Inserting the Insulation Into the Roof Ceiling

We are inserting the salvaged poly iso insulation board into the top floor ceiling of the house between the joists. All the joists have been sistered with “new” salvaged joists. You can see the bolts holding them together. We are packing four layers of poly iso board, making it an air tight R 36. The roof insulation is obviously the most important in terms of insulation so we are making it very well insulated.

Below the insulation will be a radiant barrier of aluminum foil that will reflect back the heat into the building. On top of the roof will be two inches of waterproof extruded polystyrene insulation board and then the earth for the green roof.

After all this, the roof will be very well insulated, probably close to R 50. Since the Poly ISO is salvaged from another job it is very cheap so we are using as much as we can possibly fit into the space. It is the same Poly ISO we are selling on the main page.

inserting polyiso insulation into the ceiling

Above: inserting polyiso insulation into the ceiling

Below: you can see the poly iso has all been inserted. You can also see the joists. On some we have added two more, making three sistered joists in some places. These joists are each 3x8 inches thick. We did this to make the roof as strong as possible to carry the green roof. It should last another 100 years.

About the author: Gennaro Brooks-Church

2 comments to “Inserting the Insulation Into the Roof Ceiling”

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  1. Gennaro Brooks-Church - December 19, 2008 at 9:11 pm

    Hmmm….It also depends where you are since that will determine your shipping price.

    Unlike my situation, space is not an issue for you. I need to get the absolute most R value per inch because I have to go between the joists.

    Another option you have is to use blown in cellulose. I like cellulose but it only works when you have space. It is more green than foam since foam uses petrochemicals and cellulose is just old paper. Combine that with a vapor barrier and you have a nice airtight setup.

    But that is just another option if you are not close to Brooklyn. If you are near then using my panels with a radiant/vapor barrier makes a lot of sense. You get the same airtightness as spray foam but a lot more R value per inch and a lot greener setup.

    I’ll send you an email.

  2. vinnie - December 19, 2008 at 6:58 pm

    I have been giving this avenue alot of thought. I have a 10/12 pitch attic truss roof to insulate. If I go with the ceiling insulation I plan a 2-3 inch spray foam and 12 unfaced fiberglass It gives about a real r50 but much more effective. However If I were to insulate under the actual roof deck I only have an 2×8 in member and am unsure as to airflow and deck temp issues. I have a ridge vent so there will be appropriate flow if i insulate the ceiling but If I were to follow your example I believe I would need a more airtight gap in order to replicate the spray in foams tightness and insulation value. In order to use your foam I would have to use a combination I think of both spray in and placing your panels inbetween as well as on top of the members to get the desired r value. Obviously I will not be getting a straight answer from the foam salesman. Any Ideas?
    the ceiling surface is about 35×55 whereas the ceiling deck is in total about 55×55 (both sides) If it could be figured out I could put a major dent in your foam stockpile.

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