How do you add additional insulation to
I’ve got a small two story condo built in the late 1960’s. The insulation in the attic is sub-par. In the summertime the attic is so hot it’s like sleeping under an oven. I need to put some more insulation up there but not sure what? The stuff that is there is very thin but fills in the joists. Not sure if the joists in the ceiling are 2 x 4’s or 2 x 6’s.
I want to lay another layer of insulation over the existing stuff but I’m getting conflicting information. One person said to lay it perpendicular over the existing insulation and joists. Another said to run in it in the same direction and then staple the sides to the joists directly over the insulation sitting in between the joists. I’m concerned about trapping moisture between the two layers of insulation but cannot get an answer about that either.
What is the best method to add another layer of insulation over existing insulation?
Thanks.
Replies
Theo,
Both methods of adding extra insulation should work (ie: perpendicular or parallel), but I would go for the perpendicular approach if possible.
The moisture between layers shouldn't be a concern unless there is a vapor barrier (kraft paper, or other) on the existing insulation. If no vapor barrier, just install new unfaced insulation over the existing unfaced insulation and the moisture will flow freely.
.....If the existing insulation is faced with a vapor barrier, which way is it facing?
Justin Fink - FHB Editorial
If I poke my head up through the ceiling and into the attic, I can see the yellow insulation sitting in between all the joists. The paper side is against the attic floor.
Can I get the stuff that is encapsulated on both sides and roll that out over the existing insulation? Or do I have to get insulation that has no vapor barrier? The encapsulated stuff will be easier for me to work with which is why I ask.
If the encapsulated insulation is a problem trapping moisture, can't I just take a razor after it's place and run it along the top side to break the vapor barrier or will that not work either?
Also do I need to seal or staple this stuff in place or is just laying it down loose good enough?
The good news is that your current insulation is installed correctly (as long as you don't live in an excessively hot climate).
From: http://www.ornl.gov/sci/roofs+walls/insulation/ins_12.html
"If the existing insulation is near or above the top of the joists, it is a good idea to place the new batts perpendicular to the old ones because that will help to cover the tops of the joists themselves and reduce heat loss or gain through the frame. Also, be sure to insulate the trap or access door. Although the area of the door is small, an uninsulated attic door will reduce energy savings substantially."
To answer your other questions: I'm not sure what you are referring to when you say double encapsulated insulation? But unfaced is the way to go because you don't want to create a situation where you are trapping moisture between two vapor barriers. Cutting the barrier after insulation seems pretty pointless to me, but I don't understand why you say installing this encapsulated insulation is easier? please explain....
and I also I wouldn't bother stapling anything in place, just lay the rows close together (meaning edge to edge). Justin Fink - FHB Editorial
Great website about insulation. Thanks.
Good Idea about the attic door. It currently has none.
I didn't mean double encapsulated. I just meant encapsulated all around it. I figured it would be easier to handle because it had a plastic covering instead of uncovered insulation in which case I would just be handling the fiber. I'm not that familiar with it so maybe they don't make this or the stuff I've seen was encapsulated but one side has a vapor barrier and the other has vents or holes or something. In that case it wouldn't work.
To sum... All I have to do is buy unfaced insulation so I don't create a trapped vapor barrier between my old stuff and the new stuff. Make sure it is the right thickness in order to acheive the correct total RJ rating. Run the new layer on top of and perpendicular to the joists, since they are already filled with the old insulation, and make sure not to cover the vents at the very ends of the eaves.
Now what about the existing pipes running through the attic? There is not enough room to stuff insulation between the pipes and the joists. Should I cut the new layer of insulation and butt it up against each side of the pipe or notch a piece out of the insulation on put it directly over the pipes?
Your recap sounds accurate.
As far as the pipes are concerned, I would use your best judgment. It's hard to tell just from a description, and when you're dealing with remodel work, nothing is ever easy....
My first thought would be to just lay the new insulation over the pipes, but like I said, use common sense where necessary.Justin Fink - FHB Editorial
Why not blow in cellulose? I've done two homes now and wouldn't use anything else. The first was an existing home with 6" of fiberglass, same situation as yours. I taped a broom handle to the hose and just walked down the center of the trusses, had the wife feed the machine. I did the garage too, best money ever spent. The second house was new construction with cathedral ceilings. Just slide the hose down the ceiling and pulled it up as it filled. Nothing I know of is cheaper, faster or better. Most home centers rent you the machine for free and the cost per R is less then fiberglass and I was getting the glass wholesale.
