wall batts or foam/spray in ?

Discussion in 'Alternative Energy' started by okiemom, Nov 3, 2006.

  1. okiemom

    okiemom Well-Known Member

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    I didn't want to highjack so...

    Our Arcitect is against 6" walls. Says we won't be able to recoup the loss.

    It will be brick stone on the outside everywhere to the roof ( no maintenance)

    The HVAC doing the geothermal/radient said go w/ 6" ( super insulate) but, will need even more equip. ( air handlers... ) so more $$$$. We are going to be in this house forever ( God willing) so some expense can be now instead of high bills later. A $60 electric bill instead of a $200 sounds good. Wood heat will also help, but don't want it for all the time.

    I know fuel will not go down. so We want to keep things green friendly.

    How do we pick when there are different views. no one agrees :doh: :doh:

    My husband and I talked about foam vs. batts. We like the foam but are worried about any electrical work in the future. Foam is a real pain to have to rewire

    will foam give more R value than the same of batts? foam won't break down or shirnk?

    How can we find out how much more 6" walls would be than say 4" Why can't they agree. We don't need to insulate from cold but form the heat.

    What to do. :help: :grump:
     
  2. ET1 SS

    ET1 SS zone 5 - riverfrontage Supporter

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    I just got this from

    http://hes.lbl.gov/hes/glossary_dat.html

    R-Values per inch

    Fiberglass bats : 2.6 if old and 3.2 if new

    rockwool bats : 3.1 and 3.6

    Cellulose [loose fill]: 3.2 and 3.5

    Foam-in-place Urethane : 6.0

    So 6 inch walls using fiberglass bats [at 3.2 per inch] could give you a theoretical max of R-19.2

    Using Spray foam [at 6.0 per inch] could give you a max of R-36.

    Just dont forget that using anythign else you still need a vapour barrier to seal against drafts and moisture.

    I have never heard of styrofoam shrinking [previous to here on this BBS], I have never seen a foam ice-chest shrink. the foam that I have sprayed has not shrank. but foam WILL break down if left in direct sunlight.

    good luck.
     

  3. WisJim

    WisJim Well-Known Member Supporter

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    Sounds like you may need an up-to-date architect--if he favors 4 inch walls over 6 inch walls, he is seriously 30 years behind the times.

    Six inches of insulation isn't super insulation, it is barely adequate insulation. You should need less heating etc equipment, or at least smaller, than if you used less insulation.
     
  4. SolarGary

    SolarGary Well-Known Member

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    Hi,

    6 inch walls with 24 inch stud spacing are not very much more expensive at all than 4 inch walls at 16 inch stud spacing. And, I'd agree with the comment that 6 inch walls are not at all super insulation -- its pretty much minimum in most parts of the country these days.

    The urethane foam is very good both in R value and in infilatration resistance, but also very expensive.

    The combination of the kind of cellulose that is blown in slightly wet from the inside coupled with insulated board for sheathing might be a good all around cost vs R value compromise. The insulated sheating board is important prevent the fairly large heat loss you get directly through the studs to the outside (called thermal bridging). With this type of insulation, the protection from air infiltration has to come from careful construction -- things like careful installation and taping of the house wrap.

    Some of the builders around here now use 6 inch walls, and spray about 2 inches of foam from the inside against the sheathing. They then fill the remaining part of the stud cavity with bats. The 2 inches of foam gives excellent protection against infiltration, and the 2 inches foam plus 3/5 inches of bat give a very respectable R value. Spraying only 2 inches of foam saves quite a bit of money.

    Gary
     
  5. ET1 SS

    ET1 SS zone 5 - riverfrontage Supporter

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    Also if your still in the desgin phase. You might consider a steel building. I have no studs, thus no stud spacing. My purlins are 8 inches wide. Thus my walls can be 8 inches thick. I can fill the entire walls with insulation and there is nothing in the way to form thermal-bridging and steal heat from my building.

    My 60foot by 40foot buildnig with 12foot eaves cost around $16k. [plus foundation, floor, and windows].

