I just bought a 30 yr old home with a poorly insulated attic. It has a old fiberglass batts laying between the rafters. I assume that it is OK to just blow in the new insulation over these old batts and not remove them — is this correct?
Also, the floor has no insulation between the 2×6 joists, and a small crawl space under them. I assume that my best bet there is 6 inch batts between the joist, with spring rods holding them in. Anyone have better suggestions?
Thanks!
Woody
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Replies
Yes, you can simply blow additional insulation (chopped FG or cellulose) over the existing batts. I favor cellulose up north, but down south there may be more arguments in favor of chopped FG.
The fiberglass batts & spring rods between floor joists is a poor choice for insulating floors, but there aren't that many others, especially when you're likely to have rodent problems. Probably sprayed foam or wet sprayed cellulose would be better, but considerably more expensive and not a DIY thing.
So, I have a simlar question. I want to build out over an old slab and make a nice sunroom. There will only be a few inches of clearance between slab and joist. How do I insulate this? Even vented I worry about moisture as well. And rodents.http://www.etherhuffer.typepad.com
Yours is much more difficult to answer. Why do you want it insulated?Is it slab on grade?
FPSF?
Or have a footer below frost line?
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Its a slab on grade and I want to put hardwood floors in . Trying to get it near the height of the rest of the househttp://www.etherhuffer.typepad.com
Yeah, hard to answer. How well insulated does it need to be? (3 season or 4 season, and where do you live?) Will there be heat?I'd be inclined to lay down a layer of floor sheathing, then foamboard, then another layer of sheathing (dropping the level of the joists appropriately). Or else tighly enclose the "crawl" (mouse-proof) and insulate the walls/floor of the "crawl". But you'd need to be sure there was no moisture problem down there.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
I am in Seattle but want full insulation for simple comfort too. The slab is a real moisture problem as its just below our neighbors, who are 3 feet higher. I get hydrostatic moisture in the winter. The previous owner/idiot put pressure treated down on the slab to make a sunroom, which is now well rotted.http://www.etherhuffer.typepad.com
Is the sunroom rotted or the PT on the slab?Sounds to me like you have an extreme moisture situation should maybe be dealt with before worrying about insulting the floor
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"Sounds to me like you have an extreme moisture situation should maybe be dealt with before worrying about insulting the floor"
Why would he want to insult the floor, it isn't its fault it is damp!
:)
John
how did I do that?;)
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Hey, if there weren't insults this wouldn't be Breaktime.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Heh! The sunroom was a crap job and the PT is rotted and some of the uppers. I will tear all this out and start over. But I can't alter the water from uphill. I guess I could trench down and try to divert it, but its a lake of clay under there. Ick.http://www.etherhuffer.typepad.com
You could divert with french drain.You could elevate by pouring another slab over this one, and include a sandwhich wafer of EPS foam between them, then run PT sleepers and the wood floor.If I could see all the pertinent details I might even get inspired with more
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NO WAY! Inspiration is money!!http://www.etherhuffer.typepad.com
For the attic, provide breathing baffles for ventilation from soffit to ridge then blow to your hearts content.
For the crawl, it is better in my opinion to insulate by gluing foam panels to the foundation wall, unless you have rubble stone foundation
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Piffin and DanH,
Thanks for your thoughts. No problem with the attic, just wanted to confirm I was doing right. Not sure what to do with the floor just yet. This home is in Texas, bare soil under the joists, and a definite mositure problem. Perhaps insulation the foundation is my best option, although I like allowing it to breathe as much as possible to eliminate the mositure.Woody
"letting it breathe" as you say is not eliminating any moisture. It is only mocing it from the soil into the house where it causes problems. Keep it out of the house.
