At first it sounds reasonable. You are getting a new roof, so why not scrape off the shingles, put down roofing felt, THEN radiant barrier foil and THEN shingles right on top. What an easy way to install a radiant barrier, right? I also get asked if eShield, SolarGuard or Bubble Foil Insulation will work.
Unfortunately you just wasted time and money for virtually NO additional benefit.
Radiant Heat by DEFINITION is electromagnetic radiation that travels in a waveform ACROSS a void, either an air space (or gas) or a vacuum. Without this space you CANNOT have RADIANT HEAT. Therefore, if NO radiant heat exists you CANNOT have a radiant barrier.
If you have items “sandwiched” together, you will get conductive heat. It is usually impossible to have radiant heat through solids. (some exceptions are transparent solids like glass, water etc.) I keep hearing of some roofers starting to push foil products installed between the shingles and the roof deck as radiant barriers.
If you are getting a new roof, beware of roofing companies who are selling radiant barriers under shingles. Radiant barriers without an air space don’t exist, they can’t exist, and they will never exist. They laws of physics always apply. Remember: No Air Space = No Radiant Heat = No Radiant Barrier.
Attention roofing companies: If you wrote on your invoice that you installed a “Radiant Barrier” in this method you should contact the homeowners, and make good on your mistakes.
What do you do if you are re-roofing and STILL want a radiant barrier? There is a way to incorporate radiant barrier foil into a re-roofing application. The ONLY way is if you can create an air space on one side of the foil. There are several types of roofs that have an air space between the roofing material and the roof deck. Barrel-type tiles, or roofs installed over wood battens, which create the needed air space.
With these types of roofing systems, a radiant barrier can be incorporated easily and economically. Simply roll out roofing felt or another type of underlayment. Then, roll out perforated radiant barrier foil, install battens as per manufacture instructions and attach roofing product. It is also recommended to “notch” the battens or leave spaces between the battens to allow for more airflow between the roof deck and the roofing material.
This method of installing a radiant barrier is low cost, and very effective in reducing heat gain into the home. Plus, it is profitable for the roofing contractor. Homeowners will appreciate saving money and having a radiant barrier installed the right way.
|
|
|
I've written several other posts on this that you might be interested in. Check these posts below:
Thanks for your explaination on radiant barriers. Since you have identified that when things are sandwiched together they produce conductive heat, will a Thermal barrier be benificial to reflect away 97% of the conductive heat? In other words is there a beneift in putting a thermal barrier on the roof? I really need to know if having a thermal barrier that reflects heat away will help keep my attic cooler? If so, in your opinion how much? OR is it really a wast of money? A reply ASAP will help me since I am in the process of changing out my roof.
Thanks
Danny Williams
Danny, you can’t “reflect” conductive heat. You can only slow it down since it travels through a solid. This is the concept of R-Value. Since radiant heat is in a waveform, it can be reflected. The problem with putting any R-value on a roof is that the roof is normally not really part of the “thermal envelope”. The thermal envelope is usually your walls and ceiling. The roof just keeps it dry. So, you want R-value on your attic floor and radiant barrier at the roof. This is like putting a refrigerator in the shade.
We are removing a tile roof (w batons) which is on top of felt over plywood laminated to 4″ poly-iso – over the cardeck ceiling.
The customer wants to switch to high end asphalt composition. I thought that we’d need to create a ventable air space to get a long term material warranty (beyond 10 yrs. But CertainTeed’s rep just sent me their Tech Sheet #155 which states “… if a radiant barrier is in place…” the full (even 5 star) warranty is granted. Sounds suspicious to me . Any comment ?
Id be glad to forward you the pdf
The warranty is granted? Not sure I understand what you’re trying to say. Please send the info to me here.
CAN U USE A WATER RESISTANT BARRIER UNDER A TILE ROOF THAT DOESN’T HAVE AN ATTIC? I HAVE CATHEDRAL CEILINGS
Sure, you can put one on the decking.
Why not foil laminated to osb for roof deck. Do they make that?
Yep, that is a product available in some locations. As long as the foil side of the OSB faces DOWN – toward the open attic AIR SPACE, it works!
