Unless I am missing something, by spraying the rafters, it's going to turn the ceiling/roof area into part of the warm section, whereas the ceiling should be the end of the warm area and therefore the ceiling is what should be sprayed, and the rafters should be on the cold side - and the ceiling will also be the point of moisture/air barrier (not sure if open cell counts as barrier or not) - and you need your ventilation. Otherwise if roof is warm side, you will get a snow melt/freeze thing going on, with ice damming and attendant issues. Correct me if I'm wrong.

Mightyanvil: after installation, can you visually distinguish closed from open?

Weedyacres- I hope you don't mind me asking questions about what the contractor said- am not wanting to steal your thread.I am wanting to learn more about this also. weedyacres,mightanvil and others- unless the contractor has something new, isn't the R-Value about 7 for 1 inch thickness of closed insulation? Is he going to install 2 inches? I have not come across a 14-R yet for 1 inch. I talked to a insulation place in San Antonio this past spring, and he said the 'actual' insulating factor is closer to 4-5, even if advertised at 7. This was closed cell he was talking about. Weedyacres, may I ask about
which brand he was talking about? They said the attic did not need to be vented for the same reason mightyanvil said.
This was Icynene (sp), and something like 'polyxxxxx'.
pjb999- you mentioned spraying the deck of the ceiling, meaning above the ceiling?? Wouldn't that make more sense- to spray heavily the 'outer layer' of the room below- or does it have to be the rafters, ceiling etc of the attic.
Weedy...maybe you are not on a budget, but have you thought about buying a kit and doing it yourself? I have read both ways- that it is easy to do, and then that you need to have practiced because you need to be able to cover smoothly/evenly. It is supposed to be a very fast paced job.

We'll ask the contractor the brand of the foam he uses. I think Icynene is an open-cell spray foam.

What about polyiso sheets instead of spray foam? Pros/cons? We're DIY-ers for most things, and could easily put up the foam boards ourselves. I'll look into DIY kits for the spray variety as well. I've browsed through the GW posts and the consensus seems to be that it's not a DIY job.

Weedyacres, As Mighty Anvil has been stating all along, check in with your building dept. about venting. Our county was unfamiliar about not needing venting with foam, but nevertheless would not change or issue a variance on our build. The foam company stated the importance of non-venting, but had we gone ahead and had it done, the county would have made us tear it all out and vent which would have been a big money loss nightmare.

The inspector will be here tomorrow to check our electrical, and ridge vents + spray foam is on our list to ask him.

Contractor #2 came back with a bid today: $2500 for open-cell spray foam (grr, we told him to bid closed-cell), which works out to roughly $2.50/sq ft.

The inspector came by today and I asked him about spray foam without roof venting. He said, "I've heard people say it's okay, but I wouldn't do it." I proposed baffles against the rafters and spray foam over it, and he said the baffles are made for use with fiberglass, so spray foam might crush them, or ooze into the holes around the vent or soffit, defeating the purpose.

Here's where we're leaning:
Walls: 2" polyiso (blue styrofoam) in the walls (R-10), spray foam (Great Stuff) in the gaps to make it air-tight, covered with Reflectix (aluminum bubble wrap), which adds about R-4.
Roof: R-30 fiberglass, faced with Reflectix. Don't know if we need the baffles.
Cost will be about $1/sq ft + elbow grease.

This is a west-facing room with no shade and gazillions of windows, so priority is toward blocking radiant heat so as not to overtax our HVAC system and run up our bills.

Thoughts/feedback on this tentative plan?

Your air barrier needs to line up with your insulation.

The purpose of roof venting is to allow air and humidity to leave the structure. It is not for roof venting as a result of water intrusion.

The foil is not necessary and will not appreciably increase that wall R-value any measurable amount. Foil is best, if at all, for uninsulated roof joists that benefit from a dead air space and it provides very little reflection but only if it is not covered up. Putting foam board in front of it negates all the value in it.

What is the exterior construction of the sunroom...siding, brick, block, etc?

Explain the roof detail again. Is the ceiling of the sunroom screwed into the roof joists? If that is the case, you need to insulate the choose whether or not you are going to make the underside of the roof a "conditioned" space. If so, you can close the ridge/gable vents and insulate accordingly. If not, the ceiling is what needs to be insulated. Place the kraft paper on the batts facing into the ceiling drywall. The drywall will provide the air barrior.

The foil would be on the house side of the insulation, with a small air space between it and the drywall. That's how the manufacturer says to install it. Are you saying use it in the ceiling but skip the walls?

Here are a few photos of the rooms. This is a corner shot, showing the window coverage, and then a shot of the cathedral ceiling trusses and the ridge vent.

This is the smaller upstairs roof. No ridge vent, flat ceiling. BTW, no attic access for either room, so we need to insulate from below.

And here's a photo of the outside, to provide context. Exterior is all brick (and windows, of course).

Weedy, Do you have soffit venting as well? If so, because you have what we term out here as scissor trusses, i would go with high density batts with a vapor barrier and leave the airspace from the soffit venting to the ridgeventing clear and unobstructed. You should easily get r-38 and your only obstruction concern would be to put baffles down at the wall plates where the scissor trusses top and bottom chords meet so the r-38 wont block off the soffit venting. You can also use plywood there as an alternative. Not a spray foam application,imo, because you dont have deep enough rafter cavatie space. Concerning the small hipped roof not ridgvented, we have a similar dormer only smaller that was still required to have ridge/soffit venting. Hopefully that area has at least soffit. I would consider having a roofer install a ridgeventing there unless you go the foam route and it is cleared ok by the inspector.

weedy,

I just saw your link from the other forum today, so here I am! I'll probably have to answer most of your questions over a couple of posts, but let me start with some semi-generic information. Much of it will be repetitive from what others have already posted.