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"This home is in Texas, bare soil under the joists, and a definite mositure problem. Perhaps insulation the foundation is my best option, although I like allowing it to breathe as much as possible to eliminate the mositure."NO, NO, NO!!!!I could not look up your location, your profile say LA.But go to the weather underground and you can get a history that shows, amoung otherthing, a plot of the dewpoint over a period of time. Look at the DP for july and august.You will probably find that much of the time that it is a MINIMAL of 68*F and often more and into the mid 70's.Now you bring that air in to the crawlspace. What is the tempature of the crawlspace? Bring in that nice moist air and cool it and what happends.The RH will shoot right up. Maybe it is below the dewpoint and you will get condensation..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Bill,
Now I'm confused. The house is near Dallas, TX (not in Louisiana where I currently live). It is a pier and beam construction, over bare earth. I am saying that I don't want to shut off the ventilation under the house, I want to let it breathe to get the moisture out. Also, I would like to insulate the floor of the house, the reason for my original question. I am confused about what the "no no no" refers to -- what is it that you don't want me to do? More specifically, what should I do to insulate the floor? There is a 18 inch crawl space between the earth and the floor joists.
Thanks for you input.Woody
" I want to let it breathe to get the moisture out."What is the "IT" that you want to let breathe. And what is the source of moisture that you want to let out?How I am not sure what the construction is here you said it is beam and pier. While I am not familar with that I to me it implies that the support is on piers and the side is open or only has light weight skirting around it. But here you talked about a foundation. " Perhaps insulation the foundation is my best option" To me a foundation implies a solid wall. One that is air tight or can be easily make air tight. One to which you can attach insulation.How here is the data at Dallas Love for July 1 to Aug 16.http://tinyurl.com/2a83r4In august the average DP was 69, the other 70 or over. July was only slightly better.Now if you take an "box" of air and start cooling, without adding or removing water, the relatively humidity will go up. Until you reach the dewpoint with the RH is 100% and water starts condensing.Now if you let that outside air into the crawlspace it be get much cooler and depending on the tempature and the sealing of the crawlspace walls and the AC setting, the leaks in the floor, and if any AC ducts are in the floor the temp in the crawlspace might bein the low to mid 70's. Near 100% RH or maybe even condensation. YOU DON'T WANT THAT.Now if you put up the standard FG insulation on the bottom of the floor with the wires it the insulation VB won't be sealed to air can leak in and around and get next to the (relatively) cold floor and ducts. Where it can condense and be trapped againts the sub-floor.In your climate it would be much better, if you must use FG to use faced and have the VB face to the OUTSIDE and stapled to the joints.But a really better would would be to have bottom insualted with spray foam. It is not only insulation, but also an air seal.And if you have foundation walls you also have the option to SEAL or CONDITION the crawlspace by sealing it off from the outside and insulating the walls.In any case you want to cover the ground with a vapor barrier..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I may have missed it in this two headed thread but one caveat for your blown in insulation is if you have knob & tube wiring - usually not enough insulation on those wires so good potential for heat buildup so take care of them before covering them
John, thanks for the concern. The home is not that old, it is wired with romex and it appears to be in good shape.Woody
Bill, thanks for taking the time to respond. This is a home that I recently purchased, near a lake. The moisture concern is from the earth, which is bare beneath the floor. This is a 30 yr old home built on pier and beam, with a concrete foundation/flood water barrier (apparently) around the entire perimeter. This home incurred severe water damage from some type of flooding underneath it (apparently a burst pipe, best I determine). The previous owner completely replaced every floor joist and the entire sub-floor (double layer of 3/4 and 5/8 plywood), but did not insulate it. Everything under the home was replaced, including all plumbing. The HVAC vents are all located in the attic. They placed perhaps 24 vents around the perimeter of the home to ventilate the crawl space. During the winter the house was difficult to heat, due to poor insulation in the attic and none beneath the floor. This is what I am trying to improve. I have to agree, spray foam sounds like the best bet, I will look into that. I had not considered FG with the VP to the outside, but I like that idea -- a much better vapor seal. I am still trying to determine if I have a problem with storm water under the home. I had water get under there during the recent heavy rains in Texas and that concerns me. I am still trying to track down how it got under there, as I wasn't there at the time. I don't want to close the vents until I am certain that it is permantly dry. Apparently they were added during the remodel for the purpose of venting the area, so I want reluctant to seal them off just now. Time will tell. As I said, I do appreciate the time you took to respond to me.Woody
Whatever else you do, you need to lay plastic on the floor of the crawl.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin