Radiant Barrier attic insulation?

[Nerf]

So we just ordered a bunch of this stuff to help bring down energy costs, and am wondering if anyone here has used it to any degree of success.

We got the 28lb 500sqft perforated rolls, they're supposed to be stapled to the rafters and claims of lowering cooling bills by anywhere from 20% (I find this a beleivable number) to 50% (not likely).

We're also going to be blowing in another 12" of insulation after we tack this shit up, so we won't have a before/after comparison on just the barrier alone.

It makes sense from the aspect of creating a barrier to stop the hot air from getting into the rest of the attic and channeling it up to the top where our turbines can vent it, I just don't see how it's any more effective than a non-reflective material, or creating the channel with fiber board.  It's dark in the attic, so I don't really understand how it's going to stop any heat via reflecting radiation, the radiation is stopped when it hits the opaque roof.

We're going to be adding motors to our roof vents too, so that should help as well.  Hopefully this will be the last $450 electric bill.

[MahrinSkel]

Most heat is conducted by IR, even inside materials.  There's a reason the best conductors of heat tend to be conductors of electricity as well, the high-energy electrons that normally would emit an IR photon to be captured by another atom instead bounce around between atoms, passing the energy directly and quickly.  A mylar "space blanket" has about the same insulative value as a heavy blanket as a result.  The "light" that is being reflected away from your dark attic is infra-red radiating from the roof, and in those wavelengths your sheeting (the plywood your shingles are nailed to) is very bright indeed.

50% would depend on other factors, including the color and composition of your roof tiles (light-colored wooden shakes good, dark asphalt shingles bad), as well as how insulated and air-tight the rest of the house is.

--Dave

[Nerf]

So we didn't just waste $300, awesome! 

The reason I was iffy is because all the comparisons they had on their website were along the lines of "think how much cooler your car is with a sun shade" or "hold a mirror up to the sun so it shines on your arm, you can feel the heat!".

I've never really studied how IR works and passes through things, looks like I've got some reading to do.

As always, your input is greatly appreciated Dave (:

[CharlieMopps]

Well, if you get the standard pink insulation, it comes with a radiant barrier... that's what the silver foil part is.

If you're using blow style insulation, then yea, it will probably help you if your in a really hot climate.

My house, for example, is in Wisconsin and is in almost total shade during the summer months. (it's surrounded by very large oak trees) so the cost benefit wouldn't be much for me to install a radiant barrier. In a cold climate like mine, your money is better spent getting windows that seal well in the winter... to keep heat in.

[Merusk]

Cold climates still can benefit from radiant barriers.  You put the foil on before the drywall, side facing the interior to keep the warmth in during the winter instead of radiating through your stud spaces.

[Krakrok]

We're going to be adding motors to our roof vents too, so that should help as well. 

I've always wanted to try solar attic fans.

[MahrinSkel]

Since I rent right now, there are limits to what I can do about my air conditioning bill.  Best thing I found was to take a couple of the highest-volume bathroom vent fans I could find and rig them to the passive vents with duct tape and strap iron, plugging them into an outlet timer than turns them on every morning and off every night.

Texas and its deregulated energy market (the model for the one Enron fucked over in CA) is not so great when you're having one of the hottest summers on record (coming up on 50 days over 100 this year, and summer isn't even half over).  We hit peak load and the co-op starts paying $4+ a kilowatt-hour on the spot market, and the final bill doubles as they spend more for the juice in an hour than they should be in a day.  Doesn't even matter if my usage during peak is lower because they only track my total for the month and charge based on their average cost.  I've turned my thermostats up as far as I can without making the upstairs unlivable, and my bills are still topping $400 (would be over $500 without those fans).

Hell, my "electric company" doesn't even own any generating plants, and I can't change (contract is with the Homeowner's Association, who I think are getting a kickback).  Ahh, the joys of choice in a free market.

--Dave

[Nerf]

I'm shocked that your HOA has that kind of power, I wasn't aware they could get away with shit like that.

Even though you're renting, I doubt the landlord would complain if you asked him about blowing in more insulation or putting up one of these radiant barriers.  Hell, you could probably get him to kick in some $$ for it.  This stuff is cheap enough that even if you're only saving 15-20% on your electricity bill the payback is still only a few months.

[MahrinSkel]

My landlord is in China.  And I think the name on the title is just a beard for some state mega-corp and my landlord *is* China.  Maybe they could take the HOA to court (I know some of my neighbors did and got out of the contract that way) but as a renter I apparently don't have standing.