Code: You're in Indy right? Indy has adopted some version of the IRC. Previous versions of the IRC required all attics and enclosed rafter spaces to be vented, unless approved under the "alternative methods" section of the code. But the latest version allows unvented attic assemblies if certain conditions are met.

Unvented assemblies are allowed if "no interior vapor retarders are installed on the ceiling side (attic floor) of the unvented attic assembly" and if "air-impermeable insulation is applied in direct contact with the underside/interior of the structural roof deck."

So unvented assemblies are allowed under IRC, but you might be working under an older version of the code.

Now, my previous paragraphs mentioned "...unvented assemblies are allowed if 'no interior vapor retarders are installed on the ceiling side (attic floor) of the unvented attic assembly' and if 'air-impermeable insulation is applied in direct contact with the underside/interior of the structural roof deck.'"

While open-cell foam stops air infiltration, it is not a vapor barrier. If I used an open cell foam, I'd need a vapor barrier. So in my area, my inspector interprets that so that I can't use open cell foam in an unvented roof. I'd have to use a closed cell foam, and the foam itself would have to be the vapor barrier. For closed cell foam to have a low enough perm rating to be a vapor barrier it has to be at least 2" thick.

Open cell versus closed cell. Very briefly here, open cell is also known as 1/2 lb foam, it's what icynene is. It's about R3.5 per inch. It it air barrier, but not a vapor barrier. If sprayed on thick, it develops a slightly hard "crust" but if you remove the crust the interior foam is soft and flexible. It can absorb and hold water. When sraying icynene, often times installers will fill a stud bay completely. If having to pull wires through the wall at a later date that can make things difficult.

Closed cell is also referred to as 2lb foam, it has a higher R value of about 6.5 per inch. It's an air barrier and when sprayed to >2" thickness it's also a vapor barrier. It won;t absorb water or hold water. Stud bays are not always filled to full depth. That can make it easier to run new wires at a later date.

Fire protection: If the foam is installed in an inaccessible area, it does not have to be covered with non-flammable material. If you have an access bay to service air conditioning equipment, then it does need to be protected. That protection can either be drywall, or the foam itself can be sprayed with an intumescent coating.

FOam strength: 1/2 lb (that's half-pound per cubic foot density) is soft, it provides no structural strength. If your house flexes (earthquake!) the foam would flex as the strcture flexed. 2 lb foam is rigid. It adds strength and rigidity to the structure.

Shingle life. An unvented roof has been estimated to raise the temperature of your shingles about 3 degrees. The color shingle you use has a greater effect on the life of your roof than does venting or not venting.

Off on a tangent: In your room, if you haven't, use canned foam to seal the gap between your windows and the framing. Don;t overdo it, as you don;t want to blow your windows in, so a low-expanding canned foam might be best.

Where you have studs ganged together, run a bead of caulk at the stud-to-stud seam.

Every little bit helps.

What would I use? I'm in a heating climate (CT), hands-down I'd choose a non-vented roof with 2lb closed-cell foam.

'nuff for now. A lot of rambling and no time to proof-read, so I'm hoping it makes sense.

Oh, one more thing. Ice dams. In your area and mine, they are not a concern with a well-insulated non-vented roof. But if you were in a heavy snow area where you might have a foot of snow sitting on your roof (Lake Tahoe) for weeks at a time, then the deep snow, over a long term, can act as an insulating blanket. In that case it's recommended to go with a vented roof.

Mongo

Open cell foam sprayed in thicknesses of about 5" will form a vapor barrier as well. Also, seeing as you don't require one, I would make sure the soffit vents are closed in and spray foam (open or closed) that roof and be done with it.

There is no benefit to that foil crap unless you have uninsulated roof sheathing and you want to cheaply bounce back some of the heat.

Mongoct is right about ice damning. Not really and issue where you are and especially if you have a continuous air barrier and well insulated.

"I would make sure the soffit vents are closed in and spray foam (open or closed) that roof and be done with it".

Unless the inspector wont allow it which was already stated that their inspector thought non venting was a bad idea. Most areas concerning inspectors haven't researched non venting/foam and in our counties case, venting,(ridge/soffit continous run), is mandatory.

Thanks Mongo for your lucid primer on spray foam. We will definitely hand foam the windows and caulk the studs.

We do have vented soffits and--my mistake--a ridge vent in the second-story room (it's hiding atop that beam). Which makes me lean toward leaving the attic vented and insulating below with fiberglass as sierra suggests. Also driving me in that direction are the fact that I'd get a higher R-value for a lower cost.

Still outstanding questions:
1. Any value in the aluminum radiant barrier in the attic?
2. Recommendations on the walls? Fiberglass + aluminum? styrofoam + spray foam in the cracks + aluminum? Either of the above without aluminum? Spray foam again loses the R-value battle...unless there's an airtight/watertight argument that outweighs it.

Again, living in Southern Indiana, my biggest concern is keeping the heat out. But we do get a little snow and an occasional fierce wind or thunderstorm, and they drive from the west, where the big sunroom faces.

windowsonwashington,

You wrote "Open cell foam sprayed in thicknesses of about 5" will form a vapor barrier as well."

