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Icynene insulation!!!

Stephen QStephen Q Member Posts: 1
Looking for advice. Been building a house for past two years. Doing entire mechanical systems. Installed radiant throughout,Snow melt, Wirsbo aquapex and aquasafe sprinkler system. Taking my my time to do it right in between raising six kids and running business. Good things come to those who wait, right?(Tell my wife)I'm at the point of hiring insulation contractor. Going to use Icynene insulation throughout entire exterior of house. Contractor suggests enveloping the house with the Icynene including roof rafters(no insulation between 2nd floor ceiling and attic. This elimintates the need for venting of the attic.(soffit vent and ridge vent). Conventional wisdom tells me this sounds wrong. This leaves the attic as a semi conditioned space.
Need some advice from anyone who dealt with icynene so I can make a desicion on doing roof rafters.

Not far from the finish,

Stephen Q


  • ErnieErnie Member Posts: 94

    Constantin did his house in the manner that your contractor is suggesting , I am sure he will show up shortly.
  • john woodjohn wood Member Posts: 63

    This method works well esp in a home where the roof design works against ventilation of the roof deck. Cut up framing, deck on beams, etc.

    The main purpose of attic ventilation is (in cold climes) to keep the roof cold enough that the snow does not melt and then ice dam over the eaves. Secondly, it helps to keep the roof surface cooler and gives asphalt shingles a longer life. Some shingle mfg do not warant over an insulated deck, some do. Check before you buy.

    One side benefit of foaming roof deck is that you then may install an HRV in the attic space......... or a/c or plumbing and not have a freezup issue. Also makes it much more enjoyable to work on whatever is in the attic in harsh weather.
  • joeljoel Member Posts: 931

    if your putting AC up there it's the way to go always nice to have the ductwork inside the envelope .
  • JBJB Member Posts: 85

    Try WWW Tiger for some more ideas on DIY foam,
  • jerry scharfjerry scharf Member Posts: 419
    He's got it right IMO


    I did this in my house, but used closed cell low perm foam instead of Icynene. I have many A/C/filtration ducts in the attic, so the win is big for me.

    The advantages are several:

    The heat gain in the summer is less, because the attic space will actually be hotter than the outside surface. So that means the same insulation will allow less heat gain.

    the ceiling is insulated, but what about the access doors? With the bootom of the roof deck approach, this is a non-issue.

    If you have any ducts in the attic area (filtering or A/C,) there are two advantages. First, any leakage from ducts is kept in the building envelope. Second, insulation on ducts is lower R value and less continuous.

    It sounds like you are doing some of the work. It sure is nice when you need to run a wire of adjust a damper and the attic is 80F rather than 140F or 20F.

    Now the down sides:

    When you insulate to the roof deck, you then have conditioned air against the foam face. You need to install a 15 minutes fire barrier. The code calls out 1/2 sheetrock as the standard, but I went with an intumescent paint. At $65 per gallon plus the time of an specially trained painter, it adds significantly to the cost.

    You have to explain this to the building officials. Sounds like it should be a no brainer, but it took me a couple months to convice my CBO that this is OK. The latest codes (I think 2002) discuss this construction technique, but of course those haven't been adopted yet...

    hope this helps,
  • ConstantinConstantin Member Posts: 3,782
    Sounds good to me...

    ... just be sure that the local inspector/codes will allow it. Certain building codes have been changed recently to expressly allow it (MA, for example) but the inspector also needs to keep up with the changes...

    We used Corbond in the older part of the home (where the wall thickness could not change) and Icynene in the new part (where we could have thick walls). The roof decks are insulated with both materials and to date we're very, very happy. In fact, even though temperatures have dipped outside into the 50's we have yet to really heat the house. has a good explanation of why unvented roofs are a good idea and how they save you heating and cooling costs over the vented variety. I am happy with my decision, as it opened up some space in our house to install an air handler and to run the sprinkler system without worries. Besides, if your AC system experiences any duct losses, at least they'll be in the conditioned space instead of outside it.

    All foam insulation has to be covered with a fire-rated material, we used blueboard. The joints are messy, etc. but the stuff should do the trick.

