Ask The Guru: Attic & Foam Insulation
OK, so you want to know more about Attic & Foam Insulation. First check the questions and answers below and see if your question is already here. There's a good chance that it is. If not, no problem, just use the form at the bottom of the page to send me your most burning question about Radiant Barrier and Attic & Foam Insulation and I'll send you an answer shortly.
Hi there, I am just about to re-roof due to hail damage and my roofer has recommended a solar shield material to go under the one area of my roof where I see a large rectangular frost patch on cold mornings (this is above the cathedral ceilings). Though not functioning as a radient barrier will this help prevent the heat from seeping out. Is it safe for the shingles? Is it worth the extra expense? Thank you for you help.
I'd do nothing and not spend the extra money. You actually want a "cold" roof in the winter. It means you have decent attic ventilation and will help prevent potential ice damming.
Frost on a roof is not a bad thing on a cold morning. This tells me that the area over the cathedral ceiling is staying cold and NOT loosing much heat. I would be more concerned if the area was NOT frosted. Without frost, it would mean the area was loosing heat and the surface temperature was above freezing. Often, you will see a roof with "strips" of frost. This clearly shows where the cathedral ceilings are located. By having frost, this part of the roof is keeping the heat from escaping. Areas without frost are usually over the attic part and are not frosted since heat from the house is escaping into the attic and heating up the roof. Frost won't happen unless the surface is below freezing.
Ed - would it be efficient to not only put foil on my roof rafters, but also over my insulation on the attic floor? -Kent
I've had many customers install AtticFoil in both locations with exceptional results. If you can do it as a DIY project and keep the cost down, then I would say "Do It!"
If you lay the AtticFoil over the insulation in addition to stapling it to the rafters, you will see the biggest benefit in reducing winter heat loss. Be sure to read the warnings here: http://www.atticfoil.com/applications-a-uses/attic-applications/lay-out.html about sealing up the ceiling to prevent warm-moist air from passing through the ceiling and insulation and possibly getting trapped under the AtticFoil. AtticFoil IS a perforated radiant barrier, so it can handle the "regular" amount of moisture that naturally passes through the sheetrock and insulation, but it could be overloaded if you have a large source of warm moisture laden air.
I live outside Phoenix, AZ and I have a flat roof that will be redone (no attic). Can I create a sandwich of plywood decking with foam spacers and then have a spray foam insulation installed on top?
You COULD do this. However, I think it would be a LOT of work for limited extra benefit. If you have a flat roof, consider a product like www.Duro-Last.com instead. One of the great features of a roof like this is that you could easily overlay 2-4 inches of dense ISO Board (PolyISOcyanurate), then put the Duro-Last roof on top. Products like Duro-Last are known as "cool roofs." For example, you can walk barefoot on a Duro-Last roof on a hot sunny day. By COMBINING the foam board (R-value) with the reflectivity of the white membrane roof, you will SAVE a bundle on cooling expenses AND have an awesome quality leak-proof roof to boot.
We have a multi-level flat roof house with standard roofing material. Several rooms are VERY HOT (the same temp as outside or even hotter) despite using window tinting, solar shades and drapes. We live in Sedona, AZ where in the summer it will be in the mid-high 90's at it's worst and drop down to the 70's at night. The MBR is a particular problem at the highest point of the house. It's well over 85 in there even when it is only 80 outside. We have been told that is we "foamed" the roof using either R-7 or R-14 we would see a huge decrease in this heat issue and perhaps cut our very high electric bills in 1/2. The foam (depending on R-7 or R-14 and if we do the whole house or only certain rooms) was quoted at basically $2 a square foot. If it paid for itself in a couple of years or less then that would be fine. So thoughts? Is it worth doing this? We can't insulate anywhere else as there is only a crawl space available since it is flat roof (and there is the standard pink insulation in there, I saw it when I had to take down a ceiling speaker). Thanks!