My understanding is that 5" of open cell has a perm rating of about 10. That's not even close to what's needed to qualify as a vapor barrier (Weedy,

I'm not a big fan of radiant barrier films or bubble-type sheets that are sold solely for the purpose of being a radiant barrier. Some just don;t work, others are not installed correctly, and even if htey are, they can dirty up over the years and lose their effectiveness.

I am a BIG fan of insulation that acts as a radiant barrier. Spray foams, rigid foam, celulose.

If you really want to tighten up the room, insulate your stud cavities. spray foam, dense-packed cellulose (dry versus wet), even fiberglass batts, which I normally abhor, can be used in this case, because next...

Install sheets of 1" rigid foil-faced polyiso on the walls. When you install the sheets, gap them from their neighbor by about 1/4" to 3/8ths inch. The ends of the sheets don't have to fall on the studs, the sheets can break in the middle of a stud bay.

Peak between the sheets to find the studs, and mark the centers of the studs on the face of the polyiso with a sharpie marker.

Then use canned foam to seal the gaps between the sheets. Shave off any foam squeezeout so the seams are flush with the foil face. Then use aluminum tape to cover the foamed seams. Don't forget to foam and tape the corners...wall-wall and wall-ceiling.

From here you can do one of two things on the walls:

1) Run 1"x2" furring strips horizontally across the wall, 16" on center. Fasten these by screwing these through the polyiso and into the studs.

You'll want to add a nailing backer for your trim, so you can run an additional furring strip about 6" off the floor for your baseboard. The horizontal strip on the floor and the one 6" off the floor will give you purchase when you nail your baseboard. You can do the same for crown. Around the windows you can add 3" to 4" wide vertical fill-ins between the furring strips A couple of nails through the foam will secure these to the windows' king and jack studs.

Now install the drywall with standard screws, screwing it to the furring strips.

This will thicken your wall by 1-3/4", so you'll have to pack out your door and window jambs. You'll also need to pack out your electrical boxes. Box extenders are available.

2) If the 1-3/4" is too much and you need to lose thickness, you can omit the furring strips and screw the drywall to the studs using the sharpie marks as a stud guide, however...you need to be real careful here.

You need to make sure the drywall is pushed tightly against the foam and the framing when you screw it, and you don't want to set the screw so deep that it sucks the drywall too tight and compresses the foam. A little tight is okay, but too tight and over time the foam can rebound, "push back", and cause the drywall to pop out a bit which will fracture the drywall's gypsum core.

On the ceiling, I'd use 2" foil-faced polyiso instead of 1", I'd require that the furring strips be used. Any junction boxes in the ceiling should be boxed in on the attic side with a 12" square box made from 2" polyiso. That'll air-seal the junction box and prevent it from being buried in blown in insulation.

Then you can blow insulation in the attic, covering the top of the polyiso.

Totally DIY-friendly, it sounds harder than it actually is.

The 2" of ceiling polyiso will act as a radiant barrier and prevent your somewhat hot summer attic from heating the living space. If you loose-blow cellulose on top of the polyiso it'll be even more effective.

The polyiso on the walls and ceiling will act as a thermal break, and also as an air-infiltration barier, increasing not just the overall R-value of the wall assembly, but increasing the effective R-value as well.

The polyiso will also act as a vapor barrier and even reduce sound transmission through the wall.

If you use the furring strips, the 3/4" airspace between the foil-faced polyiso and the back of the drywall will act as a radiant barrier.

Just another idea.

Another different method would be to rip 2x4's into 2x2's (or just buy 2 by 2s and run them horizontally across the studs, 16" on center.

Then add mesh netting and dry blow dense-packed cellulose insulation into the framing bays.

Cellulose absorbs radiant, it knits together to prevent air infiltration, it deadens sound transmission, and the furring strips will also act as a thermal break by taking the drywall away from the studs.

The cellulose needs to be properly dense-packed though.

As to the exterior of the house, have you considered anything like a trellis/awning over those windows to block the hot summer sun from hitting the windows?

Lemme see if I can find a few photos.

Mongo

A few photos of the 2x furring, mesh netting, and dense packed cells in wall, loose blown in attic:

ABOVE: 2-bys ripped into 2 x 2s.

ABOVE: Netting put on ceiling joists, then 2-bys installed perpendicular so the netting is clamped between the joists and the furring strips.

ABOVE: Netting put on walls.

ABOVE: Glue to glue netting to face of wall furring stips.

ABOVE: small "X" cut in mesh, hose inserted, cavity filled with dense-packed cellulose.

ABOVE: In attic, baffle installed in joist bay, then scrap osb cut to act as blocking.

ABOVE: Scrap foamed in place, sealed so attic cellulose doesn't escape into outside soffit.

ABOVE: Outside, shows the rafter bay baffle sticking out. This will eventually be framed in.

ABOVE: In attic, raised walkway built down the middle.

ABOVE: Cellulose being loose-blown into attic to the height of the walkway.

ABOVE: Bales of cellulose.

My point about the vapor barrier/retarder was in reference to air movement carrying moisture.

Kraft paper is rated at a 1 and you know how much air moves through that and ultimately moisture. I would rather have an airtight structure and negate most of the vapor that way.

OC or CC will stop all air movement and hence, most moisture from inside the structure to out.

