Ask The Guru: Attic & Foam Insulation

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1. Rating: +0

   

   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.

2. Rating: +0

   

   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/cold_climate.htm 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 perforated, 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.

3. Rating: +0

   

   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.

4. Rating: +0

   

   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.

5. Rating: +0

   

   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.

6. Rating: +0

   

   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; the video here explains how this method works: http://www.atticfoil.com/faq.htm (it's the 3rd video down on the page)

   Essentially your layers will be as so, coming from the roof down:
   Roof deck
   Air Space
   Radiant Barrier Foil
   Insulation
   Sheetrock

   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.

7. Rating: +0

   

   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; the video here explains how the cathedral ceiling method works: http://www.atticfoil.com/faq.htm (it's the 3rd video down on the page) and 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
   Air Space
   Insulation
   Sheetrock

8. Rating: +0

   

   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.

9. Rating: +0

   

   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.

10. Rating: +0

    

    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 ventilation and you'll have a system that works great.

11. Rating: +0

    

    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.

12. Rating: +0

    

    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 it 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 an installer in your area who could help you install a radiant barrier.

13. Rating: +0

    

    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, it will not cause damage 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.

14. Rating: +0

    

    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.