f13.net

f13.net General Forums => General Discussion => Topic started by: Nerf on August 09, 2008, 07:09:09 PM



Title: Radiant Barrier attic insulation?
Post by: Nerf on August 09, 2008, 07:09:09 PM
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.


Title: Re: Radiant Barrier attic insulation?
Post by: MahrinSkel on August 09, 2008, 10:37:21 PM
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


Title: Re: Radiant Barrier attic insulation?
Post by: Nerf on August 10, 2008, 01:01:27 AM
So we didn't just waste $300, awesome!  :awesome_for_real:

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 (:


Title: Re: Radiant Barrier attic insulation?
Post by: CharlieMopps on August 10, 2008, 08:28:32 AM
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.


Title: Re: Radiant Barrier attic insulation?
Post by: Merusk on August 10, 2008, 10:58:35 AM
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.


Title: Re: Radiant Barrier attic insulation?
Post by: Krakrok on August 10, 2008, 01:24:06 PM
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 (http://www.google.com/search?q=solar+attic+fans).


Title: Re: Radiant Barrier attic insulation?
Post by: MahrinSkel on August 10, 2008, 01:39:15 PM
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


Title: Re: Radiant Barrier attic insulation?
Post by: Nerf on August 10, 2008, 01:47:56 PM
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.


Title: Re: Radiant Barrier attic insulation?
Post by: MahrinSkel on August 10, 2008, 01:52:01 PM
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


Title: Re: Radiant Barrier attic insulation?
Post by: Salamok on August 11, 2008, 07:34:47 AM
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%.


Title: Re: Radiant Barrier attic insulation?
Post by: Sky on August 11, 2008, 08:55:30 AM
You guys use a lot of electricity!


Title: Re: Radiant Barrier attic insulation?
Post by: Morat20 on August 11, 2008, 09:49:13 AM
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.


Title: Re: Radiant Barrier attic insulation?
Post by: Nerf on August 11, 2008, 08:45:49 PM
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.


Title: Re: Radiant Barrier attic insulation?
Post by: Morat20 on August 12, 2008, 09:42:06 AM
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....


Title: Re: Radiant Barrier attic insulation?
Post by: Yegolev on August 12, 2008, 11:09:44 AM
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.


Title: Re: Radiant Barrier attic insulation?
Post by: Morat20 on August 12, 2008, 11:19:18 AM
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.


Title: Re: Radiant Barrier attic insulation?
Post by: kaid on August 12, 2008, 11:35:43 AM
Damn and I thought my 70$ electric bills were a bit pricy for having my AC cranking hehe.



Title: Re: Radiant Barrier attic insulation?
Post by: Morat20 on August 12, 2008, 11:47:23 AM
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.


Title: Re: Radiant Barrier attic insulation?
Post by: Yegolev on August 13, 2008, 09:09:02 AM
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.


Title: Re: Radiant Barrier attic insulation?
Post by: Merusk on August 13, 2008, 09:31:53 AM
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!"  :uhrr: :ye_gods:

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.


Title: Re: Radiant Barrier attic insulation?
Post by: Yegolev on August 13, 2008, 09:41:49 AM
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.


Title: Re: Radiant Barrier attic insulation?
Post by: Nerf on August 13, 2008, 09:50:14 AM
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.


Title: Re: Radiant Barrier attic insulation?
Post by: Yegolev on August 13, 2008, 10:02:36 AM
I'm sold.


Title: Re: Radiant Barrier attic insulation?
Post by: Merusk on August 13, 2008, 10:16:57 AM
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 (http://www.ashi.org/) 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.)


Title: Re: Radiant Barrier attic insulation?
Post by: Yegolev on August 13, 2008, 11:58:57 AM
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.


Title: Re: Radiant Barrier attic insulation?
Post by: Merusk on August 13, 2008, 12:18:01 PM
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.


Title: Re: Radiant Barrier attic insulation?
Post by: Morat20 on August 13, 2008, 12:24:28 PM
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).

Quote
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.


