I was busy putting up that clear shrink-film window covering all around,
and decided to cover the opening to my fireplace. WOW! I just couldn't
believe how much air was flowing up / down that chimney, even though the
damper was shut tightly.

It's a typical main fireplace, about 4' x 5'. Once sealed, the film
acts almost like a large human lung sometimes! It's windy here in the
Chicago area today, and at times I was wondering if the double - stick
tape was strong enough to hold the film from pulling in and out.

I've read about inflatable chimney blocks. Has anyone used one, and if
so, does it do the job?

This is amazing. I don't think it's my imagination that the rest of the
house seems warmer, since there's so much less air infiltration, even
around windows that I haven't sealed with film. This is an otherwise
well-built home, but I guess that an air-tight fireplace seal wasn't
important in the early 1940's...

Welcome to the chimney effect.
We use plexiglass inserts with gaskets.
TB

I was busy putting up that clear shrink-film window covering all around,
and decided to cover the opening to my fireplace. WOW! I just couldn't
believe how much air was flowing up / down that chimney, even though the
damper was shut tightly.

For rarely used fireplaces, I stuff a wad of fiberglas batts cut the shape
of the flue just below the damper. I leave the paper moisture barrier on the
batts, then hang a little note from the batts so next time I build a fire I
remember to move the plug, and open the damper.

I was busy putting up that clear shrink-film window covering all around,
and decided to cover the opening to my fireplace. WOW! I just couldn't
believe how much air was flowing up / down that chimney, even though the
damper was shut tightly.

It's a typical main fireplace, about 4' x 5'. Once sealed, the film
acts almost like a large human lung sometimes! It's windy here in the
Chicago area today, and at times I was wondering if the double - stick
tape was strong enough to hold the film from pulling in and out.

I've read about inflatable chimney blocks. Has anyone used one, and if
so, does it do the job?

This is amazing. I don't think it's my imagination that the rest of the
house seems warmer, since there's so much less air infiltration, even
around windows that I haven't sealed with film. This is an otherwise
well-built home, but I guess that an air-tight fireplace seal wasn't
important in the early 1940's...

Just curious, is your chimney on the main or upper level? I have a
fireplace in a basement rec-room, and have assumed heatloss wasn't too bad,
since it is in a basement. Maybe I should re-think that.

"Buck Turgidson" wrote in message news:hej092-
Just curious, is your chimney on the main or upper level? I have a
fireplace in a basement rec-room, and have assumed heatloss wasn't too
bad,
since it is in a basement. Maybe I should re-think that.

Besides wind effects that may go right down the flue, much of the heat loss
is due to a cold chimney connecting to a warm room, at any level of the
house. The more chimney length is exposed, or greater height above the roof
line, the greater the cold transfer into the flue. Cold air is denser than
warmer room air, so the air sinks rapidly and spreads into the lighter
density, warmer room air, forming a cold layer in the bottom third of the
room - right where you don't want it!

Just curious, is your chimney on the main or upper level?

1st (and only) floor.
I have a
fireplace in a basement rec-room, and have assumed heatloss wasn't too bad,
since it is in a basement. Maybe I should re-think that.



You would if you saw this film moving around. Today is only mildly
breezy, and the film just never stops moving.

Tape a sheet of newspaper from the top edge & let it hang down across
the fireplace opening. I'd bet that newspaper never stops swaying around.

"Robert Barr" wrote in message
news



Just curious, is your chimney on the main or upper level?

1st (and only) floor.
I have a
fireplace in a basement rec-room, and have assumed heatloss wasn't too
bad,
since it is in a basement. Maybe I should re-think that.



You would if you saw this film moving around. Today is only mildly
breezy, and the film just never stops moving.

Tape a sheet of newspaper from the top edge & let it hang down across
the fireplace opening. I'd bet that newspaper never stops swaying around.

Damn you. You just made me add yet ANOTHER thing to my list of annoyances to
deal with! :-)