I'd need more information to properly address this situation. What about the A/C system? Based on what you have mentioned, it appears that you might be better off just adding insulation when you replace the roof - a product like Duro-Last would be a good choice.
I have a flat roof in rowhome in Philadelphia. I'm in the middle of the block. My joists run parallel to the front/back walls, so there's no way I can vent. I need both a radiant barrier and insulation. Does the air space need to actually vent anywhere? Could I put up the foil with an air gap and then put fiberglass below? Fortunately I have full access to the underside of the roof deck. Thanks! Mike
Having sealed, or "dead air", is ok. In the Cathedral Ceiling installation method the air inside the assembly is not vented, but there is no risk or damage from "holding" the hot air in the wall. Just keep in mind that the total assembly will probably be a little warmer since it does not have the ability to vent some of the heat. Luckily, 97% of that heat will be reflected, so you're only talking about dealing with about 3% of the heat anyway.
Have you had a chance to take a look at the video: How to Install Radiant Barrier in a Cathedral Ceiling? It's the third video on the page and it explains how you can get both a radiant barrier AND traditional insulation in the wall assembly for maximum benefit.
I have a almost flat roof with no attic. Just the 4x6 beams then the ceiling and roof. How do I best improve insulation?
The downside is that there is no easy/simple way to add radiant barrier to a finished cathedral ceiling. The good news is that you do have a few options:
First, you could remove the sheetrock and install radiant barrier foil via the Cathedral Ceiling Method. This can be labor intensive and costly, but this would garner the best results.
Essentially your layers will be as so, coming from the roof down:
Radiant Barrier Foil
Or, another option is to install radiant barrier foil over the existing sheetrock, but then you have to create an airspace. The best way to do this would be to use wooden battens over the existing layer of sheetrock and then staple the foil to the battens and then install new sheetrock over it. If you wanted to keep it simple, you could just bulk up what existing insulation you have. I recommend you get 3/4" to 1.5" foam board and apply it directly over the existing ceiling and the drywall over the foam board.
Hi - We are building our entire home without any attic space. We have already bought one sided radiant OSB, 4cm polystyrene insulation, plasterboard, asphalt felting and shingles! The roof structure is of galvanized metal. What is the best way to construct our roof - we are in hot climate. Thanks for your advice.
You will build this roof like any other. Just make sure your Techshield (foil-faced OSB) is installed so the radiant barrier is facing DOWN, toward the open attic space below the rafters. After that you build the rood out as normal. The ONLY reason you would need insulation up on the roof line is if you were not actually going to keep the attic, but instead were going to convert it to living space that you heat and cool. Otherwise, insulation does NOT belong on the roofline.
If you are converting the attic space into living space that will be heated and cooled, then you will add insulation via the Cathedral Ceiling Method; essentially since you have foil on the deck already, your layers will look like this coming down into the space:
Roof deck with Radiant Barrier Foil layer facing into attic
I have an uninsulated vaulted ceiling that I want to use your product and rigid foam due to the 3" rafters (22" on Center). I need to know where I need the air spaces. I want to use 2" Foam board so that will leave me with 2 - 1/2" spaces. Your video says to have 1/2" air gap betwwen the roof and foil and then do I need an air gap between the foil and Foam Board? What about between the rigid foam and the drywall?? Thanks, Lisa in Lebec (CA) PS what would the total R Value be after I put all these products together? (My roof is made with true 3" rafters, 1x12's ran perpendicular to the rafters, Tar paper and composite shingles.)(in laywomen's terms)
You have it right - you need a space between the roof and the foil, but you do NOT need another gap between the foil and the foam board, nor do you need a gap between the foam and drywall. Honestly, if it were me, I would utilize the entire inch of space between the foil and the roof deck.
As far as the R-value, you would need to determine that based on what materials you use and in what quantities. Radiant barrier has no R-value, so it will not factor into this equation.
