I've got this red brick fireplace taking up half a wall.
Capped the chimney decades ago, but it's still siting
there conducting heat outa' the place thru the bricks.
How would one go about calculating the "R-value"
to estimate the heat loss. Any useful rules of thumb?
Trying to decide whether to put insulation over the bricks
on inside or outside or both.
Brick has an R-value of 0.8 but there are other materials behind the
brick. You'll have to identify them and add their R-values to the
Your local building permits office can probably advise.
You must provide basic information, e.g. whether the brick
wall is solid or hollow, how thick, etc.
If you want the general scientific background, the US NIST
can oblige (but its main interest appears to be fire
avoidance rather than heating fuel conservation.)
I found the reference below in my files;
Concrete block (8")
Concrete block (8") 2.0
with foam insulated cores 20
with 4" on uninsulated stud wall 4.3
I very much doubt the middle value, R of 20 for just some foam in the cores
seems way too high. The first and last value seem in the ballpark.
I have a second reference that shows brick ranging from 0.10 to 0.35 per
Seems I recall a figure of maybe adding R2-R3 for adding foam in the
I just started to install 1/2 inch foam to my block. This is glued and
together to form a vapor barrier, from moisture getting in. On top of
that I will
install studs and fiberglass or mineral insulation, and drywall.
I see the Roxul products being superior for possible damp conditions,
superior fire and acoustic control, but I'm getting off track of the
Have you talked to your tax assessor and your insurance company to see
how much you'd save each year if it wasn't there. Then calculate the
heat loss & how much it would cost to tear it down and put a proper
wall there. If you're not using it, you can probably make better
use of the wall space.
Also walk around your neighborhood, and see what percentage of the
houses have fireplaces. If yours is the only one WITHOUT a fireplace, it
could make it harder to sell when the time comes, for you or your heirs.
As pointed out the R value is not much. Whether you want thermal
mass inside is another matter, it'll take a bit longer to heat and cool off.
You may wish to consider pouring some insulation in the chimney, a
much better insulator than air. Probably would cut you cut your heat
loss dramatically. Not sure what condensation issues you would have
though. Either cellulose which can have some moisture content or
asbestos free vermiculite, I'd think.
Google "insulate unused chimney".
When I lived in Vermont I'd use wood as auxiliary heat. When it got really
cold the boiler (hydronic-oil converted to gas) wouldn't keep up, even running
flat out. A wood fire would make the place toasty anytime. No, it saved
nothing but it was nice. I went though a cord of wood every five years. ;-)
I've never studied that since i've never had to pay for wood. We have a
lifetime supply for at least 100 people of hedge (osage orange) and the
wood heat is so much more comfortable, I'd do it even if i had to pay
$100 a cord, i'd still come out ahead. you just have to have a good stove.
remove the "not" from my address to email
$225 is the going rate in this part of the world. That'll get you
maple & oak if you're lucky. Hickory or osage would bring a premium.
Just wondering how you get that "free" wood to jump from the bushes
into your stove- and season itself on the way.<g>
I understand not paying for the standing wood--- but having been there
myself many years ago, I know the amount of labor and equipment that
goes into gathering firewood. It is a good hobby and can be
cheaper than a gym membership for cardio workouts---- but it is *far*
The biggest heat loss I found with fireplaces is air leaks. Wind can
blow right in sometimes.
Create a negative house atmosphere and feel for leakage. There are
in the chimney. If you don't want the eye candy of the fireplace, seal
something like rigid fiberglass, "ceiling tiles" Foam board is
illegal, but you can also
use polyethylene insulation sheets. which is semi fire retardant and
does not need covering by
drywall. For permanent seal, insulate and drywall.
R values are varied according to which chart you use. My typical
cinderbock gets up to R 3.5
or more with fiberglass inside the holes.
For the most part, R value usually means inches of dry wood. 1 inch =
Thanks for the inputs.
I realized that I have no idea how a fireplace is constructed.
I did open up all the unheated areas and opened the heater registers.
The gas consumption went up by about 20%, which sounds reasonable
given the area added includes the patio door and fireplace.
I was surprised that the temperature of the bricks was the same as
the adjacent wall. Measured with IR thermometer, so there may be
emissivity issues not yet investigated.
The exhaust fan over my stove can pull 5 Pascals of vacuum on the house.
I turned it on and went probing with my trusty incense stick.
There's a small amount of air coming out of the fireplace,
but it's not coming down the flue. The cap works.
It's coming from the bottom near the front. Need to pull out
the homebrew heat exchanger and look under there.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.