He has a brick and mortar home and in all likelihood has a some sort of air space between the brick and sheathing, if not, his interior vapor retarders should be removed anyway because that sheathing is going to need to dry.

In the climate zone he is in, I would not have a vapor barrier on the inside of my home or one at all for that matter. A good air barrier and R-value is all he needs. That is why I would go the OC route.

Do realize that vapor can transmiss without air movement.

Take housewraps like Tyvek. They block air movement and liquid water, but allow water vapor to pass through them. Simplified, but the same concept. Icynene is similar in nature.

There most definitely is a movement away from vapor barriers, but it has to be tied in with the overall thermal envelope of the house, what type of insulation is used, how moisture affects the insulation (structurally and r-value wise), how well the insulation can store and then release moisture, can the insulation hold moisture without damaging the framing, does it dry to the interior, the exterior, and how well the envelope of the house allows that to happen. Coupled of course with in what sort of climate the house is built.

Icynene in walls? Maybe no vapor barrier, depending. Maybe. Icynene in a vented roof? Again, I can see an argument for no vapor barrier in some situations, but I'd want one. Icynene in a nonvented roof? Without a vapor barrier it'd be a disaster because it'd become a saturated sponge.

But yes, we all have differing ideas, different experiences, etc.

Best, Mongo

Yes, I am aware that vapor can move through without air, however, most of the bulk moisture that is move from inside a building to out is carried on air.

If he has his outside vapor problem addressed an does not have the brick right against the wall, there will be a breathable space that should allow for drying.

If his house, more importantly his sunroom, is airtight, that it is a non-issue in my opinion as long as he doesn't have twenty open aquarium tanks running.

I love it when people debate my questions. I learn so much. Thanks to all for taking the time. I am a little bummed that our aquarium collection has to get the boot, though. :-)

Mongo, a few follow-ups on your advice to aid my learning curve:
1. I thought an air cushion between the foil and the drywall was a must. Why not? Does it merely reduce the effectiveness of the radiant barrier rather than negate it?
2. What's the minimum thickness the furring on top of the polyiso can be? Can you get away with 1/4" ripped strips of plywood? Dropping a ceiling by 4" makes me a bit trepidatious. And claustrophobic.
3. Can you cut strips of polyiso and put them in the stud bays or does the benefit come only from having a continuous surface?
4. Do you need to put polyiso on both the walls and ceiling to get the whole-seal barrier or can you get some benefit if you've only got one or the other?
5. Is there sufficient space in the rafter area of our sunroom (cathedral ceiling scissor trusses) to use blown-in cellulose?
6. Why do you have to fur down the joists/out the walls to blow in cellulose? Why can't you just attach the netting to the studs/joists?
7. Does 1" unfaced polyiso + 1" foil-faced polyiso = 2" foil-faced? The latter isn't a stock item around here. Similarly, can you still get some benefit (and less ceiling loss) from 1" foil-faced rather than 2"?

We've given thought to a pergola or something outside the sunroom when we build our deck next year. We've got a lakeview (the reason we built the addition), so we need to be careful not to do something that would obscure that view.

Here's a photo of brickwork-in-process. Looks to me like they butted it up against the sheathing.

1. I thought an air cushion between the foil and the drywall was a must. Why not? Does it merely reduce the effectiveness of the radiant barrier rather than negate it?

For a foil surface to be an effective radiant barrier, yes, it needs an air space in front of it. If you push drywall right up against the foil, then the foil simply becomes a conducting film. But realize that that is for just a foil film on its own. Polyiso, on its own, foil or no foil, will block radiant energy. With no foil, or with foil but with something (drywall or insulation) in contact with the foil surface, the face of the board may heat up from absorbing some of the radiant energy, but the R-value of the thickness of the board will prevent the radiant energy from reaching the living space of your house. Cellulose will absorb the radiant, then dissipate that gain through the R-value of its thickness. Radiant passes right through fiberglass.

A foil face with an airspace in front of it facing the interior living space will keep radiant energy in your house, keeping you warmer in the winter.

2. What's the minimum thickness the furring on top of the polyiso can be? Can you get away with 1/4" ripped strips of plywood?

For it to hold drywall screws it should be 3/4" thick.

Dropping a ceiling by 4" makes me a bit trepidatious. And claustrophobic.

In my example you're adding 2" of polyiso and 3/4" furring, so you're only dropping your ceiling 2-3/4" lower than it would normally be, not 4". In the cellulose ceiling, you're only dropping the ceiling an additional 1-1/2", the thickness of the 2-by rips. With the cellulose and mesh netting, you could actually just go with 3/4" furring strips, so your ceiling would only be 3/4" lower than a typical ceiling. With that I'd recommend 5/8ths inch drywall on the ceiling. Although the tight mesh will hold the weight of much of the cellulose, the 5/8ths will give added anti-sag resistance.

FWIW, 5/8ths is all I ever use on all ceilings.

3. Can you cut strips of polyiso and put them in the stud bays or does the benefit come only from having a continuous surface?

Yes. You can do that, but you lose the thermal break because the stud will now be in contact with your interior drywall. It's still good insulation, it's be the equivalent of spray foam in terms of only the stud bay having foam in it. If you do it, cut the polyiso narrower than the stud bay, place it, then use canned foam to fill those gaps and "glue" the polyiso to the studs. Good air sealing.

4. Do you need to put polyiso on both the walls and ceiling to get the whole-seal barrier or can you get some benefit if you've only got one or the other?