    The only worry that could be classified as "real" is that the roof deck will be slightly warmer on a unvented roof than a vented one in the summer. measured only a 17°F difference between the temperatures of vented vs. unvented roof decks in Las Vegas, and the temperatures stayed within the safe range listed by manufacturers.

    Nevertheless, I would check to make sure that if you greatly value your roof insurance (and most aren't worth the paper they're written on), that there aren't specific clauses against unvented roofs in them. We used DuraSlate and EPDM and expect no issues (we're in a pretty cold climate).
  • TomTom Member Posts: 265
    Works great

    We did this on a house in Oklahoma a couple of years ago and it hss worked great---summer and winter. We had a bunch of days with temps over 100 this summer and the customer had no problems.

    We installed a couple of supply air ducts and 1 return air duct to temper the attic and measured the airflow to make sure that the cfm of air was equal.

    Be sure that you run all exhaust fans to the outside of the envelope.

    Tom Atchley
  • PhilPhil Member Posts: 38
    foam insulation

    Just wondering what type of roofing material you used. I was told that applying the foam to the underside of the roof sheathing is O.K. for metal roofs but that the manufacturers of fiberglass/asphalt shingles will not warrent the shingles if the underside of the roof is not vented. i.e. the heat build up lowers the shingle life. Is this fact or fiction. I agree keeping all duct work and air handlers inside the in conditioned space envelope is the way to go!
  • jerry scharfjerry scharf Member Posts: 419
    I'll let you know in 20 years

    I have closed cell foam on the roof deck and dimensioned comp shingles on top. To the best of my knowledge, there are emperical studies that say it works, and situations where it has not. I don't know of any studies that have looked at attributed failures to see if the insulation was the cause.

    In todays litigeous world, manufacturer warranties deny first and ask questions later. So the first reaction to any difference in design is to say no. They change when they perceive a large enough market that would be lost if they didn't warrantee it.

    I did it, lots of people do it, but not enough to compel the big boys to change. You may want to look beyond the few largest manufacturers to see if there is one that does warrantee this situation. I didn't bother.

    best of luck,

  • ConstantinConstantin Member Posts: 3,782

    Try to look for the article over at which details their roof deck study in Las Vegas. Allegedly, the vented roof deck was only 17°F cooler in Las Vegas than the "hot roof" unvented kind. Both were in the "safe" range specified by the manufacturer.

    In other words, I saw little reason to not go unvented considering how much I am gaining in terms of conditoned space, reduced infiltration, etc. I used DuraSlate and doubt that they will suffer any ill effects from being exposed to the sun w/o ventilation below. Then again, I'm in Boston, I have lots of mature trees around the house, and so the insolation load is negiglible compared to the likes of AZ, NV, NM, etc.
  • PhilPhil Member Posts: 38
    Sprayed in Foam insulation

    I believe that spraying foam directly on the underside of the roof sheathing is now generally accepted.  It keeps the heat out of the attic and it appears as though the increased in shingle temperature is not a significant factor is asphalt / fiberglass shingle life.

    I recently constructed a 3 story including usable attic (500 sq. ft / floor) addition.  Don't know what product to choose.  Is Icynene a generic name or is it a defined product.  I believe that it is available  in both open and closed cell?  The closed cell apparently has and R value of 7.5 per inch and the open cell is 3.8 per inch.  Some say that the open cell bends and does not crack with the thermal expansion and contractions and wind and snow loading.  Some say to spray only 1 or two inches in the bays and use fiberglass to fill out the viod.  I have received some confusing proposals from products such as dimilec (spelling) or bayseal or other products.

    What product would you use? Would you use open or closed cell or both depending on the walls (masonery or plywood sheathing).  Is off gasing of harmful vapors something to be concerned about?  I am old codger and remember when some folks used urea formaldehyde which made the building toxic.  Any suggestions greatly appreciated.
  • icesailoricesailor Member Posts: 7,265
    A great idea:

    Icynene is a great idea. I see it used all the time. Especially on old work that I have been on before the install of the Icynene. It has always been my understanding that the air space around NM wire was part of the "Listing". For cooling purposes. That's why there is a limit on how many wires you can put in a hole or conduit. I have jobs where many wire circuits were run along rim joists along with heating pipes and potable water pipes with zone valve and control valves. Completely buried in Icynene. And it is toxic if you scrape the stuff off and try to heat it to solder.