So I’m confused. Radiant Barriers do work but only on the inside of the attic then?
Hi, totallu understand your concept. Question is can aluminum “shake” roof panels be applied over battens ?
I would think the extra air gap would assist in damaging the tiles if walked on. Same for most any metal panel.
Dante,
Aluminum Shake Panels? Like these?: Radiant Barrier Under Metal Roofs I think it all depends on the specific brand. You would need to check with the manufacturer.
Back in 1992 I was on a framing crew building a custom house. The architect specified 1/4″ X 4′ X 8′ panels that were waxed cardboard with one foil side and one white side. These were affixed to the roof deck over felt, then battens, then metal roof. I am soon going to put a metal roof on my house. Any idea what those panels are called or who distributes them? I would like to put something more substantial than “foil” under my battens, but I do not want to replace the OSB roof deck with the new foil sided OSB.
Thanks.
Thanks for you comment. I have never heard of the product you mention. My concern for a cardboard based product would be deterioration over time. I think bugs might think it is “food”. You said you want something more substantial than “foil”. AtticFoil radiant barrier is a foil laminated to a virtually tearproof inner woven scrim material. We have many roofing contractors using this product and have never had a single complaint about durability. Here is the link to the page for Installing Radiant Barrier Under Metal Roofs. You can also get a Free Radiant Barrier Sample too.
I’ve got a relatively new (7 years old) composition shingle roof. It’s in great shape, so we don’t want to replace it (we’re planning on moving in the next 5 years). HOWEVER, there is no insulation between the shingles and our ceiling!! It is literally shingles -> wood -> ceiling. Is there ANYTHING we can do? As I’m sure you can imagine, it gets hotter as the day wears on, the ceiling/roof literally bakes us 🙁
You definitely would benefit from a radiant barrier and some r-value up there. Take a look at this page: How to Install Radiant Barrier and Insulation in a Cathedral Ceiling for more information on how you can achieve this. Unfortunately it IS going to require removing the sheetrock to gain access to the roof cavity, but this is cheaper than tearing off the roof and doing it from the outside. The results are immediate and the comfort is drastically improved.
There is a better way then ripping off drywall. If I were you, I would check into having a company blow foam into your walls. They would drill a few holes in the walls and fill up the cavity with foam. Not cheap, but better than what Ed says. Good luck.
Craig
Craig,
Charles is talking about having a true cathedral ceiling. These are rafters with sheetrock on one side and the roof deck on the other. He or I never proposed ripping off the drywall. He asked if he should lift the roof deck while working on/replacing the roof. This is a great option if he has it. He can insulate the space between the rafters (from the top) while the deck is off. Then, lay the deck back down and proceed with the radiant barrier and stone coated metal roof over the batten system.
While I understand the idea of an interior mounted “radiant barrier” and the flow of heat to lower the attic temperature, why would a product like “POLARALUM” which is a “thermal barrier” not work as you claim? That foil underlayment at the shingles is used all over Texas and actually acts as a reflective .97 UV block to eliminate the heat buildup from sun rays. Much like a skin sun block. Factory Mutual has evaluated and certifies this product.
Robert,
I think you are confused in the difference between UV – Ultraviolet Radiation and IR – Infrared Radiation. If it was installed on top of the roof with the foil facing up then any product will stop UV and reflect IR. The problem is that when you “sandwich” the foil (any product including AtticFoil) between two products it becomes a “conductor”. Here is a video to explain the Difference Between Radiant Heat and Conductive Heat. By definition, radiant heat is transfer by NON-CONTACT from one object (hot object) to another object. If you don’t have radiant heat, then you cannot by definition have a radiant barrier. I wish more than anyone that foil between the shingles and the felt or decking helped. My sales would go way up! As for the Factory Mutual certification, if you really read the information, they have certified the product as a roof underlayment (which is is) not anything to do with rejecting heat when installed between shingles and the deck.
Changed my roof from cedar shake to composition shingle. Installed cdx plywood with a aluminum foil backing on the inside of the roof decking.Decking was attached to the 1×4 wood strips that run across the length of the roof. If that is a conductive barrier how do I correct the error ?
