During the process of having an energy survey performed on our public library, we discovered that many sections of fiberglass insulation had fallen from where they had been installed. This resulted in open spaces from the plenum (the heating and air conditioning system return is the 3 foot high plenum of air between the drop ceiling and the insulation that spans the length of the building - I know it's not an efficient design, but's it's what currently exists) up into the attic area. Needless to say, we were pulling in extra, outside, hot air in the summer to cool, and extra, cold, outside air in the winter to heat. [I also discovered that it wasn't until 1998 that louvers were even installed in the gables. Condensation problems cuased several problems, one was that sections of insulation batts got heavy and fell. Having thermostatically-controlled motorized vents seems to have helped dramatically.]
We have received bids from insulation companies, but are trying to determine which is the BEST proposal. First, we DO plan to have our HVAC company run return ducts from the 7 air return vents to the air handler. This job will be completed AFTER the insulation situation is resolved.
Once all fallen insulation is secured, we need to decide A)how the insulation should be supported so that it does not fall again, and B)if and how we should increase the R value.
Insulation support method #1: Run 2 or 3 strands of wire under each section of batting, by attaching wire to the joists.
method #2: Run Kraft vapor barrier (reinforced "paper") under insulation batts, stapling it to the joists.
If we decide it would be worthwhile to increase the R value from 30 to 38, how would we accomplish that? One company required using method #2 with the vapor barrier, to keep any of the additional 4 inches of insulation that they would blow in on top of the existing insulation from filtering on through any air gaps.
Lastly, if we add additional insulation, is cellulose the way to go?
Cost is always a consideration, but any steps we take will be reflected in lowered energy bills (gas and electric.) I want to make the BEST recommendation possible to the Board of Trustees, who must OK any expense this large.
Thank you in advance for your comments and suggestions.