You can do one and not the other. Just make sure to seal the wall vapor barrier, whatever it may be, to the ceiling vapor barrier, whatever that may be.

5. Is there sufficient space in the rafter area of our sunroom (cathedral ceiling scissor trusses) to use blown-in cellulose?

It looks like you have somewhere around 7-8" between the top plate and the bottom of the sheathing? Sure, just do the same detail that I have in the rafter bay photo in my previous post. You can increase the depth of the insulation as you move away from the wall. Cellulose will block radiant gain, too.

6. Why do you have to fur down the joists/out the walls to blow in cellulose? Why can't you just attach the netting to the studs/joists?

You don't have to, but that house was built with 2x4 studs, so the 2" wall furring strips builds out the wall thickness for more insulation, but more importantly, it minimizes the amount of thermal bridging in the framing from the outside to the inside. Although you still have 5-1/2" of insulation and an equivalent build R-value that you'd have in a 2x6 framed house, the effective R-value of the wall is greater due to the lack of thermal bridging. It's one form of an "energy wall".

For the ceiling, strapping ceilings is an old holdover here in the northeast from the days of plastering. In this case, though, the strapping (furring) holds the mesh off the drywall, which takes the weight of the insulation off the drywall, which eliminates possible sagging of the drywall. This house was built with trusses 24" on center, the strapping also allows the on-center spacing for the drywall to be reduced to 16". I use 5/8ths inch drywall on all ceilings anyway.

7. Does 1" unfaced polyiso + 1" foil-faced polyiso = 2" foil-faced?

Yes. Just stagger the seams of the two layers of foam board when you hang it.

Similarly, can you still get some benefit (and less ceiling loss) from 1" foil-faced rather than 2"?

Yes.

I had a good experience with Tigerfoam. Do a serach and find them. I did it myself. It was kind of fun, but beware. Whatever it sticks to. it won't come off! If you get some in your hair, cut it, or wait for it to grow out. The company will provide you with everything you need but here's a good tip: I got a knife that was like a cake server so that I could scrape flat whatever foam popped out past the rafters.

Mongo: Eternally indebted for your profuse knowledge sharing. I've been reading up a lot on cellulose, and it's looking very attractive.

Cellulose is a great insulation. It's not the same cellulose of even 20 or 30 years ago.

Do realize that if you blow it onto a framed cavity, like a stud bay, or a rafter bay, that it needs to be "dense-packed".

Dense packing involves blowing it in at a density higher than cellulose's natural settling density, so it can't settle after it has been blown.

We're you to just loose blow the cellulose into a wall stud bay until it was full, over time the insulation could settle inside the bay, leaving you with 6" or so of no insulation at the top of each stud bay.

Dense-packing is not difficult.

In an open attic space you'd "loose blow" it, and you have to blow a sufficient depth so that after it settles you have sufficient thickness to provide your desired R-value.

Oh, and you're welcome!

Mongo

"Radiant passes right through fiberglass."

90 to 95% of "radiant" infra-red light energy is absorbed by fiberglass, cellulose, foam boards and other common solid construction materials that lack a low-emissivity surface, however, it will pass "right through" an unobstructed air space (or a vacuum) without warming it.

It is also misleading to suggest that an insulation material can be as effective as insulation in stopping the transfer of infra-red energy without qualifying the conditions where that might be true. Solid insulation absorbs the infra-red energy and transfers it slowly by conduction but a radiant barrier blocks almost all of it in a very small space. Whether a radiant barrier with a small air space is more effective than the same thickness of insulation depends on the kind of insulation, the temperature difference between inside and outside, the exposure of the building element, its exterior finishes, and the location of the materials in the element. In general, only very hot climates benefit substantially from a roof radiant barrier and only extreme climates benefit substantially from a radiant barrier in a wall.

"It is also misleading to suggest that an insulation material can be as effective as insulation in stopping the transfer of infra-red energy without qualifying the conditions where that might be true. Solid insulation absorbs the infra-red energy and transfers it slowly by conduction..."

That's what I tried to infer when I wrote "...the face of the board may heat up from absorbing some of the radiant energy, but the R-value of the thickness of the board will prevent the radiant energy from reaching the living space of your house. Cellulose will absorb the radiant, then dissipate that gain through the R-value of its thickness."

So I agree that they are not radiant barriers per se, but with appropriate thickness they effectively absorb the radiant and dissipate it through their thickness.

As to the raminder of your statement that "90 to 95% of "radiant" infra-red light energy is absorbed by fiberglass...", the following is from Owens-Corning themselves:

"Spun-glass forms of residential insulation, like fiberglass, prevent heat transfer by conduction and convection but have little effect on radiant energy or radiant heat transfer. (emphasis added by me) For fiberglass insulation to be effective against radiant gain, a reflective or foil barrier must be combined with the fiberglass. Reflective films can reflect 95%-97% of the radiant energy that strikes it. This film is essential with fiberglass insulation in order to maintain a stable indoor temperature by reducing unwanted heat loss or gain. The difficulty is in proper application. In residential construction radiant films are seldom properly installed, and when they are, they often lose their effectiveness over time due to dust accumulation on the foil film.

Now that info is for common fiberglass batt insulation. If you had a high density fiberglass insulation board, something along the lines of dense duct board or something like that, then yes, it would be more effective at blocking radiant energy.

As far as practical applications, I've converted a few attics spaces that were insulated with fiberglass batting.

