What does this insulation serve? I see some at The Home Depot.
Regulation? Heat reflection? Some fire protection? or all of those
reasons?? I want to put some on the basement walls over cinder block,
The foil backed insulation is a superior product and gives you more
insulation (R-value) both per dollar and per inch by my calculation
than other similar products. The foil itself not only has insulation
value but also acts as a reflective vapor barrier.
If you use two layers of foam board they can be staggered so that the
barrier is continuous. I like it also because it is less likely to be
damaged when transporting or installing compared to regualar foam
It seems more expensive at first but when you consider performance you
come out ahead. The only reason to use unfaced foam board is if you
really need a lot of total R value like a roof. It comes in larger
thicknesses and so a given R can be acheived with fewer sheets.
I don't think the foil is thick enough to count as fire protection.
This is my guess, one it is reflective of heat, and two, it keeps the
foil together from small bumps and scratches.
Just a guess......
tom @ www.FindMeShelter.com
Au contraire, it offers some real (vs code :-) fire protection, and
the ASHRAE HOF says it adds a real US R2.55 when installed vertically
with horizontal heatflow and a 3.5" air gap (exposed toward the room)
and a 50 F mean temp and a 30 F differential, eg 65 F room air and
a 35 F basement wall.
On Feb 5, 3:25 pm, firstname.lastname@example.org wrote:
I'm getting some good answers. I was thinking the foam was allready a
but I could be wrong. Its funny, foiled drywall can also help get rid
of excessive RF
radiation from local towers, etc., if used in a continuous manner. Not
perfect, but can
be used effectively.
I measured my basement wall, an above ground section, when the outside
about 10, the interior cinder block wall was about 43 degrees. I went
around over the weekend,
and must have sealed up a large area up around where the block meets
the wood. Most
of the area in the basement was leaking, the way they built it. Its a
50's home. Luckily the upstairs walls
were insulated with mineral wool batting. I added insulation in the
attic before winter. Been
sealing joints since its got to be 0 deg. here.
Unless I am remembering my physics classes wrong, we have an apples and
oranges calculation. I stand by my opinion that in the situation described
by the OP the air gap is more important than the foil in real life.
In what sense? Conductances add, and Table 2 ("Thermal resistances of Plane
Air Spaces") on page 22.2 of the 1993 ASHRAE HOF says the total airspace
conductance is the sum of the conduction-convection conductance Hc and
the radiation conductance EeffHr, which is the emittance (eg 0.05 for
a single foil and 1 for a non-foil) times a linearized radiation
conductance, 4sigmaTm^3, eg
20 L=.5'air space (inches)
30 TMP'mean temp (F)
40 HC=.159*(1+.0016*TM)/L'conduction-convection conductance (Btu/h-F-ft^2)
50 FOR EEFF=.05 TO 1.01 STEP .95'effective emittance
60 EEFFHR=.00686*EEFF*((TM+460)/100)^3'radiation conductance (Btu/h-F-ft^2)
70 C=HC+EEFFHR'U-value of air space (Btu/h-F-ft^2)
80 R=1/C'US R-value of air space (ft^2-F-h/Btu)
90 PRINT EEFF,HC,EEFFHR,R
100 NEXT EEFF
emittance Hc EffHr R-value
.05 .34344 0.045499 2.571095 with one foil
1 .34344 .909986 .797814 with no foil
The total R-value of the airspace is the reciprocal of the total conductance.
With a foil, the conduction-convection conductance does not change, but
the radiation conductance goes down, so the R-value of the airspace
goes up by a factor of 3 or so, from about 0.8 to 2.6.
I read this, and you may have referenced this to me before. I didn't
think completely covering the
wall was a good idea, except one of my walls is mostly above ground.
Thats the one that gets the
coldest. The other walls, are just going to be covered half way down,
with a good sized air space
between the future drywall.
There is one type of foam thats best for fire, but it still recommends
protection. I think I need some type of rigid fiberglass, but don't
know where to look
for it around here. It also seems to me that foam placed on top of
is partially protected just because it sits on top. i found cinderbloc
mine is about R3. I went in two suppliers around here. The foam boards
to have different R values. Some give R3 at 1/2 inch, then R3 at 1
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