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sallen2008_gw

Foam Insulation Yes or No?

sallen2008
15 years ago

I would love to hear your opinions on foam insulation. I have heard it is about 20% more but the return is very quick through reduced heating cost, etc. What do you think?

Comments (37)

  • brutuses
    15 years ago

    We haven't lived in the house yet, but already can tell the difference in the foam's insulation properties. In the winter when we'd go to the home in the morning it would be very cold inside and until we opened the doors, it stayed very cold. Now in the summer, we go in the morning and it is cool inside the house and stays that way a while unless we open the doors and windows and let in the humidity and heat. We also have this reflective stuff under the roof in the attic that reflects 25% or so of the heat coming in through the roof. We are very happy we opted for the foam and know it will definitely pay off in the long run. We have the Soy foam.

  • el1019
    15 years ago

    I purchased Tiger foam on-line and will be spraying it on myself. I have never done this, but it looks doable. My plan is to seal walls and sill plate with 1 inch foam and finish off with fiberglass batts. I do have some application concerns, but I think if I do the prep work and plan ahead I can do it.

  • armomto3boys
    15 years ago

    We're also going with foam. I believe they said we'd have R24 in our 2x4 walls.

  • sierraeast
    15 years ago

    If you have vaulted/cathedral ceilings and plan on foaming those cavaties, check in with your local code enforcers concerning venting/non venting of the rafter spaces. With foam, i believe venting the spaces aren't necessary but because our county was not familiar with the foam process, any insulation type must have an air space between the insulation and the underside roof sheathing along with soffit/ridgeventing. We almost went with foam on our build and the company said they checked with our county and no venting was necessary. This proved untrue and we would have had to remove the foam which of course renders it useless and unusable and a very costly undertaking as our plan is almost all cathedral ceilings. I like the idea of foam and at the very least doing as el1019 is doing and sealing the cavaties with a small layer of foam, which i think is it's best purpose. Check in with your local authorities to make sure they are on the same page as the foam installer.

  • garymunson-2008
    15 years ago

    My concern on foam on the underside of trusses is the impermeability of the material. It forms a very strong bond with the trusses and decking and is also watertight. Eventually your roof will leak...they all do.... When that happens, the water will be trapped between the foam and wood decking/trusses, rotting them away without you ever noticing anything is wrong. Foam in the walls is probably a good idea but unless someone can come up with a way to deal with the roof leak issue, I think you'll be setting yourself up for trouble down the road with roof-deck spray.

  • garymunson-2008
    15 years ago

    brutuses...did the insulation contractor spray the foam directly on the radiant barrier deck insulation? For proper functioning, It's not supposed to have anything against it.

  • brutuses
    15 years ago

    We applied spray to all the walls, but only a very small area in the attic. I don't know why DH had them do that one spot in the attic, but I'm sure he had a reason. I don't know all the details (and I like it that way) HA! We have conventional insulation throughout the attic space.

  • sallen2008
    Original Author
    15 years ago

    The Healthy House model in our area used foam. Foam is newer to our area. Thanks for the input...what did homebuilders do before gardenweb? Thanks!

  • mightyanvil
    15 years ago

    It is difficult to give a yes or no without knowing what kind of foam and to what other kind of insulation you are comparing it, in what climate, what kind of wall assembly and for what budget. Sure, foam is great...in the right climate and wall assembly but it is always more expensive than the alternatives. Don't try to design your building envelope one piece at a time. Think about it as a total system in a specific environment.

    Unfortunately, the last place you will get unbiased information is from an insulation contractor. The aged R-value of 3 1/2 inches of closed cell polyurethane foam is 21. That's quite a bit more than the alternatives but the cost is quite a bit more. You would need to be in an extreme climate to be sure you could pay that investment off in a reasonable time period. If you live in a more moderate climate you would need to do the ROI calculation. Most believe the most cost effective way to get to the R-20 range is with fiberglass or cellulose in a 2x6 wall.