In one case the attic rafter bays had fiberglass batts, the attic temp was 127 degrees. The FG was left in place and polyiso boards were added to the faces of the rafters. No foil face on the "roof" side of the polyiso, and the polyiso was in direct contact with the fiberglass. The attic temp cooled to 77 degrees.

Have had similar results in removing fiberglass batts from rafter bays and replacing them with either dense-packed cellulose or sprayed foam in the rafter bays.

So mightyanvil, I'm not trying to mislead anyone. I'm going off of laboratory data that has been forwarded to me by Owens-Corning, by Building Science, by researchers at UMass. I'm going off of info presented at JLC seminars by the manufacturers themselves.

I'm going of of data gained by a roof/attic mockup we did for Fine Homebuilding magazine where part of the roof was FG batts, part cellulose, part foam, where we took temp readings at the surface of the shingles, at several depths within the rafter bays, and in the mocked up attic space itself.

And I'm going off of practical experience that I've had in retrofitting different insulations in roof structures in the real world.

Best, Mongo

In a sense, after reading it, my last post comes across to me as a bit harsh, it wasn't intended to be.

Best to all!

Mongo

Mongo

You misunderstood the meaning of the Owens Corning's statement. Spun fiberglass has "little effect on radiant energy or radiant heat transfer" not because radiant energy "passes "right through fiberglass" but because radiant energy is mostly absorbed by it and then it is considered conductive rather than radiant energy.

The clear intent of the statement is to inform consumers that a foil faced membrane is the only effective "block" to radiant energy.

Porous insulations, including foams, do transfer some energy by radiation across the tiny internal spaces that are filled with air or other gasses but this is an internal characteristic and not related to the performance of an insulation when installed across an air space from a hot surface. In no way could this transfer be interpreted to mean that radiant energy "passes right though fiberglass" or that other porous insulation materials are more effective against radiant energy. They are are all poor in this regard.

Several of the demonstrations were put on by O-C representatives. They had tools that measured the performance of different insulations and different types of energy transferences within/through the insulations...radiant, convective, conductive.

Another quote from OC: "Fiberglass batt insulation could be considered to be 'transparent' to radiant energy. Essentially, radiant energy passes through the batt unimpeded."

That seems clear to me, but I suppose there are other way to interpret that as well. (no sarcasm intended)

Be well, Mongo

If you are impressed by statements at JLC events here are some quotes from an article by Martin Holladay in the June issue of the JLC.

" 'Radiant heat passes right through conventional insulation.' "
"The idea that conventional (mass) insulation products allow radiant heat to pass right through them that "mass insulation is transparent to radiant heat" Â is a scare tactic used by some marketers of radiant barriers. The misleading claim leads some builders to falsely conclude that radiant heat can travel like radio waves right through a deep layer of attic insulation, with the only solution being a layer of aluminum foil."

"A microscope reveals that most insulation products consist of fibers or pieces of material surrounded by air. If one side of an insulation blanket is exposed to radiant heat energy, most of the radiation ends up hitting a fiber or speck of material in the insulation layer, heating up that fiber. The warm fiber can then reradiate some of the absorbed heat to an adjacent fiber, as long as that adjacent fiber is at a lower temperature."

"When radiant heat hits one side of an insulation blanket, only a tiny percentage of that radiant heat is 'shine-through' radiation  that is, radiation that manages to miss all of the fibers in the insulation blanket and emerge unscathed on the other side of the blanket. 'With insulations like fiberglass or cellulose, radiation can be absorbed by one piece of material and then reradiated,' explains David Yarbrough, an insulation expert and research engineer at R&D Services in Cookeville, Tenn. 'There is very little shine-through radiation with any of these materials.' "

The only justification I can think of for the quotes you have posted would be to demonstrate the importance of a radiant barrier in a poorly insulated attic.

Lee Burlingame of Owens Corning home office called me back and said the quotes I had sent him that were attributed to his company were untrue and were most likely put out by companies selling other insulation products or radiant barriers.

I can get him to put it in writing on his company letterhead if anyone is interested.

You all have the most informative discussion on sprayfoam going that I can find anywhere. I've been following the discussion while getting a quote from a spray foam contractor in NorCal. Well I got my quote back today and it was way higher than what I thought it would be based on what i read.

Anyone in the industry care to chime inn on whether or not it sounds correct?

Also the main reason I want spray foam is because the old bat insulation was severely rodent infested. Am I right in assuming that spray foam will not provide a comfy home for them, especially being sprayed on the underside of the roof and the floor. Here are the measurements as sent to the contractor and his reply. This is breaking the bank for the first time homebuyer here .

Square footage of the house is 621- its 23 x 27.

walls are all 2 x 4
3 walls 7.5 feet high (pretty low)
back wall is 23 x 7.5
2 sidewalls are 27 x 7.5

Under the floor needs insulation, too. its 2 x 6's and easily accessible from the side of the house
It is a concrete footer using 2 x 6's and the rear wall is 23 x 4 and the sides are 27 x 3.

The roof is 4/12 pitch and is 2 x 6's

and here is my quote from the contractor.

We can install Sealection 500 Spray Foam Insulation in your home as follows:

1) Install approximately 621 square feet of R-20 Spray Foam Insulation onto the underside of the Floor in the crawl space.

2) Install approximately 727 square feet of R-38 Spray Foam Insulation onto the underside of the Roof in the attic.

3) Install approximately 650 square feet of R-13 Spray Foam Insulation into the conditioned space Exterior Walls.

Total Spray Foam Insulation Investment: $7,777.00

The local building supply quoted about $1500 for spray in loose fill in the ceiling and walls and batts under the floor . the local guys are great but what good will that insulation be in a few years ?

Everything I read seems to point towards spray foam being 2-3 times teh cost of batts .

help its gettin cold!

I put a half inch of low density fiberglass insulation in front of my infra-red TV remote and it still worked but it did not work when the thickness was doubled.

So, the carefully worded statement you usually find on radiant barrier internet sites: "remember that thin layers of fiberglass are virtually transparent to radiant energy", is a misleading exaggeration but not an outright lie.

However, the most you could say about the difference between typical installations of different insulations in buildings is that there can be some amount of radiant energy present in the first 3/4" or so of fiberglass that would not be present in foam or cellulose. In a roof rated at R-38 it is difficult to believe that the difference would be worth mentioning much less being used as a justification for eliminating fiberglass from consideration. There are many more important issues that should be considered first.

sorry not trying to highjack the thread .No responses? This is the best thread I have found. I am very surprised by the lack of info about this.

pb: try starting your own thread. That'll likely get you more responses.

First, I would like to say that this thread has been a wealth of information for me. I am in the process of building an addition and I am at the stage of insulating. I cannot find any definitive answers on the internet...until now! Thanks for this (especially Mongo) for the mini book!

Second, I would like to address mightyanvil:
"I put a half inch of low density fiberglass insulation in front of my infra-red TV remote and it still worked but it did not work when the thickness was doubled.

So, the carefully worded statement you usually find on radiant barrier internet sites: "remember that thin layers of fiberglass are virtually transparent to radiant energy", is a misleading exaggeration but not an outright lie. "

With this logic a house would NEVER benefit from a radiant barrier. Why might you ask? Because the infrared energy from a remote will not pass through shingles, OSB, walls, drywall, etc. The energy from an infrared remote is so very minute in fact that the energy in the 2 AA/AAA batteries that power these remotes will last for a year (even in a heavily used remote).

The IR energy passing through the insulation actually SUPPORTS the statements that were made regarding the passive nature of fiberglass in the presence of radiant energy. Double the fiberglass and then multiply the IR energy from the remote so that it is proportionally equivalent to realistic radiant energy. Will it NOW pass through? Comparing the low energy of a remote is not proof at all.

Think about this: if such a low energy from a remote would blaze right through the insulation, this supports earlier statement regarding fiberglass.

just me $.02.

I'm not trying to jab anyone here, just bringing up a view that others might find intetsting.

Thanks!
Boogerhead

You are intentionally or unintentionally mischaracterizing the nature of infra red light energy. It is emitted by warm materials in all directions but only through air or a vacuum and is readily absorbed to some degree by all materials even glass. The polished surfaces of certain metals don't emit or absorb it well and therefore effectively act as a barrier.

Infra red energy can travel through the air spaces between the fibers of fiberglass insulation but as it hits the fibers it is absorbed. In a typical installation of insulation with an air space in front of it, infra red light energy will penetrate a very short distance into low-density fiberglass before it is completely absorbed but it is absorbed at the surface of foam or cellulose. This distinction is hardly relevant in a wall or roof assembly.

The use of the word "transparent" to describe this gradual absorption over such a small distance leads people unfamiliar with electro-magnetic energy transfer to imagine that fiberglass does not absorb infra red light energy at all or that the hotter the source the farther the IR penetration.

It is obviously an intentional self-serving misrepresentation. Those who use this kind of tactic are usually employed by cellulose insulation manufacturers or installers. They even come on forums like this one, sometimes in pairs, pretending to be homeowners seeking or sharing information.

Usually these people disappear when challenged and I find I have been talking to myself. I suspect that is the case with these two guys.

"It is obviously an intentional self-serving misrepresentation. Those who use this kind of tactic are usually employed by cellulose insulation manufacturers or installers. They even come on forums like this one, sometimes in pairs, pretending to be homeowners seeking or sharing information.

Usually these people disappear when challenged and I find I have been talking to myself. I suspect that is the case with these two guys."

Am I one of "these two guys"?

Please, mighyanvil, are you so petty that you're characterizing me as a poser from the foam or cellulose industry?

Do I accuse you of being in bed with the fiberglass boys?

I'm not here to convince you. I'm here to share my experiences with others. That's it. Some people will read what I write and agree. Others will disagree.

It's called "choice."

Good lord!

Well i never got around to making my own thread but went ahead and bought a 3k kit from the soythane guys. Supposed to cover 4000 board feet at 1".

Its supposed to be here on a 600# pallet on monday. If anyone has any interest maybe I'll start a thread then. It came to my understanding that the quote I received from the local CA contractor was that he was going to fill all of the frame space ie. 4" in the 2 x 4 walls etc.(3.5" technically. I was told that this much is not necessary and obviously cost prohibitive. As an aside -when I told him I had a small house, He didnt want to do any job for under 6k ?? I don't guess as many people will be doing sprayfoam with the housing market in shambles.

Anyway thanks for the great thread aside from the bickering and the fact that noone wanted to help me out with my cost question.

pbbikes,

I had left this thread a couple of weeks ago so I didn't see your request for comment. A "board-foot" is 12" by 12" by 1" thick.

