Can I put a layer of insulation over the old layer in my attic? What R value should I use?

Answer 1

Yes you can! r 30 is what you want. r12 is probably what you have. I would compare the price of doing it yourself to having it blown in. I have always found it about the same, but, a lot easier to let them do it.

Answer 2

The existing insulation should have the vapor barrier (either coated paper or plastic sheeting) against the ceiling.

You can add additional fiberglass insulation as long as there is no vapor barrier attached. Either remove the paper backing or buy insulation that is "unfaced". If the new insulation has a vapor barrier and there is a breech in the existing vapor barrier (or no vapor barrier at all), you can trap moisture from the living space in the old insulation. Not good.

Blown in insulation may also be added. Blown in cellulose will diminish the effectiveness of existing bat fiberglass due to compression from the added weight. Over existing blown in cellulose it is fine. Either fiberglass batts or blown fiberglass may be added to cellulose or fiberglass without problems.

R-value depends upon what you want to spend. Higher R-value will save more on heating and cooling, but is of course more expensive.

One last note, your attic needs to be properly ventilated. If you have existing soffitt (eave) vents, be careful not to block the flow of air. Use cardboard or foam baffles if it may be an issue.

Answer 3

Just get the rolls of insulation and roll them across the rafters. There is specific insulation for what you want to do and it's all been explained here. Don't blow in more stuff to settle. Go to your Home Depot and find a knowledgeable person. Tell them what you have and ask what they suggest. Then go to another store and do the same thing. If you get the same answer, buy at the store with the better price. If you don't, go to a few more stores. It depends on where you live, what you want to pay, etc. You can't go wrong with lots of insulation. It pays for itself in the longrun.

Answer 4

If you have knob and tube wiring in the attic, it doesn't create any type of fire hazard. Insuallation is non conductive and will not cause any problems. People have done it for years.

The only hazard this might create is causing the wire be unvisable to someone working in the attic.

Answer 5

I would not hesitate to put fibreglass batts over existing insulation,this coz I went out with a guy who installed insulation and did this many times..♥

Answer 6

Absolutely - you want to end up with about 12" total. You can have more blown in right over the old stuff.

Answer 7

If you have knob and tube wiring in the attic, covering it creates a fire hazard,