Hi This is the first time I have posted here I have been reading different posts on and off . I live in upstate NY . I am looking for advise on insulation .I came across a product called “ProdexHi R ,foil foam foil .They claim it has an r-14.5 I cant believe this is true its only 1/4″ thick .I have several rooms gutted out in my house to the bare studs . I packed them out with 1/2″ so they are 5 1/2” .I was going to install r-21 then cover with poly . Its an old balloon framed house . 16″oc walls the exterior is full 1×10 shiplap with cedar siding .over that is 3/8 foil foam and aluminum siding . I am trying to get the best insulation job I can . I am not sure if this is a good product or not . My question is should I cut the foam foil and staple it to the empty cavities first then install the batts and poly ( I am afraid of double vapor barrier ???) or install the r-21 batts and staple the 4′ foam foil over the walls as a vapor barrier ,and will this way give me radiant barrier vapor barrier and higher r-value ( R-35.5 ??) . Also should there be furring installed over the studs before the foilfoam is applied or should the furring be installed over the top of the foam leaving an airspace between it and the drywall. I have heard that after a certain point that thr r values don’t go up any higher .I also thought this foil foam would help seal the airleaks that come with batt insulation.
The ceilings were dropped down to 8′ and I was going to do the same on those except using r-38 instead of r-21 .I was going to use a 1″ rigid hi R foil foam or a kraft faced foam board before I came across this foil foam insulation it costs about .30 per sq.ft.
Thanks
Roy
Replies
I forgot to mention the website for the foil foam insulation is http://www.insulation4less.com
Roy
There is no way that ¼" thick insulation has an R value of 14.5. I believe their claim is false. I would not waste your money on it.
In your case I would do R-21 fiberglass. If you want additional insulation then you could install ½" foam right across the face of the studs and then drywall over it. I would use unfaced fiberglass and apply a poly vapor barrier. I built a new home 60 miles North of Watertown with just the fiberglass and I had a very warm house with low heating bills.
You will be better off making sure you haven't missed spots than to have very thick insulation in other areas. You can loose more heat through a few small uninsulated areas than you would make up by going from R-21 to R-26 by adding the additional foam. So concentrate on getting at least some insulation everywhere, like for example, on the outside walls between the first and second floors. Also, around your rim joist in your basement, and in the attic.
Usually an airspace is bad because you can get convective circulation which increases heat loss. If the furring were horizontal it would not be so bad, but the airspace would not help and the furring would just add cost.
If you post in Breaktime your post will be seen by more people with construction knowledge.
Wayne : Thanks , I was talking with some other folks on breaktime that say the same . Some prefer to install 1" Hi r and blow in on top and others recommend the FG with the foam board as additional insulation and VB I was talking to someone local here and they said try to get the 2 part dow foam and spray it in the rim joist ( Box ) also
Roy
There are lots of effective ways and you'll find different folks have preferences. Some preferences are regional -- not every type of system is available everywhere. If it were me I'd do the extra dense R-21 in the walls and blown cellulose in the attic.
Before doing the attic I'd make sure holes into the attic, such as around wiring or plumbing are sealed with a light shot of expanding aerosol foam from a spray can. Most light fixtures, though, are not rated for being covered with insulation and you can overheat them if you do insulate too close to them. The movement of air through the walls can leak as much heat in some types of construction as conduction of heat through the wall materials themselves.
Some of the new foil types are effective--probably not as effective as they claim. You need an air space on either side in most cases to get the boost in R-value. I've had good success with the bubble-wrap stuff covered in foam---with the airspace. It was not a replacement for fiberglass, just addititive.
R-21 in the walls then covered with thick poly will make a huge difference. Take your time and don't pack it too tight. Custom trim insulation to make it fit. Don't do craft, just the raw stuff with the poly on top. Air infiltration is a huge enemy. Foam where you can.
If you want more, then you can install some of the foam boards on top too. Not sure if you would do fiber, then foam (tape seams), then poly---or poly between fiber and foam. Go to Breaktime on Fine Homebuilidng and they can help! Just remember that the foam stuff, by code, needs a fire barrier on top of it (drywall).
Hi Yes I did go to breaktime and a couple of the folks there recommended that I use FG unfaced r-21 in walls ,then cover with 1' rigid hi-r board .Then furreach stud out making an airspace of 3/4 " ,and also tape the joints in the hi-r . The cielings would be the same but I am using 2 layers of unfaded r-19 one on each direction
Im starting the foam board today . man that stuff got expensive !!!
Roy