Attic HVAC Issue

[threeboys]

We did an addition on our house and installed a two zone heat system with one of the HVAC units in a small room in our unfinished attic. There are insulated ducts in the attic also coming from the room for this system. The problem we are having is that we cannot get the temperature in the attic under about 40 degrees. We have added additional roof venting (both soffit and top of roof) with little effect. We want to get the temperature closer to the outside to prevent ice dams and condensation problems.

The HVAC room is drywalled and has insulation. The ducts are insulated the flexible insulated variety (R-4?). It seems like the only explanation is that there is heat coming from the HVAC room or duct work. Any suggestions?

Note: we live in Northern Illinois.

Thanks!

[Wild Leg]

Originally posted by threeboys
...one of the HVAC units in a small room in our unfinished attic...

What are you calling an "HVAC unit"?

[threeboys]

bwal2, it is a new Trane UX80 furnace. What do you think? Thanks.

[billygoat22]

Could be a loose duct


May not be the duct at all, but heat loss from house, like air leakage out recessed lights or missing insulation.

[Wild Leg]

Originally posted by threeboys
bwal2, it is a new Trane UX80 furnace. What do you think? Thanks.

Glad it's not a heat pump leading a sorry life in your attic.

Insulate, ventilate, keep good insurance.

[threeboys]

Thanks, guys for the input.

bwal2 -- alright, why do you say "keep good insurance"??? Don't like Trane or attic installations?

[Carnak]

Originally posted by billygoat22
Could be a loose duct


May not be the duct at all, but heat loss from house, like air leakage out recessed lights or missing insulation.

Could very well be from the house, maybe the insulation is all messed up after the HVAC install. May not be conducting from the ductwork, but maybe the heat is leaking out of the duct work.

Could be warm air leaking out of house even around the diffusers.

[threeboys]

Carnak- What is the best way to seal up the diffusers and other penetrations? Can I use expanding foam around the diffusers or is there something better? Thanks.

[Carnak]

If it is a small gap you could even use silicone.

You already checked the duct sealing, there is not hot air leaking out of ducts?

[hearthman]

Use special duct sealing mastic on duct joints. Can use foam or caulk at boots and penetrations. Keep in mind warmair supply leaks outside the thermal envelope cause massive negative pressure inside which can backdraft atmospherically vented appliances. I'd increase that duct insulation. Don't forget other attic bypasses such as around stink pipes, wiring chases, etc. Warning! Chimney clearances cannot be packed with insulation. Fire Hazard. Can and should be properly firestopped such as with sheetmetal and caulk.
HTH

[Wild Leg]

Originally posted by threeboys
Thanks, guys for the input.

bwal2 -- alright, why do you say "keep good insurance"??? Don't like Trane or attic installations?

Nothing wrong with Trane.
No better, no worse than anybody else's.
It's just simple economics.

Water + attic = $$$$

[bigalf]

Originally posted by bwal2

Originally posted by threeboys
Thanks, guys for the input.

bwal2 -- alright, why do you say "keep good insurance"??? Don't like Trane or attic installations?

Bwal,
I am getting estimates to replace a one unit, one cold air return on a two story residence with a two unit system. Of the 4 estimates I have had, 3 want to put the air handler in the attic and only one suggests leaving the upstairs air handler on the ground and building a new return duct through the floors next to the existing supply duct.
Are overflowing condensate pans your only resistance to attic units?
Thanks

Nothing wrong with Trane.
No better, no worse than anybody else's.
It's just simple economics.

Water + attic = $$$$

[Wild Leg]

The condensate pan must actually catch the water in order to do any good.
It is very common to put the furnace in the attic.
It is also very common to pay somebody to repair water damage.
If the unit freezes up, ice could form on the piping between the indoor & outdoor coil.
When that ice melts, it is anyone's guess as to where the water will go.
Also, adequate access must be provided.

Don't let somebody cram this into a corner.

Just be sure you go into this with both eyes wide open.

I haven't seen your house, and don't know your contractor. Just be sure you voice your concerns ahead of time.

[Edited by bwal2 on 02-20-2005 at 06:45 PM]

[fat eddy]

I think that if your attic is at 40 and you are causing ice dams that it is probably more of a sun issue that a heatloss through the roof issue.