Hello, My 30year old home, A/C heat is in the Attic and the flue for the other one comes up through the attic also. Should I Go with Foam or a Radiant barrier? Due to the Carbon monoxide leak if was to happen? the house also has a attic fan in it.
Foam is going to slow down conductive heat loss/gain and foil is going to stop 97% of RADIANT heat gain; one does not replace the other.
In my home I have BOTH - foam AND radiant barrier.
I'm getting conflicting info from contractors and am stymied. My home was built in 1960 and has a 4/12 pitched roof. We are adding an addition with a 9/12 roof and will be installing decking and new shingles for new and old portions. I planned to have Icynene foam sprayed in walls of the addition and have cellulose sprayed in the entire attic (and remove the old insulation as we've had mice) but had a spray foam contractor say I should spray the entire attic and if I need to save $$ use foam insulation in the new walls. We installed a HE HVAC system already (sized for the house with the addition) so reducing the tonnage is not an option. Should I follow my original plan? Or use radiant barrior or sprayed open cell foam on the underside of roof?
I think the only time you should foam the deck is if you are doing new construction and doing a fully encapsulated "non-vented" attic. Otherwise, stick with the proven combination of traditional insulation (blown-in cellulose is fine) and a radiant barrier. Combine those with some decent attic ventilation and you'll have a system that works great.
I would like to install composition shingles over underlayment over "Techshield" OSB with sprayed Iceynene closed cell foam applied to underside of the Techshield deck. Without an airspace, does this defeat the purpose of the radiant barrier and result in a "hot" roof which might degrade or damage the insulation? Would open cell foam be better?
Yes, a radiant barrier does not work without an air space and so when it is sandwiched between other layers, the heat flows conductively and aluminum is a great conductor of heat, meaning it will PROMOTE heat transfer instead of preventing it. The only way any radiant barrier will work is if radiant heat is present, and radiant heat can only exist in an air space/vacuum.
The best set up is a combination of both a radiant barrier and traditional insulation (or spray foam insulation), since the two products address two different forms of heat.
I purchased rolled R-13 insullation to put in my attic over the flooring which already has insulation in it. I asked and was told that the paper side of the insulation was to be up - away from the floor not against the floor. Last night I had an e-shield sales person look at my attic and told me that the paper side of the insulation should be down against the floor in the attic. When I purchased the insulationat lowe's I was told that paper side goes up. I am an 68 yr old female senior. i am now thoroughly confused. Do I leave the paper side of insulation up toward the ceiling or do I go up into the attic and flip the insulatin so that the paper side is down toward the house. Plesae help. I am now also trying to see if I would be smart to put in the radient barrier. from reading you info it loos as though something called AtticFoil might be just as good and less expensive - I had been quoted a bottom price of 4600 to install e-shield
Typically the batt insulation is laid so that the paper is down, closest to the drywall/ceiling of the floor below the attic.
As far as adding a radiant barrier, while radiant barrier is NOT a substitution for traditional insulation, it does work very well WITH traditional insulation to make it more effective. The combination of the two (regular insulation and radiant barrier) works to keep the home more comfortable and energy efficient, year round. EShield sells (and installs) a product that has a tiny layer of insulation in between the two foil layers, but it is really irrelevant since a person already has traditional insulation on their attic floor! What works about that product is the FOIL, not the small layer of insulation. Take a look at www.AtticFoil.com for some more information and perhaps you can even find a radiant barrier installer in your area who could help you install a radiant barrier.
Two questions first one is in a typically cold climate like North Dakotawhat kind of savings can be seen with a radiant barrier added to let's say R 16 bat in a percentage how much of a percent of my heating bill will be saved . Cold climate . . 2nd is it possible that adding a reflective insulation that is breathable or a radiant barrier could casue damage to areas where cieling is taped and mudded because the heat is being pressed down . . Being that there is no dead air between the insulation and the radiant barrier . That's my questions thanks a lot
1. There is no truthful way to tell you what kind of savings you will get because (1) every home is different and (2) energy savings amount to a whole lot of factors besides just adding a radiant barrier. I don't offer false promises; the more roof area that catches sun and you are able to cover below that, the bigger the impact.