Title: Re: Radiant Barrier attic insulation?
Post by: Yegolev on August 13, 2008, 12:52:54 PM
OK, so I don't know the terminology for house parts.  Here's a picture instead.
(http://i202.photobucket.com/albums/aa181/Yegolev/shitty_house_diagram.png)

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.


Title: Re: Radiant Barrier attic insulation?
Post by: Salamok on August 13, 2008, 01:01:18 PM
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).


Title: Re: Radiant Barrier attic insulation?
Post by: Furiously on August 13, 2008, 01:08:13 PM
Might also look at blowing in some more insulation too if it is an unused space. Attic fans might also help a lot.


Title: Re: Radiant Barrier attic insulation?
Post by: Sky on August 13, 2008, 01:41:03 PM
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.


Title: Re: Radiant Barrier attic insulation?
Post by: MahrinSkel on August 13, 2008, 01:41:22 PM
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


Title: Re: Radiant Barrier attic insulation?
Post by: Yegolev on August 13, 2008, 01:55:56 PM
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.


Title: Re: Radiant Barrier attic insulation?
Post by: Yegolev on August 13, 2008, 02:40:20 PM
(http://i202.photobucket.com/albums/aa181/Yegolev/shitty_house_diagram_2.png)


Title: Re: Radiant Barrier attic insulation?
Post by: Morat20 on August 13, 2008, 02:51:13 PM
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:
Quote
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. :)


Title: Re: Radiant Barrier attic insulation?
Post by: Salamok on August 13, 2008, 03:06:59 PM
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.

those are ridge vents and even on new construction you don't always see them (always see them on rooms with vaulted cielings).

Quote
Salamok:
Quote
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.

Ya polystyrine forms bolted together 4 inch gap inside filled with rebar and concrete.  the reason it's hard to hang stuff is that the studs are the metal ferring strips used to bolt the peices together so instead of wood studs you have sheetmetal.

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

it is relatively cheap as long as you stick with peices about the size of rock salt.



Title: Re: Radiant Barrier attic insulation?
Post by: Morat20 on August 13, 2008, 03:36:23 PM
quote]
I'm still waiting for aerogel to get cheap. :)

it is relatively cheap as long as you stick with peices about the size of rock salt.
[/quote]
I want it an inch thick everywhere. :) Heck, sandwitch a few millimeters in the doors. That stuff blocks practically all heat, and it can be treated to simply ignore water. I'm sure there's more effective insulators somewhere, but in terms of "what you can fit into a wall", I don't think you can beat it.

Of course, to properly insulate a house with it would cost a fortune.....


Title: Re: Radiant Barrier attic insulation?
Post by: Merusk on August 13, 2008, 05:41:42 PM
OK, so I don't know the terminology for house parts.  Here's a picture instead. <snip>
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.

I'm saying go ahead and add it, (R-38 is the new minimum standard using 2006 IECC) but wasn't sure where you were adding it.  R-38 is about 12" of insulation, so if you've got that much you're already at the "Minimum"  Adding more can't hurt you, though.  Here's a change to your diagram!

(http://i530.photobucket.com/albums/dd347/Merusk/ousediagram.jpg)

Dave covered why the heat in your attic isn't such a big deal.  Heat rises, after all, so it's not adding much to your house to have a really hot attic other than radiant heat that happens to bleed through everything. The thermal barrier would help reduce that though, as others have mentioned.  Attics get hot because they're covered in nice black tar, tar paper and are usually enclosed.  It's like a mini oven, whee.

  You should have a ridge vent and soffit vents both. (The soffit is the overhang of your roof)  This helps air circulate to remove water vapor and some heat from the attic space.   

Only thing is, don't use the foil-faced insulation without talking to someone more familiar with hot & humid construction.  (I'm not.)  The foil also acts as a vapor barrier and I'm embarrassed to admit I forget if it's supposed to go on the "Warm side" or the "cold side" of the insulation to avoid getting water in it.  I have a notion as to which, but I can't recall for certain.


