light and looking along the wall intersections...


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## precaud (Nov 14, 2006)

> <snip> rated R-Value of batts decreasing with temp difference <snip>  I'm assuming it happens to all insulation, nonething I have mentions it happening to cellulose but I feel the higher the temperature difference the more force but I have to assume fiberglass batts is most susceptible.



Seem like it's just a function of the porosity. A material where the air pockets are trapped and sealed won't allow penetration.



> Here's the pictures of what this years energy book says, along with the chart explaining how devastating the smallest gaps have on fiberglass batts.


OMG! 50% loss of R value with R38 and 1% gaps! That's huge.



> Oh well, the book recommends if I have fiberglass to blow cellulose over it saying the cellulose will fill any gaps/cracks I missed so I get full R-Value of the fiberglass batts and add it's own R-Value.  Maybe after I'm done remodelling   Enjoy


Yeah, it can wait...! The only downside I've read to doing that is that the cellulose, which is quite a bit heavier than the fiberglass, compresses the batt. Nevertheless, it seems like the way to go.


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