    The closed cell foam can also form a vapor barrier and that might not be compatible with your wall system. I have only used the open-cell foam, not for R-value but to avoid venting a roof.

    In general, dense pack cellulose seems to be the favorite right now. In a very cold climate a layer of foam insulation board is placed over the sheathing to reduce heat loss through the studs (This is the weak point in foamed 2x4 stud walls) Unfortunately, there is little reliable information on the internet about fiberglass and cellulose insulation; it all comes from poorly disguised industry organizations and it is often exaggerated.

    Start with the wall construction/vapor management system appropriate for your climate, consider your budget, and then think about types of insulation.

  • gardengirl53
    15 years ago

    Mightyanvil, I am hoping to use 2x6 construction, with fiberglass. I am in the Chicago area. How do you feel about a thin layer of foam and then the fiberglass? Overkill?

  • worthy
    15 years ago

    Here's how I used XPS on the exterior to bridge the 2x6 @ 16" on the house I'm currently living in. The XPS is in place of any other sheathing; the 2x6 framing is blocked all around at midpoint to provide structural strength, even though it was not Code required.

    Dow has also introduced a new stiffer XPS designed to substitute for any underlying sheathing as well. It was one of a few products cited as most innovative for 2008 by the Journal of Light Construction.

    Local Codes will decide if the XPS (and corner diagonal bracing) alone is sufficient.

    I've used cc foam on interior basement walls, rims joists, garage ceilings and any other hard to reach areas. I haven't found it cost effective on exterior walls.


    One inch thick (R-5) tongue and groove extruded polystyrene (XPS) used as exterior cladding on a brick and stone clad home. Eventually covered in brick paper, it also serves as a drainage plane

  • woodinvirginia
    15 years ago

    20% More ??? Try like 40% More than conventional, and at least 30 % More then the Blown in Fiberglass I had done with the Fabric Netting called OPTIMA from Certainteed. My walls with the "optima" netting are tight as a chinch.

    Only drawback I have with "foam" in walls is that if you ever have to run another electrical line, Alarm wiring line or any other line through your walls anywhere down the road in the next 30 years..you will catch HELL in doing it or use 3 times as much line running it through your attic or crawl space to circumvent the walls. With Blown In insulation my contractors can still fish a line through it.
    I have Cathedrals on each wing of my new home and the insulation in the ceiling must be put over a 1" vapor space so air can circulate to the vented roof via the soffit system.
    In addition to that system I also put in Radiant Guard to block the radiant heat from cooking my attic space. It has dropped my attic temperatures at least 20 degrees during the hottest days of summer.
    www.radiantguard.com
    Good Luck.

    Here is a link that might be useful: OPTIMA Insulation

  • sierraeast
    15 years ago

    We have blown in fiberglass from knauf insulations.

  • worthy
    15 years ago

    Here's how I used XPS on the exterior to bridge the 2x6 @ 16" on the house I'm currently living in. The XPS is in place of any other sheathing; the 2x6 framing is blocked all around at midpoint to provide structural strength, even though it was not Code required.

    Dow has also introduced a new stiffer XPS designed to substitute for any underlying sheathing as well. It was one of a few products cited as most innovative for 2008 by the Journal of Light Construction.

    Local Codes will decide if the XPS (and corner diagonal bracing) alone is sufficient.

    I've used cc foam on interior basement walls, rims joists, garage ceilings and any other hard to reach areas. I haven't found it cost effective on exterior walls.


    One inch thick (R-5) tongue and groove extruded polystyrene (XPS) used as exterior cladding on a brick and stone clad home. Eventually covered in brick paper, it also serves as a drainage plane

  • robin0919
    15 years ago

    worthy.....that XPS looks very interesting!......But.....how much more is it over OSB?

  • sue36
    15 years ago

    20% more? We priced it and it was 3 times the price of upgraded fiberglass. I did R21 in my walls, most interior walls, R38 in ceilings, all around stairwells and garage and it was about $6k (4000 sf house). Foam was going to be over $18k and that didn't include any interior walls. If you can get it for only 20% more I'd consider it a must-do.