    Then, the roof systems. Be sure that your rook has been replaced with Ice & Water membrane. The "Experts" all think this is a wonderful way to stop leaks. The moisture inside the envelope can not get through and the wood covering rots below the wrap. I have already seen rotten valley bottoms. There happens to be anaerobic bacteria in wood. They thrive in a no oxygen environment.

    There's no free lunch. I've been seeing 200 YO houses with the only rot being from failed flashing's around corners, windows and doors. Suddenly have accelerated rot all over the structures.

    The laws of unintended consequences? That no good deed goes unpunished?
  • GordyGordy Member Posts: 7,122

    I wonder how many new structures with the latest, and greatest energy conservation methods will make it 200 years.

    I'm all for conservation, but I think we are sacrificing longevity of a structure in the process.

    Moisture is the culprit, and the less air circulation inside cavities the longer moisture stays intact.

    We seal newly built structures like a zip lock Baggie, and you know as we'll as I the moisture content in fresh building materials is high. Lumber moisture content now verses even 60 years ago is quite different especially during the housing bubble.

    Houses that used fiberglass insulation in wall cavities verses the foam insulation I think will fair better long term. All though fiberglass is not as great an insulator.

    As far as shingle longevity. You'll will never get a straight answer out of a shingle manufacturer what the ideal temp for the longest shingle life will be. They will tell you it should be ventilated, and how much ventilation per sf but as far as attic temps from the inside its a mystery for a,reason. When it comes to failure there is a lot of outs for them when it comes to the warranty.
  • Long term questions...

    Gordy brought up some of the concerns I would have too.  One of the greatest minds from the IIT School of Architecture (my Alma mater) would bring up similiar concerns....what happens when you need to fix something?  Foam insulation bonds the wall sheathing, drywall and framing together.  This will make it very difficult to make repairs from the effects of a roof leak, for instance.  What happens when you need to run some new cable for some new communications systems that we have never seen before?  The walls are do you make any changes as technologies change? 

    It is great that ice does not absorb water, but all the materials it partially envelops does.  How do you account for moisture movement in these other materials?  

    Also, what happens when there is a fire.  15 minute fire separations are great, but typically if ductwork is installed, that 15 minute separation is not there in many areas.  Off gassing during a fire to me is a big concern.  And what happens after that 15 minutes?  Did everyone wake up and get out and can the structure still be saved before it is completely engulfed?   I don't know.

    In a perfect world, a properly designed system using ice would be fine under typical conditions,  but that is not the world we live in.  Storms hit, damage occurs, the structure goes through periods of poor maintenance,  economies go south so there is not money to make repairs immediately.   When you consider how far you can bring a structure using materials that are easily repairable (ie.  High density Fiberglass batts or high density  fiberglass blow in) and then add airtight drywall techniques to keep air leakage from the interior of the structure into the wall under control, how much gain are you going to see? 

    In my current old home, I went with Johns Mansville  high density spider wool ( a relatively unknown  non flammable product) blown into the walls and I will be using air tight methods for the interior surfaces along with vapor barrier paint. In my previous home, where the walls were gutted out, I used very well fitted r-19 or r-21 batts and airtight drywall techniques and plastic film vapor barriers.   Despite using  the original 1906 windows with upgraded weather stripping , that 3200 sq ft home with 800 sq ft of windows and doors only cost about $700.00 per year to heat in a cold northern Illinois climate ( gas hot water radiators).  How much gain is left for other techniques to make/
    The Steam Whisperer (Formerly Boilerpro)

    Chicago's Steam Heating Expert

    Noisy Radiators are a Cry for Help
  • GordyGordy Member Posts: 7,122
    edited May 2013
    Steam Whisperer

    Totally agree with all points you made. With a foamed backside of a roof deck how would you even know you had a leak. Let alone trace a leak to the point of origin which is hard enough with an exposed roof deck.