If foil is attached to the 1×4 strips it will create a air space between two aluminum sheets. What does that do ?
Jerry
Jerry,
If you put the foil directly on top of the old 1×4 lathing you will get a reduced benefit. Where the foil decking is “sandwiched” you will get no benefit as far as a radiant barrier. The “open” areas between the lathing, where you can see the foil from inside the attic (usually about 50% of area) will still help some. Because of thermal bypass into the lathing you are probably a little below 50% effectiveness. This is better than nothing. You can still come back and staple Radiant Barrier Foil to the bottom of the rafters and get great results. The first layer on the deck will act as a filter and let some of the radiant heat through. The layer stapled to the bottom of the rafters will reflect virtually all the radiant heat that makes it past the roof.
Hi Ed, I am about to re-do my roof and glad I read this. Is there any option for getting some insulation factor with a shingle roof? I am in the caribbean where the ac bill kills us! From what I have read here, it would seem that I would need to change to a metal roof of some sort so that the space can be created. Would the space then cause the roof to lift easier with a hurricane? Thanks, Lisa
Lisa,
I would look to either installing Radiant Barrier AtticFoil inside the attic or radiant barrier under a metal or tile roof. I would look to the different roofing products as to uplift data.
I have an attic with vaulted ceilings that does not allow much room to install a radiant barrier though a good portion of my home. I can do approximately about 30% of my attic. Would this be worth the time and effort? Thanks.
Jason
Jason,
Radiant Barrier has a cumulative effect. Doing part will still give a benefit. You will not see the same results as if you could get 100% coverage, but it is still probably worth the effort. Here is a video on Does Partial Coverage With Radiant Barrier Work?
I’m getting ready to put a new metal roof on my house.I currently have clay tile with no radient barrier or insulation. Needless to say my house gets quite hot in the summer. I have no attic it’s all backed up against drywall. I’m installing new sheathing with sharkskin ultra radient, then a batten system with stone coated metal on top. My question is should I be throwing any type of insulation in between the rafters while the old plywood is off. I won’t be able to do it later because its all coverd with drywall. If so what kind of insulation should I use. Thanks
If there is NO insulation between the sheetrock and the roof deck (between the rafters) then you should definitely add insulation before putting a new roof on. As for the metal roof, I would install AtticFoil Radiant Barrier below the metal roof. Here are instruction on how to Install A Radiant Barrier Under A Metal Roof.
I have a sealed cathedral ceiling in my log cabin and would like more insulation or radiant prtection,the roof is rafters with insulation and plywood on top then shingles,do I have to pull off the plywood to install a radiant barrier or is there a panel that I can put over the plywood then reshingle?
You are pretty limited in your options. One option is to do what I did on my home. Basically, I have two roof decks. The top deck has shingles on top and the bottom deck has foam on the bottom. They are separated by 2″ furring strips and I used two layers of foil. Here is the page on How To Install A Radiant Barrier With Foam Insulation.
My friends condo I have been staying at has vaulted ceilings, with exposed beams. The ceiling is actually 2×6 T&G, this also is actually the roof decking also the is 1″ of blue Styrofoam board with a torch down roll roofing on top, the roof needs replacement as it is leaking.
This is in Anchorage, Alaska where we get a considerable annual snowfall. The owner is going to replace the roof and wants to know what he can do to increase the “R” factor. the problem is that there is a serious “Glaciation” effect and the heat bills are completely off the chart. Any suggestions???
David,
I would look at this report from BuildingScience.com on High-R Value Roof Systems. You need to add significant R-value to your roofing system. The best and easiest method would be to layer and offset a couple layers of high density foam and then go with a torch or membrane type roof like http://www.Duro-Last.com
Ed,
Great site! Thanks!
I am getting ready to re-roof. it is an old home (1911) with flat roof dormers. I am considering applying some of your designs to the flat dormer and non-vented area.
1) wood deck
2) underlayment (synthetic? felt? or ice and water shield? or does it really matter?)
3) radient barrier
4) furring strips
5) Tech shield
6) underlayment – Ice and water since it is flat roof
8) flat roofing – most likely white if I can get it.
