Sealing leaks between ceiling and attic

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  #1  
Old 12-09-09, 09:29 PM
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Sealing leaks between ceiling and attic

I need some advice on reducing energy loss through my ceiling into attic.

House facts: Maryland, 1987 two story colonial on slab, budget builder, Single ridge pitch roof with asphalt shingles. Roof soffits extend about 2' from exterior wall. Attic space is between 4' to 5' at highest point. Currently, only vents are gable vents at each end and attic fan in center of roof. No ridge or soffit vents. Loose fill cellulose insulation in attic. Double pane vinyl clad aluminum windows. Vinyl siding with fiberglass rolls in walls and I think foil clad foam sheets under the vinyl. Original equipment Heat pump and Central air blower unit with back-up electric heat.

I installed the attic fan several years ago b/c we couldn't get the 2nd floor to stay cool in the summer. We also have trouble keeping house warm when its very cold out.

Next week, professionals are installing new roof. I currently plan to have them add ridge and soffit vents and remove the attic fan. Then I will close up the gable vents from inside. I've heard this is a better solution than the attic fan, and that I should solve our cooling problems by improving the attic insulation and eliminating attic air leaks.

So, step 1, I went up there with some Great Stuff, started looking for dirty insulation and started spraying foam to seal air leaks. I found a lot of air leaks / dirty insulation at the top of each wall plate, around the light fixtures, wire penetrations, and bath fans.

Is this spray foam process a good step 1?

If yes, what's the best way to proceed? I was trying to minimize disturbing the cellulose, so one section at a time, I moved away the celluose from the dirty/leaky area, sprayed foam, and then pushed the cellulose back.

Is all this hand re-laid cellulose going to insulate correctly? How would a pro handle this task?

Would it be better to blow all the cellulose clear, do all my foam sealing and then rent a cellulose blower to blow it back?

Also the cellulose was poured directly onto the drywall. Should there by some kind of barrier between the two?

The other area where I have lots of air leaks is around the plastic sheeting that was used to seal off the huge void above my stairwell and above my central aid return duct.

How should the edges of this sheeting be handled?
Should it be taped down?
If yes, what kind of tape?
 

Last edited by davidhmd; 12-09-09 at 09:59 PM.
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  #2  
Old 12-10-09, 05:58 AM
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Originally Posted by davidhmd View Post

Next week, professionals are installing new roof. I currently plan to have them add ridge and soffit vents and remove the attic fan. Then I will close up the gable vents from inside. I've heard this is a better solution than the attic fan, and that I should solve our cooling problems by improving the attic insulation and eliminating attic air leaks.

So, step 1, I went up there with some Great Stuff, started looking for dirty insulation and started spraying foam to seal air leaks. I found a lot of air leaks / dirty insulation at the top of each wall plate, around the light fixtures, wire penetrations, and bath fans.
Exhaust fans should vent to outside, not soffit area or attic. Can lights should be air tight and IC (insulation contact) rated and yes seal around the edges. If not air tight and IV rated you will need other steps. You should be using fire rated can foam.

Is this spray foam process a good step 1? Yes

If yes, what's the best way to proceed? I was trying to minimize disturbing the cellulose, so one section at a time, I moved away the celluose from the dirty/leaky area, sprayed foam, and then pushed the cellulose back.

Is all this hand re-laid cellulose going to insulate correctly? How would a pro handle this task?

Would it be better to blow all the cellulose clear, do all my foam sealing and then rent a cellulose blower to blow it back?
Hand laid cellulose is not compacted well enough the insulate or air seal as it should. If you limit your activities to just where needed and then apply 2 to 3 " of new blown in to cap everything off, it should be good. The cellulose will help a lot with the air sealing.

Also the cellulose was poured directly onto the drywall. Should there by some kind of barrier between the two?
If the wall cavities were filled with cellulose, there should have been a layer of plastic installed over the studs before the drywall. If not and you don't want to pull the drywall to install some, a couple coats of an oil based paint will function as a moisture barrier.

The other area where I have lots of air leaks is around the plastic sheeting that was used to seal off the huge void above my stairwell and above my central aid return duct.
Not sure what this is?

How should the edges of this sheeting be handled?
Should it be taped down?
If yes, what kind of tape?
Another place to air seal is all electrical boxes. I like covering them with contact paper trimmed for the device and trimmed for the cover. Caulk with the foam inserts helps, but a continuous piece of contact paper does a great job.

Sheet metal around large openings for chimneys or vents with the foam or caulk to seal it in place.

An infrared inspection would locate many smaller areas that add up to be a big hole.