     We tighten everything up, then install an ERV,or HRV to ventilate which uses energy that would never have been needed in the first place.

    We invent make problems. then invent to solve those problems.Tthe circle grows.

    Give me a house that breathes naturally, and im good. No need to make it float.

    Edit: like steam whisperer my gas bill for 2011 was 950.00 for 2100 + 1300 sf condition basement all radiant, all double hungs with storms in excellent condition taking up 40% of exterior walls. That bill includes stand alone DWH for 4 people, BBQ, and pool heater which on opening month used more gas than the coldest northern Illinois month that year with the house boiler being almost 100% bigger than the pool heater.

    Like ya said how much can you gain by spending 5-7 grand to fill walls, and roof deck with foam.
  • Jean-David BeyerJean-David Beyer Member Posts: 2,532
    what happens when you need to fix something? Foam insulation bonds

    I know what happens.

    My walls are full of urea-formaldehyde foam insulation.

    When I had my kitchen remodelled, I wanted to move the sink from one wall to another (among other things), and wanted much better electric wiring (moved electric stove too). The walls were all real plaster. They had to gut the kitchen to get all that insulation out, so they could run water, drain, and wiring. They replaced the foam in that room with fiberglass that is clearly not as effective.

    That is what happens.
  • jumperjumper Member Posts: 997
    sealed cavities ?

    Is unventilated space ever acceptable ? How about if the space contains nothing that can rot ? My opinion is that you can go too far for energy efficiency. My ideal is that every cavity should breath and drain.

    You can also consider in between measures. For example you can insulate somewhat top floor ceiling, insulate somewhat roof, and then ventilate attic a little bit with a roof vent but no soffit vents.
  • I Would Wrap The House With Foam

    On the outside, under the siding, you would have an full thermal break, for less cost and non of the problems of spray foam.

    Thanks, Bob Gagnon LEED AP
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • jumperjumper Member Posts: 997
    is it worth it ?

    Doesn't siding retard heat loss so much that foam provides diminishing return ?
  • What Do You Mean?

    A properly taped foam barrier will provide an excellent infiltration barrier and an complete thermal break against conduction, with no framing lumber conducting heat to the outside like blown in foam will. With a good infiltration barrier, fiberglass or cellulose will work great inside, because no air is blowing through it.

    Thanks, Bob Gagnon
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • Potential Problems with foam on outside.

    Big concern with foam on outside.  If it is taped AND SEALED AT ALL EDGES IT it will make a great air infiltration barrier.  However, it is also a very effective vapor barrier.  Moisture migrates from the interior to the exterior of a wall in typical northern winters.  As the temperature drops in the building materials as you move from the inside to outside at some point you will reach the dewpoint..... this is where moisture will condense in the wall.  Now if the wall is very tightly sealed on the outside, the moisture has no place to ventilate and rot will occur if this dewpoint is on the inside face of the foam insulation.  A thorough check of the temperature gradient of the wall needs to be  made.  However, even if it checks out that the dewpoint will fall within the foam, what happens when things begin to age and air leaks begin to develop in the outside surface?   The dewpoint will move inward in the wall  and maybe right into the studs and fiberglass between the studs.  Also, if water enters the wall from a roofleak in the winter (icedams for instance or frozen up gutters) there is no way for it to ventilate outside.  It may ventilate inside if the interior face of the wall if it is leaky enough, but then if the interior face of the wall is that leaky, the effectiveness of the fiberglass insulation is diminished due to conductive air currents and infiltration from the interior.  

    If you use foam as part of a frame wall assembly, I'd put it on the inside and seal the drywall or foam very tight so it acts as an infiltration barrier and vapor barrier, use well fitted high density batts ( R-15 for 2x4 or R-21 for 2x6) in the stud bays and then sheath with plywood sheathing ( do not seal the joints, as plywood acts as a vapor barrier)   and wrap the house with a breathable house wrap tightly sealed at the edges that allows moisture to leave the walls, but prevents air infiltration into the fiberglass.  However, now, you have a very flammable material (the foam)that probably off gasses really bad in a fire and this always makes me nervous. 

