Insulation

[Tinkee]

I hope this is the right place to post this question,

Im looking to reinsulate my attic. Right now there is some blown in insulation up there. My question is, should I take out the old blown in insulation and either respray/get new batting or should I spray/ put new batting on top of the old insulation? The insulation thats up there now looks to be fairly old but isnt in terrible condition, I just wanted it to be better insulated than it is now! Thanks for any advice

[pushkins]

You should be Ok to add the new insulation over the top. If there is already a vapor barrier installed (plastic between drywall and existing insulation) then buy NON faced insulation if your using rolls, otherwise blow in as much as you need over the top.
Make sure you don't block the air path from the soffits to the attic area.

[Tinkee]

been doing a little reading and have read some about baffles in the attic. Im pretty positive my attic doesnt have any baffles (but id have to get up there and look to be 100% sure). when I reinsulate should I buy baffles to put up there? If so... how do I need to install them (in every space or every other, etc.) and what exactly is the purpose of them?

And lastly! Should I need to install them, do I put them in pre insulating or post insulating?

[pushkins]

The baffles go in PRE insulation, this makes your blowing in of insulation very easy as it keeps the air pathway open while your blowing it in. There are two main points to baffle installation and both are very important.

1. They keep the air way path from soffits to roof vents open and clear of obstructions, allowing a good and constant flow of air into the attic space. This airflow is very important to help preserve your shingle life and control moisture amounts in the attic itself. Also helps dramatically reduce cooling costs in summer by allowing the hot air to exit the attic.

2. They keep the insulation from touching the underside of the roof deck where the roof deck comes down towards the outside walls of the house, this is not only important for the above reason but also it stops any insulation touching the underside of the roof deck and transferring any moisture into the insulation.

Ideally they should be installed into every rafter/truss space but at the very least they need to be installed wherever you see a soffit vent.

The old idea of insulation in the attic was to make it level with the ceiling joists, this was at best 7.5", most attic insulation should be 10-12" with cellulose blow in and 14-17" fiberglass blow in. The blow in bags will often have a chart to guide you.