2. No, radiant barrier will not cause damage to roof shingles because radiant barrier does not change the AMOUNT of heat, just the DIRECTION it travels. It's like a lamp without a shade. It puts out light in a room, but if you add a lampshade to it the light now travels in different directions, you haven't change the amount of light, just where it travels.
i have no storage space, only a very small section of the attic over the garage. however the attic is huge but has so many wood support for the roof all over unable to move. can this problem be fixed o allow storage by removing or restructure the support?
You need to talk to an engineer or architect before messing with any supports - they are there for a reason.
I have a 2500 sq. ft. bungalow in Dallas, Texas. There are seven inches of foam insulation in the attic with an R14 rating. A local company is saying that I need 19 inches for an R50 rating. Due to cost considerations, I looked at an additional five inches for a total of 12 inches and a R30 rating. The contractor who services the A/C-heating has always checked the insulation and found it adequate. Do I need the additional insulation? Tanks for your help. Peter
It's hard for me to say since I haven't been in your attic or seen what the current insulation looks like. The US Department of Energy has recommended guidelines for insulation levels based on geography in the US.
Take a look at that. Otherwise, you could also get a second opinion from another insulation contractor.
In the fall and springtime in Dallas, it is often warmer than comfortable in the daytime, and refreshingly cool at night. With an encapsulated attic, warm air from the living areas accumulates in the attic all day, and there is no way for it to escape. The solution seems to be a switch-operated or temperature-automated insulated damper or door, with perhaps a fan, at the top of a gable, or on the roof at the peak. That, combined with open windows on the ground floor would create that ideal stack effect, evacuating the accumulated heat, while drawing in the cool nighttime air. The house would quickly become nice and cool, and insulation and thermal mass would keep the house pretty cool all the next day. Have you found a product that would accomplish this? The closest I have found is this: http://www.hvacquick.com/products/residential/Whole-House-Fans/Whole-House-Fans/Tamarack-TC1000H-Whole-House-Fans but it is pretty expensive, and I don't think the fan would be necessary. Another issue is fire code. For the system to work, the ceiling would have to be penetrated. To be code compliant, you'd need a fire-rated louver or damper at the ceiling, that opened at the same time as the damper to the outside air, and closed when smoke was detected. Got any design ideas?
Considering there are only a few weeks a year where this would be an advantage I don't think I would install anything. On cool nights, we crack/open our windows and run the bathroom fans and kitchen vent hood to pull cool air in.
Another option (If you have the air handler in the attic) is to open the filter door and it will act as a return air vent that will pull air out of the attic. Depending on how tight your ceiling is, you might need to leave a door open to the attic to give the make up air a path.
I've recently seen some homes that used Tech Shield sheathing on the roof. They claimed that it would reduce hvac load in the summer and winter. The problem is that I don't see how it's possible for the foil to help during summer months because there is no air gap between the foil and the roof shingles. Diffusion of heat will basically be the same as without the foil on the underside of the sheathing. I can see some benifits in cold climates where you reflect heat back into the house, but see no benifits from summer heating. Am I missing something?
The air gap only needs to be on one side of the foil barrier for it to work. In the case of Tech Shield the air gap is the attic side air - it DOES work. However, the one downside to it is that the rafters are not covered in this application, so they can still bridge heat from the roof into the attic. That aside, the majority of the roofline is still covered so the results are pretty good.
i have an overlay of pink faced insulation should i take it out and then blow in new insulation and put the pink back down or should i blow the new insulation over the pink faced insulation
If they are unfaced batts of insulation (meaning there is a pink side facing up into the attic), I don't see a problem with blowing in cellulose over the existing insulation.