    You can build the same wall without the foam and simply strap the wall with 2x2 to break the thermal bridge of the studs very effectively.  In addition, this chaseway makes it very easy to wire and plumb the home and the fiberglass is easier to install and will the more effective because it will require very little cutting and fitting around obstructions.  Just make sure to seal the edges of this airspace so air cannot enter.  I always caulk the strapping  and drywall edges as they are installed to prevent mass air movement in the walls.  This is simply the airtight drywall techinique the Canadians began using in the 80's for their buildings.   It is the same technique I used on my previous 1906 home (less the strapping) when renovating it and our fuel bills where exceptionally low.

    Also don't let anyone convience you that foam sheathing with plywood or OSB sheathing at the corners for bracing is all you need under the siding.  When that big storm or tornado rolls through, that foam sheathing will provide almost no protection from objects going through the wall.    Also, it provides almost no security from break ins.  It is much easier to just go right through an exterior wall to enter a new home built this way than through any exterior door.  A few good strong kicks will break through most sidings, the wall, fiberglass and interior drywall.
    The Steam Whisperer (Formerly Boilerpro)

    Chicago's Steam Heating Expert

    Noisy Radiators are a Cry for Help
  • GordyGordy Member Posts: 7,122
    Steam whisperer

    That's how I built my first house only I used full 2x4's horizontal at 2' centers. So the detail went as follows from inside out.

    1/2" drywall.

    2x4 strapping horizontal at 2' centers.

    Visquine vapor barrier.

    6" fiberglass insulation. 2x6 studs.

    1" tuff r celotex.

    House wrap

    5/8" t- 111 siding.

    Very tight wall high r value, and almost no vapor transmission.

    Totally agree with what your saying.
  • Robert_HRobert_H Member Posts: 135
    I need a clearification

    Just to be sure what you are saying, Steam Whisperer and Gordy, I want to make sure I understand what you mean by strapping in this context. for example by 2x4 strapping do you mean wood 2x4s fastened to the 2x6 studs so that there is an 3.5" air gap between the vapor barrier and the drywall?

    sorry if I'm dragging this off topic but the discussion is informative and compelling.

  • GordyGordy Member Posts: 7,122
    Wall detail

    The 2x4's are nailed flat against the 2x6 studs.

    Your layout would be floor level then 2', 4', 6',, and 8'. Unless its a taller wall then keep going.

    This works out well for drywall. If your worried 2' is to much for drywall then either go 16" centers with the 2x4's , or go with 5/8" drywall. Never seemed to be a problem with spanning 2'.

    Like steam whisperer said it makes electrical a breeze to run, and some plumbing.

    Foil backed drywall was another option, as a vapor barrier back then. I opted for visquine.
  • Robert_HRobert_H Member Posts: 135
    Thanks Gordy

    that makes sense.
  • SWEISWEI Member Posts: 7,356
    Staggered studs

    Offset 2x4 studs on 2x6 or 2x8 plates.  Popular with post-production facilities and wealthy residential customers back in the '80s.  Dense pack with cellulose and life is good.  Easy to run P&E too.
  • NRT_RobNRT_Rob Member Posts: 1,009
    what I've seen and read say

    1- never use an open cell foam product in a roof assembly unless it's a layer inside a layer of closed cell. too much of a chance of moisture intrustion and then you've got a huge moisture battery in your roof assembly. I've seen people really regret that decision.

    2- always vent your cladding. this prevents any drying issues to anything important. Any time you are sealing well and using foam, vent the cladding.

    3- never put more than one vapor barrier in. but where it is doesn't matter at all as long as the assembly can dry to one side.

    4- insulation on the outside is better than on the inside. as Mr. Joe says, warm wood is happy wood. I have a shed outside my home right now, completely unheated, wood open to air on both sides. guess what? the wood rots anyway when it's near splashes and the ground. so control your water and worry a lot less about your vapor and dewpoints.

    5- you can't "naturally breath" a house to good air quality. all you can do with "natural breath" is waste energy, reduce moisture related problems, and open up large vectors for moisture intrusion and rot. Seal it tight, vent it right... we learned this 40 years ago.