1) Install approximately 621 square feet of R-20 Spray Foam Insulation onto the underside of the Floor in the crawl space. R20 is about 5-1/2" of open-cell foam. Times 621 sqft equates to about 3400 bdft of foam.

2) Install approximately 727 square feet of R-38 Spray Foam Insulation onto the underside of the Roof in the attic. 7300 bdft.

3) Install approximately 650 square feet of R-13 Spray Foam Insulation into the conditioned space Exterior Walls.2300 bdft.

Total Spray Foam Insulation Investment: $7,777.00

Unless I've screwed up my mental math (a possibility) you're getting 13000 bdft at about 60 cents a bdft installed.

Granted, they're quoting you 621 sqft of floor foam in a 621 sqft house, so they're doing rough calcs by not removing the framing from the equation. If you figure the framing is roughly 10%, or in 1.5" in a 16" oc framing bay, then you can up the cost to 66 cents per bdft.

To buy DIY open-cell foam kits you're looking at maybe 55 cents a bdft just for the materials.

A guesstimation on my part, and a late one at that, but at least a reply.

Mongo

MightyAnvil - No, I am not guilty of the charges that you have made. Please search for Boogerhead in the general forum and you will see that I have been a member here for YEARS. Most of my posts are related to my swimming pool, which I rebuilt several years ago. If you think that I would put years into this forum just to come around now to bash insulation you are wrong.

It so happens that we bought a fixer-upper that was in bad shape and we are getting around to stuff as we can aford it and as we have time (you will see that also several times in my pool posts).

My point was to discredit your 'no-so-scientific' means of research here. I wanted to use your own logic to disprove your own theories. Please provide posts to relevant research that has already been done.

The claim that any solid material is "transparent" to infra-red light energy shows a total lack of understanding of the nature of this form of electro-magnetic energy.

Do some research yourself before trying to discredit someone who is only trying to help you understand this issue.

Mongcot

Thanks for replying.

I don't think you screwed up the math but the main difference is that I decided not to go so thick.

The contractor said he would spray in r-38 in the ceiling. ?From what I understand that would be overkill. I had no option if I went with him other than to go with that much spray foam, He didnt want to do the job unless it was $6k+. No other contractors in my area .

The contractor also would not take doors and windows out of the EQ. I have 6ft sliding glass doors and large windows.

I spent $3k will do approx. 3" on the underside of the ceiling, 2" in walls and under floor. That cost also included the fast kick gun. I have 2 large emglo air compressors already sitting in tandem.

I read that 4" of lycene foam was used in making freezers , If that's true I figure I should be ok.

Am I right in thinking that I don't need "R-38"(6" or so)?

So my options were $8k for what sounds like overkill(wish I could have used half as much for $4k ad had someone else do it but he wouldn't budge.

or batt insulation for half that much .

The pallet arrived late with the gun missing .

A new gun was supposed to be here last friday. its tuesday no idea when the gun will arrive so I am sitting here ready with a pallet of foam.

This looks like a lot of work and want to get the drywall up .

but hopefully it'll be done with no major setbacks in teh next couple weeks

Mongcot

Oh and its 1.5# density closed cell foam I'm using

Mongcot

Is it nesesary to use a intumescent coating on top of the foam if it is sprayed directly under the roof with no drywall cover. Also how about in walls that are covered with wood with no sheetrock?

Thanks

Because cellulose insulation was mentioned earlier in this thread, I just wanted to add my experience regarding the product. I installed cellulose in my attic, using bails and a blower from a big box home improvement store. I blew the cellulose onto the unfinished attic floor dry, since there was no functionality that I knew of in the blower system to add water or a binding agent. It was fairly easy to install. But if I had it to do over again, I would not install cellulose. Even though I used what was labeled a "low dust" formulation, there was simply too much dust created for my liking. I don't think it is healthy to introduce that much dust into a home, even if you do a good job of sealing, as I did. Over time it may migrate around the house. Perhaps if the installer has a completely sealed wall cavity which will never allow the product to escape, the cellulose might be a cleaner install. Or installing the product wet or with a binding agent may be a good alternative, if it could eliminate the dust before and after the installation. But personally, I would not use cellulose in an unenclosed space, especially one that may be accessed, such as an attic for storage.

"Is it nesesary to use a intumescent coating on top of the foam if it is sprayed directly under the roof with no drywall cover. Also how about in walls that are covered with wood with no sheetrock?"

If the attic is inaccessible from the living space, the foam does not need to be covered with anything.

If theattic it is accessible to the living space, or if the foamed walls make up the walls of the living space, then you need some form of burn protection. Drywall is one, intumescent paint another, wood planking yet another, but the butt joints between wood planks would need to either be caulked with a fire caulking, or covered with a strip of wood, like board and batten.

When it comes to fire protection, some areas have differences in the code, so best bet would be to get the specifics form your local building inspector.

I see it is an old thread but it is like a movie breaking at the cliffhanger...

PPbikes if you are still around can you update your experiance with Soythane

and if anyone else has experiance reviews of Soythane, Tiger Foam or other closed Cell DIY foam insulation it would be apppreciated

I posted a question about this on the old house forum. If anyone that has weighed in here would be willing to give me some feedback would be much appreciated. It's posted under new roof insulation ventilation dilemma. There really does seem to be two schools of thought on this, and lots of products to be sold. I think its helpful to hear from people that have done one or the other and what their experience has been. When we aren't have a drought, which we are now, I live in a very moist region.