9) FasciaVent with a ridge vent for venting the new deck — http://www.dciproducts.com/html/fasciavent.htm
I would apply insulation on the inside of the roof between the deck and sheetrock. Would you suggest foam or fiberglass? my concern is foam may create moisture problems. What do you think? And is there anything else I should consider
It is a hipped roof and I am also considering putting in a SmartVent at the eve so that I do not have to cut up may 100 year old beadboard sofits. — http://dciproducts.com/html/smartvent_eave.htm
I would continue to use the turbines as the exhaust.
Do you have any experience with SmartVent or FaciaVent? I realize they are not your products, but thought you might have some insight.
My only other concern is tying in the 2.5″ second deck to the remaining single deck. Essentially half of the house consists of the dormer and cathedral ceilings and the other half is open attic. I assume it would be ok to make some kind of wedge to make a gradual transition from 2.5″ to 0. It is only a 6 ft section on each side of the ridge
Thanks again
Jason,
This looks like a well though out plan, and I like it. I don’t think you really need the underlayment over the bottom deck. I would go with only one waterproofing layer to the outside under the roof. Or go with a membrane type roof like http://www.Duro-Last and eliminate it all together.
As for insulation, if it’s airtight, foam or fiberglass will do. Just make sure you seal it up tight. I like edge vents – there are several brands and I have had several customers use them with good results. You should be able to make the transition in roof elevation without any big issues.
is Solarhide made by EcoChiefProducts.com any different from these other foil barriers? Their brochure states that it is a Radiant and thermal barrier.
Tina,
This is the information directly copied from their website:
“SOLARHIDE is Eco Chief’s energy saving roofing underlayment. When SOLARHIDE is properly installed in the roof system with the foil side facing an air space it acts as an energy saving radiant barrier. If SOLARHIDE is installed under composition shingles with the foil side facing down on the roof deck its an effective thermal barrier that reduces heat gain in to the attic of a home.”
I agree that IF the foil is facing up and facing an airspace typically seen in tile and metal roof applications, then it WILL act as a radiant barrier. I go into full details here on How To Install A Radiant Barrier Under A Metal Roof.
The part about the foil facing down is a little confusing. What exactly IS a THERMAL BARRIER? If you look up the definition of a “Thermal Barrier” it says “(Engineering / Aeronautics) an obstacle to flight at very high speeds as a result of the heating effect of air friction Also called heat barrier” or “Noun – thermal barrier – a limit to high speed flight imposed by aerodynamic heating”. I’m sure this product has nothing to do with the speed of an airplane going through the air. I would ask them where they got this term and what it means because in roofing and building science community I have never heard the term used. Normally, heat resistance is measured in R-Value, they do not state any r-value. I could not find any specific specifications listed, but most roofing underlayments are about 1/8″ thick and there R-Value would be less 1 and Foil really has no r-value, in fact it is a great conductor of heat when installed (sandwiched) between two other products.
Since you need an airspace to have radiant heat and therefore have a radiant barrier, and installing ANY foil (AtticFoil included) product directly between two products will make the foil a CONDUCTOR, the foil will not help reduce heat flow and more than the product it is attached too.
Hi Ed,
Been researching the last six months what to do about our roof that needs replacing. We live in the Sacramento Valley, hot days and cool evenings (usually).
We have cathedral vaulted ceilings throughout the entire one story house – mostly NO ATTIC. Our current roof configuration is this: Tounge/groove ceiling, 1/2″ ply, 2″ Polyiso (Celotex Thermax) with reflective foil covering both sides, another 1/2″ ply, felt and finally comp shingle. We have no existing grid or frame system OR venting system. We bake in the summer and freeze in the winter.
A small section of our hallway has some attic space – so we added a whole house fan earlier this year.
Due to cost, we will have to shingle using a cool roof comp. Obviously we will need some sort of ventilation and it looks like the 2X2 batten system would be best. What is the best way to incorporate your radiant barrier with using comp?
Thank you so much for your time.
Thanks for your question – it sounds like you are setting up to do a system similar to the one done on my home. You can read the article I wrote about it here: Combining Radiant Barrier with Spray Foam Insulation.
This is a VERY economical system and it boasts great results too.
