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Question DetailsAsked on 5/3/2013

Do I have to take old insulation out of the attic before adding new

House build around 1960 - 63; Original insulation looks like little cotton balls. The old insulation is very compressed or has decomposed. It use to fill the space between the boards and now there is very little. We are losing a lot of heat in the winter through the attic.
Do we put a moisture barrier over the insulation when we have finished the install? What is the best way to do this project?

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3 Answers

Voted Best Answer

A moisture barrier has to be on the warm side ie towards the heated side. Most people would not install a moisture barrier in your situation. (They also sell a paint that you can use on your interior ceiling? as a moisture barrier). Rather most homeowners would hire an insulation contractor to blow a cap over the existing insulation bringing it up to your areas reccomended levels,,Your power company can tell you the level, I would guess R 40. What you use is up to your wallet, the best is a spray foam that can be applied to the ceiling or over the whole shebang. Being a bit of a miser I would trot on down to my local big box store and buy a truckload of cellulose and get a free blower for I and a friend to self insulte. Big box= Menards, Lowes etc. Cellulose= ground up paper treated with boron for insect control and fireproofing. It has a high R value and will stop moving air loss from the home. Before you cap current mostly emply attic is ideal time to take sealant to any openings in the attic floor, like pocket doors, canister lights electircal wires and close off the air leaks from inside. If foaming skip this. Hot air rises so you save yourself a ton air sealing the home.

An attic radiant barrier is also a possiblity see my blog for nifty results on it.

Jim Casper Old Energy Conservation Guru

ps moving existing insulation use a plastic rake


Answered 7 years ago by jccasper


The old insulation can be fluffed a bit with a leaf rake, which will help. Unless you have rodent droppings or mold in the existing insulation you can leave it in place. Be careful no matter what you do in the attic. Your home was built before the ban on asbestos so unless you get the insulation tested assume it is in there. Wear a good respirator and body suit. Make sure it can't travel down into your home (which is nearly impossible to stop). I recommend getting it tested. If asbestos is found have it professionally removed by a company licensed to deal with asbestos. As for new insulation the last answer was spot on for blowing in new insulation. The box stores will loan you a blower free for 24 hours if you buy at least 30 bags of insulation. I generally blow in about 40 per 1000 square feet when adding insulation to an attic. The higher the R-value the better. Even if code only dictates R23 go up to 30 or even 40. You really don't need to go higher than that. You likely won't recoup the extra cost in energy savings at that point and the extra weight in your attic may start to cause problems and will compress the lower layers faster. The spray faom at all wiring penetrations in the walls and any other holes for duct work, etc. is a huge help as well as a slow-down for the spread of fire in the event you ever have one.

Your power company might have rebates for installing new insulation but it usually has to be done by an approved company. If the rebate is high enough it may be worth it to pay someone and get the rebate. This way you have the added bonus of not getting the insulation all over you.

Todd Shell

Todd's Home Services

San Antonio, TX

Answered 7 years ago by Todd's Home Services


Original insulation might actually be cottom balls or shredded cotton clothing - that was used from 40's into early 60's, particularly in the south and southeast states. A fair insulator, but susceptible to attracting moisture, and of course will rot. I would not consider reusing it.

You do NOT want to insulate without first seeing to moisture control - if you throw a bunch of insulation over the drywall that forms the "floor" of your attic without first putting in a vapor barrier, you will end up condensing the moist house air that is going into the attic (and currently venting into the attic) within the insulation layer, ending up with a soggy insulation mess and eventually leading to rotting roof joists or trusses. This is very important and most people (and contractors) don't think of it or know about it - they tend to think more insulation is better.

However, with your very poor insulation now the inside air passes through the thin insulation and keeps it warm, so it is still above freezing and holding most of its moisture when it vents into the attic space. This moisture will partially vent away in a well-ventilated attic, but generally results in a frost coating on the underside of the roof sheathing and on top of the insulation, but not significantly within the insulation. Put in thick insulation without stopping the moist air flow, and what happens is the "freezing front" - the point where the temperature is freezing - will move down within the insulation layer rather than above it, so the moisture will condense out and freeze in an ice layer in the insulation, and in spring thaw out and wet the insulation and joists, rotting them and causing mold. In cold climates where the attic is well below freezing pretty much all winter, I have seen this layer build up at thick as 3 FEET in extreme cases - resulting in ceiling collapse because of the weight, as well as joist, ceiling, and wall water damage when it melts.

Look several places under the existing insulation - is there a plastic "visqueen" sheet between the joists and the ceiling drywall ? It should be about as thick as the plastic in a freezer-quality heavy duty ziploc baggie - about 6-8 times thicker than standard sandwich or saran wrap, and looks sort of frosty rather than transparent. If you have that, then the thing to do it get the existing insulation out of there (without damaging the vapor barrier) and vacumn the attic floor bays (using appropriate dust inhalation protection), then get an energy consultant to do a thermal assessment and a thermal infrared camera run to mark air leaks from the house into the attic. This will include probably all ceiling light fixtures, and everywhere wires and vent pipes penetrate the ceiling into the attic. These openings need to be sealed up (do research on proper technique), and while you are at it you should get a good modern joint sealant or duct sealing taqpe on all the ducts (which might need to be replaced anyway due to rust - would also be a good time to upgrade bathroom ceiling fans, if this has not been done) and if in a climate with freezing weather, install duct insulation on them. While working around the ducts, you should check they all actually vent into roof vents, and that there is a waterproof seal beween the roof sheathing and the vent, as installers commonly just jab the vent pipe up through a large hole cut in the sheathing and call that it, so a lot of the moist vented air just circulates from the roof vent hood back down into the attic. Once you have stopped off all these existing sources of air leakage and moisture, then you can have insulation installed - either UNFACED fibreglass batting (you never want more than 1 vapor barrier in a ceiling or wall) or a blown-in product (both have their good and bad points). My personal preference is fibreglass batting with alternating layers criss-crossed, as the blown-in products tend to matt down with time, degrade with time if they are organic-based, and can blow around in heavy winds. I have actually seen 3 foot "drifts" of loose cellulose and shredded newpaper insulation in attics, from heavy wind storms moving air through the attic.

If you do NOT have a vapor barrier or if it is asphaltic impregnated or waxed paper (which is pretty useless as a vapor barrier), then you will need to retrofit vapor barrier in between the joists - a slow job, and not a efficient as a full-coverage vapor barrier installed before the ceiling drywall below, but helps a lot.

Since you say you have lost a lot of heat into the attic, I would also have it inspected by a carpenter for roof structure damage (broken trusses, loose truss plates, rot, missing wind uplift tiedowns, etc) before any insulation is put in. You should also make sure the attic has adequate ventilation (eave and ridge vents, typically).

Either way, you are in for a significant job. It is possible to do it yourself, but is backbreaking as well as cold or hot (depending on time of year), and you have to be very careful not to put any weight on the drywall ceiling below, or it will crack, pop right off the nails or you can fall through it, so you have to move pieces of plywood around on top of the joists to kneel on as you work.

Pricing depends a great deal on your specific situation, attic accessibility, etc - and also to a tremendous amount on your eligibility for tax credits for energy improvement, and if your state or power utilities have any sponsored energy rebate or credit programs, which can at times pay back from 10-20% to as much as 90% of energy improvements.

Good luck.

Answered 7 years ago by LCD


when the insulationSTAR smelling like the close in do you think it's need to be take out which new installation need to be changed out

Answered 5 years ago by wilson

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