--Dave

[Salamok]

I had some guy going door to door a few weeks ago offering to paint the interior of your attic with a radiant barrier paint, made the same 20-50% claims.  Sounded a bit fishy, I just explained to him that my highest electric bill has been around $160 and it is usually around $130 for the summer months, so his $2000 paint job would save me $150 a year at 20% and $425 a year at 50%.

[Sky]

You guys use a lot of electricity!

[Morat20]

I had some guy going door to door a few weeks ago offering to paint the interior of your attic with a radiant barrier paint, made the same 20-50% claims.  Sounded a bit fishy, I just explained to him that my highest electric bill has been around $160 and it is usually around $130 for the summer months, so his $2000 paint job would save me $150 a year at 20% and $425 a year at 50%.

I actually got that stuff put in -- I was having new insulation put in (my old blown stuff was 20+ years old, meaning I effectively HAD no attic insulation) and if I did the paint I got a discount on the insulation. Worked out to be about 400 bucks extra, tops.

I suspect the new foot of insulation did far more for my electric bill (I paid for the 2k job in 18 months, just out of savings on the electric bill), but I think the paint's worth it. It's not as good as the blankets/mylar-whatever, but from what I read and what I can tell, it lowered my attic temperature about 5 to 10 degrees on average during the summer.

I probably wouldn't spring for it if I didn't live somewhere so damn sunny and hot.

[Nerf]

If you saved that much on the paint, you should look into doing the foil shit I'm doing too, Morat.  It's only setting us back $320 delivered for 2500sqft of the stuff, install should be a breeze, just staple it up.

From all my research, the best the paint can get with optimal coverage (my biggest worry paying some guy to spray would be he saved some cash by spraying it on thin) is about 75%, the foil claims 90%+.

Anyways, we'll know for sure later this week when we get it installed, shouldn't be too bad with the ol' disconnect the AC pipes so you air condition the attic trick.  I'll make sure to post the next few months electric bills in this thread.

July 1-31 was around 2,182 kwh (@ $.189 per)  We keep the house at 78-79 at the coolest.

[Morat20]

If you saved that much on the paint, you should look into doing the foil shit I'm doing too, Morat.  It's only setting us back $320 delivered for 2500sqft of the stuff, install should be a breeze, just staple it up.

The vast bulk of my electrical savings was the foot of insulation I put in. My wife likes the house pretty cool, and I live in Houston. You don't really get worse electrical bills than that. :(

The paint did seem to make a difference in attic temperatures, though. My worries with the foil is that I've heard of it causing some problems with the shingles. Reflected heat has to go somewhere....

[Yegolev]

My worries with the foil is that I've heard of it causing some problems with the shingles. Reflected heat has to go somewhere....

Seems like it would not get hot enough to destroy an asphalt shingle, and if it did, hoo-boy.  Anyway, this thread and my new $600 electric bills have inspired me to do something in my attic.  I installed two fans, one on each gable, one spinning intake and one exhaust, but the lack of insulation underneath the roof sheeting has to come to an end.  It will have to be the staple kind if I'm doing it myself.  Maybe I won't fall through my ceiling.

[Morat20]

My worries with the foil is that I've heard of it causing some problems with the shingles. Reflected heat has to go somewhere....

Seems like it would not get hot enough to destroy an asphalt shingle, and if it did, hoo-boy.  Anyway, this thread and my new $600 electric bills have inspired me to do something in my attic.  I installed two fans, one on each gable, one spinning intake and one exhaust, but the lack of insulation underneath the roof sheeting has to come to an end.  It will have to be the staple kind if I'm doing it myself.  Maybe I won't fall through my ceiling.

I don't think it destroys the shingle -- I've heard anecdotal stuff about some forms of it simply warping the things, or the wood they're mounted on. Shingles aren't made to take heat from behind. But I can't remember if that's the radiant barrier film, or the stuff that they sandwitch between layers of plywood on before nailing shingles on or what. There's a lot of ways to do it.

Now, I've heard some things about a California's Cool Roof programs. It's shingles and roofing made from high reflectivity material (in terms of what it looks like -- it looks like a white roof. I forget what they paint the backing with, but it's white too and pretty reflective. For residences, I think they use some funky type of shingle). I hear having your roof done Cool Roof is a bit more (up to 20%, depending on what you're doing) than just a standard reroofing job -- but roof surface temperatures run about 50 degrees cooler than normal roofs.

I'm seriously considering that investment, next time I have to reroof the house. Don't know if they have federal standards for that yet.

[kaid]

Damn and I thought my 70$ electric bills were a bit pricy for having my AC cranking hehe.

[Morat20]

Damn and I thought my 70$ electric bills were a bit pricy for having my AC cranking hehe.

If you're anywhere humid, you can't use swamp coolers -- so pricey. If it's someplace like Houston, with summer temps running well above 95 and associated humidity, it can get pricey just to cool the house. And Houston is simply unliveable without AC.

I do know a guy that had his house custom built with efficiency in mind. Some serious-ass insulation in his walls and ceilings (plus steel frames, integrated hurricane shutters, and some funky stuff in his roof). He spends about a third of what I do to cool a house with three times the volume, and the damn thing would probably laugh in the face of a Cat 5 hurricane. Of course, the upfront costs were probably insane. The steel frame alone adds on a serious chunk.

[Yegolev]

We quickly discarded the fantasy of a steel frame.  That's nuts.

The wife will never go for a white roof, so it's up to me to insulate underneath the roof.  It's interesting where the builders skimped with my house, because I have blown insulation in the exterior walls, then fiberglass between the ceiling joists, then nothing at all in the rest of the attic.  I'm interested in a quick fix at this point in time, especially since my wife spent all our money on that pool and other yard things.  Another item is putting an awning on the back to shield the back doors from the nuclear radiation given off by that damned star of yours.

[Merusk]

Wait.. nothing at all in the rest of the attic other than what's between the ceiling joists?  Wtf. Your house is new, isn't it?  What fucking building inspector said, "oh hey, yeah that looks like R-30, good to go!" 

Get some R-19 min. batts up there and throw them around.  It's a day's work tops, just make sure the batts are tight to each other, tight to the eaves and you've still got ventilation from the soffit. (Usually achieved with cardboard inserts.)  If you're really worried about going through the ceiling get a piece of plywood or OSB long enough to span at least two joists and kneel on that.  When I've been in attics I just make sure to always stay perpendicular to the joists/ truss webs.

[Yegolev]

Inspector?  I live in Georgia.  Also this is the first and only house I have built, so I am still learning.  Thinking about it now, it makes sense to insulate the attic, but the house I grew up in had no insulation whatsoever, nor air conditioning, so I'm claiming ignorance here.

Right now the only question is what sort of batts to get and how much.  It's going to be a lot, and I might nail down some particleboard as a floor up there before I get started, just on the GP, since I'll need to use a ladder.

[Nerf]

Working in the attic in Texas fucking sucks, especially when you're 6'5 and it's a 4/12 pitch.  I fucking hate attics.

We got the garage done today, and the difference is fucking shocking.  At /least/ 10-20 degree difference in the areas where we installed the foil within a few minutes.

Knocking out another big chunk tomorrow, but this shit is money thus far.

[Yegolev]

I'm sold.

[Merusk]

Inspector?  I live in Georgia.  Also this is the first and only house I have built, so I am still learning.  Thinking about it now, it makes sense to insulate the attic, but the house I grew up in had no insulation whatsoever, nor air conditioning, so I'm claiming ignorance here.

Right now the only question is what sort of batts to get and how much.  It's going to be a lot, and I might nail down some particleboard as a floor up there before I get started, just on the GP, since I'll need to use a ladder.

Everyplace has plans inspectors, it's just a question of how much enforcement goes on in the residential sector.  I thought you lived near Hotlanta, but I guess not.  That sucks. I'm guessing you didn't hire a private inspector, either.

Homebuilding with private builders and no inspections or permit process is as big a scam as Realty.  Seeing people get ripped-off pisses me off as it just makes the whole industry look that much worse.

I can't speak specifically about type in Georga other than to say you don't want the paper-backed stuff laying on top of your other insulation.  The paper acts as a vapor barrier and creates a dew point within the insulation, getting it wet.  Obviously this is a BAD THING.  Other than that I'm not familiar with the building practices of the area enough to give fully reliable advice in terms of what you should be putting down and exactly how. The guys at Home Depot should be able to help you out.  They hire folks with experience whereas Lowes I've always run into the "Teen with a summer job" crowd.  

Alternativly you can find a home inspector and see what they think would be best.  Go with one registered to ASHI since anyone can toss up a sign and say "I inspect homes!" It's not a regulated area, and there several "we'll certify you in 7 days!" orginizations.  You want those guys near your home as much as you want the, "We get you MCSE certified in 2 months," guys near your servers.

If your childhood home didn't have AC it was pretty old, so it's not a surprise it didn't  have insulation.  Energy code only began to get up to "reasonable" standards in the last 10-15 years, and the Homebuilding industry has been fighting it every step of the way saying it's too expensive.  (Ohio just got rolled-back on adopting the 2006 energy code because of this.  Sure, there were some inconsistencies that didn't make sense, but it was a pure cost-saving measure on the homebuilder's front.  I know this because my Dept Head is one of the guys pushing it.)