I have a roof that i need to replace the singles on. It is a dormer set up, so very little insulation and no space to add any more. Can i use something like you describe in this with 3 tab asphalt singles?
Not unless you do a double-deck type system where the bottom deck has radiant barrier and then it’s spaced with battens before the top deck. It would have to be just like I did on my home: You can read more about it here: Radiant Barrier Double-Deck with Shingles and Spray Foam
What do you think about builders who don’t install the right amount of insulation in a home? Our specs call for R19 in exposed walls. The builders install R11. The walls are only 6″ face to face whereas the proper walls would be 8″ IF they install insulation at all. They install foam board which only has about a factor of R3.33. Heat or cool air comes out of our outlets. Place a pillow against the inside of an exposed wall and in a few hours, pull it away and it will be hot in the Summer and cold in the Winter on the side of the pillow against the wall.
Well first it depends on where you live and secondly, the effective R-value of a framed wall assembly with insulation is always less than the R-value of the insulation alone, since you have to take in to account thermal bridging through the studs, which lessens the performance of the wall. Foam should be added to walls in a way that makes the installation air tight, to be most effective. Unfortunately, it’s hard to monitor how builders are installing the insulation and to ensure they are doing every step 100% correctly. If you are concerned that you did not receive what the contract outlined, then I would suggest contacting your builder and perhaps a home energy auditor as well.
Ed Fritz,
My new Gerard metal roof was applied with battons & Solarhide on deck but with foil side down (will I get “any” benefit at all with it other than some water proofing ?? your opinion please!!!!!)
What can I do in my attic now that may help me? My attic is 14 ft. tall and accessible with 6 inches blown in insulation , 24 soffit vents, electric gable vent & 6 roof vents. 3200 sq. feet, single level
I’m in Texas near Lubbock in lower Panhandle. We’re 101 degrees today.
Thank you!!!!!
With the foil facing down all you are gonna get is the underlayment (waterproofing) qualities. I’m curious if a roofing company did this? If so, you may have some recourse since their install instructions clearly state that the metallic surface must face an airspace.
If you want do reduce the radiant heat flow, simply install by stapling up in the attic. You will see a huge difference. Ranch style homes in the South are the best case for best results. I’d also turn off the fans. Fans and roof vents don’t work well together. See my post here: Attic Ventilation – Don’t Mess It Up.
How about Lowe Therma Sheet? Various roofers want to put it under the underlayment for a roofing job. There is a layer of foam between sheets, does that create enough airspace?
Thanks!
No, foam is not an air space. An air space (or gap) would be a space that is void of any matter, meaning the only thing that can be in the space is air itself. Not airy items, or items that have air injected into them, just air. Without air, there is no radiant heat transfer and it’s a bogus claim.
Hi Ed,
I have two questions for you. I’m not from USA, but here in my country the glass wool insulation is installed between the rafters and not on top of the gypsum ceiling as I see in your videos. My parents are about to install such wool insulation between rafters and I was wondering in this case how can I still use the radiant barrier properly ? The rafters width is 10 cm but I asked and the wool can be stapled and pushed to have only 7-8 cm, leaving therefore a 2-3 cm air gap between the wool and where the foil should be stapled. In this case, is the radiant barrier still reflecting back radiation through the insulation and to the exterior ?
Secondly they already bought the aluminum foil that has, surprisingly, the shiny part only on one side. So the other question is, how should I install the foil now, with the shiny part towards the sun or facing the interior of the house ?
Thanks, and great site btw!
If you install the foil across the bottom of insulation-filled rafter cavities, then the radiant barrier foil uses EMISSIVITY to stop radiant heat (click on the hyperlink to get more info on how this works). This effect is very similar to using radiant barrier decking. In this case, the FOIL side is the side that must face the air gap; if the cavities are full of insulation, then that is not the air gap, so the foil would face DOWN, toward the air inside the attic space.