Title: Re: Radiant Barrier attic insulation?
Post by: Yegolev on August 14, 2008, 06:58:53 AM
Muh.  I have 12" of fiberglass already, so... wonder what the risks and costs of adding a ridge vent would be.  No, I don't have one.


Title: Re: Radiant Barrier attic insulation?
Post by: Merusk on August 14, 2008, 07:08:44 AM
You sure?  Ridge vent isn't an actual thing you see through, it's a cap piece filled with plastic spongy mesh (to keep bugs out) that just slaps over the ridge and is the same color as your roof, typically.  You're not going to see light through it, since that would let water in as well.


Title: Re: Radiant Barrier attic insulation?
Post by: Sky on August 14, 2008, 07:22:23 AM
If you have a ridge vent, you also want to have soffit vents and no end vents. And there's a whole thing about how the house is oriented with the prevailing winds so it sweeps up into the soffits and out the top, not in one soffit and out the other, etc.

Note when I post, unlike most people in the thread I'm in the Northeast, so we deal with both hot summers and frigid winters. Challenging to say the least.

At the least I need another 8-12" of insulation in my attic, but I've got a ton of shit on my plate before I can get to that. Wiring in the attic crawlspace not to code, no insulation on exterior walls, stuff like that. The joy of homeownership (I still wouldn't go back to renting!).
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.
Get a good roofing contractor. My general contractor specializes in roofing. I've got a 2004 roof that's in great shape, so I was wary about popping holes in it. He did a great job (it's pretty straightforward) and there've been no leaks in the torrential rains we've had this summer. Now I'm contemplating a new stove, and I want to run a vent out the roof, and I'm fairly confident in my guy's ability to make a clean chop. I'll install everything and just have him come out after work on day to cut the roof and install the outer vent piece.


Title: Re: Radiant Barrier attic insulation?
Post by: Yegolev on August 14, 2008, 07:47:27 AM
You sure?  Ridge vent isn't an actual thing you see through, it's a cap piece filled with plastic spongy mesh (to keep bugs out) that just slaps over the ridge and is the same color as your roof, typically.  You're not going to see light through it, since that would let water in as well.

I'm sure.  I'd be able to spot it from the outside, even if I didn't already know it wasn't there.  I do not have turbine vents, nor those small cap ones I have seen lately, the ones that look like a dryer vent cap.  I have two, uh, end vents?  In the gables.  That's where I put the fans.  I have soffit vents, meaning that there's a nice big gap between my roof and the outer wall in most places.


Title: Re: Radiant Barrier attic insulation?
Post by: Merusk on August 14, 2008, 09:00:30 AM
How odd. It works, as that's one of the oldest ways of venting a roof, it's just that you don't see it that much these days because it's easier to just slap on a ridge vent.   So long as there's enough square inches of vent, it's still nothing to worry about.  (And the sq. inches required is something you can't calculate without a plan or knowing the plan sq. foot of the roof and the sq. inches of the soffit vents.)


Title: Re: Radiant Barrier attic insulation?
Post by: Yegolev on August 14, 2008, 10:33:23 AM
You seem to be saying I'm screwed, assuming the end vents are large enough.  How about tacking a soaker hose to my roof peak?  I can leave that running 24x7 and it won't cost me more than $100 by a shot.


Title: Re: Radiant Barrier attic insulation?
Post by: Sky on August 14, 2008, 11:34:35 AM
How are the fans hooked up, directionally?


Title: Re: Radiant Barrier attic insulation?
Post by: Yegolev on August 14, 2008, 11:44:18 AM
(http://i202.photobucket.com/albums/aa181/Yegolev/fan_diagram.png)


Title: Re: Radiant Barrier attic insulation?
Post by: Sky on August 14, 2008, 11:51:16 AM
Hmm. Seems like there's a lot of area not getting vented. Have you checked air flow in the far end and also along the top of the attic (using a stick of incense or something)? Also, is that the direction of the prevailing winds? Excuse me if these are dumb questions, just thinking out loud. Having both vent out might better pull from the soffits on the far end of the attic. IANAC (I'm not a contractor :))


Title: Re: Radiant Barrier attic insulation?
Post by: Yegolev on August 14, 2008, 12:00:47 PM
I'm interested in putting in a vent on the far end, but that will require hiring someone.  I'm not really sure about the wind direction.  I might re-reverse the fan that is blowing into the attic and see if the soffits are up to the task of venting; the incense is a good idea.