  • marthaelena
    15 years ago

    Where are you guys getting that foam insulation 20% higher than regular fiberglass?

    Here it is 3 times more.
    last time DH and I got a bid for R23 blown in fiberglass for 2x6 walls and it was $5,000 and we requested another bid using foan (icynene) and it was $13,000 using 2x4.

    If you are relly getting that low price do not think twice - just make sure it is a good one - it is too good of a price to be true.

  • gr8smiles
    15 years ago

    We used Biobased Foam in our new home and thus far I think it may be the best decision that we have done. We also did geothermal with 4 vertical wells and we are shocked at how well our home is keeping a nice even temp. We hope to move in in the next few weeks and are thrilled thus far.

    I did not get bids for other types. I did get multiple bids from other foam companies and they were in-line with our bid. We built a 4685 ft2 house. It has nearly 6500 ft2 under roof.
    Our cost was around 23000 and that included the 'vinyl pool' liner in the crawl space and the foundation walls sprayed as well.
    {{gwi:1453331}}

  • gr8smiles
    15 years ago

    Also, we are in Nashville,Tn. Last week, out attic was was 80 degrees and the outside temp was near 100. The spec house next door was over 120 in the attic. You have to feel this stuff to believe it. Yes, it costs more;but, I think that the long term benefits are incredible. The other nice benefits are an almost complete lack of dust once the house is finished since there is no air infiltration. We have added a fresh air intake that comes on and inputs fresh air in the hvac.

  • worthy
    15 years ago

    Here is Building Science's take on unvented attics. which they like for all climates.

    Since the attic is now part of conditioned space, I wonder if the suggested benefits are outweighed by the extra costs of heating/cooling.

  • garymunson-2008
    15 years ago

    No one seems to want to tackle my comment on what happens down the road when the roof begins to leak and the water is trapped in the sheathing by the foam....

  • marthaelena
    15 years ago

    gary,
    If there is a leak, the sheathing will start to root and eventually the truss/rafter will too and nails will rust. It will not happen overnight - but it will happen and the interesting thing is: while it is happening, how will the person know if something like this is going on?

  • mightyanvil
    15 years ago

    If I were going to use a thin layer of foam I would put it on the outside face of the wall to help reduce heat loss from the studs. Using foam to make up for a poor air barrier doesn't make sense to me but then I don't use plastic air barriers if I can avoid them; I've never seen one installed well.

    Regarding the leak detection issue, when rafters are insulated with foam I always cover the entire roof with Ice & Water Shield underlayment. It's cheap insurance so I often do it anyway. I recently found a custom home builder who insisted on doing it over a conventional uninsulated attic.

  • mikeyvon
    15 years ago

    We went with standard bats. Code minimum R21 in the walls and R38 on the lid (which is a 10/12 cathedral). We looked at foam, but the cost far outweighed the benefits. Foam was almost 4 times ($3300 vs $12500) the costs here in Northern Cal. We heat with wood, which is all but free and we do not cool. From my limited experience and research, foams best quality is stopping air infiltration. You can stop air infiltration through proper use of house wrap and drywall.

    I am not a fan of super tight homes. Tight homes require HRV or ERV and those cannot (i assume) be super efficient. Mean you are still bring in some unconditioned or slightly conditioned air.

    I went with batts mainly because cost and limited benefits of foam. Any new, properly built house will be damm well efficient, batts, blow-in, or foam.

  • oruboris
    15 years ago

    I based my decsion in part on conversations with a couple builders who were very pro-foam [same with hydronic infloor heat]. They felt the tightness factor [to coin a phrase] is greater than the r-value calculations would indicate.

    There's also been some studies indicating that fiberglass in roofs looses its ability to insulate in extreme temps due to convection currents, and I didn't like the idea of cellulose or equivalents because I've seen how much mice love living in that stuff.