Theo
Unless I missed it, you didn't say where your house is located.
And, as I read it, you have two issues: Excessive heat in the summer and a fear of too little insulation to keep the heat in the house during the winter.
As I understand it, (whatever excessive means in your case) heat build up in an attic is due to improper or inadequate ventilation. So, it seems, you need to increase the amount or size of ventilation available just for the attic. You can do this by means of passive vents in the gable ends and soffits, a ridge vent running the length of the house or mechanical or electical vents through the roof. Best consult a professional to determine what your particular case requires.
As far as insulation is concerned, I wasn't impressed by the addition of extra insulation on top of the fold-up attic stairs in my attic. It seemed to get trampled every time we went up or down the stairs and eventually broke apart and fell off.
To solve that, I fabricated a cover out of 2" polystrene sheets and duct tape measuring just larger than the closed attic stairs. The poly comes in sheets 24" wide and 8' long. Cut them with a knife or an old electric meat knife if you have one to a size a bit bigger than your stairs and join the pieces together with duct tape (inside and out to seal the seams).
When you go down the stairs in the winter, pull the cover down over you. The stairs then get closed and fit snugly inside the styro cocoon you built. Cuts way down on drafts too! When you need to get up into the attic, the cover is easily pushed onto its side (as long as you have left some room for it to sit) and you can go up and down without a problem. If you're going to be up in the attic during the winter for awhile, lower the cover to keep the insulation in place. Works great in the winter.
But, of course, insulation does very little to prevent summer heat from radiating downward into your living quarters. Ventilation is the key.
Griff
Thanks for the info Griff but I think you misunderstood. There are no stairs involved in this situation. The attic is not used for anything. The only way I can get up there is by using a ladder through a small cutout in my closet ceiling. I'm located in San Rafael, CA.
I agree the ventilation is the key and mine is not up to par. This is a townhouse however so I cannot do anything to the roof or exterior of the building. That is the responsibility of the association and they say it is in the works. I cannot go another summer without anything being done. I can however put more insulation in my attic to try and keep the heat that is building up in there off of the bedrooms below it.
So are you saying, that even if I increase the layer of insulation in my attic I will not get much benefit from it in the rooms below?
I'm getting way too much conflicting information on this topic. Not only that but no one can tell me definitively what kind of insulation I should use. The stuff currently in my attic fills my joists and it has a paper side against the attic floor with the fuzzy stuff on top. Some people say to get insulation with no vapor barrier on it and lay it over the existing stuff and others say it doesn't matter. Just lay it over but they can't agree on whether the added insulation should go paper down or up in this case. I'm assuming the paper is the vapor barrier. If I'm wrong on this someone please correct me. I'm not that savvy on this topic. I'm concerned with having two vapor barriers or paper sides and trapping moisture in between them. Does anybody know the answer to this?
I'm having difficulty finding any insulation without no paper side, so I'm thinking I might go with the plastic encapsulated stuff and then rip the plastic off once it's in place. But if there is no problem with the additional vapor barrier then I don't want to do the extra work. Can I just lay the insulation over the existing stuff and be done with it?
Edited 4/14/2005 2:42 pm ET by Theo22
<< I'm concerned with having two vapor barriers or paper sides and trapping moisture in between them. Does anybody know the answer to this? >>
....You are correct Theo, the kraft facing on the insulation is the vapor barrier...If you have two paper-faced batts of insulation, there will be moisture trapped between them. DO NOT DO THIS
Go to Home Depot, Lowe's, Lumber yard....any of these places will carry "unfaced fiberglass insulation"...it's pretty common.