    :)
     
  6. Randy Rooster

    Randy Rooster Well-Known Member Supporter

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    Cellulose is only slightly more expensive than fiberglass batts. It however is much better at insulating because it much more effectively seals the wall space with a solid (sort of) mass. Around here all the quality builders are using blown in cellulose and it is what the power companies are pushing to drive down energy consumption.
     
  7. ET1 SS

    ET1 SS zone 5 - riverfrontage Supporter

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    Too bad that cellulose loose fill has such a low R-value,

    and it settles,

    and mice / snakes tunnel through it

    and it does burn [even if it has been treated to be less fire prolific, ti will still burn and must be thought of as a combustible material, unlike rockwool].

    But otherwise, it is considered by many to be a high quality insulation.
     
  8. Ross

    Ross Moderator Staff Member Supporter

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    6 inch walls are the minimum standard here, can't think of any 2x4 walls being built at all. Recoup what loss? The cost of building is reflected in the value of the house and you will recoup the building costs through energy savings if not at today's prices (your buildign costsd may be more than ours) then you will at tomorrows energy costs. I've always been an advocate of fibreglass but the foam ET1-SS is talking about is sure interesting!
     
  9. mondakkid

    mondakkid Well-Known Member

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    To Okiemom...Each type of insulation has its advantages. I do agree with the others, that a 6 in wall is the way to go. You should be able to down size both your heating and AC equipment. You will also be doing your part in conserving energy. I also consider the cost of production of the insulation...some types of insulation require a lot energy to mfg. I personally like spray on celloulose for the walls and the blow in type for the attic. I think it is a "Green" type of building material and do not have to worry about the fiberglass fibers in the air.
    Good luck on your building...mondakkid
     
  10. idahodave

    idahodave Well-Known Member

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    Energy savings derived from high R values is dependant on the inside/outside temperature difference. In cold weather areas 6" walls are a no-brainer. In warmer areas the payback might not be there.

    The thermal mass of the brick/stone covering should help isolate outdoor temperature swings.

    Ask your architect how much the 6" walls would increase cost. If he can't, find another.

    Rigid foam sheathing on the outside of 4" walls might be a compromise solution.

    Maybe the best energy savings for you dollar would be to take the additional cost of 6" walls and use it for solar hot water heating.

    Geo-thermal heat pump is a good choice.

    Have fun designing your new home.
     
  11. ET1 SS

    ET1 SS zone 5 - riverfrontage Supporter

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    When I was almost done, I finally discovered the 'secret' to spraying foam, and the technique DOUBLED the quantity of foam. I told the salesman about what I had discovered and he laughed, it is hinted at on the packaging and MSDS sheets. But they don't really want anyone to double the coverage, because then you would only buy half as much foam.

    Now that I know however, if I ever spray foam again, I will buy half as much.

    I began having problems with consistency and yield due to dropping temperatures. Then I decided to drop both bottles in our jacuzzi for half an hour before spraying. After soaking at 105 degrees, the resultant foam was much better yield.
     
  12. okiemom

    okiemom Well-Known Member

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    :help: I was looking at teh range of temp for the north to the south.
    is it more important to insulate for cold rather than heat?


    In the north the highs are in the 90's the lows are in the -25-35's for a range of 125deg

    In Ok the highs are 100-110 and the lows are 0-10 for a range of around 115degs

    Our range temps are not that different but you get cold and we get hot. Is heat easier to insulate against? our bills seem cheaper when we are cooling than heating??? more wind in the winter????

    I always thought is was the same which is why N. Mexico had thick adobe walls.

    I wonder if 4" of spray in would be good? It should make a R value of 24. better than batts at 13.

    I just can't find a true quantitative explanation of what is better.

    Great tip on soaking the foam bottles. just don't forget and have exploded bottles?! I could do something like that. :cool:
     
  13. SolarGary

    SolarGary Well-Known Member

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    Hi,
    I tried to get some of my 2 year old cellulose to burn with a propane torch. You get just a little flame for a few seconds right at the spot the torch hits, and then it goes out. You can hold the propane torch there more less indefinitely It does not spread at all -- it actually appears to protect any flamable material under the cellulose from getting hot enough to ignite. It appears to me that its considerally less combustible than the rest of the stuff my house is bulit from (like wood).
    How does the foam insulation behave under this treatment?