[Yegolev]

No, we didn't hire an inspector, mostly due to time and cost.  Building a house sucks huge balls.  There are things which need fixing but require time/effort/money and so on.  These things make me incredibly tired when I think about them.

I do live near the ATL, but the backwoods are surprisingly close to downtown, and it's still The South: everyone knows everyone else and things just get done however the contractor does it.  I live in Paulding County, a wreck of a county which is full of the people who can't afford to live in the better metro counties.  The county inspector who checked out my pool a couple months ago looked like just any old retired farmer you'd see sitting on a stool in the small-town hardware store.  He just wandered around for ten minutes before leaving, and I'm sure the house inspector did the same thing.  Might have been the same guy.

I grew up in Alabama, though, and that house is probably a century old.  So, yeah.

About the insulation, I'm going to put it under the roof sheeting where there is currently no insulation.  I can't imagine there would be condensation there but now I know to ask someone before I get this fancy RB stuff.  The existing insulation is fiberglass which is on the attic floor or top of the ceiling, and I was thinking of boarding over that.  The local Home Depot is full of jackasses but I can ask around to make sure I'm not committing a grave boo-boo.

[Merusk]

Yeah, that what I figured as soon as you said "Inspector?"  I just thought you were closer in to the greater metro area.  We've got areas like that in Cincy, too, so I understand.

No need to put the insulation into the roof rafters (which I'd guess is what you mean by "under the sheathing") unless you plan on finishing that space.   You can just lay it on top of the ceiling below over what's there for the most part.  I'm guessing you want to board over the ceiling joists so that you can store stuff up there?  If so, careful that you don't put too much load on them.

  The loading req's for ceilings are miniscule compared to floors since all you're supporting is the framing and drywall, so unless the structure was sized for "attic storage" you might do some damage.  For example, with SYP#1 you're allowed to span 15'-9" at 24"o.c. with a 2x6 for a "Limited Storage" (10psf: L/240) appliaction, but to get the same span at the same spacing for a "floor load"(30psf: L/360) application you have to use 2x10s.

Building a house CAN suck.. but only if the guy you're building with doesn't want to educate you. This, of course, is the case for 99% of the builders out there.  It's no more complicated than putting together your own home PC, really.  It's just not something you want to walk other people through most of the time.

[Morat20]

We quickly discarded the fantasy of a steel frame.  That's nuts.

I'd prefer it, but it's an additional 20% to the cost of the house right there. Given the weather and odd tornado, I'm still considering it -- but I'd probably go with wood and spend the money on better insulation and integrated hurricane shutters. (FUCK nailing up plywood. I want steel I can roll down over my windows and doors).

The wife will never go for a white roof, so it's up to me to insulate underneath the roof.  It's interesting where the builders skimped with my house, because I have blown insulation in the exterior walls, then fiberglass between the ceiling joists, then nothing at all in the rest of the attic.  I'm interested in a quick fix at this point in time, especially since my wife spent all our money on that pool and other yard things.  Another item is putting an awning on the back to shield the back doors from the nuclear radiation given off by that damned star of yours.

Next roof job, I'm getting the cool roof. I don't care what it looks like, a 50 degree difference? You bet your ass I'm all for that.

The next round of "Energy efficiency/climate control" changes I've got planned are Solar Screens for about half windows (already got double-paned) and I have to figure out SOMETHING to shade the outdoors part of my AC that's not butt ugly. Currently I got "nothing", and it gets sun all day long. I may plant a hedge or something.

Oh, and I plan to put in another tree to shade a bit more of my son's room.

[Yegolev]

OK, so I don't know the terminology for house parts.  Here's a picture instead.


So you are saying I don't need to add anymore insulation?  Even though I can cook bacon in my attic without a hotplate?

@Morat, If I lived on the Gulf, I'd be far more inclined to get a steel frame.

[Salamok]

OK, so I don't know the terminology for house parts.  Here's a picture instead.
[super cool house image]

So you are saying I don't need to add anymore insulation?  Even though I can cook bacon in my attic without a hotplate?

@Morat, If I lived on the Gulf, I'd be far more inclined to get a steel frame.

just put radiant barrier on the underside of your roof the insulation you have is in the proper place.

you all talking about steel frame or rebar reinforced cement?  I have a buddy that is a polysteel distrib stuff is pretty cool R50 insulation for you walls and can withstand insane winds (i think he said 200mph+) of course your roof would probably blow off long before the walls caved.  I'd consider it for a home I planned on living in for the rest of my life but if you are going to sell it within the next 10 years it probably isn't worth it (unless the hurricane insurance is helping pay for it).

