if they say they can do either safely within code make a desition. We don't care if your flue goes out the wall or
the chimney as long as it is safe and within code.

My thoughts--

I know gas does not have the same exhaust as oil.

I have an 90+% efficient oil furnace installed by the previous owners. It is vented out the side of the house. If you choose this option consider: the exhaust from the furnace is then below the level of the windows.

In the summer, when our the furnace kicks in to heat water the exhaust is blown into the house as the prevailing breeze blows toward the side of the house where it vents, and into the windows. it does not help that the doofuses who installed it vented it beneath an existing deck and sunroom, where the fumes invade the deck space and float into the sunroom, living room and kitchen via the windows. Occasionally, the smell will come in via a window on the side of the house next to the furnace. When I hear that sucker kick in, I shut windows like a crazy person or the house might end up smelling like bus station. Yum!

I know they are telling you that this won't happen if you go through the wall, and I know that they are saying that it is gas so it "there is no smell" or whatever. They may be right, but if they are wrong, it is a very big wrong indeed, and you won't be able to change it. I would go through the existing chimney even if it cost you a bit extra to make any chimney repairs to do it!

I hope this helps!

len

They have the vents that go on the outside of the house that contain the exhaust and intake in the same unit that look nice. I would go this route and leave the chimney in case at some point you decide you want a pellet stove or something else to vent through it. There are quite a few different ones out there to choose from.

I have one furnace telling me that the new high efficent furnaces will only last 10-13 years because they had to make them get to hot in order to get the high efficienty rating. He things high energy furnaces are a work in process and that you should make your old furncace last as long as possible because the new ones will get a lot better made in the next few years. Any thoughts. My Lennox 78% furnace is 15 years old and I kind of wanted to take care of the credit, but if the furnace only lasts 10-13 years, the energy savings will not offsetthe cost of replaceing the furnace after such a short time.

I think don't it is possible to vent a 95% efficiency furnace up through an existing chimney. The exhaust gas is too cool for it to rise. I believe high efficiency furnances must be vented horizontally through a wall. I would be very leary of a HVAC contractor would not do this.

I have not heard of high efficieny only lasting 10-13 years. This sounds like a myth from an HVAC contractor who doesn't want to install high efficiency furnaces.

It is important to interview multiple HVAC contrators when shopping for new equipment and installations. Be prepared to ask these type of questions and see if you get a consistent response. Hopefully you will eliminate the hacks.

LENVT. Your venting is HIGHLY ILLEGAL. If i was the inspector on that job i would shut off your oil until the venting was proper. MICK HOME. A 95 percent furnace can be vented up an existing chimney providing the chimney is insulated and packed with purolite or vermiculite with the proper cap.

I am taking down the chimney from my house. When I called a reputable pipefitter HVAC guy to come take a look if I could run the high eff furnace vents out the wall instead of thru the chinmey he was puzzled why it was installed in the Chimney to begin with. Also he noticed the faulty black PVC pipe that was recalled awhile back. Nice. My Furnace was installed by the previous owner with Byrant which explains alot. They are clowns that soak people for every penny, which seems to be the way with franchises.

Others had said the same thing. There is no reason to go all the way up the chinmey especially with the condensation problems it creates.

So I'm going out the wall and saying goodbye to the leak prone Chimney.
Anyway if that helps.

Did the contractor who wanted to vent through chimney mention anything about direct vent or 2 pipes?

While some HE furnaces can be installed with an exhaust pipe only, having outside combustion air makes for better comfort (less/no static shocks, reduced infiltration).

V

We are installing new high efficiency furnaces in our new home which is currently under construction in San Antonio, Tx. These furnace, like most in the south, are installed in the attic. Our home will have spray insulation on the rafters. The HVAC contract currntly has installed them with two roof vents directly above the furnaces with 180 deg elbows. This looks pretty unsightly and detracts from the home. Can these pipes be vented to an exterior wall? This would require that the venting would be below the units.

You should be able to vent the exhaust flue directly up through the roof. Not sure what you mean by "180 degree elbows". Some installers may do something like this outside to prevent rain entering the pipe, but this is not necessary. Do you have a picture?

My preference would be to have it vent out a side wall 12” below the soffit. This would eliminate 6 roof penetrations and improve the roof appearance. Can the venting for these new high efficiency units be below the unit itself with out having to install a forced draft (fan)??

The exhaust pipe contains moisture and need to slope back towards the furnace. I do not believe the intake has this restriction. You will need to read the installation manual to determine the requirements.

What is the color of your roof shingle? I suggest spray painting the PVC pipe with the matching color. From a distance it will look a lot better.