On Nov 24, 3:51*pm, George wrote:
On 11/24/2012 11:44 AM, DA wrote:

responding tohttp://www.homeownershub.com/maintenance/new-regs-to-make-furnace-rep...
DA wrote:
HeyBub *wrote:

The new energy-efficient natural gas
furnaces aren t that much more expensive themselves, but they must be
vented
directly to an outside wall rather than through the chimney, which can
increase installation costs dramatically ...

Does not have to be a *wall* per se - can still use existing chimney as a chase for the vent as well as the intake pipes. On some of the smaller furnaces all you need is a 2" PVC pipe for each. I imagine in most cases you can still find a shorter way to an outside wall but if completely stuck - there's still your old chimney right there.

I'm not sure what the big fuss is, anyhow: if you are replacing a furnace, you are already spending a considerable amount of money. Why would you not spend perhaps less than 10% more (if even that) to install a much more efficient furnace that creates the same amount of heat using less gas? Makes no sense to me to object to a good thing only because "the government mandated it". Even with gas prices falling right now, I believe it's still worth getting a more efficient furnace - never know where the price is going to be in the future. And regardless, even after the 40%+ fall this year, it's still far from being free.

But that is sensible reasoning that doesn't flow with the normal heybub
drama...

There are a number of potential problems with trying
to route the direct vent pipes up the old chimney.
One is the maximum length permitted. It's not unlimited
and there is a set maximum spec for the particular
furnace. Something like 35 feet or so. And that
included derating for any turns. So, you could easily find
that routing from the furnace, up the old chimney,
exceeds the max length allowed. An even bigger
problem is how do
you support the long runs of PVC pipe inside an
existing chimney? Again, specs for install call for
the pipe to be supported every 4 ft along their run.
Every chimney I've seen, you have access at
the bottom and top only.

Finally, when you have a gas furnace, you almost
always have a gas water heater which is also
using that chimney. You can't be running flue gases
from the water heater into a chimney that has the
PVC pipes from the furnace. So, even if you
could use the chimney, you would also have to
install a new direct vent water heater, again at
increased cost. Since you're already forced to try
to use the chimney for direct vent, it's not likely that
the water heater install is going to be easy either.
And increased cost not just for
this one time, but about every 10 years when you
have to buy a new one. And also have no hot
water when the power goes out, as it did here
with Sandy. Having a conventional water heater,
I had hot water.