See this website: http://www.bge.com/cmp/CDA/topic/0,1667,495,00.html
What are Vapor Barriers?Vapor barriers will reduce the chance of water vapor condensing and collecting in your new insulation or on the beams and rafters of your house. This is important because moisture can damage the structure of your house and reduce the effectiveness of the insulation. If you are installing batt or blanket insulation in an uninsulated attic, buy the batts or blankets with the vapor barriers attached. Install them with the vapor barrier side toward the living space. If you install additional insulation over existing insulation, use a batt with no vapor barrier. When vapor barriers are placed between existing and added insulation, moisture is trapped, which reduces the insulation value and could cause moisture damage to the house.Justin Fink - FHB Editorial
That makes sense to me Fink. I'm going with that logic. Thank you. Now I need to find unfaced fiberglass insulation.
Theo
So are you saying, that even if I increase the layer of insulation in my attic I will not get much benefit from it in the rooms below?
Sorry about the stair misunderstanding - but, I'd still do the same for the attic hatch. Build a cube out of stryofoam and cover the hatchway. I think it'll make a difference in heat loss and drafts with not much $ outlay on your part. Since the size of the hatch (at least in my mind) will be small er than a full attic stairway, you might even be able to pick up broken pieces of stryo far less expensively than a full sheet costs.
As far as the problem of summer heat radiating downward in summer months, of course there will be some benefit to additional insulation in the attic. But, think of an attic in the summer. What's the temperature up there in daytiime? 140 degrees? 160? Nothing is going to stop that kind of heat from radiating in significant amounts to anything that's cooler, and that includes your second floor bedrooms.
You've got to eliminate the heat. You can't contain it well. The laws of physics can't be changed. Heat moves in the direction of the differential - hot moves to cold in any direction it can. The hot, hot, hot attic is going to be seeking to transfer it's energy (heat) in any direction it can to a cooler spot/area. You might slow down the transmission, but you can't stop it. Not with the available insulation we have for homeowners' anyway.
I recognize the problem with dealing with an association when it owns the common areas (the outside roof and siding). I don't know the answer. Start a petition? Get estimates on the cost yourself so people know how much of an extra cost it might be and seek a special appropriation to pay for it? But a more powerful a/c?
Good luck.
Griff
I finished the job last weekend. It came out beautifully. Not an easy job. Tight spaces, lots of water pipes, wires and debris left over from contractors. I used R-30 encapsulated bats. I tore off the encapsulated plastic which left me with nice fluffy bats that were placed over the existing insulation in the attic that already had a vapor barrier. I ran down to my nearest Home Depot and that's all they had that would fit my needs. The encapsulation came off very easy. You just slice it down one side and unroll it and it's off. That was easy part. Placing the bats in the proper places in the attic was tough, my knees were shot the next day but it was all worth it.
I ended up doubling the bats in most places. R-30 on top of R-30 on top of the old existing stuff which was wafer thin. Don't worry, I left room for air flow and did not cover the vents on the eaves for the updraft.
WOW! It made a huge difference! We had a very warm week and my upstairs floor was cool. I could not be happier. With a little hard work and about $500 I was able to get rid of the sauna that used to be my second floor. The temperature is now comfortable and closely resembles my first floor. I was however very meticulous about a placing a solid layer of insulation especially in all the tight spaces and around pipes and keeping airflow. It worked!
Thanks for everyone's help. Now who wants to help me remodel my bathroom?
Go to Home depot and buy some insulation ? are you kidding???
Adding a second layer of batt insulation is almost worthless. Conditioned air easily moves throught it.
1 find and seal all the air leaks between the attic and heated space below
2 install a layer of loose blown cellulose on top
3 add attic ventingBetter yet find a professional, get an energy audit, with blower door test to find the drafts and specify the optimum amount of insulation to be added. Your'e getting lots of conflicting advice because of the tendency to apply generic boiler plate solutions. Get some on site specific advice. Do it right the first time.
You're way overthinking this Btorr.
What I did was inexpensive and it worked great! I did the labor myself so I know it was done right the first time.
Don't believe everything you read in the manual or what your boss tells you. The advice I got was solid. No one said this was the only way or the absolute best way to do it but for the results I was looking for and the price, I couldn't be happier. My upstairs floor is 90% cooler than what it was before. That's what matters the most. And it only took me a few hours two days in a row to complete.
I'll never use that blown stuff. Everyone I know that has tried it either hates it or has had it removed at one time or another. It's a mess to install and remove and it's extremely dusty. Thanks anyway.