This mental exercise is why I just take the case off my computer.


Title: Re: Radiant Barrier attic insulation?
Post by: Merusk on August 14, 2008, 12:13:34 PM
Screwed? Nope.  1) It's not what I was saying.  I was saying it they vented the roof different than standard for a modern building.  Not wrong, just different.   I just wasn't sure if they provided enough venting at the top, and I can't tell you that without a lot of house-specific information.   2) You're never screwed in construction so long as your structure is ok.

Now.. those vents seem oddly placed.  I would go ahead and close one up and open one of the same size on the opposite side, like you want.  With the way they're placed right now you're not going to cross-vent the attic.   While they'll both draw from the soffits, (smokestack effect > wind) the one end of the house is going to draw more air than the other.  I'm betting that far end of the attic gets a lot hotter than the end with the vents, yah?

Since i just noticed; if those arrows are the directions the fans are blowing you're REALLY doing it wrong.  You're blowing the stack effect of the soffits and since those fans are in-line you're just sucking air in to blow it out right at the other end.  You've done nothing more than created an invisible duct that'll shuffle outside air.  Nothing will circulate into the greater portion of the attic and pull that roof-baked air out.  The fans will draw air on their own from the soffit vents of your house so they should both blowing to outside.


Title: Re: Radiant Barrier attic insulation?
Post by: Yegolev on August 14, 2008, 12:20:53 PM
Since i just noticed; if those arrows are the directions the fans are blowing you're REALLY doing it wrong.

Alright, this would explain some of the increase this summer.  I wasn't aware of the soffit thing but it makes sense now.  I'll just get my ass up in the sweatbox and put it back so they both blow out.  I appreciate the information.


Title: Re: Radiant Barrier attic insulation?
Post by: Sky on August 14, 2008, 12:55:12 PM
Yeah, that's what I was getting at, too. You want to suck air in through the soffit vents and out through the gables. Still going to be a big dead air zone at the upper end of the attic opposite the fans, but it should have more circulation if you fix the one fan.

I wish I could find the article where I learned about roof ventilation techniques, it was very informative with lots of illustrations.


Title: Re: Radiant Barrier attic insulation?
Post by: Merusk on August 14, 2008, 02:52:59 PM
Doityourself.com, this old house.com and askthebuilder.com are all great resources if you don't have a handy, trustworthy contractor to bug.

IMO none of them use enough pictures, though.  Pictures are a requirement for explaining anything construction related.


Title: Re: Radiant Barrier attic insulation?
Post by: Yegolev on August 15, 2008, 08:39:54 AM
Because of illiteracy, rite? :awesome_for_real:


Title: Re: Radiant Barrier attic insulation?
Post by: Merusk on August 15, 2008, 09:18:34 AM
Funny, I just made that EXACT joke about 2 hours ago here at the office when someone was complaining about having to draw-up more details.

"Why does Bill want a detail of everything?! Can't I just put a note on the plans?"
"No, too many illiterates and non-English speakers in the field."

Joke aside, no, illustration and pictures just show things a lot more concicely than 5 paragraphs explaining how to do it.  Plus you can point to exactly what you're talking about.   Kind of why we have prints instead of 120 pages of text for a floor plan.  :grin:


Title: Re: Radiant Barrier attic insulation?
Post by: CharlieMopps on August 15, 2008, 09:49:20 AM
You people are friggen nutz. Stop helping dude burn his house down. He needs to hire a contractor if he doesn't even know what a joist is.

If your house wasn't inspected when you built it... you're going to be in a world of hurt when you go to sell it.