Here is an energy star link that may help.
Air Seal and Insulate with ENERGY STAR : ENERGY STAR

That will get you started
Bud
 
  #3  
Old 12-10-09, 09:36 AM
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Thank you very much.

Re: the plastic sheeting and the voids. There are 2 locations in the attic floor where there isn't any ceiling drywall to rest the cellulose on. 1 is above the sloped ceiling of my stairwell and the 2nd is above a cavity that houses duct work. In both locations, they stapled some kind of certainteed plastic sheeting over these voids to create a support surface for the cellulose. There are lots of air leaks at the edges of the sheeting. Should I tape these down? If yes, what kind of tape will stick to plastic sheeting, wood, and drywall, and tolerate the extreme attic temps.

In unfinished attic floor should there be any barrier between the drywall and the cellulose?
 
  #4  
Old 12-10-09, 11:03 AM
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Don't have a complete picture yet, but enough to be concerned. Sounds like they created a false ceiling area just to support the insulation. This could be a problem. The plastic is a vapor barrier and needs to be in contact with the an air barrier. With the space below you may have a potential for warm moist air to circulate in and raech a cooler surface and form condensation. Since you can feel air passing through, you know there is one concern. I have to run, but will check tonight to see if you can give a better description.

Bud
 
  #5  
Old 12-11-09, 11:25 AM
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I think "false ceiling area" is accurate. My stairs run from first floor to 2nd floor. Attic is above 2nd floor. The ceiling above the stairs is angled to match the slope of the stair. This created a wedge shaped dead space between the drywall ceiling of the attic stair and the attic floor plane above. This wedge is open to the attic on top (no drywall). So, from the attic, they stapled come certainteed plastic sheeting over this hole in the attic floor. Sheeting goes over the 2 x 4's truss bottoms on each side of the hole, drapes over some of the ceiling drywall on either side of the hole. The 2nd void location has the same set up, except the 2nd void houses a central air return duct.

Sounds like current false ceiling set up is bad. What corrective action do you reccomend?

And again, for the rest of the attic floor, the celluose is laid directly on the drywall ceiling from the 2nd floor. I didn't find any clear evidence of damp celluose throughout the bulk of the attic. I did find one damp spot, but the roof sheathing above was wet, so I think that's a roof problem. I have already contracted for a new roof. They will install it very soon.

Thanks again for all your help.
 
  #6  
Old 12-11-09, 04:29 PM
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Had access problems, so just got back in. Before I forget, a wet roof deck from underneath is more often right above an air leak that produces condensation. The difference is, what time of year does it occur? If now when cold, it's an air leak. If in warm weather and after rain, obviously it becomes the roof. I've seen quite a few re-shingle jobs that weren't needed, at least to stop a leak.

Now, I have encountered the open space over the stairs and it's a pain. The air barrier and the vapor barrier need to be in contact and on the warm side of the insulation. So, are the side walls and slope insulated?
Here is an energy star link :Air Seal and Insulate with ENERGY STAR : ENERGY STAR
In the picture of the house, you will see an insert, top right, of their desired "house envelope". You will have to decide where that boundary is best or easiest to create. If the side walls and slope are insulated, then that insulation is preventing necessary heat from reaching the bottom of their makeshift air/vapor barrier.

You may be able to simply remove the insulation from the plastic covering, air seal every possible leak you can see, then replace the insulation and add a bunch more. Overkill for just that small area to eliminate any cold reaching the plastic.

Bud
 
  #7  
Old 03-22-10, 12:40 PM
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Sealing around duct

I have finally got around to finishing this up. My return duct runs through an enclosed wall cavity, and I am wondering if I should fill that wall cavity it with insulation to keep the duct warmer.

The sides and bottom of the cavity are drywall. The top just had a plastic vapor barrier between cavity and attic with insulation on top of the plastic. There were lots of air gaps where the plastic was attached, so I am redoing that to make a tighter seal. I have already swept aside the cellulose, and I am getting ready to reinstall the plastic.

Is it a good idea, to dump a bunch of cellulose in there before I seal it up? The cavity isn't that big, so it wouldn't take too much. There is aleardy pink roll fiberglass insulation on the exterior wall side of the cavity.
 
  #8  
Old 03-22-10, 01:06 PM
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Any space between the duct and exterior wall can always use some extra insulation. Seal any seams on the ducts where you can see them, duct mastic or foil tape. And if this cavity is open from attic to basement, install something rigid, like sheetmetal or sheetrock to seal the cavity. Vertical cavities are fire issues as well as sources of heat loss.

Bud
 
  #9  
Old 06-20-10, 06:46 AM
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Now what

Summary of situation so far.

