Capping a Vent Pipe

Short of removing it, yes I would think a cap would be necessary....are you sure the vent isn't being used as a fresh air intake of some type? In that case a screen and cap would be the way to go...

I'd cap both ends. But, that's just me.

Even though the chimney is not used, it's still a maintenance nightmare, not to mention a prime source for water infiltration. If this is a chimney that goes up through the interior of the house, the best solution is to remove the bricks, flue, and mortar above the roof and shingle over it. If this is not desirable, I agree that it should be plugged and capped at both ends.

Have to agree with you about plugging and capping!! Cheap and quick....

I would personally not remove it as you never know what might happen in the future and the cost of removing it is simply a waste of money....

You may want check if this vent serves indirectly as an air supply for the furnace.

If it was me I would just stuff it full of old rags and stick a cap on it then maybe spray foam the whole thing over to make it weather tight.

Who knows when the day will come that for whatever reason someone may want to put it back into use.

If you cap off the vent pipe could you still have fires in the fireplace (note to other CR4 folks: I know about this chimney/fireplace. Hannes and I have discussed fireplaces in old houses ad infinitum since we both have them.)

If this vent pipe is directly over the furnace, it may be feeding fresh air to the furnace rather than sucking the warm air out of the heated rooms in the house.

I had a fresh air pipe (going through the side wall) to feed air to our furnace because the house was built 'air-tight'. It works for us, the pipe is screened at the outside, and dumps fresh air directly over our furnace.

The way this house is built, shutting a door causes a change in air pressure. Compared to the "leaky" house we came from required stuffing insulation in the window wall cavities, weathersealing the doors, and other ways of keeping the cold air out were costly and a pain.

.....so I'd like to cap it. Would a product like this be the most appropriate means?

Yes.

Sound like you got took. Not seeing the job and from your description. I doubt the slope of the pipe was 15 feet down hill. Length my have 15 and it was sloped down hill. Why didn't they just correct the slope? As you have stated the pipe is above the furnace.

Even if that was not possible they didn't finish the job. They should have capped of the pipe after they disconnected it.

Yeah, I sometimes wonder if I got hosed. And I misspoke about the pipe--it's 15 feet long and has a slight downhill slope into the old chimney. So not a 15 foot downhill slope.

What I failed to mention is that there were a lot of issues with the old chimney, according to the builders anyway--such as crumbling masonry in the furnace vent side that was difficult and costly to repair, etc. They figured for the same cost they could build a new metal chimney with better venting.

I appreciate all the good responses. I hadn't thought of fresh air to the furnace, but I'm pretty sure it was just a smoke pipe. Being that the house is 135 years old I'm not as concerned about the insulation, given that I probably have hundreds of other tiny leaks elsewhere. But I'm pretty sure I've heard animals larger than mice climbing in and out of the chimney...probably a good reason to cap.

If it is a brick and mortar chimney you may want to simply use a large cement patio stone to cover the top. A little mortar or epoxy under it and it will stay put.

To cap the top of the chimney use spray foam to form a backing for thin mortar cap on top of it. That way if it was necessary to reuse it will not be difficult to remove.

An unused chimney still draws, and will suck the heat out of your house. I would put a metal cap over the top, fasten it down squirrel tight. Once the chimney is capped, you should be able to remove the pipe and close the hole in the chimney with brick and such.

I don't know where you live, but I would be careful how you "cap" the top of the pipe. Living in New Hampshire, having some very cold days in winter, placing something with any weight on it can cause a crash when the "cap" falls due to cold/heat loosening the attachment.