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  1. #1
    Join Date
    Oct 2007
    Posts
    5

    Default How to optimize insulation investment - Fiberglass vs Foam

    This may be a bit theoretical, but I am trying to figure out if the additional cost of foam board insulation and higher R value compared to fiberglass is economical and provides a good return on investment over time, ie by figuring savings in heating cost into the equation.

    here the facts:

    - I am looking to put new insulation into my attic roof
    - The attice room will be used as liveable space
    - I live in zone 1 as defined by the DOE - recommending R49
    - 1 sq foot of R38 in fiberglass cost about 80 cents (before tax)
    - the same insulation using foam Boards is about 3$
    - the total roof is about 600 Square foot

    here is the situation - if I have enough depth in my rafters I would go for fiberglass as it is more economical, however my rafters are only 6 inch deep to the roof

    so I am trying to figure out, if I spend more money on the more expensive foam boards, I can achieve an higher R value and insulation, which over the years should save on my heating bill

    How can I calculate the savings I will get with each R I increase, ie how much heating bill savings can I expect when I increase insulation by 1 R (assuming the formular is linear, I can calculate my return on investment for different thickness of foam baord as options)

    hope this makes sense, I am sure this is not an exact science, but I am looking for some rough estimates to help me with the decisions....

    thanks, Chris
    Last edited by walenta; 10-24-2007 at 09:14 PM. Reason: change notification type

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