Question on attic ventilation

[Doug Steckel]

Hi All,

I have a question on attic ventilation. We just fired up the air conditioner in the new home and nothing. I'll cut to the chase and say that I think much of the problem if not all is inadequate attic ventilation. I think the attic unit and flexible, insulated tubing are just a giant heat exchanger taking pretty cool air at the unit and warming it by the time it gets to the vent. I felt the air at the vent this morning before the attic heated up and it was noticeably cooler. I'm sure that the attic had cooled down a bit over night.

Today when I got home. Outside temp - 91 Temp at vent - 81 Temp in attic - 119

We have a hip roof type, I guess that's what it's called, w/ about 20' of ridge vent. (The 1" thick floor buffer material like stuff in the ridge vent) There are soffit vents most of the way around but most were also blocked with insulation. Tonight I cleared most of it. I'm sure that will make some difference but I'm still unsure if we have enough ridge venting to cut it. I've heard you need about 1 sq. ft of venting (both for soffit and ridge, not combined) for ever 300 sq ft of attic. Is that attic floor space or attic roof? They aren't always the same because of cathedral ceilings cutting into some of that.

Anyway, besides that question any other ideas, insights, should we have to add additional venting, would be appreciated.

Thanks to the group in advance!

Doug

[m Ransley]

You need a pro to look at your unit.

[Glenn]

The attic may be hot but 119 don't sound too unreasonable on a hot day. I've certainly been a bunch of them a darned sight hotter. The first thing I would do is get some good blanket insulation, wrap one run from the air exchanger and see if that makes a difference on that run. I'm betting it will. Then raise hell with the builder for a poor insulation job.

[Joseph Meehan]

119 is not at all bad.

What is "Temp at vent" and how did you measure it?

[Doug Steckel]

Temp at vent = Temperature at output at ceiling vent by taping thermometer to vent for 10 minutes. Temp in house by the way was ~ 86.

[Al Bundy]

"Doug Steckel" wrote in news: [e-mail]:

You should see an average minimum of 16 degrees between the air intake and the vent outputs is the feeling I get from HVAC people.

As mentioned, 120 in an attic on a sunny hot day is not high.I've heard it can get to 140. I've been up in an attic on a sunny 95 deg day with the HVAC guy in the afternoon. Sweat was literally pouring off me. Then he fired up the mapp gas torch. You never complain about the service fee after that experience.

Anyway, assuming you have good airflow from the vents, if flexible duct is in the attic I would guess it has to be r6 or better. If the hard plastic duct it should be wrapped with insullation.

If the attic unit has a seam gap or something similar, it's possible is's sucking hot air and mixing it with cool.

Has anyone looked at the compressor and put gauges on it? It may be low on freon (or whatever they use now). If it is as little as 1 lb low, the freon may not hit it's "flash point". AC guy showed me that one since he saw I was interested. I had a unit that was putting out cooler air but only a few degrees (not the 16 deg differential). He put the gauges on it and said it was down a pound. Told me to put my hand on the freon line coming from the compressor and it felt cool to me. Says keep my hand on it while he pumps in another pound. Boy did that go from cool to cold.

Just some thoughts and experiences...

[Craig K.]

[Ben]

Since you said new home, my first thought is that either the installer did not charge the unit properly or that there is a leaking solder joint in the lines. New units come pre-charged with a "holding charge" which is just enough freon to give a positive pressure on the unit and keep moisture from entering the loop. Most units are installed just before the inspector gives the power company approval to connect electricity to the house, so the installer has to make a return trip to charge the system to specification. The most frequent problem is that the installer fails to come back for this final step. Call the installer back to leak check and charge the system and your problem will probably be over.

Ben

[Doug Steckel]

[Doug Steckel]

We have no soffits so I'll have to make the 20 ft of ridge vent work, or add other venting, if that's needed. So is there some thermostat, fan unit available to retrofit existing ridge joints to boost air flow?

Thanks,

[Doug Steckel]

Thanks,

Good advice. The home is new to us but not brand new. Builder long gone. If venting isn't the only problem we may need to bring HVAC person out to take a look at it. Thanks, Doug

[m Ransley]

It would be cheaper and smarter to get in a pro, he will check things out. Starting with expensive duct work when just a proper charge may be all that is necessary is backwards, insulated ducts and venting probably wont help.

[Joseph Meehan]

Good.

It could be as you suspect, but it also could be a problem with the A/C unit itself. First I would make sure there are no leaks in the system (no leaks in either the supply or return air) if you are sure about them, then adding insulation will not hurt, but it may not fix the problem which could well be a A/C problem.

[Needing Advice]

I would focus on the unit itself. Uncovering the soffit vents was a good idea. Is your condensor actually coming on? Have a pro come out and inspect it. The bill will not be fun but 100 degree house temps are a lot worse.

I just had to replace a capasitor on my unit. $80 service charge and $50 for the part.

Joseph Meehan wrote:

[CJT]

Surely there's more than just ridge vents ... you need someplace for cool air to enter, not just for hot air to exit.

[Doug Steckel]

[CJT]

That makes a lot more sense.

I think gables are wonderful, especially with a gable fan, but as the Rolling Stones have taught us, you can't always get what you want. :-)

[Al Bundy]

"Needing Advice" wrote in news: [e-mail]:

A thought for this one. Put unit on blower/fan only. Go look at meter thingy spinning. Turn on AC and go look at meter thingy again. Spinning a lot faster? (make sure in the meantime someone hasn't turned on the stove, couple of hair dryers, elec hot water kicked in, etc).

The thing is that even if the condensor is coming on, I think if it hasn't enough refrigerant it will not suck as much power sonce it is not condensing anything.

[Al Bundy]

"Doug Steckel" wrote in news: [e-mail]:

Get a tech out there bottom line. No matter how poorly insulated/ventilated things were you should see some differential. You have zero.