    So is foam worth it? I've no idea. While the house seems wonderfully glued together, there's no way to know how it would have felt with fiberglass. Can't exactly compare utility bills, either.

    And I'm out some extra money because I also added an HRV system-- worried that it would be too tight for good air quality.

    Lacking the ability to see the future, all any of us can do is pay our money and take our chances.

  • worthy
    15 years ago

    garymunson-2008 said: "No one seems to want to tackle my comment on what happens down the road when the roof begins to leak and the water is trapped in the sheathing by the foam...."

    From my Building Science link above:

    Controls Rain Leakage  Closed-cell spray foam has negligible water permeability, minimal water absorption, and excellent adhesion allowing it to act as a secondary rainwater barrier to limit damage when primary roof assembly rainwater control membranes leak. Rainwater migration is severely limited due to the low water transmission and high adhesion ("waterproofing") characteristics of the foam and damage is limited to the area immediately adjacent the hole in the primary rainwater control membrane. This tends to contain the damage, making it easier to identify the source and preventing it from spreading throughout the assembly and to interior finishes which can be costly to repair. [Emphasis added.]

  • worthy
    15 years ago

    robin0919 asked: worthy.....that XPS looks very interesting!......But.....how much more is it over OSB?

    My material prices are the same. But if you choose or are required to also include OSB sheathing, the price is obviously double.

    XPS is very popular here for mass townhouse developments. But the reasoning is a little different. By adding XPS to the exterior, the framing can be done with 2x4s, which are a whole lot cheaper than the 2x6s that would otherwise be needed to provide space for Code minimal insulation. When I've used XPS it has been in addition to Code minimum and is over 2x6 framing.

    (btw, sorry for the above double-posting.)

  • energy_rater_la
    15 years ago

    It was nice to look at your build twice worthy!

    In my area foam is much higher than conventional insulations, ROI is 15+ years, and in cases of foam
    on the roofline for a semi conditioned attic ROI can
    reach 20+ years, depending on pitch of roof.

    IMHO that is a long long payback for any one building
    componet.

    My answer to the yes or no questioin would be no.

    locate hvac system in conditioned space..use R-8 ductwork
    in attic and radaint barrier roof decking is a more cost effective for my area install.
    if in design stage..locate ducts with in conditioned space also.

    Like worthy I like the foam to the exterior, and use a foil faced closed cell sheating board behind brick, t&g
    blue board behind other materials that don't have an air space. conventional insulation in walls, air tight drywall approach to interior of wall.

    We have stick built homes built as described above with wall R values of R-5.6 sheathing, plus R-15 insulation for an overall R-value of 20.6. not shabby for the price.
    with proper air sealing these homes achieve same lowered infiltration rates as foam insulated homes, and in some cases better.
    .25 ach (air changes per hour) is the goal. once infiltration rates fall below this number fresh air is needed. filtering the air, controlling how much air in introduced,cooling and dehumidifying the air before it
    enters the conditioned space is what we do here.
    it is not at all inefficient if done correctly.

    many people assume that their home is tight enough to need fresh air (make up air). it is only with testing that the
    amount of air changes per hour is determined.
    houses leak in the damndest places!

    testing various methods of buildings with a blower door
    shows how same results can be achieved with different materials and costs. it is not a crapshoot if you know what you are doing and take the steps in the building process to achieve the end means.

    better building practices consiter the house as a whole and how componets function with each other..low e windows..lower heat gain..smaller hvac..

    savings from building a tighter home is not only lower utility costs, but smaller hvac systems.
    unfortunately most people spend big bucks on lots of things but do not feel the need to pay for a load calculation, duct design or duct sizing calculations.
    there in lies the problem.

    built tight and ventilate right..

    best of luck.

  • sallen2008
    Original Author
    15 years ago

    Wow! I believe I will print the entire thread and have a long talk with local builders. This has been great help! I am thinking the best thing to do is get a couple of quotes and present them with the issues you have raised. This is GREAT! Thanks!

