I started a new tread because the last one became carried away...
First you should consider insluation as a "Home System" and not just a part of the home.
When we built our home last year I did a lot of research on RB. I have resources that cover the insluation industry and the government. we were going to use foam inslulation but in my area for what I wanted that was a budget buster. we decided on Foil/Foam/foil (FfmF) Rd because of the added R value of 14.5. When I ran the loads I only put the added R value in the outside walls because I didn't fully beleive I would get the full value for the attic insluation. I only added RB to the attic load.
Our design was the power company requirments of R-13 in the outside walls and R-30 in the Attic (the AHU was to be in a closet and the ductwork in the attic). the FfmF was put on the outside of the home just before the bricks, the air gap was between the RB and the brick and up into the soffet. In this area we have weep slots every x # of bricks which ties into the "ventilation" of the space. (See thumbnail 1)
The RB was stapled to the bottom of the rafters (see thumbnail 2). This left an air space between the bottom of the rafter and the roof decking. We installed a continous roof vent along the top ridge to vent the upper end of this space. the other end of the roof rafter was opened to the soffet area which was covered with cont. perf. vynal for the indroduction of cooler air to the space.
We used the styrofoam fillers (I don't know what they are called) in every rafter space to keep the batted insluation from closing or reducing this space.
Our crew did a very good job of sealing the overlaping joints of the RB (as you can see in thumbnail 3 ) and the very top of the attic was tented for a collection space before the air existed thru the roof vent. after the attic insluation was installed this made an insluation/RB seal acroos the entire attic something like you would have with a foam insluation home (see last thumbnail). Most of the construction of the home was during the hottest part of our swamp like summer. Very high humidity and 90~95+ days give you a full body sweat!
Every trad that worked on the home was amazed by the temp. difference it made. We installed a 3 ton 2 speed HP with dehum control with just under 2000 sq. ft. living. After we moved in I locked high speed out and have only been cooling and heating with low speed (aprox. 21,000 btu). Our power bills have only broken $100.00 once and are usually around $70.00. Our first year test was with NO ventalation in the attic. The attic stays only slightly warmer than the outside in the middle of the day.
We did spend more on insluation than the normal home, but not as much as foam insluation. Was it worth it YES! None of the homes in our area have power bills as low as ours. And this will only get better as time and power cost go up!
Buy the way, I have a friend who is a roofing dist. He contacted the factorys and they claim this will have no affect on shingles. As long as you buy their better grade.
First you should consider insluation as a "Home System" and not just a part of the home.
When we built our home last year I did a lot of research on RB. I have resources that cover the insluation industry and the government. we were going to use foam inslulation but in my area for what I wanted that was a budget buster. we decided on Foil/Foam/foil (FfmF) Rd because of the added R value of 14.5. When I ran the loads I only put the added R value in the outside walls because I didn't fully beleive I would get the full value for the attic insluation. I only added RB to the attic load.
Our design was the power company requirments of R-13 in the outside walls and R-30 in the Attic (the AHU was to be in a closet and the ductwork in the attic). the FfmF was put on the outside of the home just before the bricks, the air gap was between the RB and the brick and up into the soffet. In this area we have weep slots every x # of bricks which ties into the "ventilation" of the space. (See thumbnail 1)
The RB was stapled to the bottom of the rafters (see thumbnail 2). This left an air space between the bottom of the rafter and the roof decking. We installed a continous roof vent along the top ridge to vent the upper end of this space. the other end of the roof rafter was opened to the soffet area which was covered with cont. perf. vynal for the indroduction of cooler air to the space.
We used the styrofoam fillers (I don't know what they are called) in every rafter space to keep the batted insluation from closing or reducing this space.
Our crew did a very good job of sealing the overlaping joints of the RB (as you can see in thumbnail 3
) and the very top of the attic was tented for a collection space before the air existed thru the roof vent. after the attic insluation was installed this made an insluation/RB seal acroos the entire attic something like you would have with a foam insluation home (see last thumbnail). Most of the construction of the home was during the hottest part of our swamp like summer. Very high humidity and 90~95+ days give you a full body sweat!Every trad that worked on the home was amazed by the temp. difference it made. We installed a 3 ton 2 speed HP with dehum control with just under 2000 sq. ft. living. After we moved in I locked high speed out and have only been cooling and heating with low speed (aprox. 21,000 btu). Our power bills have only broken $100.00 once and are usually around $70.00. Our first year test was with NO ventalation in the attic. The attic stays only slightly warmer than the outside in the middle of the day.
We did spend more on insluation than the normal home, but not as much as foam insluation. Was it worth it YES! None of the homes in our area have power bills as low as ours. And this will only get better as time and power cost go up!
Buy the way, I have a friend who is a roofing dist. He contacted the factorys and they claim this will have no affect on shingles. As long as you buy their better grade.