I live in Birmingham, AL, have a 1-12 pitched roof with ridge-vents,vaulted interior ceiings. My Insulation in the attic is r-25: 1-Will a radiant barrier help? If so, how mucm? 2-Should I cover soffit to ridge-vents and also lay blanket of film over batt/and blown insulation in attic? Thank you for you advice.
Does radiant barrier work? Yes, it is proven science, it works. The question people often hope to address when they ask this question is typically how much can they expect to save? If this is what you are wondering, I have to be honest: it can be hard to quantify since every home is different but in general the more space you have in direct sunlight that you are able to cover with a radiant barrier, the more you stand to gain by adding one. Check out this article on Expected Savings with Radiant Barrier Foil.
As far as doing both methods - I have seen this becoming more and more popular. While only one layer of application is necessary to get 97% heat block, many people are opting to do both methods to see the best results year round. For more information, here is a good article: Installing radiant barrier on attic rafters and over attic insulation.
hi ed my attic over my garage share the stairwell to the upstairs and the vaulted ceiling of the family room the high end the stairwell going up the stairs has warm spots on the living side of the wall they put r11 on the studs 2x4 studs and then the drywall would the radiant barrier help for this or install foam board cellotex and radiant barrier spaced away from the insulation
If you can get the radiant barrier between the ROOF and the insulation up there, then it will offer tremendous help! See this page for more information on this application technique: How to Install Radiant Barrier in a Cathedral Ceiling.
we want to put up a radiant barrier in the third floor before we finish it for living space. Were would we place the barrier, right up against the roof then put a baffle for an air space then regular insulation then drywall? Or, do we keep a space between the roof plywood, then the barrier then the baffle, then insulation and drywall?
Ideally you would keep a space between the roof deck and the foil. This is a common installation called the Cathedral Ceiling method - it works well for converting unconditioned spaces into living spaces - see photos, a video and install tips here.
Hi Ed, I've started usic Attic Foil and am pleased with it (particularly with the strength of the foil.. does not tear easily). I've already spanned my attic rafters with one piece that is 24 feet long. Just stapled it in place. My question is do you recommend using it as an insulation baffle right next to the soffit on the floor. I want to blow-in fiber glass insulation and need a baffle to keep it a safe distance from the soffit intake. There exist thin black plastic baffles (Accuvent) which I have purchased, but my rafter spacing is somewhat irregular and the baffles have irregular surfaces. So I'm thinking it might be easiest just to use attic foil for this. I realize Attic Foil does have small perforations (it's not a moisture barrier), but should it provide a good enough barrier between the environment in the soffit intake and the blown-in fiberglass on the floor? Thanks
Yep - that will work fine to use the foil as backstop to prevent insulation from clogging the soffit vents.
I live in Albany County, New York and we are looking to have our house insulated, including our large, walk-up attic. We would like to spray foam the roof of the attic and eventually finish the space, but we were told once we spray foam we need to sheet rock or spray a thermal barrier almost immediately, adding a significant cost to the project. The last quote we received was the only contractor who told us this was necessary so now we are concerned about the cost moving forward but our 1890 house has NO insulation in a very cold climate! Any idea if sheetrock/thermal barrier is immediately required? The attic is strictly used for storage.
I am not sure what the building/remodeling codes in your county dictate - I would contact a local building code office to get the most accurate information. I can't imagine why this would be mandated on a non-conditioned space, but I'd check with your county to be sure of what you need to do.
We just moved into a new home, and the living portion of the house has batt in the walls and open cell foam elsewhere. It's really great! Our garage is 20 x 27 and has ZERO insulation, and therefore it gets quite hot in the attic over the garage. There are no vents. Would it be more cost efficient to foam the roof (we have a 12' pitch roof) or just batt the ceiling, and would this be enough to keep the garage cool in our hot Georgia summers? Thanks so much
For a garage, or any non-conditioned space (meaning you aren't heating and/or cooling the area), the best option is to just add a radiant barrier because there is nothing better than radiant barrier to keep it cool; basically, you are looking for shade from the HEAT. As it stands you are gaining 100% of radiant heat (that heat is coming from the sun) into that space, which you probably know since you feel it! Traditional insulation is NOT needed (or recommended) on a non-conditioned spaces like garages. Simply staple the foil to the bottom of the rafters above the garage, just like you would in an attic space.
Installation guide is here: Radiant Barrier Staple up installation
If the garage door or garage walls are also catching sunlight, you need to add some radiant barrier on those surfaces as well. Here is an article on: adding radiant barrier to the garage door and garage walls
On a 30 yr old flat roof townhouse with no attic. From a roof leak, partial ceiling & insulation caved into upstairs bathroom. Looking up into the 18x24 hole in the ceiling, I can see plywood above the insulation. Before I replace the insulation & ceiling, should the plywood also be replaced? Would hardi-plank be appropriate?
I'd recommend you talk to a roofing professional about this repair. From an insulation standpoint, you should consider adding radiant barrier up there while you have the roof open. The cathedral ceiling method would be the way to go over an area like this with a flat roof: cathedral ceiling method installation click here
I have a house im doing work at, and the interior perrimiter walls are foam board and i bave to install my gas lines on the block wall can i cut out the foam to install lines and re silver tape back over it
You will want to use some type of foam to seal the hole, not just tape.
I have a lake cottage that has an old flat tar roof that covered the portion of the house that was not 2 stories. The flat roof rafters are 2 x 6 with 6 inch insulation and the old roofing material is a tar material about 1 inch thick. The previous owner put on a new roof (12/3 pitch) structure over the old roof, adding a 8' veranda porch. There is a 2 ft to 3.5 ft gap between the old tar roof and the new roof. Can I put insulation over or on top of the old tar roof? Will there be moisture problem? Can I use blown in insulation? If so, I was thinking going with 18 inches of blown insulation. Dave
Yes, you can add insulation over the old roof. The better option in this case would be to add a perforated radiant barrier in combination with some traditional insulation or even foam board. Moisture should only be a problem if the area below the old roof is not air tight & therefore is leaking air into the air space. Make the old roof airtight then add your insulation and top it off with the radiant barrier foil open to at least a 3/4" air gap facing the new roof.
My home is insulated with spray foam. The entire roof joist is foamed. Currently have on insulation on the attic floor, I assume that was by design. Would it be safe for me to now use blown-in cellulose on the attic floor?
If you have a fully foam encapsulated attic then there is no need for additional insulation on the attic floor.
We have a cottage that we use in the winter months. As we had no intention of using it year round when we built the insulation in the attic is only R24. We have been told that we should have foam insulation blown into the livingroom, dining room and living room areas (one big room) and that it is ok to leave the bedrooms?? What do you think.
I think if you are going to go through the trouble, you should do the whole thing. Furthermore, if you are only using it part of the year, you'll probably have a better investment using a radiant barrier to help hold the heat inside. Radiant barrier will make the insulation you already have more effective. The best way to install it would be closest to the inside of the home: http://www.atticfoil.com/applications-a-uses/walls/inside-behind.html
hello,i have loose fill fiberglass insulation now. im thinking of instaling spray foam between the rafters in the attic making it a non vented attic.will this shorten the life on my asfalt shingles since it has no ventilation?will i have to remove fiberglass or is this a plus?i live in deep south texas very mild winters,hot 100+ degrees from may to sept.attic is large 8"pitch with large span.
Are you wanting to add spray foam to tackle the problem of the heat load that comes with your location? If so, your better bet would be to get a radiant barrier up on the rafters and block 97% of the heat from coming in to the attic space in the first place. One thing that often happens when foaming an existing home is that now the AC system is so oversized it can result in not removing enough moisture. The AC system will only run short period of time to remove the sensible load (heat) but does not run long enough to remove the latent load (moisture). I love foam closed attics (I have one) but usually only recommend doing it on new construction when you can properly design the AC system for it.