Maryland, 1984, two story, colonial on slab, with heat pump and electrical back-up heat. Attic has ridge and soffit vents, with loose fill fiberglass insulation. I recently added spray foam around all top plate edges and wire penetrations, corrected false ceiling problems, and repaired sagging drywall ceiling over bathroom. I also ran some new electrical wiring for closet lights.

With all this activity I significantly disturbed HUGE sections of loose fill.

Because I had disturbed so much insulation and because I had an uninsulated duct cavity, I decided to move some of this disturbed insulation into the duct cavity. I'm afraid this may have been a dumb idea or a poor execution, but I already did it. I need to know if I should undo any of this duct cavity work.

The duct cavity began at the end of 2nd floor hallway, ran above 2 closets and under the attic floor to the end of the house, then turned 90 degrees down toward the first floor. Originally this duct cavity had no insulation. From the attic, it was loosely covered with some plastic sheeting to make a false ceiling and the insulation was laid on top of the sheeting from the attic. The insulation had lots of air movement dirt.

I removed the existing insulation and sheeting. Then, I wrapped some plastic sheeting / vapor barrier under the duct from the start of the duct at the hall end to the edge of the closet ceiling. I did not add any vapor barrier to the vertical part of the duct. So for the vertical part of the duct cavity on the three interior sides, there is the duct, loose fill fiberglass, then the drywall of the interior walls. On the fourth exterior side, these is duct, loose fill, fiberglass roll with paper backing on the inside, and cork style exterior sheeting separating this duct cavity from the garage attic space. I can see through duct cavity into garage attic through a gap between a double stud in that wall. I can seal that gap from garage attic with spray foam.

Now what?

Should I remove the loose fill fiberglass from the duct cavity?

How much should I expect to pay to have some additional loose fill sprayed in to re-fill all the disturbed areas?

This raises another large issue. Our heat pump is 26 years old and inefficient. We've been thinking about replacing it for years. A local company is offering free attic insulation with heat pump installation.

We've always had two major complaints with our HVAC system. On really cold days, house doesn't feel warm. On really hot days, 2nd floor is always hot. If we spend the money to replace the heat pump and blower and still have these problems, we will be very upset. My instinct says that a new system should heat more efficiently, but that the cooling problem is really more of a balancing / system design problem. In summer, we think the current system could easily do the job if we could completely close all the vents on the first floor. First floor gets too cold, while 2nd floor stays hot.

Thanks again for all your help.
 
  #10  
Old 06-24-10, 05:58 PM
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I'll be honest, I started to read your post, but long posts and short time do not mix. But don't feel bad, My answers put people to sleep at times. The message, we both need to learn how to tweet .

let me grab a couple of issues and you kick back one at a time what I miss.

Closing ducts is generally a bad thing, unless summer and winter positions have been designed in. The catch is that the units need a certain amount of air flow and we as home owners want it one place in the summer and another place in the winter. You'll need to sort out that balance as it fits your system and house.

Heating and cooling systems should be sized based upon the heat loss/gain calculations, commonly referred to as Manual J. Improved performance can be achieved by installing a larger unit with resulting increased operating costs (better efficiency will help), or improving your insulation, air sealing and such (as you have been doing) which reduces the required size unit and related operating costs.

Your unit has some years on it, but your improvements may make the resulting performance better. If you choose to go with a new unit, don't let them simply size it based upon what you currently have, insist upon a Manual J calculation to determine the proper size. Also consider some extra ducts to allow summer and winter air balancing.

As for the duct cavity you filled with insulation, if this is a metal duct and you have installed insulation into the cavity around the duct, there should be no problem. Obviously if the cavity is acting as the duct, with no metal duct, then it can't be filled with insulation. The hard part is air leaks in ducts in locations where you acn't seal them. Then the best you can do is seal tops and bottoms.

My tweet runnith over .

Bud
 
  #11  
Old 06-26-10, 06:27 AM
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a couple of comments,

pictures are worth a 1000 words.

Keep in mind, ceiling insulation wont help alot for the cooling problem, since it doesn't stop radiant heat well. Ventilation will help it, by reducing the roof temp, which will produce less radiant heat. I'm not sure if the cooling demand in MD would justify a radiant barrier. What are your heating and cooling degree days for your area?

I would also consider a programmable fan for your heat pump, so you can move the air more inside the house. When your heat/AC runs less because you have a well insulated house, it gives the air more time to stratisfy in your house. I use a thermostat that you can program to run the fan. It also has a circulate function that will run the fan 33% of the time regardless of the heat/ac demand.
 
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