    Not sure what you mean by lower R value in loose fill -- its much better than fiberglass:
    http://coloradoenergy.org/procorner/stuff/r-values.htm
    R 3.1 per inch for cellulose and R 2.2 per inch for fiberglass. And, it does not loose its effectiveness under cold conditions as fiberglass does:
    http://www.homeenergy.org/archive/hem.dis.anl.gov/eehem/92/920510.html

    Its listed as R3.7 per inch for walls, which, while not as good as polyurethane foam, is quite respectable considering its low cost. It will not settle in walls at all if installed at the right density.

    I've heard the mice tunnels story for fiberglass, cellulose and foam, but I've never actually seen this -- has anyone else?

    Gary
     
  14. ET1 SS

    ET1 SS zone 5 - riverfrontage Supporter

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    Under direct flame form a torch, it will melt and drip.

    Which is not nearly as good as rockwool.

    It does need to be protected from flames just the same as cellulose does. building codes requires that it be covered with something that is fire-rated.



    I have heard both.

    Salesmen saying that cellulose does not settle, and other folks saying it does.

    I tend to believe the D.O.E. who says that it does settle as much as 10% leaving an air gap at the top of each cavity.



    I have only 'seen' it in cellulose.

    Which is not to say that it would not happen in fiberglass or foam.

    My understanding is that only rockwool really stops the mice, is they can not digest it.
     
  15. idahodave

    idahodave Well-Known Member

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    Insulation doesn't know if it's keeping heat in or out. The R value is a measure of how easy (or hard) it is for heat to move through it.

    Looking at the temperature span is the right idea, but you need to think of the span above and below 70 degrees. Hot days may have a 30 degree (70 inside and 100 outside) difference, while cold nights in the north may have a 100 degree (inside 70 and outside -30) difference. The big difference in winter is why houses in the north need high R value insulation.

    Adobe houses are built in areas that have a wide day/night temperature swing. During the day they absorb heat and are slow to warm up. During the evening stored heat keeps the house warm. The thermal mass of the brick/stone will help your new house moderate outdoor temperature swings.
     
  16. fantasymaker

    fantasymaker Well-Known Member

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    LOL how longs it going to take ya to be 300 bucks ahead?Do the math to bild a 2x4 wall a 2x6 wall and a double 2x4 wall on a 40x80 foot house the aditional cost is about $300 to build double wall over single and likely cheaper than 2x6!
    If you want a really well sealed house build the outside wall and then spray some foam on it you will get an amazingly well sealed wall then add more insulation If you use fiber glass or sheet type that you can attach to theoutside wall yo then have a freestanding inside wall that can be so handy it might save more in electrical and plumbing instalation cost than the 300 bucks cost for double wall!
     
  17. gccrook

    gccrook Well-Known Member

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    We had some mice tunnels in our fiberglass batt we removed in the process of adding on to our house. Pretty impressive how nice and perfect they were.
     
  18. mondakkid

    mondakkid Well-Known Member

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    To add one more comment. When you blow cellulose in a attic. It will settle some in time. That is just the law of gravity. When a contractor blows cellulose in your wall. If it is done properly, it should not settle. It is done under pressure and the end result is cellulose with a higher density than in an attic. I used to insulate houses years ago for extra income and did run across houses that were done with the "One hole" system and the cellulose did settle some when it was done that way. The "Two hole" system is a much better way of doing it and should not settle. I will be moving to the Kingman, Az area next year and hope to barter for doing spray/blow insulation jobs for people.
     
  19. kermeg

    kermeg Active Member

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    I just put in cocoon cellulose blowin from Lowes in our back grandma house and its great. Had a few bags left for the main house and put it on one end. What a huge change. That end stays 2 to 4 degrees warmer with just the heat given off from the kitchen. With the wood stove going its now very hot. The stuff is easy to blow in and lowes will loan the blower for 24 hours if you buy twenty bags. I will install more of the cellulose this week. I have been monitoring the temps of my house for over a year in prep. for doing this. so I am sure of my data. Great stuff!
     
  20. offGridNorthern

    offGridNorthern Well-Known Member

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    I would start by getting a new architect :)

    We have 6" walls but then the difference is that we are insulating against the cold (e.g. minus 40)

    What does your builder say?