I have spray foamed the underside of the roof in the attic area. However, I am having a problem with condensation in the living space. Does the attic and the living space need to 'talk'? Right now I don't think there is any free air flow between the the attic and the living space. I literally have water on the walls.
Sounds like you have reduced the load of the home so much that your air conditioner is too oversized and it is not running long enough to dehumidify. This can be an unintended consequence of retrofitting an existing home with a sealed foam attic. I would consult a very good air conditioning company. Generally, you have several options: Install a dehumidifier, install a "mini-split" ac system that will run at "part load" and both cool and dehumidify or replace your ac system with a smaller tonnage system.
I recently had a fire in my two year old home. The fire wasn't so bad , but the smoke completely filled the attic space. I suspect the radiant barrier was compromised. The radiant barrier is attached to the roof decking and one option is to remove the roof and replace the radiant barrier / roof. Would adding foam insulation to the roof be a good alternative solution ?
If the foil is still shiny and sturdy, it should still work fine. Foam isn't going to perform like radiant barrier. It, just like traditional insulation, slows conductive heat gain/loss but it doesn't stop it. Radiant barrier blocks 97% of radiant heat. You can either replace the radiant barrier decking with new radiant barrier decking (quite economical) or you can add radiant barrier foil over your rafters before the roof deck is put in place. Having a radiant barrier as your first line of defense up on your roof is going to be the best bang for the buck.
Should we make the attempt to to cut the ridge and install ridge-vent? We are installing a new roof on a 10-15 year old contemporary post and beam home that has 6+ inches of spray foam directly to the osb sheathing with no air space alloted for a continuous vent system. I was at least going to try to cut away the foam to see if the drywall was part of the panel but do not want to damage the interior finish at that hard to get at area to make repairs. Should we save the homeowner some money and just cap it after a determination is made whether or not air space even exists? We ripped some very crispy shingles that are first generation architect that should have ten years of life left judging by the rear porch which is 3 season. I am thinking the ridge-vent will help the cap but not much more. Thanks for any input!
I'd need more information to accurately provide some guidance. Based on what you've described - I say you need to go all or nothing on the sealed, foamed attic space. Either it is air tight and foam sealed, or it is vented - and vented well with holes in the bottom of the attic and holes in the top.
I am building a garage/workshop with a loft. The side walls are 6" studs. I had 1" closed cell foam applied to the sidewalls and 6" open cell foam sprade on the roof trusses. I have a metal shingle (Decra) roof. I am going to add an additional R13 to the sidewalls. Should I consider adding a radiant barrier and if so, what would you recommend? The entire building will be heated/AC.
Adding the radiant barrier inside your sealed space if going to have a very minimum benefit since there is already so much foam in place. To get the best results you'd need to add it from the outside, like right below the metal roof. If that is not an option, then you probably aren't going to see much of a benefit from installing it inside your attic space.
For more info on combining a foam-sealed attic with radiant barrier, take a look at this article I wrote: http://www.radiantbarrierguru.com/combining-radiant-barrier-with-spray-foam-insulation/
I have passive gable vents at each end of my 1948 home and no soffit or ridge vents. I want to install a radiant barrier in the attic. Can I run the barrier to the soffit area and cover them up and can I cover the ridge area up as well since I have the gable vents or should I add soffit vents, if so how many? Would a fan at each end of the gable to pull air out be advised? I will add blow insulation after the barrier is installed.