Title: Re: Radiant Barrier attic insulation?
Post by: Yegolev on August 15, 2008, 12:20:35 PM
I'm not selling shit.  You'll have to blast my ass out of here with dynamite.


Title: Re: Radiant Barrier attic insulation?
Post by: Nerf on August 15, 2008, 01:27:12 PM
Almost finished with the install, the difference in the areas that have the foil up versus the ones that don't is amazing.  I figured it was all snakeoil, maybe a small difference, but holy shit.  The electric bill will be the real test, and we should have at least of month of just the barrier before we blow in another 12" of insulation.

Looks like we bought way too much as well, house is 1800sqft or so, we picked up 2500sqft of the foil, we've only got a small chunk left and still have maybe 1200sqft of foil.

If I ever build a house, the whole fucking place, floor to ceiling, is getting a layer of this shit.


Title: Re: Radiant Barrier attic insulation?
Post by: Morat20 on August 15, 2008, 01:41:23 PM
Almost finished with the install, the difference in the areas that have the foil up versus the ones that don't is amazing.  I figured it was all snakeoil, maybe a small difference, but holy shit.  The electric bill will be the real test, and we should have at least of month of just the barrier before we blow in another 12" of insulation.

Looks like we bought way too much as well, house is 1800sqft or so, we picked up 2500sqft of the foil, we've only got a small chunk left and still have maybe 1200sqft of foil.

If I ever build a house, the whole fucking place, floor to ceiling, is getting a layer of this shit.
Have someone who knows what they're doing put it in, so you don't get problems with water condensing on it.

You really only need it in the attic. That's where the heat collects. Put down a Cool Roof or a reflective backing to lower attic temperatures and roof-surface temps, and good insulation to keep the warm air up there, and with solid venting you're gold. It won't do shit in your walls or between floors or anything like that.


Title: Re: Radiant Barrier attic insulation?
Post by: Merusk on August 15, 2008, 03:16:05 PM
It'll block the gub'ment x-ray and listening devices, though. :tinfoil:


Title: Re: Radiant Barrier attic insulation?
Post by: Morat20 on August 15, 2008, 04:46:04 PM
It'll block the gub'ment x-ray and listening devices, though. :tinfoil:
Might hose your wireless, although I doubt it. :)


Title: Re: Radiant Barrier attic insulation?
Post by: Salamok on August 15, 2008, 07:08:07 PM
From the exterior all a ridge vent looks like is a raise ridge shingle, so the shingles at the very top (peak line of the roof) will just look like they have about a 1 inch drop to the shingle beneath  as opposed to just laying flat like all the other shigles.

(http://www.inspect-ny.com/exterior/Ridge_Vent195-DFs.jpg)


The dryer exhaust looking vents you were tallking about aren't ridge vents (they are roof louvers) and are usually located about 2 feet below the actual ridge (unless they are venting something specific like a bathroom fan you don't need these if you have ridge vents).

(http://www.allaroundinc.com/images/DCP_2099.JPG)

so are you sure you don't have ridge vents?



Title: Re: Radiant Barrier attic insulation?
Post by: Yegolev on August 18, 2008, 08:11:53 AM
What does a ridge vent look like from the bottom?  My roof is really tall, hard to see.  If I do have roof vents, I suppose I'm screwed for real.


Title: Re: Radiant Barrier attic insulation?
Post by: Morat20 on August 18, 2008, 09:50:13 AM
What does a ridge vent look like from the bottom?  My roof is really tall, hard to see.  If I do have roof vents, I suppose I'm screwed for real.
Um, back up a bit so you can see the top of your roof? It looks like the peak of your roof is wearing a hat. It's not subtle. You can tell from 200 yards away.

Your roof comes to a peak, right? Well, right there on the peak is a little upside-down shaped V sitting right on top of it.

Here's a flickr shot (http://www.flickr.com/photos/linqink/34501470/) and another (http://www.flickr.com/photos/vinylindustries/429247059/) of someone's ridge vent. It's impossible to miss.