Insulation thickness

C

Chadwick

New member
I'm putting home depot type batting insulation in an existing single 2x4 constructed wall. What thickness should I use? R-13 has a thickness of 3.5 inches. What effect would cramming thicker batting like r19 or r30 (10 inches thick) have on the STC?

I'm also removing the existing windows in the room and was going to add a wall a/c unit and add some sealed doors over to help isolate when not in use. Should I go that route or should I use one of those portable units that exhausts through a 4 inch hose? I think the second way would be harder to isolate when not in use than the wall unit.

Thanks,
Chad
 
Use the R-13 insulation. If you pack R-19 into a 3.5 inch wall you will actually lose about half of the insulating effort of the R-19. In squashing the insulation you will be making the insulation more dense and less effective for heating, cooling, and sound.

cottonmouth
 
Everest's Handbook says almost nothing is gained with denser fibreglass between walls. Make sure the batts are stuffed, but not overstuffed. I mean, have them about 3/4-1/2" thicker than the space required.


Herwig
 
Thanks for your help. Great news! This will be the first time since I started dumping money on gear and materials I've been told less is better.

Chad
 
Thanks John. I'm assuming this is a wall with an appox. 3.5 inch cavity. 75mm of insulation would fill it perfectly and 50mm would leave an air space. I wonder what the effect of 150 mm compressed would be.

Chad
 
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