Hi, Ed,
We are in Sacramento, CA (hot days, cool nights, no snow)2700 sq foot, one story ranch house, vented attic. Roofer has proposed replacing shake roof on skip sheathing with Gerard stone coated metal roof nailed to 2 x 2 batten, then layer of Low -E therma sheet (foil/polystyrene/foil), then 1 x 4 batten (counter batten grid system) over synthetic felt underlayment. Beneath this is most of attic space with old R19 blown insulation and HVAC with ducting on attic floor. Ridge vent with 26 soffit vents. Do you think this is effective installation and do you think that this would be better in terms of $ energy savings than simply forgetting Low-E Therma sheet and blowing in more fiberglass insulation to get up to R38 insulation? Essentially this is a question of should we do Low-E Therma Sheet (advertised R6)versus more blown fiberglass insulation (another R19 worth of blown insulation)?
Evelyn,
Personally, I think the batten counter batten system does not provide enough additional benefit for the added cost compared to a standard single batten system. That said, you should definitely install a radiant barrier – given the chance on ANY metal or tile roof. Getting foil to the “outside” of your home is almost like putting a tree over the roof part of your house. The cost is about 13 cents per sq. ft Purchase AtticFoil Here and we have complete into how to install here. Radiant Barrier Under Metal And Tile Roofs Don’t believe anyone who tells you the product has an R-Value of 6. This is probably the number used by some unique test method/system which is not how it’s installed under a metal roof. Here is a page/video where I explain how some products only 1/4″ thick (bubble foil) claim to have an R-value of 11. Bubble Foil R-Value Scams Finally, R19 is a little wimpy on the insulation. I’d do the roof first and see what kind of results you get. Then, if you need want to add more insulation either hire a company or you can DIY from Lowes/Home Depot. They offer free blowers with purchase of insulation. Feel free to call/email us with any more questions! http://www.AtticFoil.com
Due to storm damage, we are in the process of a full roof replacement. We are in Southeast Texas (Houston area) and house feels like it bakes in the summer. The multiple partial attics take on heat like crazy. (We have A/C bills to prove it.) House is a 2 story with vaulted ceilings and we get loads of afternoon sun across the back of the house. When asked about materials that might drop down the “bake” factor, roofer mentioned Polaralum and Cool Series shingles. Thoughts? It looks like from above that Polaralum would not help significantly. It certainly seems like it is being pushed by several large roofing companies in our area.
I would not recommend Polaralum product at all. Are you replacing the deck too? If so, I’d actually recommend draping some AtticFoil down between each rafter bay as shown here: Radiant Barrier Under New Roof Decking
As a secondary option, I’d recommend radiant barrier decking in this situation – it’s inexpensive and it’s effective. Check out the info on it here: Radiant Barrier Decking Dept of Energy Study. Both of those options are great if you’re replacing the deck. If not, then you’re really best off getting a standard roof and then adding the foil from inside the attic. As the Dept of Energy article shows, that’s truly the most effective method at blocking radiant heat transfer from outside.
I am a professional roofing contractor and I am researching and seeking the best method to assist my clients in reducing attic and home heat increases. I am often replacing the roof at this time.
I have been looking at the LOWE product, but based upon your information this would not be a proper application for a composition roofing system. Since no air space is provided between the shingles and Lowe.
How about using the LOWE product in the attic stapled to the bottom of the rafters. This would provide about 7.5″ or 9.5″ of airspace. This seems to offer the benifits of a Raidant Barrieer system. Correct.
Doug Hodne
Seeking the best for my customers!
Hey Doug,
No need to use LowE on the bottom of the rafters, AtticFoil works just as good (if not better) in this application and it costs less!
In replacing plywood with Radian Barrier OSB would you recommend also using a 50lb felt radiant barrier
I’m not sure why you would use a 50lb felt with radiant barrier attached unless you were installing under a metal or tile roof. The foil (or radiant barrier) is useless unless you have an airspace on ONE side of the foil. Here is How To Install Radiant Barrier In Metal and Tile Roofing Products
I just might add, while inferior to having a true radiant barrier roof, for someone in my situation where I have some “hot” rooms with no attic space to install a radiant barrier I wonder if an aluminum thermal regulator like this underlayment might not be beneficial for regulating the room temperature (make it easier to cool in the summer and heat in the winter).