You still need to leave gaps for air flow regardless of the ventilation you do/do not have. Watch my video that explains this: Leaving Gaps in your Radiant Barrier Installation for Air Flow
Hi there Ed, I'm in Madison Wisconsin. We have a 'hot roof', no venting, with 2" foam on the roof deck under the shingles, then the roof deck, then we've put about 3" of closed cell spray foam between the rafters and on the gable end walls. Some rafters are 2x4's (original to the 1914 house) and some are 2x6's (on the new attic dormer). So there's a little bit of air space left on the interior of 2x4 rafters and gable end wall studs (1/2" to 1"), and more air space on the interior of the 2x6 rafters (perhaps 2"-3"). With the cold winters, I'm wondering if there would be a benefit to either a foil layer over the remaining air space, or using foil-backed drywall? Or might this be more of a benefit for the couple of warm weeks we have in the summer? I looked at your page http://www.radiantbarrierguru.com/combining-radiant-barrier-with-spray-foam-insulation/ and it seems that our system is quite different from what you put together there. Alternatively, do you think it'd be worth it to pack the 2x6 rafter cavities with cellulose for the added R value? The full 5.5 inches of foam was going to be too expensive, so we didn't do that. Thanks for your advice
If heat retention is your primary goal, then I do think adding radiant barrier to the bottom of the rafters would benefit you. Placing the foil there (or even on the attic floor) will give the foil the best chance to hold heat in the living space below the attic. Whether you staple to the rafters or lay it on the floor, the foil will be open to an airspace on at least one side so it will work.
Hello, I have been doing research in preparation to finish our 3rd floor attic and I am getting so much conflicting information I'm stymied. Currently the room has ~12 " of blown cellulose on the floor. The pitched attic roof deck is uninsulated and the space is vented with soffit vents, gables and ridge vent. If we finish and condition the space, i am getting info that we should use baffles from the soffit to the ridge, apply the closed cell foam to seal, then either another open cell foam coat or batts to increase R value. I realize I would also need to do rigid foam at the soffit vents. I am getting other information that here in zone 4 (VA) you can forego the baffles and apply open cell foam directly on roof deck. Can you please help me determine the correct method of these, if either? I am completely confused.
From experience I can tell you the best way to tackle this room is to use a combination of both a RADIANT BARRIER and foam (rigid foam board works best as far as attaching it to the rafter bays, spray foam will actually need something better than foil to adhere to, so many people use foam board on top of the foil and then spray foam the board until the cavity is filled). Basically you want it to look like this: roof deck, air gap (with or without baffles), radiant barrier foil, spray foam, interior of the room. This page has a detailed video on how to add the foil and insulation into the cavity so that the proper air gap for air flow is maintained, I highly recommend you take a look at it (and some of the photos on the bottom of the page) to familiarize yourself with the basics of how to set this up: Adding Radiant Barrier to a Cathedral Ceiling & Adding Radiant Barrier to a Wall
The main ideas are: get the foil closest to the outside/roof with the proper air gap (and on any walls that share a space with the attic), allow air to flow between the foil and the roof deck (to help keep the assembly cooler, and utilize traditional (R-value) insulation closest to the inside of the room. If you can achieve these 3 goals, the room will be more comfortable year round.
Can I spray open cell foam over LP Techshield?
NO. Doing so will effectively eliminate the air space Techshield relies on in order for it to work. If you do this, you will render the radiant barrier useless. Not to mention spray foam doesn't adhere well to foil. If you're set on adding spray foam, you need to create an air space on top of the foil before the foam. Your best bet is to install like a cathedral ceiling with spacers and instead of adding a foil layer (since you already have one) you can add foam board. This will help add r-value AND the spray foam attaches better to the foam board than the foil.
is there a advantage with radiant plywood vs open foam in a a new house
Yes, combining radiant barrier decking and foam work well together - I have this system in my own home. Read more about it here: Combining Radiant Barrier with Spray Foam Insulation
I am building a new single storey home almost 6000 sq.ft. We have installed radiant barrier plywoods and shingles on top. Should I go for spay foam insulation (Inceyne) or Fiberglass(Blown and Batts)?
If your radiant barrier is radiant barrier decking, then it's using the attic space as an air space so you can't cover it with spray foam. In this case you could use spray foam (or batt insulation) on the attic FLOOR, but not directly on the foil in between the roof rafters.