air sealing materials top plate of wall
My house is 100 years old (roughly). It is balloon framed with barnboard sheathing on the exterior of the stud walls and a brick veneer outside of that. I am finally getting on with my attic insulation project.
Suggestions from here about removing wooden laths and plaster from the walls and ceilings have been very helpful. I prefer doing my pounding with a light minisledge hammer instead of a length of 2×4, but hey, same thing. It comes off really easily and is the most unpleasant job I have ever done.
I will be bringing the kneewall space into the conditioned space. The main insulation will be accomplished with dense packed cellulose.
As far as the “floor” of the kneewall area goes. Does anyone have any suggestions for air sealing it with the smallest amount of work and the smallest amount of money. I do realize that I will have to compromise with both of those since I don’t intend to compromise on the final results.
Right now I have bare joists in that area. The rest of the attic has T&G floorboards. I could have my insulation installers (I am just setting up and designing the job) seal it up with polyurethane. I could use foam board and caulking or dry wall and caulking…
Any suggestions?
I was hoping that there was some kind of fairly inexpensive “stuff” I could mix up and pour into the area (just to cover the the surface 1/4″ to 1/2″ deep or so) that would dry and have good air sealing properties and not damage the house. Just exploring options.
Replies
if you went with a foam insulation instead of cellulose you would do what you want in one application. good insulation and get the air seal you need. the price should not be that much more then the cellulose. try the Icynene.com web site and ask a local Installer for a comparison price and how he could save you from doing extra steps to get the same results.
Edited 8/3/2005 12:21 am ET by FoamMan
If you are bringing the kneewall into the conditioned space, the floor area becomes an 'inside' partition.
Really just the top plate area of the floor needs to be sealed and insulated. Rigid foam is a good choice, if you can cut blocks to fit. Another option would be to build a 'dam' to hold back some cellulose with blocking between the joists. Fill foam is good too, but expensive.
Are you trying to do a venting scheme, or sealing tight?
My intention is to seal it all tight. No vents.I am getting the cellulose blown in densely by a professional so that my learning curve in blowing the stuff doesn't mess up the results.I have done all the design. The only catch is that the owner of the insulation company is a civil engineer. I made a deal with him that I could do it my way if I can convince him that it will work. I am still in the process of doing all the calculations in detail. My preliminary work shows that it will function fine with no vents.(ontario, canada, around 7500 degrees Fahrenheit heating days)The plan is R60, dense pack cellulose and extreme care in air sealing otherwise. No vents. No vapour barrier to allow drying in the summer (when the stack effect will be down).If anyone is interested I will post the full details.If my house wasn't a 100 years old... there would go a really fine hobby.
Whoa! Do I understand you right? You are doing an unvented attic in Ontario with cellulose suspended in the rafter cavities? If that is the case, we need to talk. That method is not safe in your climate. RSVP.
I agree not commonly accepted, but why the word "unsafe"?
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This method will work in my climate here in central TX but further north it has been found to cause moisture problems on the underside of the roof deck. No matter how densely you pack cellulose with a blower, it will settle. The airspace that is created between the cellulose and the deck allows for convective currents to form. The moisture in the space will concentrate near the peak and will be worse on the north facing roof.
Spray foam, when carefully applied, will eliminate the air gap and then moisture can only flow through diffusion(a much slower process). In ontario, I would have to do more research before I would apply spray foam in the rafters. It may require an additional layer of foam above the roof line to control the temperatures of the first condensing surface. A vented cold roof above the insulated structural roof is another possibility.
I would not recommend suspended cellulose insulation in the roof rafter bays in climates that experience average january temperatures below 40 dgrees F without adding foam sheeting to the topside of the roof. The amount would vary by climate.
In a cold climate, foam insulation, properly applied is a much safer product from a moisture control standpoint.
for this to work you really should consider foam insulation!!
Icynene foam insulation is made in your area of the world and you might get a good price on it. Go to there web site( Icynene.com) and look up your local installer.
Cellulose will settle in a few short years ( or sooner) and you will not have the R-value you had when it was installed.
Also is there any duct work in the attic? if yes then consider that they will leak from day 1.
if no then you have no worry of heating the air in the attic and having condensation problems or ice damming. I hope this helps, any questions ill be glade to answer them
When I did my first post on the plaster removal I had just been working on the walls. When I got to the ceiling of the first room I discovered my self that the hook on a wrecking bar is really efficient. I had the ceiling down in less time than the walls (and the ceiling is a lot bigger). It was messier, but since the whole job is messy... it doesn't make much difference.I will complete my design calculations an post for comment.If my house wasn't a 100 years old... there would go a really fine hobby.
"Cellulose will settle in a few short years ( or sooner) and you will not have the R-value you had when it was installed."My understanding with cellulose is that it settles to approximately 2.5 lbs / cu. ft. and that if you blow it in denser than that (say 3.5 to 4.5 lbs/ cu.ft) it won't settle. I suppose that I've never actually asked here about that particular assumption.Anyone have any experience with densely packed cellulose?If my house wasn't a 100 years old... there would go a really fine hobby.
If you have things all stripped down, spraying foam underside teh sheathing is the best way to go. you will never regret it.
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i'm no fan of cellulose, but denspacked cellswill not settle. Foam is a superior product that can stand on it's own mertits without making false claims about cellulose. Maybe you missed the part about it being bnlown densepacked.
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I'm not trying to down the cellulose product, I have at times recommended it to my clients. this doesn't change the fact that recycled paper or wool rot over time!
I vote that your method will work, so long as the air sealing details are attended to. Running drywall down the rafters to to floor makes for a good and inexpensive air barrier.
I know you like your method of plaster and lath removal, but I got a job doing that once in a commercial building (the part I did was apartments above a store). The guy showed me what he wanted me to do--he took a claw hammer and beat on the plaster and then pried at the lath. He'd been working on this for days in his spare time and had removed a patch maybe five feet square. I took an old wrecking bar and taped the straight part at the end with racketball handle cushioned tape and held that end and smashed through the plaster, then used the hook to rip down and pull out on the lath at the same time. I got a rhythm going and could clear a room, ceilings and walls in about 20 minutes. The plaster usually fell of in sheets after the first couple blows, then it was just ripping the lath off the studs. It's not a method for the timid. The worst part was then getting the debres down to the dumpster at the other end of a parking lot, but that's another story.