  • teddas
    15 years ago

    I must add that the "skill" of the installer is critical to the process. I sprayed the entire of my home ( closed envelope) and found that the foam had shrunk away from the studs. I had them come out and fill in the areas. It was quit a chore... but If you get air leaks then it defeats the purpose of the envelope.

  • bdpeck-charlotte
    15 years ago

    On the roof leak questions, let me add to Worthy's quote from Building Science and point out that the roof sheathing should be allowed to breathe to the outside. So most of the new poly roof underlayments should be avoided. Standard roofing felt should be used with a non-vented attic, unless you spring for the one vapor permeable underlayment out there, the name escapes me right now.

    As for Foam being the right choice, every home and decision is different. I'm choosing 2 inches of CC in my 2x6 walls with an unfaced R-13 batt over the top and an unvented attic. I'll have R-24ish walls, and still be able to snake wires. Costs, very expensive. I'm hoping to get $100 a month lower energy bills... which is a 10+ year payback horizon at current energy rates.

  • dallasbill
    15 years ago

    Closed cell has to have some kind of answer to the fact that it it impervious to a leak, so they say it 'controls it to one loaction.'

    So, how is one to locate this one leaky location, hmmmmmmmm? Go up in the attic and poke holes each time it rains and see if water pours out?! I'm being fascetious, of course, but HOW?

    We have open cell (Sealection500) and we had 2 separate leaks in our metal roof flashing above a foamed vaulted ceiling. There is no way in hell we ever would have found them it hadn't come through the side wall 5 hours after the storm. I'd much rather deal with a warranty covered repair now than discover something months/years down the road with a closed cell foam leak.

  • worthy
    15 years ago

    Vapor permeable underlayment. (Delta Foxx and Delta VentS)

    I'd much rather deal with a warranty covered repair now than discover something months/years down the road with a closed cell foam leak.

    Good point!


    For a "cathederalized" roof, I just can't see the advantage of heating and cooling all that space that's not being used as living space.

    I used oc foam once around basement rim joists. It was applied in the winter and by the time we were ready for drywalling, the foam had shrunk back considerably. I was forced to try and fill the gaps with handheld cans of polyurethane spray; trying to spray it upside down while standing on a ladder, I got as much foam on the floors and me as I did in the gaps!

  • mightyanvil
    15 years ago

    I recommend putting full coverage self-adhering modified bitumen (or butyl) underlayment under a metal roof (be careful to use the right type for your climate) That combination is probably the most reliable residential roof covering possible.

  • meldy_nva
    15 years ago

    One thing to keep in mind about "pay-back" comparisons. Many on-line sites are based on 2005 fuel prices, even the more up-to-date sites use 2007 figures. In 2005 a barrel of oil was about $58US, in mid-2007 about $87US [DOE figures]; yesterday, $124US. Comparative payback years are drastically reduced as the cost of fuel goes up. You need to do your own math [folks with cheap hydroelectric will not see as much change] before you can truly say how long it takes for the "payback".

  • dallasbill
    15 years ago

    The big advantage we "see" is the lovely, open-beamed cathedral roof.

    The house is ICF, and with the foam, the roof there is essentially a SIP. So, I guess we'd be paying a bit less in July to cool without it, instead of 185 with it. ;-) At the same time, once you have a large, sealed, insulated volume of air established at a certain temp, it takes a lot to move to another temp. The temp at floor is 77F and the temp at 28ft is 79.5F, all the time now, so we'll live with that, for the view.

    I can't see building stick, myself... ;-)

  • garymunson-2008
    15 years ago

    Whoa....On roof leaks...remember, the OUTER membrane has failed for the leak to happen....first of all, water is going to spread between the felt/ice dam/whatever and the wood decking. With normal fiberglass insulation, as soon as the water finds a seam in the decking, it shows up as a spot on the drywall. With the foam, a very large area will proceed to get waterlogged. It seems to me Dallasbill was lucky to have seen the leak at the wall area....