We have done tests and been on actual roofs where foil was installed between the shingles and the roof deck. Usually a roofing underlayment with foil attached. The bottom of the deck is unchanged with/without the foil. The thickness of the foil is so thin that any different is not measurable. With this said, if you can’t measure it, it’s not worth doing it. Did you see our videos on Installing RoofingFoil Under Metal and Tile Radiant Barrier? We are in the process of getting “proof” videos done with thermal imaging cameras. Just waiting for it to get really hot. Radiant Barrier For Metal Roofs Video
Also, aluminum foil is a great thermal regulator for cooking. If I stick a potato in the oven to bake, it will burn on the outside before the inside is completely cooked. If I wrap it in foil, the potato will cook evenly throughout, so we know for sure that aluminum is an excellent thermal regulator. It blocks the extreme heat from getting in allowing the conductive heat inside to slowly cook the potato. The same principle should allow me to regulate the temperature inside my “hot” rooms more easily. If I install this stuff, I’ll post a youtube video to report on whether or not it worked. I’m intrigued by it because I’ve heard from some folks here in Texas that it actually did make a difference.
Steve, thanks for the comment. Radiant barrier in Texas? Yes it works and usually makes a noticeable difference in comfort and efficiency. Did you get a chance to install it yet?
Hi ed
had a radiant barrier osb sheathing installed when roofing shingles where replaced
they installed the foil back side facing down after removing
all the skip sheathing so you can see the the foil side when in the attic
will adding attic Foil benefit us and do i install it over the insulation or to the bottom of the roof rafters
John, It depends. If you are in a mostly cold climate and you did the Over Insulation Method then it would help with reducing Winter heat loss AND give SOME additional Summer benefit. Adding radiant barrier inside the attic AFTER you already have radiant barrier decking will provide SOME additional benefit, but not much. Probably not worth the time/effort/money. I would only do the over-insulation method if I were going to put in a 2nd radiant barrier. Radiant Barrier Installed Over Attic Insulation
Ed, I am looking at a shake roof to light weight tile conversion. I am located in Northern California in the temperate SF Bay area. The contractor has suggested a OSB Radiant barrier product and is also recommending XXX for the roof (7//32″ foam sandwiched between 2 layers of aluminum foil). Are both of these products necessary or would one do the job? Is it worth the additional cost of about $1/sqft installed for the XXX?
Mitch, with a tile roof, you should have the required airspace to get the foil on TOP of the deck. This is by far the best option as apposed to using decking with the foil facing the attic. The reason is that the deck itself will never get as hot. If you HAVE to replace the deck then go ahead and do BOTH. The radiant barrier decking AND RoofingFoil on top of the underlayment. The foil decking is only about $1.50 per sheet more then regular OSB – so it’s pretty cheap. Take a look at my website: RoofingFoil.com As for the product mentioned? It will work, but spending additional money for 7/32″ of foam for an application like this is a waste. The foil radiant barrier is all you need under the tile – we sell the heavyweight tear-proof foil for under metal and tile roofs for about $.13 sq. ft. Any additional insulation would be put in the attic on the floor. Any other questions Call Us Here
Hi. Great article. I would like to use the MOST EFFECTIVE insulation method for my low angle shingle roof in South Florida. Please, advise me what would be the best way to >considerably reduce the heat< entering my house.
Here is what I want to do:
1, Having a regular insulation over my ceiling installed, I would like to cover it (looking from the attic side) with double sided foam radiant insulation 2" thick.
2, Then I would like to cover my rafters with another double sided foam radiant insulation 2" thick or if there is no real benefit over the thin radiant insulation, then I would go with the liner. Please tell me if that is the case and what is the best.
3, I would like to know if I should further insulate the space between the radiant barrier and roof bottom. Or is it BETTER to leave it opened completely for the air circulation.
I know, if there is no air, there is not radiant barrier (I understand); however my utmost concern is to lower the temperatures of my attic. Almost every day my temperatures reach above 130 – 140 Fahrenheit. I want to bring it down to 80 – 90 in full sun. Please, advise what do you think is the best way to do this.
The best way to lower your attic temps is going to be to staple ONE LAYER of foil up on the rafters (not the foam/foil, just the foil) and install it with the proper gaps at the top and bottom to allow air flow. Then, make sure you have PLENTY of ventilation in the attic space. Good ventilation with a layer of AtticFoil on the rafters can get that attic equal to ambient, easily. Every week we have people call in with those results. Refer to How to Install Radiant Barrier on Your Attic in Hot Climates.
