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envoys 01-15-2007 01:57 PM

Heating for finished attic

The house I purchased has a finished attic that is sort of like a loft area. The one side has access for storage and the other side has access for the heating. Now, the heating and cooling does not get up to this level very well so I decided to investigate. The installation of the piping is 5" steel running from the furnace to the top of the attic, both cold air return and heat/cooling. Ok, now upstairs, when the furnace is on or the AC, there is very little, and i mean very little air coming out of the vents. I crawled in behind where they ran the pipe and found out that they have used some weird pipe I have never seen before, it is 5" insulated pipe, but inside the insulation looks something like a hose you would use on your dryer. The steel pipe comes up from the basement, and is T'd off for 2 vents. The T is very warm when the furnace is on, so I know the heat is up there, not could it be this "insulated" pipe causing me the grief and should I switch it to steel or have someone come in and look at the furnace?

Thanks. I hope I was clear enough.

glennjanie 01-15-2007 04:03 PM

Welcome to the Forum Envoys:
What you have discovered is called Flex-Duct. When it first came out it was stated to be limited to 3' runs, anything more just wears the air out trying to jump over the wires. Yes, you do need to change it out for steel pipe with sleeve insulation on it. The smooth steel will allow the air to speed up to the attic and the insulation sleeve will prevent loss of heat. Let us know how it turns out.

envoys 01-16-2007 07:48 AM

Thanks for the info! Designed for 3' runs huh? No wonder why its not getting any heat up there, there is 1 run of 30'! I will be changing this out this weekend and will let you all know how it goes. Thanks.

glennjanie 01-16-2007 11:05 AM

Hey Envoys:
Just for a "before and after" test; hold a candle near a register with the flex pipe on it then, after the steel pipe is in, hold a candle in the same place. You will be thrilled with the difference!

envoys 01-16-2007 12:18 PM

Ok, I will definately do that, maybe I'll do a short video of it for proof...that's if the candle even moves in the wind with the flex pipe on hehe.

Daryl 01-16-2007 10:10 PM

Possible too that there is to sharp of a bend in the are of change over that it's actually pinching off the air flow. You should have an air flow of 100 cfm at the register opening. I know, not every one has an air flow meter! 100 cfm is enough of a flow you can very easily detect it as movement over your hand. If there are several turns in the pipe between the furnace and the register this will severely cut down your air flow. (especially if they are 90deg. turns. THis causes a whirlwind effect at the turn which restricts the flow.

hvachawk 01-20-2007 02:56 PM

the flex duct can be ran more then 3ft ,but the way they did it is not right .
there must be a kink in it or it is torn in the wall some were.

with out looking at it its hard to tell you what to do ,so if you can post some pictures it will help.


envoys 01-22-2007 01:28 PM

Ok well I replaced all the flex duct with galv steel pipe, the air flow is still rather low but it is better then before...i will try and explain how the pipe gets up to the attic, it might not be the proper way they did it but you tell me... off the furnace comes a pipe that going to the register in the bathroom, that pipe has a T in it and then off the T is the pipe that goes upstairs...and obviously to go up, there is 1, 90deg on it, when it gets the the attic, there is another T that splits to 2 registers. That's all I can think of for now, maybe you guys can shed some light on this situation why it is so low...the register in the bathroom shoot the heat out like a hair dryer, same with the other registers in the house.

Quattro 01-22-2007 01:41 PM

Have you tried closing your bathroom register 1/2 way or more to see if that increases flow to the attic? It's a quick and dirty test, but won't solve the problem...and your bathroom will be cooler!

envoys 01-22-2007 02:08 PM

I've tried before and it didn't seem to do much, I'll try again with this new piping when I get home from work.

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