    6- if you're still using fiberglass batts without an exterior foam layer, you're doing it wrong. Batts are poor quality insulation.

    7- polyiso offgasses and loses R value as it gets colder. dont' waste the money. use EPS for rigid foam. it's greener too.

    8- thermal bridging is serious business and so continuous rigid foam is better than cavity foam in almost all cases.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • GordyGordy Member Posts: 7,122
    And Rob

    What we consider right today in 40 years or less will be wrong.

    I see a lot of old houses 100 plus years old still standing . If there was any moisture issues causing wood to rot it was from lack of maintaining the property, or a drainage problem.

    My home is 60 years old no mold no rot, and it does not have a high tech wall assembly.

    I see homes with not ten years on them with moisture related issues.

    Sometimes we think we solve problems only to create other problems, and then come up with solutions to solve the secondary problems created, and think we have really achieved something.

    We are not wasting energy by using HRV , or an ERV to control how we ventilate a tight home? Not that an HRV is a huge energy consumer, but what about the manufacturing process to make them? Again another invention to solve an issue created by trying to solve another issue, and that's reduce a homes energy consumption.

    I do,agree fiberglass is a poor insulator, but look at all of it out there in homes, and still being put in homes.

    Sure we have learned a lot over the years, and there are lots of ways to do envelopes high tech low energy, but they also cost a lot of money up front to achieve. ROI is just not there unless its a dweller for a long time.

    Lets take windows for instance I have double hung single pane with well fitting storms. They all work fine and actually as good as new. To replace them with a triple glazed argon filled unit would cost 36000.00 with a top of the line window manufacturer that's me installing them. I can tell you that they won't perform that good to get a ROI in an except able time frame. Sure it saves me switching storms for screens every year.
  • NRT_RobNRT_Rob Member Posts: 1,009

    HRV/ERVs do more than one thing. They reduce energy loss, that's true. and that's important. they can eliminate bath fans, which is a nice way to offset some of their cost and improve the economics of their usage. but they also can filter incoming air, which is a very nice benefit, and most importantly, they ensure good air quality to all areas you duct them too... at least as good as filtered outside air.

    no leaky building can say the same. just because air leaks in... somewhere, under some conditions, at some speed, through a dirty wall cavity or floor cavity or whatever... that does not mean you have consistent or predictable good quality air. All you can say is that in climates where outside air is dry that you've mitigated some potential for moisture problems. but leakage where you don't want it can pose greater moisture risks in many cases than you solve. Exfiltrating 2nd floor air in the winter, for example... bad news. it's warm and moist. it crosses a dew point. consistently and for a long time, right there in the wall cavity. you carry WAY more moisture in the air than you do through simple vapor transmission through any material...

    tight homes can screw up their building science too, and have rot and mold... absolutely. You still have to get it right. but almost everything I posted above is straight from and Joe knows his stuff pretty well. Certainly we know better than to build leaky homes in a high cost energy environment (i.e., the world, these days). And if you actually care about health, controlled fresh air delivery cannot be beat.

    Fiberglass is poor. so why use it? cellulose is much better. cellulose with exterior rigid foam is a whole 'nother league. and not much more money. economics are excellent there.

    Window upgrades are a separate issue, sure. double pane low-e is still pretty good. right now there aren't many economical triple pane options that make trading up worthwhile unless you have big glass near sedentary space and you want the comfort improvement. but there are some lower cost triple panes out there from what I've seen... are they any good? dunno. but at any rate just because building tight is the right thing to do, that doesn't mean that every possible energy upgrade you can do has good ROI... absolutely agreed on that.

    I have a shop with all exterior rigid foam walls (over zipwall) and a cellulose ceiling.. we stuck with double pane low-e windows as well. only made sense. wish I'd planned my southern overhangs better and knocked out some western glass. blah. live and learn.

    from a health, comfort, AND energy perspective all together though, ERVs do.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • RichRich Member Posts: 2,243
    A wall is a roof is a slab

    This has been working for a long time guys .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC 732-751-1560
    Serving most of New Jersey , Eastern Pa .
    Consultation , Design & Installation
    Rich McGrath 732-581-3833
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