Originally Posted by acerunner
not sure about water heater yet. But yes to 95% furnace.
What difference would the efficiency of water heater make?
Most water heaters are not very efficient. The ones that are more then 70% efficient are very expensive..
I don't think you can T the water heater with the furnace unless you stick to a 80% furnace and 70% water heater and use B-vent, not PVC. Then you will need enough combustible indoor air which kinda sucks.
The standard water heater (and 80% furnace) typically needs a "Natrual draft" B-Vent type of venting. The B-vent is galvanized steel with an aluminum liner. The water heater is inefficient because it needs the waste heat to create the natural draft.
If you look a the 95% furnace, it uses PVC pipe for the vent because the waste is only 80 degrees.. 80 degree air is not going to rise on it's self so you need a blower to get it to go out. If you tried to T this, then when one appliance is on, the other would be blowing into the off one. Code is going to barf all over this. They use PVC because all the cracks in the vent need to be sealed, because unlike natural draft, the CO2 and the nasties are now pressurized and will escape through any cracks and come into living spaces and make problems for your health etc..
They make water heaters with blowers, they also make on-demand water heaters with PVC venting, but in either case I don't think you can T them together.
You are likely going to wind up with a standard water heater and a 95% furnace and two separate vents.
I have the two in one vent on my furnace where the inlet air comes in around a little ^ and the exaust goes out the middle and it works great, it looks much better then the vents with the little wrap around vent and straight vents right next to each other..
If you want to shove it in a closet and not use indoor combustible air you could get a 95% furnace, a 90-95% on demand water heater.
Take the two pvcs from each into their own concentric vent combiner and then run two vents out from your closet. (actually 4 vents, but only two come out your house)
Whats more important to you? Only 1 vent or not using indoor combustible air?