[Furiously]

Might also look at blowing in some more insulation too if it is an unused space. Attic fans might also help a lot.

[Sky]

Attic fans would help, also you might have to rethink the entire strategy (if there even was one) about how your attic is vented. My attic crawlspace is a total bitch, and I've spent a few hours up there installing various things and trying to bring some other things up to code. It amazes me some people don't know or care about that kind of thing. The kid I bought it from had never been in the crawlspace in three years, I had spent more time in there in the first walkthrough I did of the house.

Knowledge = power.

[MahrinSkel]

Basic physics: How much heat gets from your attic to your house is a function of how hot the attic gets and how well-insulated the attic is from the rest of the house.  So either lower the temperature of the attic, or increase the insulation between the attic and the rest of the house, or both.  Better ventilation (especially fans) or keeping the heat from getting into the attic (reflective roofing materials or under-layers) keeps the attic cooler.  More layers of insulation keeps the heat out of the house, as does ensuring that there is no airflow between the attic and the house.

If you can keep the attic closer to exterior ambient, then your insulation doesn't matter so much.  If there's R50+ worth of insulation between the house and the attic, it doesn't matter how hot it gets up there.  If you're in a very hot climate that routinely gets to 100 degrees, I'd recommend a 2 out of 3 combination of the radiant barrier stuff Nerf is using or something similar like the paint, an active ventilation system (doesn't take a lot, even my bathroom vent fans are reducing the attic temp by 20-30 degrees), and another layer of insulation over the ceiling joists (since conduction by those from the attic ambient to the ceiling drywall below is probably high enough you could see their outlines in IR inside).  

The extra layer of insulation doesn't have to be a full-up R-19 fiberglass roll or equivalent, you could use a few layers layers of "house wrap" similar to the radiant barrier, or you could use "sheathing", which is basically styrofoam "boards" the same dimensions as plywood or drywall (4 foot by 8).  That last is especially a good option for the edges of a low-pitch roof, where you can't get to the corners without laying belly-down in the existing insulation and you can do the whole space much more quickly (not fun  to be up there even if you do it in the winter).  Whatever you do, take some spray-paint and mark the lines of the ceiling joists as you go so you can tell where to put your feet the next time you go up there.  You can get "foil faced" sheathing that gives you a twofer.

--Dave

[Yegolev]

Attic fans would help, also you might have to rethink the entire strategy (if there even was one) about how your attic is vented.

I tried this one already, installing two fans.  Trouble is the vents are in nonoptimal places.  I really don't want to fuck with the roof since, you know, it's not leaking now... but I might put in another vent if I determine it's worth it.  Afternoon highs are around 97F lately, so I might not get much more from adding a vent.

Putting another layer on top of the ceiling joists would be a hell of a lot easier than stapling insulation to the underside of the roof.  I'm going to have to think about it some more.

I was talking about steel frame, as in steel studs under drywall/sheathing.  Costly and of dubious benefit in my location.

[Yegolev]

[Morat20]

Might also look at blowing in some more insulation too if it is an unused space. Attic fans might also help a lot.

Modern roofs -- those with the weird "double peak" at the top, already vent air really effectively. I don't think fans add much to that.

Given where I live, I'm okay with a foot of blown, the paint, and a ridged roof vent. When it comes time to replace the roof (if I'm still living there), I'll defintely pay the premium for a Cool Roof (assuming anyone in the area does a decent job installing them) because my wife likes the house cold, and I live in freakin' Houston.

Solar screens on the windows, some decent shade trees, and that works out to a lot of saved money.

Salamok:

you all talking about steel frame or rebar reinforced cement?  I have a buddy that is a polysteel distrib stuff is pretty cool R50 insulation for you walls and can withstand insane winds (i think he said 200mph+) of course your roof would probably blow off long before the walls caved.  I'd consider it for a home I planned on living in for the rest of my life but if you are going to sell it within the next 10 years it probably isn't worth it (unless the hurricane insurance is helping pay for it).

That insulation look basically like an ice cooler? :) I think that's what my friend has. It's solid, and cut and fitted for the walls. I don't know exactly what sort of frame he has, but a good portion has to be steel because he mentions the only downside is trying to hang shit on the walls, and he has to remember to warn contractors lest they fuck up a drill.

I'm still waiting for aerogel to get cheap. :)