I live in Northern California were it is 80-100 everyday during the spring and summer with my house in direct sunlight all day. I’m getting ready to have a 25 year old composition shingle roof removed and replaced over the existing plywood. From what I am reading and hopefully understanding here, any of these radiant or conductive barriers sandwiched between the composition shingles and the roofing felt or roof deck are only providing insulation benefits to the roofers bank account. Is that correct? If so, is just going back with quality roofing felt and composite shingle the best to do? Any other options or recommendations on roofing felt weight or composition shingle construction, thickness, types or specs?
For a shingled roof, there isn’t really a way to add a radiant barrier unless you were re-decking or building a new roof on top of the old one (the new roof being metal or tile with the required air space minimum the foil needs.
There’s nothing (structurally) with a standard shingle construction roof, but heat gain wise – it doesn’t offer much protection. Honestly, the next best thing is to get in the attic and staple some foil up on the underside of those roof rafters. This page shows you how: The Only Way to Add Radiant Barrier Under a Shingle Roof.
WONDERING IF I PUT TECH SHIELD ON WITH FOIL FACING UP BECAUSE I AM SPRAY FOAMING UNDERNEATH. THEN ICE AND WATER SHEILD ON TOP OF IT. THEN PUT MY BATTONS ON AND TILE ON TOP OF THAT. WILL ICE AND WATER SHEILD INTERFERE WITH MY RADIANT BARRIER?
Yes, since it will eliminate the airspace on once side of the foil, it will loose it’s benefit. Better off just using regular OSB and Ice/Water Shield.
We own a one story 1720 sq ft. 1960 post and beam home with a flat gravel roof with a 3% pitch in LA. It has a 8 inch high border around it and has no attic. The inside of the entire home has a cedar ceiling and there isn’t any real insulation between the ceiling and the roof. It gets very hot in our home in the summer even with the air running all day. Our only option is to either put a reflective paint on the roof, which is in great shape or lift it up a bit to create space for a radiant barrier. We are also seriously considering solar, but some the the cool roof applications advise against walking on it. What would you suggest would solve this issue long term? Many thanks!
You can install AtticFoil Radiant Barrier Foil on the roof. You should easily get at least 5 years service (probably longer) even though it’s not exactly what it’s designed for. I have a customer in Mexico that installed the foil on a roof of a concrete shopping center and the results were instant and dramatic. Basically, it’s like putting a tree over the building or home. The best way is to install some type of “sleepers” 2×4″s or other product to keep the foil a couple inches off the roof. Then, depending on the wind load, you may need to use bricks, cinder blocks etc. to weight it down combined with stapling to the sleepers. Finally, I would drill a few holes into the roll to make a “swiss cheese” effect to allow rainwater to easily pass through. This will reduce “pooling” and dirty spots on top of the foil. More info here on Installing Radiant Barrier On Flat Roofs.
I’d like to re-roof a wood shake roof. My consideration is to tear down and remove the roof and 1×4 slats on top of the rafters with foil back 5/8″ OSP followed by a batten system and metal shakes. Will the foil back OSP provide the desired radiant barrier properties?
Foil back OSB works off the emissivity quality of aluminum as compared to the reflectivity quality. Here is a link to the Department Of Energy Study on Radiant Barriers. Basically, it says that OSB radiant barrier is good, but that radiant barrier that is stapled to the bottom of the rafters is best. A good in between install method is shown here where you Overlay The Radiant Barrier On TOP of The Rafters Before Installing A Roof Deck.
By just installing horizontal batten like showing on the photos, you will end up with bad ventilation below the roofing and in the worst case mold/rot if there was any water intrusion caused by a leak. Double strapping/batten should be standard in any roof application with or without radiant barrier.
First, the vertical batten is installed for proper airflow and for water to run off. Remember creating a ventilation intake on the eaves and exhaust on the ridge. The Horizontal batten on top of the vertical will be primarily for the roof installation (metal, clay, slate,…)